DS1210S/T&R/C02 - Maxim Integrated Products, Inc.

1 of 6 090503

FEATURES

§ Converts CMOS RAMs into Nonvolatile

Memories

§ Unconditionally Write Protects when VCC is

Out-of-Tolerance

§ Automatically Switches to Battery when

Power-Fail Occurs

§ Space-Saving 8-Pin DIP

§ Consumes <100nA of Battery Current

§ Tests Battery Condition on Power up

§ Provides for Redundant Batteries

§ Optional 5% or 10% Power-Fail Detection

§ Low Forward Voltage Drop on the VCC

Switch

§ Optional 16-Pin SOIC Surface Mount

Package

§ Optional Industrial (N) Temperature Range of

-40°C to +85°C

PIN ASSIGNMENT

PIN DESCRIPTION

VCCO - RAM Supply

VBAT1 - + Battery 1

TOL - Power Supply Tolerance

GND - Ground

CE - Chip Enable Input

CEO - Chip Enable Output

VBAT2 - + Battery 2

VCCI - + Supply

NC - No Connect

DESCRIPTION

The DS1210 Nonvolatile Controller Chip is a CMOS circuit which solves the application problem of

converting CMOS RAM into nonvolatile memory. Incoming power is monitored for an out-of-tolerance

condition. When such a condition is detected, chip enable is inhibited to accomplish write protection and

the battery is switched on to supply the RAM with uninterrupted power. Special circuitry uses a low-

leakage CMOS process which affords precise voltage detection at extremely low battery consumption.

The 8-pin DIP package keeps PC board real estate requirements to a minimum. By combining the

DS1210 Nonvolatile Controller Chip with a CMOS memory and batteries, nonvolatile RAM operation

can be achieved.

DS1210

Nonvolatile Controller Chip

www.maxim-ic.com

VCCO

VBAT1

TOL

GND

VCCI

VBAT2

CEO

DS1210 8-pin DIP (300-mil)

See Mech. Drawin

s Section

VCCO

VBAT1

TOL

GND

VCCI

VBAT2

CEO

DS1210S 16-pin SOIC (300-mil)

See Mech. Drawings Section

DS1210

2 of 6

OPERATION

The DS1210 nonvolatile controller performs five circuit functions required to battery back up a RAM.

First, a switch is provided to direct power from the battery or the incoming supply (VCCI) depending on

which is greater. This switch has a voltage drop of less than 0.3V. The second function which the

nonvolatile controller provides is power-fail detection. The DS1210 constantly monitors the incoming

supply. When the supply goes out of tolerance a precision comparator detects power-fail and inhibits chip

enable ( CEO ). The third function of write protection is accomplished by holding the CEO output signal to

within 0.2 volts of the VCCI or battery supply. If CE input is low at the time power-fail detection occurs,

the CEO output is kept in its present state until CE is returned high. The delay of write protection until

the current memory cycle is completed prevents the corruption of data. Power-fail detection occurs in the

range of 4.75 volts to 4.5 volts with the tolerance Pin 3 grounded. If Pin 3 in connected to VCCO, then

power-fail detection occurs in the range of 4.5 volts to 4.25 volts. During nominal supply conditions

CEO will follow CE with a maximum propagation delay of 20ns. The fourth function the DS1210

performs is a battery status warning so that potential data loss is avoided. Each time that the circuit is

powered up the battery voltage is checked with a precision comparator. If the battery voltage is less than

2.0 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 2.0V and data is in

danger of being corrupted. The fifth function of the nonvolatile controller 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 DS1210 controller 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 take over the load. The switch to a

redundant battery is transparent to circuit operation and to the user. A battery status warning will occur

when the battery in use falls below 2.0 volts. A grounded VBAT2 pin will not activate a battery-fail

warning. In applications where battery redundancy is not required, a single battery should be connected to

the BAT1 pin. The BAT2 battery pin must be grounded. The nonvolatile controller contains circuitry to

turn off the battery backup. This is to maintain the battery(s) at its highest capacity until the equipment is

powered up and valid data is written to the SRAM. While in the freshness seal mode the CEO and VCCO

will be forced to VOL. When the batteries are first attached to one or both of the VBAT pins, VCCO will not

provide battery back-up until VCCI exceeds VCCTP, as set by the TOL pin, and then falls below VBAT.

Figure 1 shows a typical application incorporating the DS1210 in a microprocessor-based system. Section

A shows the connections necessary to write protect the RAM when VCC is less than 4.75 volts and to back

up the supply with batteries. Section B shows the use of the DS1210 to halt the processor when VCC is

less than 4.75 volts and to delay its restart on power-up to prevent spurious writes.

DS1210

3 of 6

SECTION A - BATTERY BACKUP Figure 1

BATTERY BACKUP CURRENT DRAIN EXAMPLE

CONSUMPTION

DS1210 IBAT 100 nA

RAM ICC02 10 mA

Total Drain 10.1 mA

SECTION B - PROCESSOR RESET

DS1210

4 of 6

ABSOLUTE MAXIMUM RATINGS*

Voltage on Any Pin Relative to Ground -0.3V to +7.0V

Operating Temperature 0°C to +70°C, -40°C to +85°C for N parts

Storage Temperature -55°C to +125°C

Soldering Temperature See IPC/JEDEC J-STD-020A

* 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 (See Note 9)

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 VCCI 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

DC ELECTRICAL CHARACTERISTICS

(See Note 9; VCCI = 4.75 to 5.5V PIN 3 = GND)

(VCCI = 4.5 to 5.5V, PIN 3 = VCCO)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Supply Current ICCI 5mA3

Supply Voltage VCCO VCC-0.2 V 1

Supply Current ICCO1 80 mA 4

Input Leakage IIL -1.0 +1.0 µA

Output Leakage ILO -1.0 +1.0 µA

CEO Output @ 2.4V IOH -1.0 mA 5

CEO 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

(See Note 9; VCCI = < VBAT)

CEO Output VOHL VBAT-0.2 V 7

VBAT1 or VBAT2

Battery Current IBAT 100 nA 2, 3

Battery Backup Current

@ VCCO = VBAT – 0.3V ICCO2 50 µA 6, 7

DS1210

5 of 6

CAPACITANCE (TA = 25°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Input Capacitance CIN 5pF

Output Capacitance COUT 7pF

AC ELECTRICAL CHARACTERISTICS

(See Note 9; VCCI = 4.75V to 5.5V, PIN 3 = GND)

(VCCI = 4.75V to 5.5V, PIN 3 = GND)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

CE Propagation Delay tPD 51020ns5

CE High to Power-Fail tPF 0ns

(See Note 9; VCCI = 4.75V, PIN 3 = GND; VCCI < 4.5, PIN 3 = VCCO)

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-Down tR0µs

CE Pulse Width tCE 1.5 µs 8

NOTES:

1. All voltages are referenced to ground.

2. Only one battery input is required. Unused battery inputs must be grounded.

3. Measured with VCCO and CEO open.

4. ICC01 is the maximum average load which the DS1210 can supply to the memories.

5. Measured with a load as shown in Figure 2.

6. ICC02 is the maximum average load current which the DS1210 can supply to the memories in the

battery backup mode.

7. tCE max. must be met to ensure data integrity on power loss.

8. CEO can only sustain leakage current in the battery backup mode.

9. All AC and DC electrical characteristics are valid for the full temperature range. For commercial

products, this range is 0 to +70°C. For industrial products (N), this range is -40°C to +85°C.

10. DS1210 is recognized by Underwriters Laboratory (U.L.®) under file E99151.

DS1210

6 of 6

TIMING DIAGRAM: POWER-UP

TIMING DIAGRAM: POWER-DOWN

OUTPUT LOAD Figure 2