Micropower, Latching Voltage Monitors

in SOT23-5

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7

The Typical Operating Circuit for the MAX834/MAX835

Load-Disconnect Switch

The circuit in Figure 5 is designed to prevent a lead-

acid battery or a secondary battery such as an NiCd,

from sustaining damage through deep discharge. As

the battery reaches critical undervoltage, OUT switches

low. Q1 and Q2 turn off, disconnecting the battery from

the load. The MAX835’s latched output prevents Q1

and Q2 from turning on again as the battery voltage

relaxes to its open-circuit voltage when the load dis-

connects. CLEAR can be connected to a pushbutton

switch, an RC network, or a logic gate to reset the latch

when the battery is recharged or replaced.

CLEAR

LATCH

OUT

R2

R1

0.1

μF

OUT

CLEAR

GND

IN

MAX834

MAX835

(UNITS ARE OHMS AND VOLTS)

*MAX834 ONLY

R1 + R2

R2

CLEAR

LATCH

R1

R2

OUT

CLEAR

GND

N

Q2

P

Q1

1M

Ω

IN

MAX835

0.1

μF

Figure 5. Load-Disconnect Switch