ICL7665 Просмотр технического описания (PDF) - Intersil
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ICL7665 Datasheet PDF : 11 Pages
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RP
R21
R31
R11
VIN
V+
OUT1
OUT2
HYST1 HYST2
SET1
SET2
ICL7665S
RP
R22
R32
R12
Applications
Single Supply Fault Monitor
Figure 12 shows an over/under voltage fault monitor for a
single supply. The over voltage trip point is centered around
5.5V and the under voltage trip point is centered around
4.5V. Both have some hysteresis to prevent erratic output
ON and OFF conditions. The two outputs are connected in a
wired OR configuration with a pullup resistor to generate a
power OK signal.
+5V SUPPLY
FIGURE 11. AN ALTERNATIVE HYSTERESIS CIRCUIT
TABLE 1. SET-POINT EQUATIONS
NO HYSTERESIS
Over-Voltage VTRIP =
R11 + R21
R11
Over-Voltage VTRIP =
R12 + R22
R12
HYSTERESIS PER FIGURE 10A
x VSET1
x VSET2
VU1 =
R11 + R21 + R31
x VSET1
R11
Over-Voltage VTRIP
VL1 =
R11 + R21
R11
x VSET1
VU2 =
R12 + R22 + R32
x VSET2
R12
Under-Voltage VTRIP
VL2 =
R12 + R22
R12
x VSET2
HYSTERESIS PER FIGURE 11
VU1 =
R11 + R21
R11
x VSET1
Over-Voltage VTRIP
R21R31
VL1 =
R11 + R21 +
R31
x VSET1
R11
VU2 =
R12 + R22
R12
x VSET2
Over-Voltage VTRIP
VL2 =
R22R32
R12 + R22 + R32 x VSET2
R12
R21 324KΩ
13MΩ
5%
R31
100KΩ
OPEN VOLTAGE
DETECTOR
VU = 5.55V
VL = 5.45V
V+
HYST1 HYST2
VSET1 VSET2
OUT1 OUT2
249KΩ R22
R32
7.5MΩ
5%
100KΩ
OPEN VOLTAGE
DETECTOR
V+
VU = 4.55V
VL = 4.45V
1MΩ
POWER
OK
FIGURE 12. FAULT MONITOR FOR A SINGLE SUPPLY
Multiple Supply Fault Monitor
The ICL7665S can simultaneously monitor several supplies
when connected as shown in Figure 13. The resistors are
chosen such that the sum of the currents through R21A,
R21B, and R31 is equal to the current through R11 when the
two input voltage are at the desired low voltage detection
point. The current through R11 at this point is equal to
1.3V/R11. The voltage at the VSET input depends on the
voltage of both supplies being monitored. The trip voltage of
one supply while the other supply is at the nominal voltage
will be different that the trip voltage when both supplies are
below their nominal voltages.
The other side of the ICL7665S can be used to detect the
absence of negative supplies. The trip points for OUT1
depend on both the negative supply voltages and the actual
voltage of the +5V supply.
3-69
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