SN74BCT2414

MEMORY DECODER

WITH ON-CHIP SUPPLY VOLTAGE MONITOR

SCBS059B – MARCH 1989 – REVISED NOVEMBER 1993

2–7

POST OFFICE BOX 655303

APPLICATION INFORMATION

A typical application circuit for a battery-buffered memory in a microcomputer system is shown in Figure 1 which uses

the SN74BCT2414. When power fails, the supply-voltage supervisor (TL7705) resets the microcomputer and

disables the memory by switching the shutdown input SD of the memory decoder to a logic zero. All memory decoder

outputs are forced to a logic one. Abnormal write commands from the microprocessor, which may be issued during

further voltage breakdown, no longer affect the contents of the memory. When the system supply voltage becomes

lower than approximately 3.65 V, the voltage monitor inside the SN74BCT2414 memory decoder disconnects the

input buffers of this circuit from the decoding logic internally and keeps all outputs at a logic one. The VS output is

also switched off, disconnecting the system supply voltage from the memory circuits. During this low-voltage

condition, the memory decoder and the memory circuits are supplied by the battery.

CE

VCC

SD

G

2A

1A

1B

2B

2G

VCC

VS

8

16

A15

A14

A13

1G

1Y0

1Y1

1Y2

1Y3

2Y0

2Y1

2Y2

2Y3

R1

R2

R3

1 k

Ω

Q1

D1

1N4148

D3

VCC

D0 – D7

A0 – A15

DBIN

WE

RESET

Microprocessor

SN74BCT2414

A0 – A12

OE

WR

10 k

Ω

0.1

µF

5 V

0.1

µF

SENSE

VREF

RES

RESIN

Ct

8-

× 8K-Byte CMOS RAM

TL7705A

Vbat

VCC

GND

For further information on this device, please contact factory.

Figure 1. Memory System With Battery Backup