LT2940 Datasheet by Analog Devices Inc.

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LT2940
1
2940f
TYPICAL APPLICATION
DESCRIPTION
Power and Current Monitor
The LT
®
2940 measures a high side current and a differ-
ential voltage, multiplies them and outputs a current
proportional to instantaneous power. Bidirectional high
side currents and bipolar voltage differences are correctly
handled by the four-quadrant multiplier and push-pull
output stage, which allows the LT2940 to indicate forward
and reverse power fl ow.
An integrated comparator with inverting and noninvert-
ing open-collector outputs makes the LT2940 a complete
power level monitor. In addition, an output current pro-
portional to the sensed high side current allows current
monitoring. The current mode outputs make scaling,
ltering and time integration as simple as selecting ex-
ternal resistors and/or capacitors.
Load Monitor Alarms Above 60W
FEATURES
APPLICATIONS
n Four-Quadrant Power Measurement
n ±5% Power Measurement Accuracy
n 4V to 80V High Side Sense, 100V Max
n Current Mode Power and Current Outputs
n Output Bandwidth Exceeds 500kHz
n ±3% Current Measurement Accuracy
n 6V to 80V Supply Range, 100V Max
n Inverting and Noninverting Open-Collector
Comparator Outputs
n Available in 12-Pin DFN (3mm × 3mm) and 12-Lead
MSOP Packages
n Board Level Power and Current Monitoring
n Line Card and Server Power Monitoring
n Power Sense Circuit Breaker
n Power Control Loops
n Power/Energy Meters
n Battery Charger Metering
CMP+
PMON IMON
CMPOUT
CMPOUT
LATCH
V
V+
I
I+
2940 TA01a
VCC
110k
+
10.0k
0A TO 10A
LED ON WHEN
PLOAD > 60W
PLOAD = VLOAD • ILOAD
VLOAD
6V TO 80V
ILOAD
LT2940
GND
20m
2W
5V
1k
VIMON = ILOAD • 100 mV
A
VPMON = PLOAD • 20.75 mV
W
24.9K 4.99k
LOAD
kV =
kI = 20m
1
12
ILOAD (A)
PLOAD (W)
0
VPMON (V)
2.0
1.5
1.0
48
2610 12 14
0.5
0
2.5
96
72
48
24
0
120
80V
30V
15V
10V
2940 TA01b
LED ON
LED OFF
VLOAD =6V
60W ALARM
Monitor Output Level and Load Power
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
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LT2940
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ABSOLUTE MAXIMUM RATINGS
VCC , I+, I, LATCH ....................................0.3V to 100V
V+, V, CMP+ .............................................0.3V to 36V
Voltage Sense (V+ – V) .........................................±36V
Current Sense (I+ – I) ............................................ ±36V
PMON, IMON (Note 3) ...... 0.3V to VCC + 1V, Up to 16V
CMPOUT, CMPOUT ....................................0.3V to 36V
CMPOUT, CMPOUT DC Output Current ..................22mA
(Notes 1, 2)
TOP VIEW
DD PACKAGE
12-LEAD (3mm s 3mm) PLASTIC DFN
12
13
11
8
9
10
4
5
3
2
1VCC
I+
I
LATCH
V+
V
CMPOUT
CMPOUT
CMP+
PMON
IMON
GND 67
TJMAX = 125°C, θJA = 43°C/W
EXPOSED PAD (PIN 13) PCB GND CONNECTION OPTIONAL
1
2
3
4
5
6
CMPOUT
CMPOUT
CMP+
PMON
IMON
GND
12
11
10
9
8
7
VCC
I+
I
LATCH
V+
V
TOP VIEW
MS PACKAGE
12-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 135°C/W
PIN CONFIGURATION
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT2940CDD#PBF LT2940CDD#TRPBF LDPP 12-Lead Plastic DFN 0°C to 70°C
LT2940IDD#PBF LT2940IDD#TRPBF LDPP 12-Lead Plastic DFN –40°C to 85°C
LT2940CMS#PBF LT2940CMS#TRPBF 2940 12-Lead Plastic MSOP 0°C to 70°C
LT2940IMS#PBF LT2940IMS#TRPBF 2940 12-Lead Plastic MSOP –40°C to 85°C
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to: http://www.linear.com/tapeandreel/
Operating Temperature Range
LT2940C ................................................... 0°C to 70°C
LT2940I ................................................40°C to 85°C
Storage Temperature Range ...................65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MSOP Package ................................................. 300°C
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ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Supply
VCC Supply Voltage Operating Range l680V
ICC Supply Current IPMON = +200µA, IIMON = +200µA
(Note 2)
l2 3.5 5 mA
VCC(UVLC) Supply Undervoltage Latch Clear VCC Falling l2.3 2.5 2.7 V
∆VCC(HYST) Supply Undervoltage Hysteresis VCC Rising l20 75 100 mV
Voltage Sense
VVSEN(OR) Voltage Sense Pin Operating Range VCC ≤ 12V l–0.1 VCC – 3 V
12V < VCC < 30V l–0.1 9 V
V+ Pin and V Pin VCC ≥ 30V l–0.1 18 V
VVVoltage Sense Differential Input Voltage Range
(Note 5)
VCC < 11V l±(VCC – 3) V
VV = VV+ – VVVCC ≥ 11V l±8 V
VV(CL) Voltage Sense Differential Clipping Limit
(Note 5)
VCC ≥ 12V l±9 V
IVSEN Voltage Sense Input Bias Current
V+ Pin and V Pin
l–300 –100 100 nA
∆IVSEN Voltage Sense Input Offset Current
∆IVSEN = IV+ – IV
VV+ = VVl±50 ±150 nA
Current Sense
VISEN(OR) Current Sense Pin Operating Range
I+ Pin and I Pin
l480V
VICurrent Sense Differential Input Voltage
Range (Note 6)
VI = VI+ – VI
l±200 mV
VI(CL) Current Sense Differential Clipping Limit
(Note 6)
l±225 mV
IISEN Current Sense Input Bias Current
I+ Pin and I Pin
l75 100 125 µA
∆IISEN Current Sense Input Offset Current
∆IISEN = II+ – II
VI+ = VIl±200 ±800 nA
Power Monitor (Note 2)
IPMON(OR) Power Monitor Output Current Operating
Range
l ±200 µA
IPMON(CAPA) Power Monitor Output Current Capability VCC ≥ 12V, VPMON ≥ 0V, and
VV = –9V, VI = –225mV, or
VV = 9V, VI = 225mV
l900 1200 µA
VCC ≥ 12V, VPMON ≥ 0.5V, and
VV = –9V, VI = 225mV, or
VV = 9V, VI = –225mV
l–240 –1200 µA
VCC ≥ 12V, VPMON ≥ 4V, and
VV = –9V, VI = 225mV, or
VV = 9V, VI = –225mV
l–800 –1200 µA
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at TA = 25°C. All specifi cations apply at 6V ≤ VCC ≤ 80V, unless otherwise specifi ed.
LT2940 L7LJCUEN2
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SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VPMON Power Monitor Output Compliance Voltage VCC ≤ 12V, IPMON ≥ 0µA l0V
CC – 4.5 V
12V < VCC < 30V, IPMON ≥ 0µA l0 7.5 V
VCC ≥ 30V, IPMON ≥ 0µA l012V
VCC ≤ 12V, IPMON < 0µA l0.5 VCC – 4.5 V
12V < VCC < 30V, IPMON < 0µA l0.5 7.5 V
VCC ≥ 30V, IPMON < 0µA l0.5 12 V
EPMON Power Monitor Output Total Error (Note 4) |VV • VI| ≤ 0.4V2±2 ±5 %FS
|VV • VI| ≤ 0.4V2, 25°C < TA ≤ 85°C ±2.5 ±7 %FS
|VV • VI| ≤ 0.4V2, LT2940C l±2.5 ±9 %FS
|VV • VI| ≤ 0.4V2, LT2940I l±3.5 ±12 %FS
Quadrants I and III of Shaded Region
in Figure 4
l±5 ±15 %FS
KPMON Power Monitor Scaling Coeffi cient
IPMON = KPMON • VV • VI
|VV • VI| = 0.4V2l485 500 515 µA/V2
VV(OSP) Power Monitor Voltage Sense Input-Referred
Offset Voltage
VV = 0V l±40 ±100 mV
VI(OSP) Power Monitor Current Sense Input-Referred
Offset Voltage
VI = 0mV l±2 ±6 mV
IPMON(OS) Power Monitor Output Offset Current VV = 0V, VI = 0mV l±6 ±15 µA
BWPMON Power Monitor Output Bandwidth RPMON = 2k 0.5 MHz
Current Monitor (Note 2)
IIMON(FS) Current Monitor Output Current Operating
Range
l±200 µA
VIMON Current Monitor Output Compliance Voltage VCC ≤ 12V, IIMON ≥ 0µA l0V
CC – 4.5 V
12V < VCC < 30V, IIMON ≥ 0µA l0 7.5 V
VCC ≥ 30V, IIMON ≥ 0µA l012V
VCC ≤ 12V, IIMON < 0µA l0.5 VCC – 4.5 V
12V < VCC < 30V, IPMON < 0µA l0.5 7.5 V
VCC ≥ 30V, IPMON < 0µA l0.5 12 V
EIMON Current Monitor Output Total Error (Note 4) |VI| ≤ 200mV, 25°C ≤ TA ≤ 85°C ±1.5 ±3 %FS
|VI| ≤ 200mV, LT2940C l±2 ±3.5 %FS
|VI| ≤ 200mV, LT2940I l±2 ±4 %FS
200mV < |VI| ≤ 225mV l±2.5 ±5 %FS
GIMON Current Monitor Scaling, IIMON = GIMON • VIVI = ±200mV l975 1000 1025 µA /V
VI(OSI) Current Monitor Current Sense Input-Referred
Offset Voltage
l±2.5 ±7 mV
BWIMON Current Monitor Output Bandwidth RIMON = 2k 1 MHz
Comparator
VCMP(TH) Comparator Threshold Voltage CMP+ Rising l1.222 1.240 1.258 V
∆VCMP(HYST) Comparator Threshold Hysteresis CMP+ Falling l–15 –35 –60 mV
ICMP(BIAS) Comparator Input Bias Current 1V ≤ VCMP+ ≤ 1.5V l±100 ±300 nA
ICMPOUT(OL) CMPOUT Output Low Voltage CMP+ High, ICMPOUT = 3mA l0.2 0.4 V
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at TA = 25°C. All specifi cations apply at 6V ≤ VCC ≤ 80V, unless otherwise specifi ed.
LT2940 vac 2 UV ‘ VPMDN = 0 5V ./ 72v L7 LJUW
LT2940
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VI (mV)
–200
400
600
200
0
0 200
–200
–400
800
2940 G01
VV = –8V
–4V
VV = VV+ – VV
VI = VI+ – VI
VCC ≥ 11V
VPMON = 0.5V
–2V
0V
2V
8V4V
IPMON (µA)
VI (mV)
–200
1
2
0
–1
0
–100 100 200
–2
–3
3
2940 G02
VV = 8V
VV = 8V
–4V
|VV • VI| ≤ 0.4V2
TA = 25°C
–2V
0V
2V
4V
EPMON (%FS)
ONE REPRESENTATIVE UNIT
TEMPERATURE (°C)
–50
–4
EPMON (%FS)
–3
–1
0
1
4
3
050 75
–2
2
–25 25 100 125
2949 G03
–8V ≤ VV ≤ 8V
–200mV ≤ VI ≤ 200mV
|VV • VI| ≤ 0.4V2
VCC = 12V
VCC = 80V
VCC = 80V
VCC = 12V
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: All currents into pins are positive, and all voltages are referenced
to GND unless otherwise noted. Current sourced by the PMON pin or the
IMON pin is defi ned as positive; current sunk as negative.
Note 3: The LT2940 may safely drive its own PMON and IMON output
voltages above the absolute maximum ratings. Do not apply any external
source that drives the voltage above absolute maximum.
Note 4: Full-scale equals ±200µA.
Note 5: V+ and V pin voltages must each fall within the voltage sense pin
operating range specifi cation.
Note 6: I+ and I pin voltages must each fall within the current sense pin
operating range specifi cation.
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at TA = 25°C. All specifi cations apply at 6V ≤ VCC ≤ 80V, unless otherwise specifi ed.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
ICMPOUT(LK) CMPOUT Leakage Current CMP+ Low, VCC = 36V,
0.4V ≤ VCMPOUT ≤ 36V
l±0.15 ±1 µA
ICMPOUT(OL) CMPOUT Output Low Voltage CMP+ Low, ICMPOUT = 3mA l0.2 0.4 V
ICMPOUT(LK) CMPOUT Leakage Current CMP+ High, VCC = 36V,
0.4V ≤ VCMPOUT ≤ 36V
l±0.15 ±1 µA
tDLY Comparator Propagation Delay Output Pulling Down l0.7 2 µs
VLATCH(IL) LATCH Input Low Voltage l0.5 0.8 1.2 V
VLATCH(IO) LATCH Input Open Voltage l1.25 1.5 1.95 V
VLATCH(IH) LATCH Input High Voltage l2.0 2.2 2.5 V
ILATCH(LK) LATCH Input Allowable Leakage in
Open State
l±10 µA
ILATCH(BIAS) LATCH Input Bias Current VLATCH = 0V l–11 –17 –23 µA
VLATCH = 80V l11 17 23 µA
TYPICAL PERFORMANCE CHARACTERISTICS
PMON Output Current
vs Sense Input Voltages
PMON Total Error
vs Sense Input Voltages PMON Error Band vs Temperature
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–4
–1500
–1000
–500
0
500
1500
–2 0
2940 G04
24
1000
VPMON = 0V
VPMON = 0.5V
IPMON (µA)
VV • VI (V2)
VCC ≥ 15V
VV = 40 • VI
VPMON = 4V
–5
–300
–200
–100
0
100
300
05
2940 G05
10 15 20
200 I = 200µA
OUTPUT CURRENT (µA)
OUTPUT VOLTAGE (V)
TA = 25°C
VCC = 6V VCC = 12V
VCC = 30V
I = –200µA
VCC = 6V VCC = 12V VCC =
30V
0
2.4
2.6
2.8
3.0
3.2
3.6
20 40
2940 G06
60 80 100
3.4 IPMON = 200µA
IIMON = 200µA
IPMON = 0µA
IIMON = 0µA
ICC (mA)
VCC (V)
IPMON = –200µA
IIMON = –200µA
–300
–300
–200
–100
0
100
300
–200 –100 0 100
2940 G07
200 300
200
VIMON = 0V
VIMON = 0.5V
IIMON (µA)
VI (mV)
VI = VI+VI
OUTPUT CURRENT IS
APPROXIMATELY FLAT
TO ABSOLUTE MAXIMUM
VOLTAGE LIMITS
VI (mV)
–200
1
0
–1
0 200
–2
2
2940 G08
EIMON (%FS)
VCC = 12V
VCC = 80V
ONE REPRESENTATIVE UNIT
TEMPERATURE (°C)
–50
EIMON (%FS)
–3
–1
0
1
3
050 75
–2
2
–25 25 100 125
2949 G09
–200mV ≤ VI ≤ 200mV
VI = 12V
VCC = 12V
VCC = 80V
VCC = 80V
VCC = 12V
TYPICAL PERFORMANCE CHARACTERISTICS
PMON Current
vs Power Sense Product
PMON and IMON Voltage
Compliance Supply Current vs Supply Voltage
IMON Current vs Current
Sense Voltage
IMON Total Error vs Current
Sense Voltage IMON Error Band vs Temperature
PMON Step Response PMON Step Response IMON Step Response
500ns/DIV
VIMON
200mV/DIV
2940 G10
RPMON = 2k ON 2VDC BIAS
CL= 8pF
VCC = 12V
TA= 25°C
VV = ±2V
VI = 200mV
250ns/DIV
VIMON
200mV/DIV
2940 G11
RPMON = 2k ON 2VDC BIAS
CL= 8pF
VCC = 12V
TA= 25°C
VI = ±200mV
VV = 2V
250ns/DIV
VIMON
200mV/DIV
2940 G12
RIMON = 2k ON 2VDC BIAS
CL= 8pF
VCC = 12V
TA= 25°C
VI = ±200mV
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TYPICAL PERFORMANCE CHARACTERISTICS
PMON Input Feedthrough
vs Frequency
PMON Frequency Response
to Voltage Sense
PMON Frequency Response
to Current Sense
IMON Frequency Response
to Current Sense
Open Collector Current
vs Open Collector Voltage
Power Supply Rejection Ratio
vs Frequency
FREQUENCY (Hz)
SEE TEST CIRCUITS FOR LOADING CONDITIONS
–30
PMON OUTPUT SIGNAL (dBVPK)
–10
100 100k 1M 10M
–60
–50
1k 10k
0
–20
–40
2940 G14
VV = ±2VPK
VI = 0mV, dV = 0
VI = ±200mVPK
VV = 0V, dI = 0
RELATIVE TO ±1VPK
RPMON = 5k ON 2VDC BIAS
TA = 25°C
FREQUENCY (Hz)
SEE TEST CIRCUITS FOR LOADING CONDITIONS
–30
RELATIVE PMON VOLTAGE (dBVPK)
–10
100 100k 1M 10M
–40 1k 10k
10
0
–20
2940 G15
VV = ±2VPK
VI = 200mVDC
IPMON = ±200µAPK (NOM)
TA = 25°C
RL = 2k
I-TO-V
AMP
OUTPUT
RL = 5k
RELATIVE TO DC GAIN
FREQUENCY (Hz)
SEE TEST CIRCUITS FOR LOADING CONDITIONS
–30
RELATIVE PMON VOLTAGE (dBVPK)
–10
100 100k 1M 10M
–40 1k 10k
10
0
–20
2940 G16
VV = 2VDC
VI = ±200mVPK
IPMON = ±200µAPK (NOM)
TA = 25°C
RL =
2k
I-TO-V
AMP
OUTPUT
RL = 5k
RELATIVE TO DC GAIN
FREQUENCY (Hz)
SEE TEST CIRCUITS FOR LOADING CONDITIONS
–30
RELATIVE IMON VOLTAGE (dBVPK)
–10
100 100k 1M 10M
–40 1k 10k
10
0
–20
2940 G17
VI = ±200mVPK
IIMON = ±200µAPK (NOM)
TA = 25°C
RL =
2k
I-TO-V
AMP
OUTPUT
RL = 5k
RELATIVE TO DC GAIN
FREQUENCY (Hz)
REJECTION RATIO (dBV)
40
100 100k 1M 10M
01k 10k
80
60
20
2940 G13
VCC = 12V
RPMON = 5k ON 2VDC BIAS
RIMON = 5k ON 2VDC BIAS
TA = 25°C
IMON PMON
OPEN COLLECTOR VOLTAGE (V)
0.1
0
OPEN COLLECTOR CURRENT (mA)
5
10
15
20
25
110
2940 G18
100
TA = 25°C
OUTPUT PULLING LOW
VCC = 6V
VCC = 80V
LT2940 L7LJCUEN2
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PIN FUNCTIONS
CMPOUT (Pin 1): Inverting Open-Collector Comparator
Output. When the LATCH pin’s state does not override the
comparator, CMPOUT pulls low when CMP+ > 1.24V. The
pull-down shuts off when CMP+ < 1.21V, or VCC < 2.5V or
when the LATCH pin is low. CMPOUT may be pulled up to
36V maximum. Do not sink more than 22mA DC.
CMPOUT (Pin 2): Noninverting Open-Collector Comparator
Output. When the LATCH pin’s state does not override the
comparator, CMPOUT pulls low when CMP+ < 1.21V, or
VCC < 2.5V, or when the LATCH pin is low. The pull-down
shuts off when CMP+ > 1.24V. CMPOUT may be pulled up
to 36V maximum. Do not sink more than 22mA DC.
CMP+ (Pin 3): Positive Comparator Input. The integrated
comparator resolves to high when the pin voltage exceeds
the 1.24V internal reference. The comparator input has
35mV of negative hysteresis, which makes its falling trip
point approximately 1.21V. Do not exceed 36V. Tie CMP+
to GND if unused.
PMON (Pin 4): Proportional-to-Power Monitor Output. This
push-pull output sources or sinks a current proportional
to the product of the voltage sense and current sense
inputs. A resistor from PMON to GND creates a positive
voltage when the power product is positive. The full-scale
output of ±200µA is generated for a sense input product
of ±0.4V2. Do not exceed VCC + 1V, up to 16V maximum.
Tie PMON to GND if unused.
IMON (Pin 5): Proportional-to-Current Monitor Output.
This push-pull output sources or sinks a current propor-
tional to the voltage at the current sense input, which is
typically generated by a sense resistor that measures a
current. A resistor from IMON to GND creates a positive
voltage when the sensed current is positive. The full-scale
output of ±200µA is generated by a current sense input
of ±200mV. Do not exceed VCC + 1V, up to 16V maximum.
Tie IMON to GND if unused.
GND (Pin 6): Device Ground.
V+, V (Pins 8, 7): Voltage Sense Inputs. The voltage
difference between these pins is the voltage input factor
to the power calculation multiplier. The difference may be
positive or negative, but both pin voltages must be at or
above GND – 100mV. The input differential voltage range
is ±8V. Do not exceed 36V on either pin.
LATCH (Pin 9): Comparator Mode Input. Conditions at this
three-state input pin control the comparators behavior.
When LATCH is open, the comparators outputs track its
input conditions (with hysteresis). When LATCH is held
above 2.5V, the comparators outputs latch when CMP+
exceeds 1.24V (CMPOUT open, CMPOUT pull-down). While
LATCH ≤ 0.5V or VCC < 2.5V, the comparators outputs clear
(CMPOUT pull-down, CMPOUT open) regardless of the
CMP+ pin voltage. The LATCH pin high impedance input
state tolerates ±10µA of leakage current. Bypass this pin
to GND to compensate for high dV/dt on adjacent pins.
Do not exceed 100V on this pin.
I+, I (Pins 11, 10): Current Sense Inputs. The voltage differ-
ence at these pins represents the current input factor to the
power calculation multiplier and to the current scaler. The
difference may be positive or negative, but both pin voltages
must be at least 4V and no more than 80V above GND,
completely independent of the VCC voltage. Both pins sink
approximately 100µA of bias current in addition to having
an effective 5k shunt between them. The input differential
voltage range is ±200mV. Do not exceed ±36V differ-
entially or 100V on either pin.
VCC (Pin 12): Voltage Supply. The voltage supply operat-
ing range is 6V to 80V. When operating with VCC > 15V,
package heating can be reduced by adding an external
series dropping resistor. Bypass this pin to GND to improve
supply rejection at frequencies above 10kHz as needed.
Do not exceed 100V on this pin.
Exposed Pad (Pin 13 in DFN Package): The exposed pad
may be left open or connected to device ground. For best
thermal performance, the exposed pad must be soldered
to the PCB.
LT2940 L7 LJUW
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FUNCTIONAL BLOCK DIAGRAM
TEST CIRCUITS
5
8
7
4
1
2
V+
I+
V
1.24V
UVLC
LATCHLO
LATCHHI
IMON
11
I
10
PMON
CMPOUT
CMPOUT
2940 BD
12
6
VCC
GND
VCC
3CMP+
9LATCH
+
BGAP REF
AND UVLC
DQ
CLR LE
4-QUADRANT
MULTIPLIER
THREE-STATE
DECODE
KPMON = 500 µA
V2
GIMON = 1000 µA
V
+
+
PMON
OR
IMON
2940 TC02
2V
VOUT
12V
Q1
2N2369
RC
499
RFB
4.99k
PMON
OR
IMON
2940 TC01
2V
VOUT
RL
Resistor on DC Bias I-to-V Amplifi er
LT2940 L7LJCUEN2
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APPLICATIONS INFORMATION
Introduction
The LT2940 power and current monitor brings together
circuits necessary to measure, monitor and control power.
In circuits where voltage is constant, power is directly
proportional to current. The LT2940 enables power moni-
toring and control in applications where both the current
and the voltage may be variable due to supply voltage
uncertainty, component parametric changes, transient
conditions, time-varying signals, and so forth.
The LT2940’s four-quadrant multiplier calculates in-
stantaneous power from its voltage sense and current
sense inputs. Its output driver sources and sinks cur-
rent proportional to power (magnitude and direction),
which affords fl exible voltage scaling, simple fi ltering
and, into a reference, bipolar signals. Its onboard
comparator is the fi nal piece required for integrated
power monitoring. In addition, the LT2940 provides a
proportional-to-current output that allows for equally
straightforward scaling, fi ltering and monitoring of the
sensed current.
Please note: although standard convention defi nes cur-
rents as positive going into a pin (as is generally the case
in the Electrical Characteristics table), the opposite is
true of the PMON and IMON pins. Throughout this data
sheet the power and current monitor output currents
are defi ned positive coming out of PMON and IMON,
respectively. Adopting this convention lets positive voltage
differences at the current and voltage sense pins yield
positive currents sourced from PMON and IMON that
can be scaled to positive ground referenced voltages
with a resistor.
Multiplier Operation
The LT2940 power and current monitor contains a four-
quadrant multiplier designed to measure the voltage and
current of a generator or load, and output signals propor-
tional to power and current. Figure 1 shows a signal path
block diagram. The operating ranges of the voltage sense
and current sense inputs are included. To simplify the
notation, the differential input voltages are defi ned as:
V
V = VV+ – VV (1a)
V
I = VI+ – VI (1b)
The full scale output of the multiplier core is ±0.4V2
, which
the PMON output driver converts to current through a
scale factor of KPMON.
I
PMON = KPMON • VV • VI (2)
KµA
V
PMON =500 2
(3)
The voltage across the current sense input pins is converted
to a current by the IMON output driver through the scale
factor of GIMON.
I
IMON = GIMON • VI (4)
GµA
V
IMON =1000
(5)
Both the PMON and IMON outputs reach full-scale at
±200µA.
The headroom and compliance limits for the input and
output pins are summarized in Table 1 for easy reference.
It is important to note that the current sense inputs, I+
and I, operate over a 4V to 80V range completely inde-
pendent of the LT2940’s supply pin, VCC. Note also that
the inputs accept signals of either polarity, and that the
Figure 1. LT2940 Signal Path Diagram
LT2940
VI = VI+ – VI
±200mV (MAX)
2940 F01
±200µA
FULL-SCALE
7
8
11 10
PMON
V+
V
I+I
VV • VI = ±0.4V2 FULL-SCALE
4
KPMON = 500 V2
µA
±200µA
FULL-SCALE
IMON 5
GIMON = 1000 V
µA
VV = VV+ – VV
±8V (MAX)
+
+
LT2940 ‘PMON , zuauA IOWA suuA 25w: ‘ZSUA L7 LJUW
LT2940
11
2940f
Table 1. LT2940 Essential Operating Parameters to Achieve Specifi ed Accuracy (VCC Operating Range = 6V to 80V)
PARA-
METER
SENSE
INPUT
PINS
PIN VOLTAGE
LIMIT
INPUT
OPERATING
RANGE
SCALING
TO
OUTPUT
MONITOR
OUTPUT
PINS
OUTPUT
OPERATING
RANGE
OUTPUT
VOLTAGE COMPLIANCE
Voltage V+, V0V to VCC – 3V at VCC ≤ 12V
0V TO 9V at 12V < VCC < 30V
0V to 18V at VCC ≥ 30V
VV = ±8V - - - -
Current I+, I4V to 80V* VI = ±200mV GIMON =
1000µA /V
IMON IIMON =
±200µA
Sourcing:
0V to VCC – 4.5V at VCC ≤ 7.5V
0V to 7.5V at 12V < VCC < 30V
0V to 12V at VCC ≥ 30V
Sinking:
As Above, Except Minimum is 0.5V
Power V+, V
,
I+, ISee Above Limits VV • VI = ±0.4V2KPMON =
500µA/V2PMON IPMON =
±200µA
* The current sense range is completely independent of the supply voltage.
APPLICATIONS INFORMATION
PMON and IMON outputs are capable of indicating forward
and reverse fl ow of power and current, provided they are
advantageously biased.
The multiplier core full-scale product of ±0.4V2 may
be reached over a range of voltage and current inputs,
as shown in Figure 2. For example, voltage sense and
current sense combinations of 8V and 50mV, 4V and
100mV, and 2V and 200mV each multiply to 0.4V2, and
thus produce 200µA at PMON. This arrangement allows
the core to operate at full-scale, and therefore at best ac-
curacy, over a 4:1 range of current and voltage, a readily
appreciated feature when monitoring power in variable
supply applications.
Essential Design Equations
A few equations are needed to calculate input scaling factors
and achieve a desired output. Consider the basic applica-
tion in Figure 3, where the power PIN is to be measured
as the product of voltage VIN and current IIN:
P
IN = VIN • IIN (6)
The actual measured quantities VIN and IIN are scaled to be
level-compatible with the LT2940. In this basic application,
a simple resistive voltage divider scales VIN, and a sense
resistor scales IIN.
V
V = VIN • kV (7a)
kR
RR
V=
+
1
12
(7b)
V
I = IIN • kI (8a)
k
I = RSENSE (8b)
The PMON output current is given by:
I
PMON = KPMON • VIN • kV • IIN • kI (9a)
or
I
PMON = PIN • KPMON • kV • kI (9b)
The output current may be positive (sourcing) or
negative (sinking) depending on the signs of VIN, kV
,
IIN, and kI. Provided that the magnitudes of VV and VI
do not exceed 8V and 200mV as shown in Figure 2, at
Figure 2. PMON Output Current as a Function
of Sense Input Voltages
2940 F02
VV = VV+ – VV (V)
VI = VI+ – VI (mV)
100
14
25
50
12.5
200
0.5 28
IPMON
= 200µA
25µA
50µA
100µA
12.5µA
LT2940 W ”W L7LJCUEN2
LT2940
12
2940f
APPLICATIONS INFORMATION
the full-scale output current of ±200µA, the achievable
full-scale power is:
PV
kk
IN FS VI
()
.
=04 2
(10)
In some applications the PMON output is converted to a
voltage by a load resistor:
V
PMON = IPMON • RPMON (11)
The complete end-to-end scaling is then given by:
V
PMON = PIN • KPMON • kV • kI • RPMON (12)
The current monitor output current at IMON is found by
combining Equations 4 and 8a:
I
IMON = IIN • GIMON • kI (13)
The output current may be positive (sourcing) or negative
(sinking) depending on the signs of IIN and kI. Provided
that the magnitude of VI does not exceed 200mV, at the
full-scale output current of ±200µA the achievable full-
scale input current is:
IV
k
IN FS I
()
.
=02
(14)
If IMON current is converted to a voltage by a load resis-
tor, then:
V
IMON = IIMON • RIMON (15)
and the fi nal end-to-end scaling is given by:
V
IMON = IIN • GIMON • kI • RIMON (16)
Accuracy
The principal accuracies of the power and current monitor
outputs are characterized as absolute percentages of full-
scale output currents, using the nominal values of scaling
parameters. The total error of the IPMON output, EPMON, is
typically ±2%, and is defi ned as:
E
IµA
VVV
µA
PMON
PMON V I
=
500
200 100
2•( • )
•%
(17)
Contributors to the power output accuracy such as the scal-
ing (KPMON), the output offset (IPMON(OS)), and the voltage
and current sense input offsets (VV(OSP) and VI(OSP)), are
separately specifi ed at key conditions and may be totaled
using the root sum-of-squares (RSS) method.
The total error of the IIMON output, EIMON, is typically
±1.5%, and is defi ned as:
E
IA
VV
A
IMON
IMON I
=
1000
200 100
μ
μ
•%
(18)
Contributors to the current output accuracy such as the
scaling (GIMON) and the current sense input offset (VI(OSI))
are separately specifi ed at key conditions. Here again, use
the RSS method of totaling errors.
Figure 3. Basic Power Sensing Application Showing Derivation of kV and kI
LT2940
PIN = VIN • IIN
2940 F03
7
8
11 10
PMON
R1
LOAD
V+
V
I+I
4
IMON 5mkV =
VI = IIN • RSENSE mkI = RSENSE
VV = VIN R1 + R2
R1
R1 + R2
R1
VIN
R2
RSENSE
IIN
RIMON
VIMON
IIMON
RPMON
VPMON
IPMON
+
+
LT2940 ififivi ‘mm = zflfluA mm H) mm 25w GUARANTEED Accumv \\\ ‘s L7 LJUW
LT2940
13
2940f
APPLICATIONS INFORMATION
Multiplier Operating Regions
The operating regions of the four-quadrant multiplier are
illustrated in Figure 4. Note that while Figure 2’s axes em-
ployed logarithmic (octave) scales to allow constant-power
trajectories to be straight lines, Figure 4’s axes are linear
to better accommodate negative inputs. Constant-power
trajectories are thus arcs.
The heavy line circumscribing the guaranteed accuracy
region is limited both by the product of the sense inputs
(the curved edges) and by each sense input’s differential
range (the straight edges). The maximum product that
realizes the specifi ed accuracy is VV • VI = ±0.4V2, and it
produces nominally full-scale output currents of IPMON =
±200µA. At the same time, the voltage and current sense
inputs must not exceed ±8V and ±200mV, respectively.
In the shaded functional region, multiplying occurs but
the output current accuracy is derated as specifi ed in the
Electrical Characteristics section.
The shaded functional region offers headroom beyond the
guaranteed range in all quadrants, and excellent sourcing
current operation beyond the standard +0.4V2 sense prod-
uct limit in quadrants I and III. In quadrants II and IV, the
PMON current is limited by compliance range, so accuracy
is not specifi ed. See the Electrical Characteristics and Typi-
cal Performance Characteristics sections for operation in
these regions. Inputs beyond those ranges, and out to the
absolute maximum ratings, are clipped internally.
Range and Accuracy Considerations
The LT2940’s performance and operating range may best
be exploited by letting the broad application category steer
design direction.
Constant-power applications comprise power level alarm
circuits, whether tripping a circuit breaker, activating aux-
iliary circuits, or simply raising an alarm, and single-level
power servo loops. In such applications, accuracy is best
when the full-scale output current of the LT2940 represents
the power level of interest, i.e., the IPMON = 200µA load
line (A) on Figure 5. Spans of voltage or current up to 4:1
naturally fi t into the operating range of the LT2940.
Special constant-power applications are the same types of
circuits (level measuring, servos) with additional restric-
tions. If operating within the guaranteed accuracy region
of Figure 4 is important over voltage or current spans
wider than 4:1, let a PMON current less than full-scale
represent the power level. For example, the load line (B)
of IPMON = 50µA in Figure 5 covers a span of 16:1 (VV = 8V
to 0.5V and VI = 200mV to 12.5mV). Note that operating
along line (C), IPMON = 25µA allows a span of 32:1, but the
channel offsets reduce the value of doing so. Operating
VV (V)
–12
VI (mV)
–100
150
200
250
300
–8 –4 0
–200
50
–150
100
–250
–300
0
–50
–10 –6 412
–2 28106
2940 F04
CURRENT SENSE CLIPPED
LIMITED
BY PMON
COMPLIANCE
II I
III IV
GUARANTEED
ACCURACY
CURRENT SENSE CLIPPED
VOLTAGE SENSE CLIPPED
VOLTAGE SENSE CLIPPED
LIMITED
BY PMON
COMPLIANCE
Figure 5. Various Constant-Power Curves in Quadrant I
2940 F05
VV (V)
VI (mV)
100
400
14
25
50
12.5
200
0.5 2816
CURRENT SENSE CLIPPING
IPMON
= 200µA
GUARANTEED
ACCURACY
(A)
25µA
50µA
100µA
VOLTAGE SENSE CLIPPING
I
(D)
(B)(C)
Figure 4. Multiplier Operating Regions vs Sense Input
Voltages. Accuracy Is Derataed in Shaded Areas
LT2940 L7LJCUEN2
LT2940
14
2940f
APPLICATIONS INFORMATION
Figure 6. LATCH Pin Protective Damping
below full-scale also affords scaling fl exibility. Line (D)
along IPMON = 100µA covers a 4:1 range like (A), but the
maximum VI is 100mV, which reduces voltage drop and
dissipation in the sense resistor.
Variable power applications comprise power measuring,
whether battery charging, energy metering or motor
monitoring, variable load-boxes, and other circuits where
the signifi cant metric is not a single value, and voltage
and current may be independent of each other. Design in
this case requires mapping the LT2940’s sense ranges to
cover the maximum voltage and the maximum current,
while considering whether the power represented is at,
above, or below full-scale IPMON. For example, setting it
at full-scale puts all values in the accurate range, setting
it above puts more accuracy in nominal power levels and
less accuracy in perhaps rarely encountered high levels,
and setting below might afford fl exibility to lower dissipa-
tion in the current sense resistor.
Output Filtering and Integration
Lowpass fi ltering the output power or current signal is as
simple as adding a capacitor in parallel with the output
voltage scaling resistor at PMON or IMON. For example,
adding 1nF in parallel with the PMON load resistor on the
front page application creates a lowpass corner frequency
of approximately 6.4kHz on the power monitor voltage.
Loaded by only a capacitor, the PMON pin voltage is pro-
portional to the time-integral of power, which is energy.
The integrating watt-hour meter application shown on
the back page takes advantage of this convenience. In a
similar way, a capacitor load on IMON produces a volt-
age proportional to charge that can be used to create a
coulomb counter.
Comparator Function
The LT2940’s integrated comparator features an internal
xed reference, complementary open-collector outputs
and confi gurable latching. A rising voltage at the CMP+
pin is compared to the internal 1.24V threshold. 35mV
(typical) negative hysteresis provides glitch protection and
makes falling inputs trip the comparator at about 1.21V.
The comparator result drives the open-collector CMPOUT
and CMPOUT pins which, when pulling down, sink at
least 3mA down to 0.4V. See the Typical Performance
Characteristics for more information. Complementary
comparator outputs save external components in some
applications. The CMPOUT and CMPOUT pins may be
pulled up externally to 36V maximum.
Comparator Latching
The LATCH pin controls the behavior of the comparator
outputs. When the LATCH pin is open, the comparator
output latch is transparent. Leakage currents up to ±10µA
will not change the decoded state of the LATCH pin. Internal
circuits weakly drive the pin to about 1.5V. Adding a 10nF
capacitor between LATCH and GND protects against high
dV/dt on adjacent pins and traces. Where more than 30V
and long inductive leads will be connected to LATCH,
damp potentially damaging ringing with a circuit like that
shown in Figure 6.
LATCH
I
I+
2940 F06
C2
10nF
R9A
20k
RESET
4V TO 80V
LT2940
GND
R9B
49.9k
LONG
WIRE
LT2940 “k I ‘WT "FILM L7 LJUW
LT2940
15
2940f
APPLICATIONS INFORMATION
Figure 7. Supply Resistor Reduces Package Heating by Reducing VCC Voltage
When the LATCH pin voltage exceeds 2.5V, the next high
result from the comparator also enables the comparator
latch. The CMPOUT pin goes open (high), and the CMPOUT
pin sinks current (low) regardless of the changes to the
CMP+ level until the latch is cleared. Latch activation is
level sensitive, not edge sensitive, so if CMP+ > 1.24V
when LATCH is brought above 2.5V, the comparator result
is high, and the latch is set immediately. The LATCH pin
voltage may be taken safely to 80V regardless of the VCC
pin voltage.
The latch is released and the comparator reports a low
when LATCH ≤ 0.5V or when VCC < 2.3V regardless of the
CMP+ pin voltage. In this state, the CMPOUT pin sinks
current (low), while the CMPOUT pin goes open (high).
As with latching, clearing is level-sensitive: comparator
outputs react to the input signal as soon as LATCH ≥ 1.25V
and VCC > 2.7V.
Thermal Considerations
If operating at high supply voltages, do not ignore package
dissipation. At 80V the dissipation could reach 400mW;
more if IMON or PMON current exceeds full-scale. Pack-
age thermal resistance is shown in the Pin Confi guration
section. Package dissipation can be reduced by simply
adding a dropping resistor in series with the VCC pin, as
shown in Figure 7. The operating range of the current sense
input pins I+ and I, which extends to 80V independent
of VCC, make this possible. The voltage ranges of the V+,
V, PMON and IMON pins are, however, limited by VCC.
Consult Table 1 during design. Operating an open-col-
lector output pin with simultaneously large current and
large voltage bias also contributes to package heating and
must be avoided.
CMP+
PMON IMON
CMPOUT
CMPOUT
LATCH
V
V+
I
I+
2940 F07
VCC
R2
140k
LOAD
R1
10.0k
5mA
MAX
0A TO 1.3A100V MAX
VPMON
R4
13.7k
R3
6.19k
OVP
30V TO 80V
OVERPOWER (OVP) GOES HIGH
WHEN LOAD POWER > 40W
RS
LT2940
GND
R12
3.9k
10% 1/8W
150m
1/2W
36V MAX
R14
20k
SCALE = 10
40W FULL-SCALE
W
V
kV =
kI = 150m
1
15
LT2940 «HH L7LJCUEN2
LT2940
16
2940f
TYPICAL APPLICATIONS
120W Supply Monitor Includes ICC of LT2940
CMP+
PMON IMON
CMPOUT
CMPOUT
LATCH
V
V+
I
I+
2940 TA02
VCC
R2
140k
LOAD
R1
10.0k
5mA
MAX
0A TO 4A
VPMON
R4
13.7k
R3
6.19k
OVP
SUPPLY
30V TO 80V
100V (MAX)
OVERPOWER (OVP) GOES HIGH
WHEN SUPPLY POWER > 120W
RS
LT2940
GND
R12
3.9k
1/8W
50m
1W
VLOGIC
R14
3.9k
SCALE = 30
120W FULL-SCALE
W
VkV =
kI = 50m
1
15
12.5W PWM Heat Source
CMP+
IMONPMON
CMPOUT
CMPOUT
LATCH
V
V+
I
I+
VCC
2940 TA03
R2
102k
R1
25.5k
Q1
FDS3672
INPUT
9.5V TO 14.5V
RS
LT2940
GND
200m
3
R4
15.0k
C4
4.7µF
* SEVEN 50, 5W RESISTORS IN PARALLEL.
MULTIPLE UNITS FACILITATE SPREADING HEAT.
C1
100µF
25V
kV =
kI =
tOFF z1.7ms
200m
3
1
5
HEATSINK
Q = 12.5W
R6
10k
R5
10k
Q3
2N3906
Q2
TP0610
R7*
7
D1
1N5819
+
LT2940 oooooo , «m .. W Tit-HF }\ PLAN».— zzzzzz "H I— L7 LJUW
LT2940
17
2940f
TYPICAL APPLICATIONS
30W Linear Heat Source
Wide Input Range 10W PWM Heat Source
PMON IMON
V
V+
II+
VCC
2940 TA04
R2
102k
LM334
R1
25.5k
R6
51 Q1
VN2222
D1
1N457
D2
27V
10A/V
10V TO 40V
RS
LT2940
GND
200m
3
R5
6.8k R7
3.3k
C3
470pF
C2
22nF
R3
10k
R4
680
V
V+
R
R8
1k
R9
10k
Q2
TIP129
HEATSINK
Q = 30W
Q3
D44VH11
R10
100
R11
100m
kV =
kI = 200m
3
1
15
C1
100µF
50V
+
CMP+
IMONPMON
CMPOUT
CMPOUT
LATCH
V
V+
I
I+
VCC
2940 TA05
D2
1N4148
Q2
BSS123
22.4V TO 72V
RS
LT2940
GND
200m
3
R4
68k
C4
4.7µF
C1
100µF
100V
kV =
kI =
tOFF z2ms
200m
3
13
233
HEATSINK
Q = 10W
R6
10k
R5
10k R7
50
25W
Q3
2N3906
12V
D1
MUR1100E
Q1
FDS3672
R2
220k
R1
13k
D3
1N4148
C2
100nF
+
12V
LT2940 L7LJCUEN2
LT2940
18
2940f
TYPICAL APPLICATIONS
8V to 32V, 8W Load
Adjustable 0W to 10W Load Box with UVLO and Thermal Shutdown
PMONIMON
V
V+
II+
VCC
2940 TA06
Q1
FDB3632
8V TO 32V
RS
200m
LT2940
GND
12V
12V
kV =
kI = 200m
1
4
R2
30k
R1
10k
R7
6.8
10W
LM334
D1
1N457
R5
6.8k
C1
100nF
C4
100nF
200µA/A
CURRENT
MONITOR
OUTPUT
R3
2k
R4
680
V
V+
R
R6
10
+
CMP+
PMON
IMON
CMPOUT
CMPOUT
LATCH
V
V+
I
I+
VCC
2940 TA07
Q2
2N3904*
Q1
FDB3632
1A/V
CURRENT
MONITOR
OUTPUT ICONTROL
= 50mW/µA
10V TO 40V
INPUT
LT2940
GND
12V
12V
12V
LT1635
0W TO 10W ADJ
10-TURN REF
200mV
kV =
kI = 200m
1
5
R12
12k
R10
500
TEMP
ADJ
*THERMAL SHUTDOWN; COUPLE TO Q1’s HEAT SINK
D1
1N4003
R4
4.99k
R13
10k
R3A
13k
UVLO
RS
200m
R3B
91k
R14
10
R1
30k
R2
120k
C11
10nF
R11
33
Q4
2N3906
+
R17
100
R18
1k
R16
10k
R15
10k
C13
10nF
R19
10k
OA
Q3
2N3906
LT2940 P .||— 22222 L7 LJUW
LT2940
19
2940f
TYPICAL APPLICATIONS
1-Cell Monitor with Bottom-Side Sense
Motor Monitor with Circuit Breaker
CMP+
PMONIMON
CMPOUT
CMPOUT
RESET LATCH
V
V+
I
I+
VCC
2940 TA09
R2A
10k
1% MUR120
R1
10k
1%
R2B
10k
1%
Q1
FDB3632
VPMON
100W/V
VIMON
6.5A/V
12V
RS
LT2940
GND
GE
5BPA34KAA10B
12V, 8A
PM FIELD
25m
2
R5
12.4k
C5
33nF
R4
4.99k
C4
100nF
C10
100µF
25V
R3
10k
kV =
kI =
OVERCURRENT TRIP = 8A
25m
2
1
3
+
+
IMON
PMON
V
V+
I
I+
VCC
2940 TA08
LT2940
LT1635
GND
C1
100nF
kV = = 0.8
kI = 200m
121
151
R12
1k
5%
12V
12V
200mV
CYCLON
2V, 4.5AH
DT CELL*
LOAD
CHARGER
R1
121k
R5
4.99k
R2
30k
1%
R4
12.4k
1W/V
±2.5W MAX
1A/V
±1A MAX
RS1
215
RS2
215
+
REF
OA
Q1
2N3904
*www.hawkerpowersource.com
(423) 238-5700
Q2
2N3904
D1
5.1V
R6
1k
1%
R7
200
1%
R9
200
1%
RS3
200m
R8
1k
1%
LOAD+
CHARGER+
LT2940 L7LJCUEN2
LT2940
20
2940f
TYPICAL APPLICATIONS
28V Power to Frequency Converter
Secondary-Side AC Circuit Breaker
CMP+
PMON
IMON
CMPOUT
CMPOUT
LATCH
IN+
IN
HYST
REF
V
V+
I
I+
VCC
2940 TA10
R1A
30k R1B
30k
R2
120k
Q3
D4
D3
LOAD
OPTO-ISOLATOR
28V INPUT
10V TO 40V
RS
LT2940
GND
200m
C4
2.2nF
R4B
10k
D2
R4A
240k
C7
10nF
D1
10V
CENTRAL SEMI
CCLM2700
kV =
kI = 200m
PMAX = 10W
fOUT = 10W
1000Hz
1
5
= 1N4148
= 2N7000
R5, 100k Q2
VCC
R6, 100k
VCC
+
C5
F
WIMA
VGND
V+
OUT
Q1
C6
100nF
VCC
R9
1M
LTC1440
CMP+
IMON
PMON
CMPOUT
CMPOUT
LATCH
V
V+
I
I+
VCC
2940 TA11
RS
LT2940
GND
200m
3
D3
5.1V
12.6VAC
SECONDARY
kV = =
kI = 200m
3
1
5
30
150
T1
D1
1N4001
R12
10k
R11
10k
D2
1N4001
10W/V
30WPK
1A/V
3APK
1.25A
TRIP
C1B
220µF
25V
+
C1A
220µF
25V
+
R0
10
RESISTIVE
LOAD
R10
1k
R6
1k
R7
1k
R3
15k
R4
15k
Q3
Q1 Q2
Q6 Q7
Q4
Q5
VCC
R2
120k
2X
FDS3732
R9
10k R1
30k
Q8
= 2N3906
LT2940 zzzzzz n— .| : +I- ' L7 LJUW
LT2940
21
2940f
TYPICAL APPLICATIONS
AC Power and Current Monitor
Fully Isolated AC Power and Current Monitor
IMON
PMON
V
V+
I
I+
VCC
VCC
VCC
2940 TA13
LT2940
GND
15V
10.8V 117V
T2
D2
1
500
R5
4.99k
ISOLATION
BARRIER
R4
4.22k
R12
1k R1A
68.1
R1B
68.1
1kW/V
±853 WPK
10A/V
±10APK
T1
C12
100nF
D1
5.1V
C1
47µF
25V
RS1
4.99
RS2
4.99
R6
10k
R7
10k
D4
D3 D5
C2
100nF R2B
200
1%
R2A
200
1%
117V
“N”
117V
“L”
= 1N4148
T1 = MINNTRONIX 4810966R
T2 = 1168:108 POTENTIAL TRANSFORMER
IN CONSTRUCTING THIS CIRCUIT, THE CUSTOMER AGREES THAT, IN ADDITION TO THE TERMS AND CONDITIONS ON LINEAR TECHNOLOGY CORPORATION’S
(LTC) PURCHASE ORDER DOCUMENTS, LTC AND ANY OF ITS EMPLOYEES, AGENTS, REPRESENTATIVES AND CONTRACTORS SHALL HAVE NO LIABILITY,
UNDER CONTRACT, TORT OR ANY OTHER LEGAL OR EQUITABLE THEORY OF RECOVERY, TO CUSTOMER OR ANY OF ITS EMPLOYEES, AGENTS,
REPRESENTATIVES OR CONTRACTORS, FOR ANY PERSONAL INJURY, PROPERTY DAMAGE, OR ANY OTHER CLAIM (INCLUDING WITHOUT LIMITATION, FOR
CONSEQUENTIAL OR INCIDENTAL DAMAGES) RESULTING FROM ANY USE OF THIS CIRCUIT, UNDER ANY CONDITIONS, FORESEEABLE OR OTHERWISE.
CUSTOMER ALSO SHALL INDEMNIFY LTC AND ANY OF ITS EMPLOYEES, AGENTS, REPRESENTATIVES AND CONTRACTORS AGAINST ANY AND ALL LIABILITY,
DAMAGES, COSTS AND EXPENSES, INCLUDING ATTORNEY’S FEES, ARISING FROM ANY THIRD PARTY CLAIMS FOR PERSONAL INJURY, PROPERTY DAMAGE,
OR ANY OTHER CLAIM (INCLUDING WITHOUT LIMITATION, FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES) RESULTING FROM ANY USE OF THIS CIRCUIT,
UNDER ANY CONDITIONS, FORESEEABLE OR OTHERWISE.
7A
LOAD
IMONPMON
V
V+
I
I+
VCC
2940 TA12
RS
LT2940
GND
200m
3
R5
15k
D3
5.1V
12.6VAC
SECONDARY
kV =
kI = 200m
3
1
5
C1A
220µF
25V
T1
D1
1N4001
R2
120k
R1
30k
D2
1N4001
1A/V
±3APK
R4
15k
10W/V
±30WPK
+
C1B
220µF
25V
+
R3
10
R6
1k
LOAD
kV=+
++ +
=
68 1 68 1
200 200 68 1 68 1
108
1168
1
42 5
..
..
.88
499 499
500
10
501
kI=+=
..
LT2940 7,7r7,7 3 :4— Wm \ \mnm‘ \‘ unninus M7 w L7LJCUEN2
LT2940
22
2940f
PACKAGE DESCRIPTION
3.00 ±0.10
(4 SIDES)
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD AND TIE BARS SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
0.40 ± 0.10
BOTTOM VIEW—EXPOSED PAD
1.65 ± 0.10
0.75 ±0.05
R = 0.115
TYP
16
127
PIN 1
TOP MARK
(SEE NOTE 6)
0.200 REF
0.00 – 0.05
(DD12) DFN 0106 REV A
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
0.23 ± 0.05
0.25 ± 0.05
2.25 REF
2.38 ±0.05
1.65 ±0.05
2.10 ±0.05
0.70 ±0.05
3.50 ±0.05
PACKAGE
OUTLINE
PIN 1 NOTCH
R = 0.20 OR
0.25 × 45°
CHAMFER
2.38 ±0.10
2.25 REF
0.45 BSC
0.45 BSC
DD Package
12-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1725 Rev A)
LT2940 , LN m L W + W J ‘ W 0% W7 r , T9 -7? m, i 3 _H_ iml Km W, , _H_ U+ g 4 ‘ _H_ _H_ H. H. 7LT H. DP , m a: j, , mi m iv. L7 LJUW
LT2940
23
2940f
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
PACKAGE DESCRIPTION
MSOP (MS12) 1107 REV Ø
0.53 p 0.152
(.021 p .006)
SEATING
PLANE
0.18
(.007)
1.10
(.043)
MAX
0.22 – 0.38
(.009 – .015)
TYP
0.86
(.034)
REF
0.650
(.0256)
BSC
12 11 10 9 8 7
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.254
(.010) 0o – 6o TYP
DETAIL “A”
DETAIL “A”
GAUGE PLANE
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
0.889 p 0.127
(.035 p .005)
RECOMMENDED SOLDER PAD LAYOUT
0.42 p 0.038
(.0165 p .0015)
TYP
0.65
(.0256)
BSC
4.039 p 0.102
(.159 p .004)
(NOTE 3)
0.1016 p 0.0508
(.004 p .002)
123456
3.00 p 0.102
(.118 p .004)
(NOTE 4)
0.406 p 0.076
(.016 p .003)
REF
4.90 p 0.152
(.193 p .006)
MS Package
12-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1668 Rev Ø)
LT2940 II < 5%}="" fif‘?‘="" l7ljcuen2="">
LT2940
24
2940f
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2009
LT 1109 • PRINTED IN USA
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TYPICAL APPLICATION
PART NUMBER DESCRIPTION COMMENTS
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Converter
2.7V to 12V Supply Voltage, 170A Supply Current
LTC1968 Precision Wide Bandwidth RMS-to-DC Converter 4.5V to 6V Supply Voltage, 500kHz 3dB-Error BW
LTC6101/
LTC6101HV
High Voltage, High Side, Precision Current Sense
Amplifi ers
4V to 60V/ 5V to 100V, Gain Confi gurable, SOT-23
LTC6104 Bidirectional High Side, Precision Current Sense
Amplifi er
4V to 60V, Gain Confi gurable, 8-Pin MSOP
LTC6106 Low Cost, High Side Precision Current Sense
Amplifi er
2.7V to 36V, Gain Confi gurable, SOT23
LTC4151 High Voltage I2C Current and Voltage Monitor Wide Operating Range: 7V to 80V
LTC4215 Positive Hot Swap Controller with ADC and I2C 8-Bit ADC Monitoring Current and Voltages, Supplies from 2.9V to 15V
LT4256-1/
LT4256-2
Positive 48V Hot Swap Controllers with Open-
Circuit Detect
Foldback Current Limiting, Open-Circuit and Overcurrent Fault Output,
Up to 80V Supply
LTC4260 Positive High Voltage Hot Swap Controller With
ADC and I2C Monitoring
Wide Operating Range: 8.5V to 80V
LTC4261 Negative Voltage Hot Swap Controller With ADC
and I2C Monitoring
Floating Topology Allows Very High Voltage Operation
Integrating Watt-Hour Meter
CMP+
PMON IMON
CMPOUT
IN
6V TO 80V
1024 COUNTS
= 1 WATT-HOUR
CD4040
0A TO 2A
S1B
S2B
S3B
CB+
CB
S4B
OUT
ADJ
SHDN
RESET
F
LT3014
CMPOUT
LATCH
V
V
V+
I
I+
LT2940
CT
2.2µF
C16
F
2940 TA14
VCC
VDD
VSS
COSC SHA
Q
GND
V+
LTC6702
GND
+
+
5V
LTC6943
5V
5V
12V
R14
20.0k
R13
4.99k
C18
0.1µF
R2
215k
R1
11.3k
RESET
RS
100m
R17
309k
R18
49.9k
R16
100k
C17
0.47µF
C1
F
R15
24.9k
Q1
2N7002
GND
S1A
S2A
S3A
CA+
CA
V+
LOAD
(80W MAX)
S4A
C19
0.1µF
C20
0.1µF
kV =
kI = 100m
1
20

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