DS1212 Datasheet by Maxim Integrated

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FEATURES
Converts full CMOS RAM into nonvolatile
memory
Unconditionally write protects when VCC is
out of tolerance
Automatically switches to battery when
power-fail occurs
4 to 16 decoder provides control for up to 16
CMOS RAMs
Consumes less than 100 nA of battery
current
Tests battery condition on power-up
Provides for redundant batteries
Power fail signal can be used to interrupt
processor on power failure
Optional 5% or 10% power-fail detection
Optional 28-pin PLCC surface mount
package
Optional industrial temperature range of
-40°C to +85°C
PIN DESCRIPTION
A, B, C, D - Address Inputs
CE - Chip Enable
CE0 -CE15 - Chip Enable Outputs
GND - Ground
VBAT1 - + Battery 1
VBAT2 - + Battery 2
TOL - Power Supply Tolerance
VCCI - +5V Supply
VCCO - RAM Supply
PF - Power Fail
PIN ASSIGNMENT
DESCRIPTION
The DS1212 Nonvolatile Controller x16 Chip is a CMOS circuit that solves the application problem of
converting CMOS RAMs into nonvolatile memories. Incoming power is monitored for an out-of-
tolerance condition. When such a condition is detected, the chip enables are inhibited to accomplish write
protection and the battery is switched on to supply the RAMs with uninterrupted power. Special circuitry
uses a low-leakage CMOS process that affords precise voltage detection at extremely low battery
consumption.
DS1212
Nonvolatile Controller x 16 Chip
www.dalsemi.com
VBAT1
VCCO
TOL
PF
CE15
CE14
CE13
CE12
CE11
D
C
B
A
GND
VCCI
VBAT2
CE
CE0
CE1
CE2
CE3
CE4
CE5
CE6
CE7
CE8
CE9
CE10
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
28-Pin DIP (600-mil)
See Mech. Drawings Section
28-Pin PLCC
See Mech. Drawings Section
CE15
CE14
CE13
CE12
CE11
D
C
PF
TOL
VCCO
VBAT1
VCCI
VBAT2
CE
25
24
23
22
21
20
19
5
6
7
8
9
10
11
4 3 2 1 28 27 26
12 13 14 15 16 17 18
CE0
CE1
CE2
CE3
CE4
CE5
CE6
B
A
GND
CE10
CE9
CE8
CE7
DS1212
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By combining the DS1212 Nonvolatile Controller chip and lithium batteries, nonvolatile RAM operation
can be achieved for up to 16 CMOS memories.
OPERATION
The DS1212 performs six circuit functions required to decode and battery back up a bank of up to 16
RAMs. First, the 4-to-16 decoder provides selection of one of 16 RAMs. Second, a switch is provided to
direct power from the battery or VCCI supply, depending on which is greater. This switch has a voltage
drop of less than 0.2V. The third function the DS1212 provides is power-fail detection. It constantly
monitors the VCCI supply. When VCCI falls below 4.75 volts or 4.5 volts, depending on the level of
tolerance Pin 3, a precision comparator outputs a power-fail detect signal to the decoder/chip enable logic
and the PF signal is driven low. The PF signal will remain low until VCCI is back in normal limits.
The fourth function of write protection is accomplished by holding all chip enable outputs (CE0 -CE15 ) to
within 0.2 volts of VCCI or battery supply. If CE is low at the time power fail detection occurs, the chip
enable outputs are kept in their present state until CE is driven high. The delay of write protection until
the current memory cycle is completed prevents corruption of data. Power-fail detection occurs in the
range of 4.75 volts to 4.5 volts with tolerance Pin 3 grounded. If Pin 3 is connected to VCCO, then power-
fail occurs in the range of 4.5 volts to 4.25 volts. During nominal supply conditions the chip enable
outputs follow the logic of a 4-to-16 decoder, shown in Figure 1.
The fifth function the DS1212 performs is a battery status warning so that data loss is avoided. Each time
the circuit is powered up, the battery voltage is checked with a precision comparator. If the battery
voltage is less than 2 volts, the second memory cycle is inhibited. Battery status can, therefore, be
determined by performing a read cycle after power-up to any location in memory, verifying that memory
location content. A subsequent write cycle can then be executed to the same memory location, altering the
data. If the next read cycle fails to verify the written data, then the batteries are less than 2.0 volts and
data is in danger of being corrupted.
The sixth function of the DS1212 provides for battery redundancy. In many applications, data integrity is
paramount. In these applications it is often desirable to use two batteries to ensure reliability. The
DS1212 provides an internal isolation switch which allows the connection of two batteries during battery
backup operation. The battery with the highest voltage is selected for use. If one battery should fail, the
other will then assume the load. The switch to a redundant battery is transparent to circuit operation and
the user. A battery status warning will only occur if both batteries are less than 2.0 volts. For single
battery applications the unused battery input must be grounded.
DS1212
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NONVOLATILE CONTROLLER/DECODER Figure 1
INPUTS OUTPUTS
CE DCBACE0 CE1 CE2 CE3 CE4 CE5 CE6 CE7 CE8 CE9 CE10 CE11 CE12 CE13 CE14 CE15 PF
HXXXXHHHHHHHHHHHHHHHHH
XXXXXHHHHHHHHHHHHHHHHL
LLLLLLHHHHHHHHHHHHHHHH
LLLLHHLHHHHHHHHHHHHHHH
LLLHLHHLHHHHHHHHHHHHHH
LLLHHHHHLHHHHHHHHHHHHH
LLHLLHHHHLHHHHHHHHHHHH
LLHLHHHHHHLHHHHHHHHHHH
LLHHLHHHHHHLHHHHHHHHHH
LLHHHHHHHHHHLHHHHHHHHH
LHLLLHHHHHHHHLHHHHHHHH
LHLLHHHHHHHHHHLHHHHHHH
LHLHLHHHHHHHHHHLHHHHHH
LHLHHHHHHHHHHHHHLHHHHH
LHHLLHHHHHHHHHHHHLHHHH
LHHLHHHHHHHHHHHHHHLHHH
LHHHLHHHHHHHHHHHHHHLHH
LHHHHHHHHHHHHHHHHHHHLH
H = High Level
L = Low Level
X = Irrelevant
Note: VCCI input is 250 mV lower when TOL PIN3 = VCCO.
Vcco Vccx VCCI VBAT IBAT Vccn VBATI
DS1212
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ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground -0.3V to +7.0V
Operating Temperature 0°C to 70°C
Storage Temperature -55°C to +125°C
Soldering Temperature 260°C for 10 seconds
* This is a stress rating only and functional operation of the device at these or any other conditions
above those indicated in the operation sections of this specification is not implied. Exposure to
absolute maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS (0°C to 70°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Pin 3 = GND Supply Voltage VCCI 4.75 5.0 5.5 V 1
Pin 3 = VCCO Supply Voltage VCCO 4.5 5.0 5.5 V 1
Logic 1 Input VIH 2.2 VCC+0.3 V 1
Logic 0 Input VIL -0.3 +0.8 V 1
Battery Input VBAT1,
VBAT2
2.0 4.0 V 1, 2
(0°C to 70°C; VCCI = 4.75 to 5.5V PIN 3 = GND)
(0°C to 70°C; VCCI = 4.5 to 5.5V, PIN 3 = VCCO)
DC ELECTRICAL CHARACTERISTICS
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Supply Current ICCI 5mA3
Supply Current @
VCCO= VCCI-0.2 ICCO1 80 mA 1, 4 ,10
Input Leakage IIL -1.0 +1.0 µA
Output Leakage ILO -1.0 +1.0 µA
CE0 - CE15 , PF Output @ 2.4V IOH -1.0 mA 5
CE0 - CE15 , PF Output @ 0.4V IOL 4.0 mA 5
VCC Trip Point (TOL=GND) VCCTP 4.50 4.62 4.74 V 1
VCC Trip Point (TOL=VCCO)V
CCTP 4.25 4.37 4.49 V 1
(0°C to 70°C; VCCI < VBAT)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
CE0 -CE15 Output VOHL VBAT-0.2 V 3, 7
Battery Current IBAT 0.1 µA 2, 3
Battery Backup Current
@ VCCO = VBAT1 – 0.5V ICC2 100 µA 6, 10, 11
IN OUT VCCO
DS1212
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CAPACITANCE (TA = 25°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Input Capacitance CIN 5pF
Output Capacitance COUT 7pF
(0°C to 70°C; VCCI = 4.75 to 5.5V, PIN 3 = GND)
(0°C to 70°C; VCCI = 4.5 to 5.5V, PIN 3 = VCCO)
AC ELECTRICAL CHARACTERISTICS
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
CE Propagation Delay tPD 51020ns5
CE High to Power-Fail tPF 0ns
Address Setup tAS 20 ns 9
(0°C to 70°C; VCCI < 4.75V, PIN 3 = GND)
(0°C to 70°C; VCCI < 4.5V, PIN 3 = VCCO)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Recovery at Power-Up tREC 2 80 125 ms
VCC Slew Rate Power-Down tF300 µs
VCC Slew Rate Power-Down tFB 10 µs
VCC Slew Rate Power-Up tRs
CE Pulse Width tCE 1.5 µs 7, 8
Power Fail to PF Low tPFL 300 µs
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DS1212
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TIMING DIAGRAM: DECODER
TIMING DIAGRAM: POWER-UP
TIMING DIAGRAM: POWER-DOWN
A B C ”51212 g" '6 D _ _ ‘ (TE fi-cas am _ am PF _ 552 GND ‘5 vou‘s 1.1K DALI soon-MM sopF
DS1212
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TYPICAL APPLICATION Figure 2
OUTPUT LOAD Figure 3
NOTES:
1. All voltages referenced to ground.
2. Only one battery input is required.
3. Measured with VCCO and CE0 -CE15 open.
4. ICC01 is the maximum average load which the DS1212 can supply to the memories.
5. Measured with a load as shown in Figure 3.
6. ICC02 is the maximum average load current which the DS1212 can supply to the memories in the battery backup
mode.
7. Chip enable outputs CE0 -CE15 can only sustain leakage current in the battery backup mode.
8. tCE max. must be met to ensure data integrity on power loss.
9. tAS is only required to keep the decoder outputs glitch-free. While CE is low, the outputs ( CE0 -CE15 ) will be
defined by inputs A through D with a propagation delay of tPD from an A through D input change.
10. For applications where higher currents are required, please see the Battery Manager chip data sheet (DS1259).
11. The DS1212 has a 5 kohm resistor in series with the battery input. As current from the battery increases over
100 µA, the voltage drop will increase proportionately. The device cannot be damaged by higher currents in the
battery path.

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