Chip information, Monitoring voltages other than v, Load-disconnect switch – Rainbow Electronics MAX835 User Manual
Page 7
MAX834/MAX835
Micropower, Latching Voltage Monitors
in SOT23-5
_______________________________________________________________________________________
7
Monitoring Voltages Other than V
CC
The typical operating circuit for the MAX834/MAX835
monitors V
CC
. Voltages other than V
CC
can easily be
monitored, as shown in Figure 4. Calculate V
TRIP
as
in the section
Programming the Trip Voltage.
When
monitoring voltages other than V
CC
, ensure that the
maximum value for V
MON
is not exceeded:
V
MON(MAX)
= (V
CC
- 1)(R1 + R2) / R2
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 disconnects.
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
V
CC
V
CC
V
CC
V
MON
R2
R1
R
L
*
0.1
µ
F
OUT
CLEAR
GND
IN
MAX834
MAX835
V
TRIP
= (1.204)
(UNITS ARE OHMS
AND VOLTS)
*
MAX834 ONLY
R1 + R2
R2
Figure 4. Monitoring Voltages Other than V
CC
CLEAR
LATCH
R
LOAD
V
CC
R1
V
BATT
R2
OUT
CLEAR
GND
N
Q2
P
Q1
1M
IN
MAX835
V
CC
0.1
µ
F
Figure 5. Load-Disconnect Switch
TRANSISTOR COUNT: 74
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