ICL7665AESA Maxim Integrated Products, ICL7665AESA Datasheet - Page 8

• Manufacturer Part Number: ICL7665AESA
• Description: Supervisory Circuits Integrated Circuits (ICs)
• Manufacturer: Maxim Integrated Products

Specifications of ICL7665AESA

• Number Of Voltages Monitored: 2
• Undervoltage Threshold: 1.275 V, 1.225 V
• Overvoltage Threshold: 1.325 V, 1.375 V
• Manual Reset: Not Resettable
• Watchdog: No Watchdog
• Supply Voltage (max): 16 V
• Supply Voltage (min): 2 V
• Supply Current (typ): 15 uA
• Maximum Power Dissipation: 471 mW
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-8
• Minimum Operating Temperature: - 40 C
• Lead Free Status / Rohs Status: No

Microprocessor Voltage Monitor with
Dual Over/Undervoltage Detection
Figure 5. Threshold Detector, V
8
1) Choose a resistor value for R11. Typical values are
2) Calculate R21 for the desired upper trip point, V
3) Calculate R31 for the desired amount of hysteresis:
4) The trip voltages are not affected by the absolute
OVERVOLTAGE
_______________________________________________________________________________________
R21 = R11
or, if V+ = V
in the 10k to 10M range.
using the formula:
value of the resistors, as long as the impedances
are high enough that the resistance of R31 is
much greater than the HYST output’s resistance,
and the current through R31 is much higher than
the HYST output’s leakage current. Normally, R31
will be in the 100k
dividing all three resistors by the same factor will
not affect the trip voltages.
R31 = ————————— = —————————
R31 = ————————— = —————————
R31
R21
R11
(R21) (V+ – V
(R21) (V
OUT1
OUT2
V
(
IN
——————
V
V
IN
U
V
U
:
U
– V
L
– V
HYST1
SET1
OUT1
V
- V
SET
– V
V
L2
L
L
ICL7665
SET
SET
SET
GND
V
to 22M
V
V+
U2
IN
IN
)
)
HYST2
V
)
OUT2
SET2
L1
= V+
= R11
V
U1
(R21) (V+ – 1.3V)
(R21) (V
range. Multiplying or
(
—————
V
V
V
R32
R22
R12
U
U
U
UNDERVOLTAGE
1.3V
– V
L
– 1.3V
– V
– 1.3V)
L
L
Figure 4
)
U,
Figure 6 shows a typical over/undervoltage fault monitor
for a single supply. In this case, the upper trip points (con-
trolling OUT1) are centered on 5.5V, with 100mV of hys-
teresis (V
(controlling OUT2) are centered on 4.5V, also with 100mV
of hysteresis. OUT1 and OUT2 are connected together in
a wire-OR configuration to generate a power-OK signal.
The ICL7665 can simultaneously monitor several power
supplies, as shown in Figure 7. The easiest way to calculate
the resistor values is to note that when the V
the trip point (1.3V), the current through R11 is 1.3V / R11.
The sum of the currents through R21A, R21B and R31 must
equal this current when the two input voltages are at the
desired low-voltage detection point. Ordinarily, R21A and
R21B are chosen so that the current through the two resis-
tors is equal. Note that, since the voltage at the ICL7665
V
monitored, there will be some interaction between the low-
voltage trip points for the two supplies. In this example,
OUT1 will go low when either supply is 10% below nominal
(assuming the other supply is at the nominal voltage), or
when both supplies are 5% or more below their nominal
voltage. R31 sets the hysteresis, in this case, to about 43mV
at the 5V supply or 170mV at the 15V supply. The second
section of ICL7665 can be used to detect overvoltage or, as
shown in Figure 7, can be used to detect the absence of
negative supplies. Note that the trip points for OUT2 depend
on both the voltages of the negative power supplies and
the actual voltage of the +5V supply.
__________Applications Information
SET
1) Select a value for R11, usually between 10k
2) Calculate R21:
3) Calculate R31:
4) As in the other circuits, all three resistor values may
R21 = R11
10M .
be scaled up or down in value without changing V
and V
three resistors, if the absolute values are such that
the hysteresis output resistance and the leakage
currents of the V
be ignored.
input depends on the voltage of both supplies being
R31 = R11
U
L
= 5.55V, V
. V
Fault Monitor for a Single Supply
U
(
——————
and V
(
Multiple-Supply Fault Monitor
V
—————
L
V
V
– V
V
SET
L
U
SET
SET
= 5.45V); and the lower trip points
L
– V
SET
depend only on the ratio of the
input and hysteresis output can
L
)
)
= R11
(
—————
V
L
SET
– 1.3V
1.3
input is at
Figure 5
)
and
U