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DS1213B SmartSocket 16k/64k
www.dalsemi.com
FEATURES
Accepts standard 2K x 8 or 8K x 8 CMOS static RAMs Embedded lithium energy cell retains RAM data Self-contained circuitry safeguards data Data retention time is greater than 10 years with proper RAM selection IC socket permits upgrading from 2K x 8 to 8K RAM Proven gas-tight socket contacts Operating temperature range 0C to 70C
PIN ASSIGNMENT
1 2 3 4 5 6 7 8 9 10 11 12 13 GND 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 VCC VCC
CE
28-Pin Intelligent Socket
PIN DESCRIPTION
CE - Conditioned Chip Enable VCC - Switched VCC GND - Ground All pins pass through except 20, 26 and 28.
DESCRIPTION
The DS1213B SmartSocket is a 28-pin, 600 mil DIP socket with a built-in CMOS controller circuit and an embedded lithium energy source. It accepts either 24-pin 2K x 8 (lower-justified) or 28-pin 8K x 8 JEDEC bytewide CMOS static RAM. When the socket is mated with a CMOS RAM, it provides a complete solution to problems associated with memory volatility. The Smart-Socket monitors incoming VCC for an out-of-tolerance condition. When such a condition occurs, the internal lithium energy source is automatically switched on and write protection is unconditionally enabled to prevent data corruption. Using the SmartSocket saves printed circuit board space since the SRAM/SmartSocket combination occupies no more area than the SRAM alone. The SmartSocket modifies only pins 20, 26 and 28, to nonvolatize the RAM. All other pins are passed straight through.
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022900
DS1213B
OPERATION
The DS1213B SmartSocket performs five circuit functions required to battery back up a CMOS memory. The first function involves switching between the battery and the VCC supply, depending on which is greater. The switch has a voltage drop of less than 0.2 volts. The second function is power-fail detection. The DS1213B constantly monitors the VCC supply. When VCC falls below 4.75 volts, a precision comparator detects the condition and inhibits the RAM chip enable. The third function, write protection, is accomplished by holding the RAM chip enable signal to within 0.2 volts of VCC or the battery supply whichever is greater. If the incoming chip enable signal is active at the time power fail detection occurs, write protection is delayed until after the current memory cycle is complete to avoid corruption of data. Power fail detection occurs in the range of 4.75 to 4.5 volts. During nominal power supply conditions the chip enable signal will be passed through from the socket pin to the socket contact with a maximum propagation delay of 20 ns. The fourth function the DS1213B performs is to check battery status to warn of potential data loss. Each time that VCC power is restored to the SmartSocket the battery voltage is checked with a precision comparator. If the battery supply is less than 2.0 volts, the second memory access to the SmartSocket is inhibited. Battery status can, therefore, be determined by a three-step process. First, a read cycle is performed to any location in the memory, in order to save the contents of that location. 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 battery voltage is less than 2.0V and data is in danger of being corrupted. The fifth function the SmartSocket provides is battery redundancy. In many applications, data integrity is paramount. In these applications it is desirable to use two batteries to ensure reliability. The DS1213B SmartSocket provides two batteries and an internal isolation switch to select between them. During battery back up, the battery with the highest voltage is selected for use. If one battery fails, the other automatically takes over. The switch between batteries is transparent to the user. A battery status warning will occur if both batteries are less than 2.0 volts. Each of the two internal lithium cells has a 45 mAh capacity.
NOTE:
As shipped from Dallas Semiconductor, battery voltage cannot be measured on the VCC socket contact. Only after VCC has been applied to the device for the first time and then removed will the battery voltage be present on socket contacts 28, 26 and 20.
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DS1213B
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature -0.3V to +7.0V 0C to 70C -40C to +70C 260C 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
PARAMETER PIN 26 L, PIN 28 L Supply Voltage Logic 1 PIN 20 L Logic 0 PIN 20 L SYMBOL VCC VIH VIL MIN 4.75 2.2 -0.3 TYP 5.0 MAX 5.5 VCC +0.3 +0.8
(0C to 70C)
UNITS V V V NOTES 1,3 1,3 1,3
DC ELECTRICAL CHARACTERISTICS
PARAMETER PIN 26 L, PIN 28 L Supply Current PIN 26 U, PIN 28 U Supply Voltage PIN 26 U, PIN 28 U Supply Current PIN 20 L CE Input Leakage PIN 20 U CE Output @ 2.4V PIN 20 U CE Output @ 4V SYMBOL ICC VCCO ICCO IIL IOH IOL -1.0 -1.0 MIN
(0C to 70C; VCC = 4.75 to 5.5V)
TYP MAX 5 UNITS mA V 80 +1.0 4.0 mA A mA mA NOTES 3,4,5 1,3,8 3,8 3,4 2,3 2,3
VCC -0.2
DC ELECTRICAL CHARACTERISTICS
PARAMETER PIN 20 Output PIN 26 U, PIN 28 U Battery Current PIN 26 U, PIN 28 U Battery Voltage SYMBOL VOHL IBAT VBAT 2 3 MIN VCC -0.2 VBAT- 0.2 TYP
(0C to 70C; VCC < 4.5V)
MAX UNITS V A V NOTES 1,3 3,6 1,3
1 3.6
CAPACITANCE
PARAMETER Input Capacitance PIN 20 L Output Capacitance PIN 20 U SYMBOL CIN COUT MIN TYP MAX 5 7 UNITS pF pF
(TA = 25C)
NOTES 3 3
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DS1213B
AC ELECTRICAL CHARACTERISTICS
PARAMETER CE Propagation Delay CE High to Power Fall SYMBOL tPF tPD MIN 5
(0C to 70C; VCC = 4.75 to 5.5V)
TYP 10 MAX 20 0 UNITS ns ns NOTES 2,9
AC ELECTRICAL CHARACTERISTICS
PARAMETER Recovery at Power -Up VCC Slew Rate 4.75 - 4.5 V VCC Slew Rate 4.5-3 V VCC Slew Rate 4.5-4.75 V CE Pulse Width SYMBOL tREC tF tFB tR tCE MIN 2 300 10 0 TYP 80
(0C to 70C; VCCI < 4.75 V)
MAX 125 UNITS s s s s s NOTES
1.5
7
TIMING DIAGRAM: POWER-DOWN
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DS1213B
TIMING DIAGRAM: POWER-UP
WARNINGS:
Under no circumstances are negative undershoots, of any amplitude, allowed when device is in battery backup mode. Water washing for flux removal will discharge internal lithium source because exposed voltage pins are present.
NOTES:
1. All voltages are referenced to ground. 2. Measured with a load as shown in Figure 1. 3. Pin locations are designated "U" (for upper) when a parameter definition refers to the socket receptacle and "L" (for lower) when a parameter definition refers to the socket pin. 4. No memory inserted in the socket. 5. Pin 26 L may be connected to VCC or left disconnected at the PC board. 6. IBAT is the maximum load current which a correctly installed memory can use in the data retention mode and meet data retention expectations of more than 10 years at 25C. 7. tCE max. must be met to ensure data integrity on power loss. 8. VCC is within nominal limits and a memory is installed in the socket. 9. Input pulse rise and fall times equal 10 ns.
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DS1213B
OUTPUT LOAD Figure 1
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DS1213B
DS1213B INTELLIGENT SOCKET 28 PIN (FOR 600-MIL DIP)
PKG DIM A IN. MM B IN. MM C IN. MM D IN. MM E IN. MM F IN. MM G IN. MM H IN. MM J IN. MM K IN. MM L IN. MM 28-PIN MIN MAX 1.380 1.420 35.05 36.07 0.690 0.720 17.53 18.29 0.420 0.470 10.16 11.94 0.035 0.065 0.89 1.65 0.055 0.075 1.39 1.90 0.120 0.160 3.04 4.06 0.090 0.110 2.29 2.79 0.590 0.630 14.99 16.00 0.008 0.012 0.20 0.30 0.015 0.021 0.38 0.53 0.380 0.420 9.65 10.67
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