LT1764 Series Datasheet by Analog Devices Inc.

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1
LT1764 Series
1764fb
3A, Fast Transient
Response, Low Noise,
LDO Regulators
Optimized for Fast Transient Response
Output Current: 3A
Dropout Voltage: 340mV at 3A
Low Noise: 40
µ
V
RMS
(10Hz to 100kHz)
1mA Quiescent Current
Wide Input Voltage Range: 2.7V to 20V
No Protection Diodes Needed
Controlled Quiescent Current in Dropout
Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 3.3V
Adjustable Output from 1.21V to 20V
<1µA Quiescent Current in Shutdown
Stable with 10µF Output Capacitor
Reverse Battery Protection
No Reverse Current
Thermal Limiting
Available in 5-Lead TO-220, DD and 16-Lead
TSSOP Packages
The LT
®
1764 is a low dropout regulator optimized for fast
transient response. The device is capable of supplying 3A
of output current with a dropout voltage of 340mV. Oper-
ating quiescent current is 1mA, dropping to <1µA in
shutdown. Quiescent current is well controlled; it does not
rise in dropout as it does with many other regulators. In
addition to fast transient response, the LT1764 has very
low output voltage noise which makes the device ideal for
sensitive RF supply applications.
Output voltage range is from 1.21V to 20V. The LT1764
regulators are stable with output capacitors as low as 10µF.
Internal protection circuitry includes reverse battery pro-
tection, current limiting, thermal limiting and reverse cur-
rent protection. The device is available in fixed output
voltages of 1.5V, 1.8V, 2.5V, 3.3V and as an adjustable
device with a 1.21V reference voltage. The LT1764 regu-
lators are available in 5-lead TO-220, DD and Exposed Pad
16-lead TSSOP packages.
Dropout Voltage
3.3VIN to 2.5VOUT Regulator
3.3V to 2.5V Logic Power Supply
Post Regulator for Switching Supplies
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
IN
SHDN
10µF
1764 TA01
OUT
VIN > 3V
SENSE
GND
LT1764-2.5
2.5V
3A
10µF
++
LOAD CURRENT (A)
0 0.5
DROPOUT VOLTAGE (mV)
1.0 2.01.5 2.5 3.0
1764 TA02
400
350
300
250
200
150
100
50
0
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents,
including 6144250, 6118263.
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2
LT1764 Series
1764fb
ABSOLUTE MAXIMUM RATINGS
W
WW
U
PACKAGE/ORDER INFORMATION
W
UU
(Note 1)
IN Pin Voltage ........................................................ ±20V
OUT Pin Voltage .................................................... ±20V
Input to Output Differential Voltage (Note 12) ....... ±20V
SENSE Pin Voltage ............................................... ±20V
ADJ Pin Voltage ...................................................... ±7V
SHDN Pin Voltage ................................................. ±20V
Output Short-Circuit Duration ......................... Indefinite
Operating Junction Temperature Range 40°C to 125°C
Storage Temperature Range ................. 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
LT1764ET
LT1764ET-1.5
LT1764ET-1.8
LT1764ET-2.5
LT1764ET-3.3
ORDER PART NUMBER
LT1764EQ
LT1764EQ-1.5
LT1764EQ-1.8
LT1764EQ-2.5
LT1764EQ-3.3
ORDER PART NUMBER
T
JMAX
= 150°C, θ
JA
= 30°C/ W
*PIN 5 = SENSE FOR LT1764-1.5/LT1764-1.8/
LT1764-2.5/LT1764-3.3
= ADJ FOR LT1764
*PIN 5 = SENSE FOR LT1764-1.5/LT1764-1.8/
LT1764-2.5/LT1764-3.3
= ADJ FOR LT1764
T
JMAX
= 150°C, θ
JA
= 50°C/ W
Q PACKAGE
5-LEAD PLASTIC DD
TAB IS
GND
FRONT VIEW
SENSE/ADJ*
OUT
GND
IN
SHDN
5
4
3
2
1
T PACKAGE
5-LEAD PLASTIC TO-220
SENSE/
ADJ*
OUT
GND
IN
SHDN
FRONT VIEW
TAB IS
GND
5
4
3
2
1
LT1764EFE
LT1764EFE-1.5
LT1764EFE-1.8
LT1764EFE-2.5
LT1764EFE-3.3
ORDER PART
NUMBER
FE PACKAGE
16-LEAD PLASTIC TSSOP
EXPOSED PAD (PIN 17) IS GND. MUST BE
SOLDERED TO THE PCB.
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
GND
NC
OUT
OUT
OUT
SENSE/ADJ*
GND
GND
GND
NC
IN
IN
IN
NC
SHDN
GND
17
T
JMAX
= 150°C, θ
JA
= 38°C/ W
*PIN 6 = SENSE FOR LT1764-1.5/
LT1764-1.8/LT1764-2.5/
LT1764-3.3
= ADJ FOR LT1764
1764EFE
1764EFE15
1764EFE18
1764EFE25
1764EFE33
FE PART
MARKING
L7LJCUW
3
LT1764 Series
1764fb
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Input Voltage I
LOAD
= 0.5A 1.7 V
(Notes 3, 11) I
LOAD
= 1.5A 1.9 V
I
LOAD
= 2.7A, 110°C < T
J
125°C 2.3 2.7 V
I
LOAD
= 3A, –40°C T
J
110°C 2.3 2.7 V
Regulated Output Voltage LT1764-1.5 V
IN
= 2.21V, I
LOAD
= 1mA 1.477 1.500 1.523 V
(Note 4) 2.7V < V
IN
< 20V, 1mA < I
LOAD
< 3A, –40°C T
J
110°C 1.447 1.500 1.545 V
2.7V < V
IN
< 20V, 1mA < I
LOAD
< 2.7A, 110°C < T
J
125°C 1.447 1.500 1.545 V
LT1764-1.8 V
IN
= 2.3V, I
LOAD
= 1mA 1.773 1.800 1.827 V
2.8V < V
IN
< 20V, 1mA < I
LOAD
< 3A, –40°C T
J
110°C 1.737 1.800 1.854 V
2.8V < V
IN
< 20V, 1mA < I
LOAD
< 2.7A, 110°C < T
J
125°C 1.737 1.800 1.854 V
LT1764-2.5 V
IN
= 3V, I
LOAD
= 1mA 2.462 2.500 2.538 V
3.5V < V
IN
< 20V, 1mA < I
LOAD
< 3A, –40°C T
J
110°C 2.412 2.500 2.575 V
3.5V < V
IN
< 20V, 1mA < I
LOAD
< 2.7A, 110°C < T
J
125°C 2.412 2.500 2.575 V
LT1764-3.3 V
IN
= 3.8V, I
LOAD
= 1mA 3.250 3.300 3.350 V
4.3V < V
IN
< 20V, 1mA < I
LOAD
< 3A, –40°C T
J
110°C 3.183 3.300 3.400 V
4.3V < V
IN
< 20V, 1mA < I
LOAD
< 2.7A, 110°C < T
J
125°C 3.183 3.300 3.400 V
ADJ Pin Voltage LT1764 V
IN
= 2.21V, I
LOAD
= 1mA 1.192 1.210 1.228 V
(Notes 3, 4) 2.7V < V
IN
< 20V, 1mA < I
LOAD
< 3A, –40°C T
J
110°C 1.168 1.210 1.246 V
2.7V < V
IN
< 20V, 1mA < I
LOAD
< 2.7A, 110°C < T
J
125°C 1.168 1.210 1.246 V
Line Regulation LT1764-1.5 V
IN
= 2.21V to 20V, I
LOAD
= 1mA 2.5 10 mV
LT1764-1.8 V
IN
= 2.3V to 20V, I
LOAD
= 1mA 310mV
LT1764-2.5 V
IN
= 3V to 20V, I
LOAD
= 1mA 410mV
LT1764-3.3 V
IN
= 3.8V to 20V, I
LOAD
= 1mA 4.5 10 mV
LT1764 (Note 3) V
IN
= 2.21V to 20V, I
LOAD
= 1mA 210mV
Load Regulation LT1764-1.5 V
IN
= 2.7V, I
LOAD
= 1mA to 3A 3 7 mV
V
IN
= 2.7V, I
LOAD
= 1mA to 3A, –40°C T
J
110°C23mV
V
IN
= 2.7V, I
LOAD
= 1mA to 2.7A, 110°C < T
J
125°C23mV
LT1764-1.8 V
IN
= 2.8V, I
LOAD
= 1mA to 3A 4 8 mV
V
IN
= 2.8V, I
LOAD
= 1mA to 3A, –40°C T
J
110°C25mV
V
IN
= 2.8V, I
LOAD
= 1mA to 2.7A, 110°C < T
J
125°C25mV
LT1764-2.5 V
IN
= 3.5V, I
LOAD
= 1mA to 3A 4 10 mV
V
IN
= 3.5V, I
LOAD
= 1mA to 3A, –40°C T
J
110°C30mV
V
IN
= 3.5V, I
LOAD
= 1mA to 2.7A, 110°C < T
J
125°C30mV
LT1764-3.3 V
IN
= 4.3V, I
LOAD
= 1mA to 3A 4 12 mV
V
IN
= 4.3V, I
LOAD
= 1mA to 3A, –40°C T
J
110°C40mV
V
IN
= 4.3V, I
LOAD
= 1mA to 2.7A, 110°C < T
J
125°C40mV
LT1764 (Note 3) V
IN
= 2.7V, I
LOAD
= 1mA to 3A 2 5 mV
V
IN
= 2.7V, I
LOAD
= 1mA to 3A, –40°C T
J
110°C20mV
V
IN
= 2.7V, I
LOAD
= 1mA to 2.7A, 110°C < T
J
125°C20mV
Dropout Voltage I
LOAD
= 1mA 0.02 0.05 V
V
IN
= V
OUT(NOMINAL)
I
LOAD
= 1mA 0.10 V
(Notes 5, 6, 11) I
LOAD
= 100mA 0.07 0.13 V
I
LOAD
= 100mA 0.18 V
I
LOAD
= 500mA 0.14 0.20 V
I
LOAD
= 500mA 0.27 V
I
LOAD
= 1.5A 0.25 0.33 V
I
LOAD
= 1.5A 0.40 V
I
LOAD
= 2.7A, 110°C < T
J
125°C 0.66 V
I
LOAD
= 3A 0.34 0.45 V
I
LOAD
= 3A, –40°C T
J
110°C 0.66 V
ELECTRICAL CHARACTERISTICS
The denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2)
4
LT1764 Series
1764fb
GND Pin Current I
LOAD
= 0mA 1 1.5 mA
V
IN
= V
OUT(NOMINAL)
+ 1V I
LOAD
= 1mA 1.1 1.6 mA
(Notes 5, 7) I
LOAD
= 100mA 3.5 5 mA
I
LOAD
= 500mA 11 18 mA
I
LOAD
= 1.5A 40 75 mA
I
LOAD
= 2.7A, 110°C < T
J
125°C 120 200 mA
I
LOAD
= 3A, –40°C T
J
110°C 120 200 mA
Output Voltage Noise C
OUT
= 10µF, I
LOAD
= 3A, BW = 10Hz to 100kHz 40 µV
RMS
ADJ Pin Bias Current (Notes 3, 8) 310µA
Shutdown Threshold V
OUT
= Off to On 0.9 2 V
V
OUT
= On to Off 0.25 0.75 V
SHDN Pin Current V
SHDN
= 0V 0.01 1 µA
(Note 9) V
SHDN
= 20V 7 30 µA
Quiescent Current in Shutdown V
IN
= 6V, V
SHDN
= 0V 0.01 1 µA
Ripple Rejection V
IN
– V
OUT
= 1.5V (Avg), V
RIPPLE
= 0.5V
P-P
,5563dB
f
RIPPLE
= 120Hz, I
LOAD
= 1.5A
Current Limit V
IN
= 7V, V
OUT
= 0V 4 A
LT1764-1.8, LT1764-2.5, LT1764-3.3
V
IN
= V
OUT(NOMINAL)
+ 1V, V
OUT
= – 0.1V, – 40°C T
J
110°C 3.1 A
V
IN
= V
OUT(NOMINAL)
+ 1V, V
OUT
= – 0.1V, 110°C < T
J
125°C 2.8 A
LT1764, LT1764-1.5
V
IN
= 2.7V, V
OUT
= – 0.1V, – 40°C T
J
110°C 3.1 A
V
IN
= 2.7V, V
OUT
= – 0.1V, 110°C < T
J
125°C 2.8 A
Input Reverse Leakage Current V
IN
= –20V, V
OUT
= 0V 1mA
Reverse Output Current (Note 10) LT1764-1.5 V
OUT
= 1.5V, V
IN
< 1.5V 600 1200 µA
LT1764-1.8 V
OUT
= 1.8V, V
IN
< 1.8V 600 1200 µA
LT1764-2.5 V
OUT
= 2.5V, V
IN
< 2.5V 600 1200 µA
LT1764-3.3 V
OUT
= 3.3V, V
IN
< 3.3V 600 1200 µA
LT1764 (Note 3) V
OUT
= 1.21V, V
IN
< 1.21V 300 600 µA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT1764 regulators are tested and specified under pulse load
conditions such that T
J
T
A
. The LT1764 is 100% tested at T
A
= 25°C.
Performance at –40°C and 125°C is assured by design, characterization
and correlation with statistical process controls.
Note 3: The LT1764 (adjustable version) is tested and specified for these
conditions with the ADJ pin connected to the OUT pin.
Note 4. Operating conditions are limited by maximum junction
temperature. The regulated output voltage specification will not apply for
all possible combinations of input voltage and output current. When
operating at maximum input voltage, the output current range must be
limited. When operating at maximum output current, the input voltage
range must be limited.
Note 5: To satisfy requirements for minimum input voltage, the LT1764
(adjustable version) is tested and specified for these conditions with an
external resistor divider (two 4.12k resistors) for an output voltage of 2.42V.
The external resistor divider will add a 300µA DC load on the output.
Note 6: Dropout voltage is the minimum input to output voltage differential
needed to maintain regulation at a specified output current. In dropout, the
output voltage will be equal to: V
IN
– V
DROPOUT
.
Note 7: GND pin current is tested with V
IN
= V
OUT(NOMINAL)
+ 1V or
V
IN
= 2.7V (whichever is greater) and a current source load. The GND pin
current will decrease at higher input voltages.
Note 8: ADJ pin bias current flows into the ADJ pin.
Note 9: SHDN pin current flows into the SHDN pin.
Note 10: Reverse output current is tested with the IN pin grounded and the
OUT pin forced to the rated output voltage. This current flows into the OUT
pin and out the GND pin.
Note 11. For the LT1764, LT1764-1.5 and LT1764-1.8 dropout voltage will
be limited by the minimum input voltage specification under some output
voltage/load conditions.
Note 12. All combinations of absolute maximum input voltage and
absolute maximum output voltage cannot be achieved. The absolute
maximum differential from input to output is ±20V. For example, with
V
IN
= 20V, V
OUT
cannot be pulled below ground.
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
The denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2)
o f /‘ / 4/ / / / / // / , / /‘// T ? __-————-—""|T=TmA 0 ~ T ’50 725 U 25 50 75 T00 I2 TEMPERATUREL‘C] i / // / / / / / n *SEI *25 U 25 50 75 T00 ‘25 *50 *25 [I 25 5D 750 *25 U 25 5D TEMPERATURE (‘6) TEMPERATURE (‘0) TEMPERATURE (“(3) 322 H90 0 7507250 2550 75TEIEIT25 75uiz5n 255n75wu‘25 0‘23455739m TEMPERATURE (’C) TEMPERATURE (my TNPUT VOLTAGE (V) T754 L7LJCUW 5
5
LT1764 Series
1764fb
TEMPERATURE (°C)
–50
0.8
1.0
1.4
25 75
1764 G04
0.6
0.4
–25 0 50 100 125
0.2
0
1.2
QUIESCENT CURRENT (mA)
LT1764-1.8/2.5/3.3
LT1764
V
IN
= 6V
R
L
=
I
L
= 0
V
SHDN
= V
IN
TEMPERATURE (°C)
–50
OUTPUT VOLTAGE (V)
25
1756 G05
–25 0 50
1.84
1.83
1.82
1.81
1.80
1.79
1.78
1.77
1.76 75 100 125
I
L
= 1mA
TEMPERATURE (°C)
–50
OUTPUT VOLTAGE (V)
25
1756 G06
–25 0 50
2.58
2.56
2.54
2.52
2.50
2.48
2.46
2.44
2.42 75 100 125
I
L
= 1mA
OUTPUT CURRENT (A)
0
0
DROPOUT VOLTAGE (mV)
100
200
300
400
600
0.5 1.0 1.5 2.0
1764 G01
2.5 3.0
500
TJ = 125°C
TJ = 25°C
OUTPUT CURRENT (A)
0
700
600
500
400
300
200
100
01.5 2.5
1764 G02
0.5 1.0 2.0 3.0
GUARANTEED DROPOUT VOLTAGE (mV)
= TEST POINTS
T
J
125°C
T
J
25°C
TEMPERATURE (°C)
–50
DROPOUT VOLTAGE (mV)
400
500
600
25 75
1764 G03
300
200
–25 0 50 100 125
100
0
I
L
= 3A
I
L
= 1.5A
I
L
= 0.5A
I
L
= 100mA
I
L
= 1mA
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Quiescent Current LT1764-1.8 Output Voltage LT1764-2.5 Output Voltage
LT1764-3.3 Output Voltage LT1764 ADJ Pin Voltage LT1764-1.8 Quiescent Current
TEMPERATURE (°C)
–50
OUTPUT VOLTAGE (V)
25
1756 G07
–25 0 50
3.38
3.36
3.34
3.32
3.30
3.28
3.26
3.24
3.22 75 100 125
I
L
= 1mA
TEMPERATURE (°C)
–50
ADJ PIN VOLTAGE (V)
25
1756 G08
–25 0 50
1.230
1.225
1.220
1.215
1.210
1.205
1.200
1.195
1.190 75 100 125
I
L
= 1mA
INPUT VOLTAGE (V)
0
QUIESCENT CURRENT (mA)
40
35
30
25
20
15
10
5
0
8
1764 G09
246 107135 9
T
J
= 25°C
R
L
=
V
SHDN
= V
IN
Typical Dropout Voltage Guaranteed Dropout Voltage Dropout Voltage
D V 2 3 4 5 5 7 E 9 ID WPUT VOLTAGE (V) LT1764-1.fl END Pin Current n uTzaafieTasTu INPUT VOLTAGE (V) LT1764-Z.5 END Pin Current 0 2 4 5 8 “1‘2 I4 WPUT VOLTAGE (V) T6 T3 20 LT1764-3.3 END Pin Current ZUU mzzsac T75 7 w VW’WN * W ‘FORVumzlav ‘FORVumzzw ‘FORVUUFESV E ‘5“ E E v v RL=5U v E (25 apasu R :5“ E V E 2 L l 2 \ =5DDMA E‘ ‘L‘mm |L=3UUMAV E‘ L E‘ “L45“ 5 WE g g \pfiflflmA‘ D D 0 arm: 5 75 E ‘ E /|L=EDDmA‘ .3, .3, prumA o 5 5n 5 E “Hm NEVUUMA‘ 25 Rpm: / \LzlflflmA‘ O U V 2 3 4 5 5 7 8 9 W U V 2 3 4 5 G 7 8 9 W D V 2 3 4 5 5 7 8 9 ID WPUT VOLTAGE (V) WPUT VOLTAGE (V) WPUT VOLTAGE (V) LT1764 END Pin Currenl LT17fi4-1.8 GND Pin Current LT17fi4-2.5 GND Pin Current ‘5 ED 200 T) 25°C T)=25“C ysuuuva VW=VW n ‘ w ‘2 FOR v0)”: I 2w m ‘an VGUT = T EV ‘60 FOR V0)”: 25v E E E ‘ ‘ V \ V \ v RL=083U % 9 g 90 ‘~— g m L=3N E E E \ a K a a \\ E s E 50 5 an o R o a mam) 57‘” E ‘L E E /‘ Oz) 5A‘ 7A 3 3D —_/_ r U V 2 3 4 5 5 7 E 3 If] U V 2 3 4 5 5 7 8 9 ID 3 4 5 5 7 E 3 ID WPUT VOLTAGE (V) WPUT VOLTAGE (V)
6
LT1764 Series
1764fb
INPUT VOLTAGE (V)
0
GND PIN CURRENT (mA)
9
12
15
8
1764 G16
6
3
0246
19
35710
R
L
= 2.42
I
L
= 500mA*
R
L
= 12.1
I
L
= 100mA*
R
L
= 4.33
I
L
= 300mA*
T
J
= 25°C
V
SHDN
= V
IN
*FOR V
OUT
= 1.21V
INPUT VOLTAGE (V)
0
GND PIN CURRENT (mA)
90
120
150
8
1764 G17
60
30
0246
19
35710
R
L
= 0.6
I
L
= 3A*
R
L
= 2.57
I
L
= 0.7A*
R
L
= 1.2
I
L
= 1.5A*
T
J
= 25°C
V
SHDN
= V
IN
*FOR V
OUT
= 1.8V
INPUT VOLTAGE (V)
0
GND PIN CURRENT (mA)
120
160
200
8
1764 G18
80
40
0246
19
35710
R
L
= 0.83
I
L
= 3A*
R
L
= 3.57
I
L
= 0.7A*
R
L
= 1.66
I
L
= 1.5A*
T
J
= 25°C
V
SHDN
= V
IN
*FOR V
OUT
= 2.5V
TYPICAL PERFOR A CE CHARACTERISTICS
UW
LT1764-1.8 GND Pin Current LT1764-2.5 GND Pin Current LT1764-3.3 GND Pin Current
LT1764 GND Pin Current LT1764-1.8 GND Pin Current LT1764-2.5 GND Pin Current
INPUT VOLTAGE (V)
10
GND PIN CURRENT (mA)
20.0
17.5
15.0
12.5
10.0
7.5
5.0
2.5
0
9
1764 G13
3578246 10
T
J
= 25°C
V
SHDN
= V
IN
*FOR V
OUT
= 1.8V
R
L
= 3.6
I
L
= 500mA*
R
L
= 18
I
L
= 100mA*
R
L
= 6
I
L
= 300mA*
INPUT VOLTAGE (V)
10
GND PIN CURRENT (mA)
40
35
30
25
20
15
10
5
0
9
1764 G14
3578246 10
T
J
= 25°C
V
SHDN
= V
IN
*FOR V
OUT
= 2.5V
R
L
= 5
I
L
= 500mA*
R
L
= 25
I
L
= 100mA*
R
L
= 8.33
I
L
= 300mA*
INPUT VOLTAGE (V)
10
GND PIN CURRENT (mA)
80
70
60
50
40
30
20
10
0
9
1764 G15
3578246 10
T
J
= 25°C
V
SHDN
= V
IN
*FOR V
OUT
= 3.3V
R
L
= 6.6
I
L
= 500mA*
R
L
= 33
I
L
= 100mA*
R
L
= 11
I
L
= 300mA*
LT1764-2.5 Quiescent Current LT1764-3.3 Quiescent Current LT1764 Quiescent Current
INPUT VOLTAGE (V)
0
QUIESCENT CURRENT (mA)
40
35
30
25
20
15
10
5
0
8
1764 G10
246 107135 9
T
J
= 25°C
R
L
=
V
SHDN
= V
IN
INPUT VOLTAGE (V)
0
QUIESCENT CURRENT (mA)
40
35
30
25
20
15
10
5
0
8
1764 G11
246 107135 9
T
J
= 25°C
R
L
=
V
SHDN
= V
IN
INPUT VOLTAGE (V)
0
QUIESCENT CURRENT (mA)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
16
1764 G12
4 8 12 20142 6 10 18
T
J
= 25°C
R
L
= 4.3k
V
SHDN
= V
IN
am To 09 03 07 05 05 no 03 02 m SHDN PIN THRESHOLD (v) SHDN PIN THRESHOLD M u n ’50 725 U 25 50 75 T00 ‘25 750 725 u 25 50 75 we T25 11 2 4 TEMPERATURE m TEMPERATURE (“Cl 5 a TuTzlaTsTazn DN PW VOLTAGE (v) SHDN Pin Inpul Current ADJ Pin Bias Currant Currant Limit \ \\\ \ / CURRENT LIMIT (A) SHDN PIN INPUT CURRENT (NM n 750 725 u 25 50 75 Inn 125 750 725 u 25 50 4 a T2 T5 20 TEMPERATURE TEMPERATURE (we, TNPuT/OUTPUT DTEEERENTTAL (V) L7LJCUW
7
LT1764 Series
1764fb
TYPICAL PERFOR A CE CHARACTERISTICS
UW
SHDN Pin Input Current ADJ Pin Bias Current Current Limit
TEMPERATURE (°C)
–50
0
SHDN PIN THRESHOLD (V)
0.1
0.3
0.4
0.5
1.0
0.7
050 75
1764 G22
0.2
0.8
0.9
0.6
–25 25 100 125
I
L
= 1mA
TEMPERATURE (°C)
–50
0
SHDN PIN THRESHOLD (V)
0.1
0.3
0.4
0.5
1.0
0.7
050 75
1764 G23
0.2
0.8
0.9
0.6
–25 25 100 125
IL = 3A
IL = 1mA
SHDN PIN VOLTAGE (V)
0
SHDN PIN INPUT CURRENT (µA)
6
8
10
16
1764 G24
4
2
5
7
9
3
1
04812
218
610 14 20
TEMPERATURE (°C)
–50
0
SHDN PIN INPUT CURRENT (µA)
1
3
4
5
10
7
050 75
1764 G25
2
8
9
6
–25 25 100 125
VSHDN = 20V
TEMPERATURE (°C)
–50
ADJ PIN BIAS CURRENT (µA)
25
1756 G26
–25 0 50
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
075 100 125
INPUT/OUTPUT DIFFERENTIAL (V)
0
CURRENT LIMIT (A)
2
4
6
1
3
5
4 8 12 16
1764 G27
2020 6 10 14 18
T
J
= –50°C
T
J
= 125°C
T
J
= 25°C
LT1764-3.3 GND Pin Current LT1764 GND Pin Current GND Pin Current vs I
LOAD
INPUT VOLTAGE (V)
0
GND PIN CURRENT (mA)
120
160
200
8
1764 G19
80
40
0246
19
35710
R
L
= 1.1
I
L
= 3A*
R
L
= 2.2
I
L
= 1.5A*
T
J
= 25°C
V
SHDN
= V
IN
*FOR V
OUT
= 3.3V
R
L
= 4.71
I
L
= 0.7A*
INPUT VOLTAGE (V)
0
GND PIN CURRENT (mA)
90
120
150
8
1764 G20
60
30
0246
19
35710
R
L
= 0.4
I
L
= 3A*
R
L
= 0.81
I
L
= 1.5A*
T
J
= 25°C
V
SHDN
= V
IN
*FOR V
OUT
= 1.21V
R
L
= 1.73
I
L
= 0.7A*
OUTPUT CURRENT (A)
0
GND PIN CURRENT (mA)
60
80
100
1.5 2.5
1764 G21
40
20
00.5 1.0 2.0
120
140
160
3.0
V
IN
= V
OUT(NOM)
+ 1V
SHDN Pin Threshold
(Off-to-On) SHDN Pin Input Current
SHDN Pin Threshold
(On-to-Off)
LTl764 Series WPICflL PEBFORITIflnCE CHHBHCTEBISTICS RIPPLE REJEDTION ma) vnm = nv n 750 725 u 25 50 75 I00 I25 TEMPERATURELW} Reverse Output Current I: 3 av (Emma a) / 7/ LTI 25 50 75 I00 I25 EMPERATURE (In) Ripple Rejection 75 llrISA I V0M< iiif="" ceramlc="" cum:="" wnf="" |l="l" 5a="" tantalum="" vin="VnUTINnMI" '="" ‘v="" i="" eumvrms="" ripple="" ll?="" “10="" lk="" wk="" luuk="" lm="" frequencv="" (hz)="" lt1764="" minimum="" input="" voltage="" 3="" u="" 2="" 5="" \\="" i="" 3a="" \="" l="2" n="" \="" \t‘="" \="" \="" ii="5A" \\="" \="" ‘="" 5="" \:7="" \="" ii="500InA" ll="IDDmA" l="" u="" u="" 5="" a="" fan="" 725="" u="" 25="" 50="" 75="" i00="" i2="" temperature("ci="">
8
LT1764 Series
1764fb
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Ripple Rejection
Ripple Rejection LT1764 Minimum Input Voltage
FREQUENCY (Hz)
20
RIPPLE REJECTION (dB)
30
50
70
80
10 1k 10k 1M
1764 G31
10
100 100k
60
40
0
C
OUT
= 100µF
TANTALUM +
10 × 1µF
CERAMIC
C
OUT
= 10µF
TANTALUM
I
L
= 1.5A
V
IN
= V
OUT(NOM)
+ 1V
+ 50mV
RMS
RIPPLE
TEMPERATURE (°C)
50 –25
50
RIPPLE REJECTION (dB)
60
75
050 75
1764 G32
55
70
65
25 100 125
IL = 1.5A
VIN = VOUT(NOM) + 1V
+ 0.5VP-P RIPPLE
AT f = 120Hz
TEMPERATURE (°C)
–50
MINIMUM INPUT VOLTAGE (V)
2.0
2.5
3.0
25 75
1764 G33
1.5
1.0
–25 0 50 100 125
0.5
0
I
L
= 3A
I
L
= 1.5A
I
L
= 100mA
I
L
= 500mA
Current Limit Reverse Output Current
Reverse Output Current
TEMPERATURE (°C)
–50
CURRENT LIMIT (A)
4
5
6
25 75
1764 G28
3
2
–25 0 50 100 125
1
0
VIN = 7V
VOUT = 0V
OUTPUT VOLTAGE (V)
0
REVERSE OUTPUT CURRENT (mA)
3.0
4.0
5.0
8
1764 G29
2.0
1.0
2.5
3.5
4.5
1.5
0.5
0246
19
35710
T
J
= 25°C
V
IN
= 0V
CURRENT FLOWS
INTO OUTPUT PIN
V
OUT
= V
ADJ
(LT1764)
V
OUT
= V
FB
(LT1764-1.8/-2.5/-3.3)
LT1764
LT1764-1.8
LT1764-2.5
LT1764-3.3
TEMPERATURE (°C)
–50
0
REVERSE OUTPUT CURRENT (mA)
0.1
0.3
0.4
0.5
1.0
0.7
050 75
1764 G30
0.2
0.8
0.9
0.6
–25 25 100 125
V
IN
= 0V
V
OUT
= 1.21V (LT1764)
V
OUT
= 1.8V (LT1764-1.8)
V
OUT
= 2.5V (LT1764-2.5)
V
OUT
= 3.3V (LT1764-3.3)
LT1764-1.8/-2.5/-3.3
LT1764
E s s mm 5 s E 5 s E’ mm” 3 3) PE 01 :5 ‘5 w mans w m & c. g anraa g 4 "mom: 3 7V(L'H754) E \ nurmnMHV 5: (mums/a ma) 2 u Onm ’50 ’25 0 25 50 75 V00 ‘25 m we 1k Ink 100 TEMPERATURE m) EREquch mz) LT1764-3.31flHzln1DflkHz OutpuINnise 7% > 5 E z E S 9 new com um 01 m LOAD CURRENT (A) LT1764—3.3 Transient Respnnse 4 a g uzAsamuzuwsmzn 4 nzAsamwzuwsmzn T‘MEms) T‘MEms) L7LJCUW%
9
LT1764 Series
1764fb
LT1764-3.3 10Hz to 100kHz
Output Noise
LT1764-3.3 Transient Response
TEMPERATURE (°C)
–50
LOAD REGULATION (mV)
25
1764 G34
–25 0 50
10
5
0
–5
–10
–15
–20
–25
–30 75 100 125
LT1764
LT1764-3.3
LT1764-2.5
LT1764-1.8
I
L
= 1mA TO 3A
V
IN
= 2.7V (LT1764)
V
IN
= V
OUT(NOM)
+ 1V
(LT1764-1.8/-2.5/-3.3)
FREQUENCY (Hz)
10
0.01
OUTPUT NOISE SPECTRAL DENSITY (µV/Hz)
0.1
1
100 1k 10k 100k
1764 G35
LT1764-3.3 LT1764-2.5
LT1764-1.8
LT1764
COUT = 10µF
ILOAD = 3A
LOAD CURRENT (A)
10
OUTPUT NOISE (µV
RMS
)
15
25
35
40
0.0001 0.01 0.1 10
1764 G36
5
0.001 1
30
20
0
LT1764-3.3
LT1764-2.5
LT1764-1.8
LT1764
C
OUT
= 10µF
VOUT
100µV/
DIV
COUT = 10µF 1ms/DIV 1764 G37
IL = 3A
TIME (µs)
0
OUTPUT VOLTAGE
DEVIATION (V)
LOAD CURRENT (A)
0.1
0.1
0.2
0
0.2
16
1764 G38
1.00
0.50
0.75
0.25
0462812 14 18
10 20
VIN = 4.3V
CIN = 3.3µF TANTALUM
COUT = 10µF TANTALUM
LT1764-3.3 Transient Response
TIME (µs)
0
OUTPUT VOLTAGE
DEVIATION (V)
LOAD CURRENT (A)
0.1
0.1
0.2
0
0.2
16
1764 G39
2
3
1
0462812 14 18
10 20
V
IN
= 4.3V
C
IN
= 33µF
C
OUT
= 100µF TANTALUM
+ 10 × 1µF CERAMIC
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Load Regulation Output Noise Spectral Density
RMS Output Noise vs Load Current
(10Hz to 100kHz)
I | EM
10
LT1764 Series
1764fb
OUT (Pin 4/Pins 3, 4, 5): Output. The output supplies
power to the load. A minimum output capacitor of 10µF is
required to prevent oscillations. Larger output capacitors
will be required for applications with large transient loads
to limit peak voltage transients. See the Applications
Information section for more information on output ca-
pacitance and reverse output characteristics.
SENSE (Pin 5/Pin 6): Sense. For fixed voltage versions of
the LT1764 (LT1764-1.8/LT1764-2.5/LT1764-3.3), the
SENSE pin is the input to the error amplifier. Optimum
regulation will be obtained at the point where the SENSE
pin is connected to the OUT pin of the regulator. In critical
applications, small voltage drops are caused by the resis-
tance (R
P
) of PC traces between the regulator and the load.
These may be eliminated by connecting the SENSE pin to
the output at the load as shown in Figure 1 (Kelvin Sense
Connection). Note that the voltage drop across the exter-
nal PC traces will add to the dropout voltage of the
regulator. The SENSE pin bias current is 600µA at the
nominal rated output voltage. The SENSE pin can be pulled
below ground (as in a dual supply system where the
regulator load is returned to a negative supply) and still
allow the device to start and operate.
ADJ (Pin 5/Pin 6): Adjust. For the adjustable LT1764, this
is the input to the error amplifier. This pin is internally
clamped to ±7V. It has a bias current of 3µA which flows
into the pin. The ADJ pin voltage is 1.21V referenced to
ground and the output voltage range is 1.21V to 20V.
SHDN (Pin 1/Pin 10): Shutdown. The SHDN pin is used to
put the LT1764 regulators into a low power shutdown
state. The output will be off when the SHDN pin is pulled
low. The SHDN pin can be driven either by 5V logic or
open-collector logic with a pull-up resistor. The pull-up
resistor is required to supply the pull-up current of the
open-collector gate, normally several microamperes, and
the SHDN pin current, typically 7µA. If unused, the SHDN
pin must be connected to V
IN
. The device will be in the low
power shutdown state if the SHDN pin is not connected.
IN (Pin 2/Pins 12, 13, 14): Input. Power is supplied to the
device through the IN pin. A bypass capacitor is required
on this pin if the device is more than six inches away from
the main input filter capacitor. In general, the output
impedance of a battery rises with frequency, so it is
advisable to include a bypass capacitor in battery-pow-
ered circuits. A bypass capacitor in the range of 1µF to
10µF is sufficient. The LT1764 regulators are designed to
withstand reverse voltages on the IN pin with respect to
ground and the OUT pin. In the case of a reverse input,
which can happen if a battery is plugged in backwards, the
device will act as if there is a diode in series with its input.
There will be no reverse current flow into the regulator and
no reverse voltage will appear at the load. The device will
protect both itself and the load.
GND (Pin 3/Pins 1, 7, 8, 9, 16, 17): Ground. The exposed
pad (FE Package) is ground and must be soldered to the
PCB for rated thermal performance.
Figure 1. Kelvin Sense Connection
IN
SHDN
1764 F01
RP
OUT
VIN SENSE
GND
LT1764
RP
3
5
4
1
2
+
+
LOAD
UU
U
PI FU CTIO S
(DD and TO-220/TSSOP)
L7LJCUW ”Hm— I”— -|—«M—l—«M—< .u.)="" |_.="">
11
LT1764 Series
1764fb
The LT1764 series are 3A low dropout regulators opti-
mized for fast transient response. The devices are capable
of supplying 3A at a dropout voltage of 340mV. The low
operating quiescent current (1mA) drops to less than 1µA
in shutdown. In addition to the low quiescent current, the
LT1764 regulators incorporate several protection features
which make them ideal for use in battery-powered sys-
tems. The devices are protected against both reverse input
and reverse output voltages. In battery backup applica-
tions where the output can be held up by a backup battery
when the input is pulled to ground, the LT1764-X acts like
it has a diode in series with its output and prevents reverse
current flow. Additionally, in dual supply applications
where the regulator load is returned to a negative supply,
the output can be pulled below ground by as much as 20V
and still allow the device to start and operate.
Adjustable Operation
The adjustable version of the LT1764 has an output
voltage range of 1.21V to 20V. The output voltage is set by
the ratio of two external resistors as shown in Figure 2. The
device servos the output to maintain the voltage at the ADJ
pin at 1.21V referenced to ground. The current in R1 is
then equal to 1.21V/R1 and the current in R2 is the current
in R1 plus the ADJ pin bias current. The ADJ pin bias
current, 3µA at 25°C, flows through R2 into the ADJ pin.
The output voltage can be calculated using the formula in
Figure 2. The value of R1 should be less than 4.17k to
minimize errors in the output voltage caused by the ADJ
pin bias current. Note that in shutdown the output is turned
off and the divider current will be zero.
The adjustable device is tested and specified with the ADJ
pin tied to the OUT pin for an output voltage of 1.21V.
Specifications for output voltages greater than 1.21V will
Figure 2. Adjustable Operation
be proportional to the ratio of the desired output voltage to
1.21V: V
OUT
/1.21V. For example, load regulation for an
output current change of 1mA to 3A is –3mV typical at
V
OUT
= 1.21V. At V
OUT
= 5V, load regulation is:
(5V/1.21V)(–3mV) = –12.4mV
Output Capacitance and Transient Response
The LT1764 regulators are designed to be stable with a
wide range of output capacitors. The ESR of the output
capacitor affects stability, most notably with small capaci-
tors. A minimum output capacitor of 10µF with an ESR in
the range of 50m to 3 is recommended to prevent
oscillations. Larger values of output capacitance can de-
crease the peak deviations and provide improved transi-
ent response for larger load current changes. Bypass
capacitors, used to decouple individual components pow-
ered by the LT1764-X, will increase the effective output
capacitor value.
Extra consideration must be given to the use of ceramic
capacitors. Ceramic capacitors are manufactured with a
variety of dielectrics, each with different behavior across
temperature and applied voltage. The most common di-
electrics used are specified with EIA temperature charac-
teristic codes of Z5U, Y5V, X5R and X7R. The Z5U and Y5V
dielectrics are good for providing high capacitances in a
small package, but they tend to have strong voltage and
temperature coefficients as shown in Figures 3 and 4.
When used with a 5V regulator, a 16V 10µF Y5V capacitor
can exhibit an effective value as low as 1µF to 2µF for the
DC bias voltage applied and over the operating tempera-
ture range. The X5R and X7R dielectrics result in more
stable characteristics and are more suitable for use as the
output capacitor. The X7R type has better stability across
temperature, while the X5R is less expensive and is
available in higher values. Care still must be exercised
when using X5R and X7R capacitors; the X5R and X7R
codes only specify operating temperature range and maxi-
mum capacitance change over temperature. Capacitance
change due to DC bias with X5R and X7R capacitors is
better than Y5V and Z5U capacitors, but can still be
significant enough to drop capacitor values below appro-
priate levels. Capacitor DC bias characteristics tend to
improve as component case size increases, but expected
capacitance at operating voltage should be verified.
IN
1764 F02
R2
OUT
V
IN
V
OUT
ADJ
GND
LT1764
R1
+
VV
R
RIR
VV
IA
OUT ADJ
ADJ
ADJ
=+
+
()()
=
121 1 2
12
121
3
.
.
µ AT 25 C
OUTPUT RANGE = 1.21V TO 20V
APPLICATIO S I FOR ATIO
WUUU
\ x5»: 400 Figure 3. an 20 a 720 7m V5v 750 CHANGE IN VALUE (m ,gn , ,m x x x x ’50 ’25 0 25 50 75 ‘00 I2 TEMPERATURE (an) Figure 4. Ceramic Capacitor Temparalure Cha 12
12
LT1764 Series
1764fb
Figure 4. Ceramic Capacitor Temperature Characteristics
The protection is designed to provide some output current
at all values of input-to-output voltage up to the device
breakdown.
When power is first turned on, as the input voltage rises,
the output follows the input, allowing the regulator to start
up into very heavy loads. During the start-up, as the input
voltage is rising, the input-to-output voltage differential is
small, allowing the regulator to supply large output cur-
rents. With a high input voltage, a problem can occur
wherein removal of an output short will not allow the
output voltage to recover. Other regulators, such as the
LT1085, also exhibit this phenomenon, so it is not unique
to the LT1764 series.
The problem occurs with a heavy output load when the
input voltage is high and the output voltage is low. Com-
mon situations are immediately after the removal of a
short circuit or when the SHDN pin is pulled high after the
input voltage has already been turned on. The load line for
such a load may intersect the output current curve at two
points. If this happens, there are two stable output oper-
ating points for the regulator. With this double intersec-
tion, the input power supply may need to be cycled down
to zero and brought up again to make the output recover.
Output Voltage Noise
The LT1764 regulators have been designed to provide low
output voltage noise over the 10Hz to 100kHz bandwidth
while operating at full load. Output voltage noise is typi-
cally 50nVHz over this frequency bandwidth for the
LT1764 (adjustable version). For higher output voltages
(generated by using a resistor divider), the output voltage
noise will be gained up accordingly. This results in RMS
noise over the 10Hz to 100kHz bandwidth of 15µV
RMS
for
the LT1764 increasing to 37µV
RMS
for the LT1764-3.3.
Higher values of output voltage noise may be measured
when care is not exercised with regards to circuit layout
and testing. Crosstalk from nearby traces can induce
unwanted noise onto the output of the LT1764-X. Power
supply ripple rejection must also be considered; the LT1764
regulators do not have unlimited power supply rejection
and will pass a small portion of the input noise through to
the output.
TEMPERATURE (°C)
–50
40
20
0
–20
–40
–60
–80
100
25 75
1764 F04
–25 0 50 100 125
Y5V
CHANGE IN VALUE (%)
X5R
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
APPLICATIO S I FOR ATIO
WUUU
Figure 3. Ceramic Capacitor DC Bias Characteristics
DC BIAS VOLTAGE (V)
CHANGE IN VALUE (%)
1764 F03
20
0
–20
–40
–60
–80
100 04810
26 12 14
X5R
Y5V
16
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
Voltage and temperature coefficients are not the only
sources of problems. Some ceramic capacitors have a
piezoelectric response. A piezoelectric device generates
voltage across its terminals due to mechanical stress,
similar to the way a piezoelectric accelerometer or micro-
phone works. For a ceramic capacitor the stress can be
induced by vibrations in the system or thermal transients.
Overload Recovery
Like many IC power regulators, the LT1764-X has safe
operating area protection. The safe area protection de-
creases the current limit as input-to-output voltage in-
creases and keeps the power transistor inside a safe
operating region for all values of input-to-output voltage.
L7LJCUW
13
LT1764 Series
1764fb
APPLICATIONS INFORMATION
WUUU
Thermal Considerations
The power handling capability of the device is limited
by the maximum rated junction temperature (125°C).
The power dissipated by the device is made up of two
components:
1. Output current multiplied by the input/output voltage
differential: (I
OUT
)(V
IN
– V
OUT
), and
2. GND pin current multiplied by the input voltage:
(I
GND
)(V
IN
).
The GND pin current can be found using the GND Pin
Current curves in the Typical Performance Characteris-
tics. Power dissipation will be equal to the sum of the two
components listed above.
The LT1764 series regulators have internal thermal limit-
ing designed to protect the device during overload condi-
tions. For continuous normal conditions, the maximum
junction temperature rating of 125°C must not be
exceeded. It is important to give careful consideration to
all sources of thermal resistance from junction to ambient.
Additional heat sources mounted nearby must also be
considered.
For surface mount devices, heat sinking is accomplished
by using the heat spreading capabilities of the PC board
and its copper traces. Surface mount heatsinks and plated
through-holes can also be used to spread the heat gener-
ated by power devices.
The following tables list thermal resistance for several
different board sizes and copper areas. All measurements
were taken in still air on 1/16" FR-4 board with one ounce
copper.
Table 1. Q Package, 5-Lead DD
COPPER AREA THERMAL RESISTANCE
TOPSIDE* BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT)
2500mm
2
2500mm
2
2500mm
2
23°C/W
1000mm
2
2500mm
2
2500mm
2
25°C/W
125mm
2
2500mm
2
2500mm
2
33°C/W
Table 2. FE Package, 16-Lead TSSOP
COPPER AREA THERMAL RESISTANCE
TOPSIDE* BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT)
2500mm
2
2500mm
2
2500mm
2
38°C/W
1000mm
2
2500mm
2
2500mm
2
43°C/W
225mm
2
2500mm
2
2500mm
2
48°C/W
100mm
2
2500mm
2
2500mm
2
60°C/W
T Package, 5-Lead TO-220
Thermal Resistance (Junction-to-Case) = 2.5°C/W
Calculating Junction Temperature
Example: Given an output voltage of 3.3V, an input voltage
range of 4V to 6V, an output current range of 0mA to
500mA and a maximum ambient temperature of 50°C,
what will the maximum junction temperature be?
The power dissipated by the device will be equal to:
I
OUT(MAX)
(V
IN(MAX)
– V
OUT
) + I
GND
(V
IN(MAX)
)
where,
I
OUT(MAX)
= 500mA
V
IN(MAX)
= 6V
I
GND
at (I
OUT
= 500mA, V
IN
= 6V) = 10mA
So,
P = 500mA(6V – 3.3V) + 10mA(6V) = 1.41W
Using a DD package, the thermal resistance will be in the
range of 23°C/W to 33°C/W depending on the copper
area. So the junction temperature rise above ambient will
be approximately equal to:
1.41W(28°C/W) = 39.5°C
The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:
T
JMAX
= 50°C + 39.5°C = 89.5°C
* Device is mounted on topside
* Device is mounted on topside
kug ba mums HUGH 3
14
LT1764 Series
1764fb
Protection Features
The LT1764 regulators incorporate several protection
features which make them ideal for use in battery-powered
circuits. In addition to the normal protection features
associated with monolithic regulators, such as current
limiting and thermal limiting, the devices are protected
against reverse input voltages, reverse output voltages
and reverse voltages from output to input.
Current limit protection and thermal overload protection
are intended to protect the device against current overload
conditions at the output of the device. For normal opera-
tion, the junction temperature should not exceed 125°C.
The input of the device will withstand reverse voltages of
20V. Current flow into the device will be limited to less than
1mA and no negative voltage will appear at the output. The
device will protect both itself and the load. This provides
protection against batteries which can be plugged in
backward.
The output of the LT1764-X can be pulled below ground
without damaging the device. If the input is left open circuit
or grounded, the output can be pulled below ground by
20V. For fixed voltage versions, the output will act like a
large resistor, typically 5k or higher, limiting current flow
to typically less than 600µA. For adjustable versions, the
output will act like an open circuit; no current will flow out
of the pin. If the input is powered by a voltage source, the
output will source the short-circuit current of the device
and will protect itself by thermal limiting. In this case,
grounding the SHDN pin will turn off the device and stop
the output from sourcing the short-circuit current.
The ADJ pin of the adjustable device can be pulled above
or below ground by as much as 7V without damaging the
device. If the input is left open circuit or grounded, the ADJ
pin will act like an open circuit when pulled below ground
and like a large resistor (typically 5k) in series with a diode
when pulled above ground.
In situations where the ADJ pin is connected to a resistor
divider that would pull the ADJ pin above its 7V clamp
voltage if the output is pulled high, the ADJ pin input
current must be limited to less than 5mA. For example, a
resistor divider is used to provide a regulated 1.5V output
from the 1.21V reference when the output is forced to 20V.
The top resistor of the resistor divider must be chosen to
limit the current into the ADJ pin to less than 5mA when the
ADJ pin is at 7V. The 13V difference between OUT and ADJ
pins divided by the 5mA maximum current into the ADJ pin
yields a minimum top resistor value of 2.6k.
In circuits where a backup battery is required, several
different input/output conditions can occur. The output
voltage may be held up while the input is either pulled to
ground, pulled to some intermediate voltage, or is left
open circuit. Current flow back into the output will follow
the curve shown in Figure 5.
When the IN pin of the LT1764-X is forced below the OUT
pin or the OUT pin is pulled above the IN pin, input current
will typically drop to less than 2µA. This can happen if the
input of the device is connected to a discharged (low
voltage) battery and the output is held up by either a
backup battery or a second regulator circuit. The state of
the SHDN pin will have no effect on the reverse output
current when the output is pulled above the input.
APPLICATIONS INFORMATION
WUUU
Figure 5. Reverse Output Current
OUTPUT VOLTAGE (V)
012345678910
REVERSE OUTPUT CURRENT (mA)
1764 F05
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
LT1764-2.5
LT1764-3.3
LT1764-1.8
LT1764
T
J
= 25°C
V
IN
= OV
CURRENT FLOWS INTO
OUTPUT PIN
V
OUT
= V
ADJ
(LT1764)
V
OUT
= V
FB
(LT1764-1.8,
LT1764-2.5, LT1764-3.3)
L7LJCUW M "HI-
15
LT1764 Series
1764fb
TYPICAL APPLICATIO S
U
+
A1
LT1006
+
C1B
1/2 LT1018
+
C1A
1/2 LT1018
LT1004
1.2V
1764 TA03
1µF
1N4148
1N4148
10k
10k
750
750
2.4k
22µF
1N4002
TO
ALL “V+
POINTS
200k
34k*
12.1k*
0.1µF
V+
V+
V+
V+
10k
V+
0.033µF
+
10000µF
+
22µF
VOUT
3.3V
3A
+
1N4002 1N4002
1k
10V AC
AT 115VIN
1N4148
L1
500µH
90V AC
TO 140V AC
10V AC
AT 115VIN
LT1764-3.3
GND
IN
SHDN
OUT
FB
L1: COILTRONICS CTX500-2-52
L2: STANCOR P-8560
*1% FILM RESISTOR
NTE5437
L2
NTE5437
“SYNC”
SCR Preregulator Provides Efficiency Over Line Variations
-II—I|I|— "H |__ {i .|._ _
16
LT1764 Series
1764fb
TYPICAL APPLICATIO S
U
Adjustable Current Source
LT1764-1.8
GND
IN
SHDN
R8
100k
OUT
FB
+
R7
470
4
8
1764 TA04
C2
3.3µF
C3
1µF
R1
1k
R3
2k
C1
10µF
V
IN
> 2.7V LT1004-1.2
R5
0.01
R2
40.2k
R4
2.2k
2
3
1
R6
2.2k
+
LOAD
1/2 LT1366
ADJUST R1 FOR 0A TO 3A
CONSTANT CURRENT
l E ass, 1 HHHHH * W a 057 f 050: «7+ V43:g;§ ‘ (V702) flaHe (7mm: uza 038 550 maaurusm macs 9 «7 [35324553 (DNVUSGS) ' WP R 8‘ ¢ \ \ 350 [ 325 205 555 L 555 I] DUI] I] DUI] W 057 »‘ ‘+u42 067 4‘ ‘9 RECOMMENDED SDLDER PAD wow RECOMMENDED SOLDER PAD LAVOUT FOR TH‘CKER SDLDER PASTE APPLICAHONS L7LJCUW
17
LT1764 Series
1764fb
PACKAGE DESCRIPTION
U
Q Package
5-Lead Plastic DD Pak
(LTC DWG # 05-08-1461)
Q(DD5) 0502
.028 – .038
(0.711 – 0.965)
TYP
.143 +.012
–.020
()
3.632 +0.305
0.508
.067
(1.702)
BSC
.013 – .023
(0.330 – 0.584)
.095 – .115
(2.413 – 2.921)
.004 +.008
–.004
()
0.102 +0.203
0.102
.050 ± .012
(1.270 ± 0.305)
.059
(1.499)
TYP
.045 – .055
(1.143 – 1.397)
.165 – .180
(4.191 – 4.572)
.330 – .370
(8.382 – 9.398)
.060
(1.524)
TYP
.390 – .415
(9.906 – 10.541)
15° TYP
.420
.350
.565
.090
.042
.067
RECOMMENDED SOLDER PAD LAYOUT
.325
.205
.080
.565
.090
RECOMMENDED SOLDER PAD LAYOUT
FOR THICKER SOLDER PASTE APPLICATIONS
.042
.067
.420
.276
.320
NOTE:
1. DIMENSIONS IN INCH/(MILLIMETER)
2. DRAWING NOT TO SCALE
.300
(7.620)
.075
(1.905)
.183
(4.648)
.060
(1.524)
.060
(1.524)
.256
(6.502)
BOTTOM VIEW OF DD PAK
HATCHED AREA IS SOLDER PLATED
COPPER HEAT SINK
18
18
LT1764 Series
1764fb
PACKAGE DESCRIPTION
U
T5 (TO-220) 0399
0.028 – 0.038
(0.711 – 0.965)
0.067
(1.70) 0.135 – 0.165
(3.429 – 4.191)
0.700 – 0.728
(17.78 – 18.491)
0.045 – 0.055
(1.143 – 1.397)
0.095 – 0.115
(2.413 – 2.921)
0.013 – 0.023
(0.330 – 0.584)
0.620
(15.75)
TYP
0.155 – 0.195*
(3.937 – 4.953)
0.152 – 0.202
(3.861 – 5.131)
0.260 – 0.320
(6.60 – 8.13)
0.165 – 0.180
(4.191 – 4.572)
0.147 – 0.155
(3.734 – 3.937)
DIA
0.390 – 0.415
(9.906 – 10.541)
0.330 – 0.370
(8.382 – 9.398)
0.460 – 0.500
(11.684 – 12.700)
0.570 – 0.620
(14.478 – 15.748)
0.230 – 0.270
(5.842 – 6.858)
BSC
SEATING PLANE
* MEASURED AT THE SEATING PLANE
T Package
5-Lead Plastic TO-220 (Standard)
(LTC DWG # 05-08-1421)
iElmElElElliEl nus 358 J ii; ;nnngmqgn; RECOMMENDED SDLDER PAD LA 43n745u~ (1597 m) 2n mums» i wuss), mm (m7 can) L7LJCUW 4904“? 358 HJWHHHH H7 I F 1 A \ + HHHHHHHH7 (13%»1L 005*0I5 ass ( msiuzn 4 e (nun, nus) ’ TVP \mavmmmn mmsnan w Lmaav Tatnnnmgy Cavpuvalmn .s hehaved m be mums am vename Hawever nu vesponsmmy \s assumefl lm us use Lmeav Tecnuomgy Cuvpnmhau makes nu [ewesenr mummamammmmmauunzsmvcunsasaesmmeahemnwmnmmmngeununsungpa‘emngh‘s
19
LT1764 Series
1764fb
FE Package
16-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663)
Exposed Pad Variation BB
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
PACKAGE DESCRIPTION
U
FE16 (BB) TSSOP 0204
0.09 – 0.20
(.0035 – .0079)
0° – 8°
0.25
REF
0.50 – 0.75
(.020 – .030)
4.30 – 4.50*
(.169 – .177)
134
5678
10 9
4.90 – 5.10*
(.193 – .201)
16 1514 13 12 11
1.10
(.0433)
MAX
0.05 – 0.15
(.002 – .006)
0.65
(.0256)
BSC
2.94
(.116)
0.195 – 0.30
(.0077 – .0118)
TYP
2
RECOMMENDED SOLDER PAD LAYOUT
0.45 ±0.05
0.65 BSC
4.50 ±0.10
6.60 ±0.10
1.05 ±0.10
2.94
(.116)
3.58
(.141)
3.58
(.141)
MILLIMETERS
(INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
2. DIMENSIONS ARE IN
3. DRAWING NOT TO SCALE
SEE NOTE 4
4. RECOMMENDED MINIMUM PCB METAL SIZE
FOR EXPOSED PAD ATTACHMENT
6.40
(.252)
BSC
20
LT1764 Series
1764fb
LT 1205 REV B • PRINTED IN USA
© LINEAR TECHNOLOGY CORPORATION 2005
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
FAX: (408) 434-0507
www.linear.com
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LT1120 125mA Low Dropout Regulator with 20µA I
Q
Includes 2.5V Reference and Comparator
LT1121 150mA Micropower Low Dropout Regulator 30µA I
Q
, SOT-223 Package
LT1129 700mA Micropower Low Dropout Regulator 50µA Quiescent Current
LT1175 500mA Negative Low Dropout Micropower Regulator 45µA I
Q
, 0.26V Dropout Voltage, SOT-223 Package
LT1374 4.5A, 500kHz Step-Down Converter 4.5A, 0.07 Internal Switch, SO-8 Package
LT1521 300mA Low Dropout Micropower Regulator with Shutdown 15µA I
Q
, Reverse Battery Protection
LT1529 3A Low Dropout Regulator with 50µA I
Q
500mV Dropout Voltage
LT1573 UltraFastTM Transient Response Low Dropout Regulator Drives External PNP
LT1575 UltraFast Transient Response Low Dropout Regulator Drives External N-Channel MOSFET
LT1735 Synchronous Step-Down Converter High Efficiency, OPTI-LOOP® Compensation
LT1761 Series 100mA, Low Noise, Low Dropout Micropower Regulators in SOT-23 20µA Quiescent Current, 20µV
RMS
Noise, SOT-23 Package
LT1762 Series 150mA, Low Noise, LDO Micropower Regulators 25µA Quiescent Current, 20µV
RMS
Noise, MSOP Package
LT1763 Series 500mA, Low Noise, LDO Micropower Regulators 30µA Quiescent Current, 20µV
RMS
Noise, SO-8 Package
LT1962 300mA, Low Noise, LDO Micropower Regulator 20µV
RMS
Noise, MSOP Package
LT1963 1.5A, Low Noise, Fast Transient Response LDO 40µV
RMS
Noise, SOT-223 Package
UltraFast is a trademark of Linear Technology Corporation.
OPTI-LOOP is a registered trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
U
Paralleling of Regulators for Higher Output Current
LT1764-3.3
GND
IN
SHDN
OUT
FB
LT1764
GND
IN R6
6.65k
C2
22µF
3.3V
6A
SHDN
OUT
ADJ
SHDN
+
R7
4.12k
R5
1k
C3
0.01µF
3
R4
2.2k
R2
0.01
R3
2.2k
2
1
8
1764 TA05
4
+
C1
100µF
+
1/2 LT1366
R1
0.01
VIN > 3.7V

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