ICL7665CPA+ [MAXIM]
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| 型号： | ICL7665CPA+ |
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MAXIM INTEGRATED PRODUCTS |
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19-0001; Rev 2; 8/97
Mic ro p ro c e s s o r Vo lt a g e Mo n it o r w it h
Du a l Ove r/Un d e rvo lt a g e De t e c t io n
ICL765
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
♦ µP Over/Undervoltage Warning
The ICL7665 warns microprocessors (µPs) of overvolt-
age and undervoltage conditions. It draws a typical
operating current of only 3µA. The trip points and hys-
teresis of the two voltage detectors are individually pro-
grammed via external resistors to any voltage greater
than 1.3V. The ICL7665 will operate from any supply
voltage in the 1.6V to 16V range, while monitoring volt-
ages from 1.3V to several hundred volts. The Maxim
ICL7665A is an improved version with a 2%-accurate
♦ Improved Second Source
♦ Dual Comparator with Precision Internal Reference
♦ 3µA Operating Current
♦ 2% Threshold Accuracy (ICL7665A)
♦ 1.6V to 16V Supply Voltage Range
♦ On-Board Hysteresis Outputs
♦ Externally Programmable Trip Points
♦ Monolithic, Low-Power CMOS Design
V
SET
threshold and guaranteed performance over
1
temperature.
The 3µA quiescent current of the ICL7665 makes it
ideal for voltage monitoring in battery-powered sys -
tems. In both battery- and line-powered systems, the
unique combination of a reference, two comparators,
and hysteresis outputs reduces the size and compo-
nent count of many circuits.
______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
PIN-PACKAGE
8 Plastic DIP
8 Plastic DIP
8 Plastic DIP
8 SO
ICL7665CPA
ICL7665ACPA
ICL7665BCPA
ICL7665CSA
ICL7665ACSA
ICL7665BCSA
ICL7665CJA
ICL7665ACJA
ICL7665BCJA
________________________Ap p lic a t io n s
µP Voltage Monitoring
8 SO
Low-Battery Detection
8 SO
Power-Fail and Brownout Detection
Battery Backup Switching
8 CERDIP
8 CERDIP
8 CERDIP
Power-Supply Fault Monitoring
Over/Undervoltage Protection
High/Low Temperature, Pressure, Voltage Alarms
Ordering Information continued on last page.
_________________P in Co n fig u ra t io n s
TOP VIEW
OUT1
HYST1
SET1
1
2
3
4
8
7
6
5
V+
__________Typ ic a l Op e ra t in g Circ u it
OUT2
SET2
ICL7665
V
IN1
V+
V
IN2
GND
HYST2
8
OVERVOLTAGE
DETECTION
UNDERVOLTAGE
DETECTION
V+
1
3
7
6
DIP/SO
OUT1
SET1
OUT2
NMI
V+ (CASE)
OUT2
8
ICL7665
OUT1
1
7
SET2
2
HYST1
6
SET2
GND
4
ICL7665
4
3
5
SET1
HYST2
GND
TO-99
SIMPLE THRESHOLD DETECTOR
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
Mic ro p ro c e s s o r Vo lt a g e Mo n it o r w it h
Du a l Ove r/Un d e rvo lt a g e De t e c t io n
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (Note 1) .........................................-0.3V to +18V
Output Voltages OUT1 and OUT2
(with respect to GND) (Note 1)..........................-0.3V to +18V
Output Voltages HYST1 and HYST2
(with respect to V+) (Note 1) .............................+0.3V to -18V
Input Voltages SET1 and SET2
Continuous Power Dissipation (T = +70°C)
A
Plastic DIP (derate 9.09mW/°C above +70°C) ............727mW
SO (derate 5.88mW/°C above +70°C) ........................471mW
CERDIP (derate 8.00mW/°C above +70°C) ................640mW
TO-99 (derate 6.67mW/°C above +70°C) ...................533mW
Operating Temperature Ranges
(Note 1)........................................(GND - 0.3V) to (V+ + 0.3V)
Maximum Sink Output Current
OUT1 and OUT2.............................................................25mA
Maximum Source Output Current
ICL7665C_ _.......................................................0°C to +70°C
ICL7665I_ _ .....................................................-20°C to +85°C
ICL7665E_ _....................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
ICL765
HYST1 and HYST2 ........................................................-25mA
Note 1: Due to the SCR structure inherent in the CMOS process used to fabricate these devices, connecting any terminal to volt-
ages greater than (V+ + 0.3V) or less than (GND - 0.3V) may cause destructive latchup. For this reason, we recommend
that inputs from external sources that are not operating from the same power supply not be applied to the device before its
supply is established, and that in multiple supply systems, the supply to the ICL7665 be turned on first. If this is not possi-
ble, currents into inputs and/or outputs must be limited to ±0.5mA and voltages must not exceed those defined above.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V+ = 5V, T = +25°C, unless otherwise noted.)
A
PARAMETER
SYMBOL
CONDITIONS
= +25°C
MIN
1.6
1.8
2.0
1.6
1.8
TYP
MAX
16
UNITS
T
A
ICL7665
T
= T
= T
to T
to T
16
A
MIN
MIN
MIN
Operating Supply Voltage
V+
ICL7665A
ICL7665B
T
A
16
V
MIN
T
A
= +25°C
10
T
A
= T
to T
10
MIN
MIN
V+ = 2V
V+ = 9V
2.5
2.6
2.9
10
10
15
ICL7665,
= +25°C;
T
A
GND ≤ V
SET1,
ICL7665A,
= T to T
V
SET2
≤ V+,
µA
Supply Current
I+
T
A
MIN
MAX V+ = 15V
all outputs open
circuit
V+ = 2V
V+ = 9V
2.5
10
ICL7665B,
= +25°C
T
A
2.6
10
V
1.150
1.200
1.275
1.225
1.250
1.215
1.300
1.300
1.300
1.300
1.300
1.300
100
1.450
1.400
1.325
1.375
1.350
1.385
SET1
ICL7665, ICL7665B, T = +25°C
A
V
SET2
V
SET1
Input Trip Voltage
V
SET
ICL7665A, T = +25°C
A
V
V
SET2
V
SET1
ICL7665A, T = T
to T
MAX
A
MIN
V
SET2
V
Tempco
ppm/°C
%/V
SET
Supply Voltage Sensitivity
of V , V
R
, R
, R
, R
= 1MΩ
0.004
OUT1 OUT2 HYST1 HYST2
SET1 SET2
2
_______________________________________________________________________________________
Mic ro p ro c e s s o r Vo lt a g e Mo n it o r w it h
Du a l Ove r/Un d e rvo lt a g e De t e c t io n
ICL765
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 5V, T = +25°C, unless otherwise noted.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
10
MAX UNITS
OUT1, OUT2
200
All grades, V
= 0V or
SET
V
SET
≥ 2V, T = +25°C
A
HYST1, HSYT2
-10
-100
ICL7665, ICL7665A,
V+ = 15V,
OUT1, OUT2
2000
nA
-500
Output Leakage Current
I
I
,
OLK
HLK
HYST1, HSYT2
T = T
to T
MAX
A
MIN
OUT1, OUT2
2000
-500
0.50
ICL7665B, V+ = 9V,
T = T to T
A
MIN
MAX
HYST1, HSYT2
ICL7665, ICL7665B: V+ = 2V
ICL7665A: V+ = 2V
All grades: V+ = 5V
ICL7665, ICL7665A: V+ = 15V
ICL7665B: V+ = 9V
All grades: V+ = 2V
All grades: V+ = 5V
ICL7665, ICL665A: V+ = 15V
ICL7665B: V+ = 9V
All grades: V+ = 2V
All grades: V+ = 5V
ICL7665, ICL665A: V+ = 15V
ICL7665B: V+ = 9V
0.20
0.20
0.10
0.06
0.06
-0.15
-0.05
-0.02
-0.02
0.20
0.15
0.11
0.11
V
Saturation
V
SET1
= 2V,
OUT1
0.30
0.20
0.25
-0.30
-0.15
-0.10
-0.15
0.50
0.30
0.25
0.30
V
Voltage
I
= 2mA
OUT1
V
Saturation
V
SET1
= 2V,
HYST1
V
V
Voltage
I
= -0.5mA
HYST1
V
Saturation
V
SET2
= 0V,
OUT2
Voltage
I
= 2mA
OUT2
V
= 2V,
= -0.2mA
SET2
All grades: V+ = 2V
-0.25
-0.80
I
HYST2
All grades: V+ = 5V
ICL7665: V+ = 15V
ICL7665A: V+ = 15V
ICL7665B: V+ = 9V
-0.43
-0.35
-0.35
-0.35
-1.00
-0.80
-1.00
-1.00
V
Saturation
HYST2
V
Voltage
V
= 2V,
= -0.5mA
SET2
I
HYST2
V
Input Leakage
SET
GND ≤ V
≤ V+
I
±0.01
±10
nA
SET
SET
Current
V
Input Change for
SET
R
V
OUT
= 4.7kΩ, R
LO = 1% V+, V
= 20kΩ,
HYST
OUT
∆V
Complete Output
Change
0.1
mV
SET
HI = 99% V+
OUT
Difference in Trip
Voltage
V
V
–
SET2
SET1
R
R
, R
= 1MΩ
= 1MΩ
±5
±50
mV
mV
OUT HYST
Output/Hysteresis
Difference
, R
±0.1
OUT HYST
_______________________________________________________________________________________
3
Mic ro p ro c e s s o r Vo lt a g e Mo n it o r w it h
Du a l Ove r/Un d e rvo lt a g e De t e c t io n
AC OPERATING CHARACTERISTICS
(V+ = 5V, T = +25°C, unless otherwise noted.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
85
MAX
UNITS
t
SO1d
SH1d
SO2d
V
switched from 1.0V to 1.6V,
SET
t
90
Output Delay Time,
Input Going High
R
R
= 4.7kΩ, C = 12pF,
µs
OUT
L
t
55
= 20kΩ
HYST
ICL765
t
t
t
55
SH2d
SO1d
SH1d
SO2d
75
V
switched from 1.6V to 1.0V,
SET
80
Output Delay Time,
Input Going Low
R
R
= 4.7kΩ, C = 12pF,
µs
µs
µs
OUT
L
t
60
= 20kΩ
HYST
t
60
SH2d
t
0.6
0.8
7.5
0.7
0.6
0.7
4.0
1.8
O1r
V
switched between 1.0V and 1.6V,
SET
t
O2r
Output Rise Times
Output Fall Times
R
= 4.7kΩ, C = 12pF,
OUT L
t
H1r
H2r
R
HYST
= 20kΩ
t
t
O1f
V
switched between 1.0V and 1.6V,
= 4.7kΩ, C = 12pF,
L
= 20kΩ
SET
t
O2f
R
R
OUT
t
t
H1f
HYST
H2f
_______________________________________________________S w it c h in g Wa ve fo rm s
1.6V
INPUT
V
V
SET1, SET2
1.0V
t
SO1d
t
V+ (5V)
SO1d
OUT1
GND
t
O1r
t
O1f
V+ (5V)
t
SH1d
HYST1
GND
t
H1r
t
t
H1f
SH1d
t
t
SO2d
SO2d
V+ (5V)
OUT2
GND
t
O2r
t
O2f
V+ (5V)
t
SH2d
HYST2
GND
t
SH2d
t
H2r
t
H2f
4
_______________________________________________________________________________________
Mic ro p ro c e s s o r Vo lt a g e Mo n it o r w it h
Du a l Ove r/Un d e rvo lt a g e De t e c t io n
ICL765
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(T = +25°C, unless otherwise noted.)
A
SUPPLY CURRENT AS A
FUNCTION OF SUPPLY VOLTAGE
SUPPLY CURRENT AS A
FUNCTION OF AMBIENT TEMPERATURE
OUT1 SATURATION VOLTAGE AS A
FUNCTION OF OUTPUT CURRENT
2.0
5.0
4.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0V ≤ V , V
≤ V+
0V ≤ V , V
≤ V+
SET1 SET2
SET1 SET2
V+ = 2V
V+ = 15V
V+ = 9V
4.0
3.5
1.5
T = -20°C
A
V+ = 5V
3.0
2.5
2.0
1.5
1.0
0.5
0
V+ = 9V
T = +25°C
A
1.0
V+ = 15V
T = +70°C
A
V+ = 2V
0.5
0
0
2
4
6
8
10 12 14 16
-20
0
20
40
60
0
5
10
15
20
SUPPLY VOLTAGE (V)
AMBIENT TEMPERATURE (°C)
I
OUT1 (mA)
OUT
OUT2 SATURATION VOLTAGE AS A
FUNCTION OF OUTPUT CURRENT
HYST1 OUTPUT SATURATION VOLTAGE
vs. HYST1 OUTPUT CURRENT
HYST2 OUTPUT SATURATION VOLTAGE
vs. HYST2 OUTPUT CURRENT
2.0
0
-0.4
-0.8
0
-1
-2
1.5
1.0
V+ = 15V
V+ = 9V
V+ = 2V
V+ = 5V
V+ = 9V
V+ = 15V
V+ = 9V
V+ = 5V
V+ = 15V
-1.2
-1.6
-2.0
-3
-4
-5
V+ = 2V
V+ = 5V
0.5
0
V+ = 2V
0
5
10
15
20
-20
-16
-12
-8
-4
0
-5
-4
-3
-2
-1
0
I
OUT2 (mA)
HYST1 OUTPUT CURRENT (mA)
HYST2 OUTPUT CURRENT (mA)
OUT
_______________________________________________________________________________________
5
Mic ro p ro c e s s o r Vo lt a g e Mo n it o r w it h
Du a l Ove r/Un d e rvo lt a g e De t e c t io n
V+
4.7k
OUT1
HYST1
4.7k
1
2
3
4
V+
8
7
6
5
OUT1
ICL765
OUT2
HYST1 ICL7665
OUT2
SET2
INPUT
SET1
GND
HSYT2
HSYT2
1.6V
1.0V
12pF
12pF
20k
20k
12pF
12pF
Figure 1. Test Circuit
_______________De t a ile d De s c rip t io n
V+
As shown in the block diagram of Figure 2, the Maxim
ICL7665 c omb ine s a 1.3V re fe re nc e with two c om-
parators, two open-drain N-channel outputs, and two
open-drain P-channel hysteresis outputs. The refer-
ence and comparator are very low-power linear CMOS
circuits, with a total operating current of 10µA maxi-
mum, 3µA typ ic a l. The N-c ha nne l outp uts c a n s ink
greater than 10mA, but are unable to source any cur-
rent. These outputs are suitable for wire-OR connections
and are capable of driving TTL inputs when an external
pull-up resistor is added.
SET1
HYST1
OUT1
1.3V
BANDGAP
REFERENCE
TO V+
The ICL7665 Truth Table is shown in Table 1. OUT1 is
an inverting output; all other outputs are noninverting.
HYST1 a nd HYST2 a re P-c ha nne l c urre nt s ourc e s
whose sources are connected to V+. OUT1 and OUT2
are N-channel current sinks with their sources connect-
ed to ground. Both OUT1 and OUT2 can drive at least
HYST2
OUT2
SET2
one TTL load with a V of 0.4V.
OL
Table 1. ICL7665 Truth Table
INPUT*
> 1.3V
OUTPUT
HYSTERESIS
Figure 2. Block Diagram
V
OUT1 = ON = LOW HYST1 = ON = HI
SET1
HYST1 = OFF = LOW
HYST2 = ON = HI
HYST2 = OFF = LOW
V
< 1.3V
> 1.3V
< 1.3V
OUT1 = OFF = HI
OUT2 = OFF = HI
OUT2 = ON = LOW
SET1
In spite of the very low operating current, the ICL7665
has a typical propagation delay of only 75µs. Since the
comparator input bias current and the output leakages
are very low, high-impedance external resistors can be
used. This design feature minimizes both the total sup-
ply current used and loading on the voltage source that
is being monitored.
V
SET2
V
SET2
OUT1 is an inverting output; all others are noninverting. OUT1
and OUT2 are open-drain, N-channel current sinks. HYST1
and HYST2 are open-drain, P-channel current sinks.
* See Electrical Characteristics
6
_______________________________________________________________________________________
Mic ro p ro c e s s o r Vo lt a g e Mo n it o r w it h
Du a l Ove r/Un d e rvo lt a g e De t e c t io n
ICL765
V
IN1
V+
V
IN2
V
IN1
V+
V
IN2
OUT1
OUT2
OUT1
SET1
OUT2
R22
R12
R21
R11
R22
R21
R11
ICL7665
HYST1
R31
R32
ICL7665
HYST2
SET1
SET2
SET2
R12
V+
0V
OUT1
OUT1
0V
V+
V
L1
V
U1
V
OUT2
V
IN1
V
IN1
V
TRIP1
OUT2
V
TRIP2
IN2
V
V
L2 U2
V
IN2
Figure 3. Simple Threshold Detector
Figure 4. Threshold Detector with Hysteresis
the difference between the upper and lower trip points)
keeps noise or small variations in the input signal from
repeatedly switching the output when the input signal
remains near the trip point for a long period of time.
Ba s ic Ove r/Un d e rvo lt a g e
De t e c t io n Circ u it s
Figures 3, 4, and 5 show the three basic voltage detec-
tion circuits.
The third basic circuit, Figure 5, is suitable only when the
voltage to be detected is also the power-supply voltage for
the ICL7665. This circuit has the advantage that all of the
current flowing through the input divider resistors flows
through the hysteresis resistor. This allows the use of
higher-value resistors, without hysteresis output leakage
having an appreciable effect on the trip point.
The simplest circuit, depicted in Figure 3, does not
have any hysteresis. The comparator trip-point formulas
can easily be derived by observing that the comparator
changes state when the V
input is 1.3V. The exter-
SET
nal resistors form a voltage divider that attenuates the
input signal. This ensures that the V terminal is at
SET
1.3V when the input voltage is at the desired compara-
tor trip point. Since the bias current of the comparator
is only a fraction of a nanoamp, the current in the volt-
age divider can be less than one microamp without los-
ing accuracy due to bias currents. The ICL7665A has a
2% threshold accuracy at +25°C, and a typical temper-
ature coefficient of 100ppm/°C including comparator
offset drift, eliminating the need for external poten-
tiometers in most applications.
Resistor-Value Calculations
Figure 3
1) Choose a value for R11. This value determines the
amount of current flowing though the input divider,
equal to V
/ R11. R11 can typically be in the
SET
range of 10kΩ to 10MΩ.
2) Calculate R21 based on R11 and the desired trip
point:
Figure 4 adds another resistor to each voltage detector.
This third resistor supplies current from the HYST out-
put whenever the V
old . As the formula s s how, this hys te re s is re s is tor
affects only the lower trip point. Hysteresis (defined as
input is above the 1.3V thresh-
SET
V
– V
V
– 1.3V
TRIP
SET
TRIP
R21 = R11 ——————— = R11 ——————
(
)
(
)
V
1.3V
SET
_______________________________________________________________________________________
7
Mic ro p ro c e s s o r Vo lt a g e Mo n it o r w it h
Du a l Ove r/Un d e rvo lt a g e De t e c t io n
Figure 5
V
IN
1) Select a value for R11, usually between 10kΩ and
10MΩ.
R31
R21
2) Calculate R21:
R32
R22
V+
V – V
V – 1.3V
L
L
SET
HYST1
HYST2
R21 = R11 —————— = R11 —————
(
)
(
)
V
1.3
SET
ICL7665
ICL765
3) Calculate R31:
SET1
SET2
OVERVOLTAGE
R11
UNDERVOLTAGE
R12
V – V
U
L
OUT1
OUT2
R31 = R11 —————
(
)
GND
V
SET
4) As in the other circuits, all three resistor values may
be scaled up or down in value without changing V
U
and V . V and V depend only on the ratio of the
three resistors, if the absolute values are such that
the hysteresis output resistance and the leakage
L
U
L
OUT1
OUT2
V
L1
V
U1
currents of the V
input and hysteresis output can
SET
be ignored.
__________Ap p lic a t io n s In fo rm a t io n
V
V
L2 U2
V
IN
Fa u lt Mo n it o r fo r a S in g le S u p p ly
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-
Figure 5. Threshold Detector, V = V+
IN
teresis (V = 5.55V, V = 5.45V); and the lower trip points
U
L
Figure 4
(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.
1) Choose a resistor value for R11. Typical values are
in the 10kΩ to 10MΩ range.
2) Calculate R21 for the desired upper trip point, VU,
using the formula:
Mu lt ip le -S u p p ly Fa u lt Mo n it o r
The ICL7665 can simultaneously monitor several power
supplies, as shown in Figure 7. The easiest way to calculate
V - V
V – 1.3V
U
U
SET
R21 = R11 —————— = R11 —————
(
)
(
)
the resistor values is to note that when the V
input is at
SET
V
1.3V
3) Calculate R31 for the desired amount of hysteresis:
(R21) (V+ – V (R21) (V+ – 1.3V)
SET
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
)
SET
R31 = ————————— = —————————
V – V V – V
U
L
U
L
or, if V+ = V :
IN
V
SET
input depends on the voltage of both supplies being
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.
(R21) (V – V
)
(R21) (V – 1.3V)
L
L
SET
R31 = ————————— = —————————
V – V V – V
U
L
U
L
4) The trip voltages are not affected by the absolute
value of the resistors, as long as the impedances
a re hig h e noug h tha t the re s is ta nc e 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 100kΩ to 22MΩ range. Multiplying or
dividing all three resistors by the same factor will
not affect the trip voltages.
8
_______________________________________________________________________________________
Mic ro p ro c e s s o r Vo lt a g e Mo n it o r w it h
Du a l Ove r/Un d e rvo lt a g e De t e c t io n
ICL765
exceeds 10.2V. When the 110V AC power-line voltage
is either interrupted or reduced so that the peak voltage
is less than 10.2V, C1 will be charged through R1.
OUT2, the power-fail warning output, goes high when
the voltage on C1 reaches 1.3V. The time constant R1 x
C1 determines the delay time before the power-fail warning
signal is activated, in this case 42ms or 21⁄2 line cycles.
Optional components R2, R3 and Q1 add hysteresis by
increasing the peak secondary voltage required to dis-
charge C1 once the power-fail warning is active.
Co m b in a t io n Lo w -Ba t t e ry Wa rn in g a n d
Lo w -Ba t t e ry Dis c o n n e c t
Nickel cadmium (NiCd) batteries are excellent recharge-
able power sources for portable equipment, but care
must be taken to ensure that NiCd batteries are not
damaged by overdischarge. Specifically, a NiCd battery
should not be discharged to the point where the polarity
of the lowest-capacity cell is reversed, and that cell is
reverse charged by the higher-capacity cells. This reverse
charging will dramatically reduce the life of a NiCd battery.
The Figure 8 circuit both prevents reverse charging and
gives a low-battery warning. A typical low-battery warning
voltage is 1V per cell. Since a NiCd “9V” battery is ordi-
narily made up of six cells with a nominal voltage of 7.2V,
a low-battery warning of 6V is appropriate, with a small
hysteresis of 100mV. To prevent overdischarge of a bat-
tery, the load should be disconnected when the battery
voltage is 1V x (N – 1), where N = number of cells. In this
case, the low-battery load disconnect should occur at
5V. Since the battery voltage will rise when the load is
disconnected, 800mV of hysteresis is used to prevent
repeated on/off cycling.
Ba t t e ry S w it c h o ve r Circ u it
The circuit in Figure 11 performs two functions: switch-
ing the power supply of a CMOS memory to a backup
battery when the line-powered supply is turned off, and
lighting a low-battery-warning LED when the backup
battery is nearly discharged. The PNP transistor, Q1,
connects the line-powered +5V to the CMOS memory
whe ne ve r the line -p owe re d +5V s up p ly volta g e is
greater than 3.5V. The voltage drop across Q1 will only
be a couple of hundred millivolts, since it will be satu-
rated. Whenever the input voltage falls below 3.5V,
OUT1 goes high, turns off Q1, and connects the 3V
lithium cell to the CMOS memory.
P o w e r-Fa il Wa rn in g a n d
P o w e r-Up /P o w e r-Do w n Re s e t
The second voltage detector of the ICL7665 monitors the
voltage of the lithium cell. If the battery voltage falls below
2.6V, OUT2 goes low and the low-battery-warning LED
turns on (assuming that the +5V is present, of course).
Figure 9 illustrates a power-fail warning circuit that
monitors raw DC input voltage to the 7805 three-termi-
nal 5V regulator. The power-fail warning signal goes
high when the unregulated DC input falls below 8.0V.
When the raw DC power source is disconnected or the
AC power fails, the voltage on the input of the 7805
Another possible use for the second section of the
ICL7665 is the detection of the input voltage falling
below 4.5V. This signal could then be used to prevent
the microprocessor from writing spurious data to the
CMOS memory while its power-supply voltage is out-
side its guaranteed operating range.
decays at a rate of I
/ C (in this case, 200mV/ms).
OUT
Since the 7805 will continue to provide a 5V output at
1A until V is less than 7.3V, this circuit will give at
least 3.5mIsN of warning before the 5V output begins to
drop. If additional warning time is needed, either the
trip voltage or filter capacitance should be increased,
or the output current should be decreased.
S im p le Hig h /Lo w Te m p e ra t u re Ala rm
The circuit in Figure 12 is a simple high/low tempera-
ture alarm, which uses a low-cost NPN transistor as the
sensor and an ICL7665 as the high/low detector. The
NPN transistor and potentiometer R1 form a Vbe multi-
plier whose output voltage is determined by the Vbe of
the transistor and the position of R1’s wiper arm. The
voltage at the top of R1 will have a temperature coeffi-
cient of approximately -5mV/°C. R1 is set so that the
The ICL7665 OUT2 is set to trip when the 5V output has
decayed to 3.9V. This output can be used to prevent
the microprocessor from writing spurious data to a
CMOS battery-backup memory, or can be used to acti-
vate a battery-backup system.
AC P o w e r-Fa il a n d Bro w n o u t De t e c t o r
By monitoring the secondary of the transformer, the cir-
cuit in Figure 10 performs the same power-failure warn-
ing function as Figure 9. With a normal 110V AC input
to the tra ns forme r, OUT1 will d is c ha rg e C1 e ve ry
16.7ms when the peak transformer secondary voltage
voltage at V
equals the V
trip voltage when the
SET2
SET2
temperature of the NPN transistor reaches the level
selected for the high-temperature alarm. R2 can be
adjusted so that the voltage at V
is 1.3V when the
SET1
NPN transistor’s temperature reaches the low-tempera-
ture limit.
_______________________________________________________________________________________
9
Mic ro p ro c e s s o r Vo lt a g e Mo n it o r w it h
Du a l Ove r/Un d e rvo lt a g e De t e c t io n
+5V SUPPLY
+5V
HYST2
R21A
V+
HYST1
274k
100k
V+
R31
+5V
HYST1
HYST2
22M
22M
ICL7665
324k
13M
5%
249k
7.5M
5%
SET2
SET1
ICL7665
R21B
ICL765
1.02M
OUT2
OUT1
301k
787k
R11
49.9k
SET1
100k OUT1
SET2
OUT2
+15V
OVERVOLTAGE
DETECTOR
UNDERVOLTAGE
DETECTOR
+5V
100k
-5V -15V
POWER OK
V ≈ 5.55V
V ≈ 4.55V
U
U
V ≈ 5.45V
L
V ≈ 4.45V
L
POWER OK
Figure 6. Fault Monitor for a Single Supply
Figure 7. Multiple-Supply Fault Monitor
+5V, 1A
OUTPUT
R31
R32
1M
100Ω
V+
V+
OUT2
OUT1
HYST1
R21
HYST2
SENSE
R22
R12
ICL7665
ICL7663
SET
SET1
SET2
OUT2
SHDN
R11
OUT1 GND
GND
LOW-BATTERY WARNING
LOW-BATTERY SHUTDOWN
Figure 8. Low-Battery Warning and Low-Battery Disconnect
5V, 1A
UNREGULATED
DC INPUT
5V, 1A
OUTPUT
7805
5V REGULATOR
20V CENTER
TAPPED TRANS
7805
5V REGULATOR
4700µF
10VAC
60Hz
4700µF
470µF
22M
BACK-UP
BATTERY
+5V
V+
HYST1
V+
HYST2
HYST1
HYST2
R1
681k
100k
5.6M
715k
ICL7665
ICL7665
2.2M
SET1
SET2
SET1
SET2
R2
1M
RESET
OR
WRITE
ENABLE
OUT1
OUT2
130k
1M
OUT1
OUT2
R3
1M
C1
Q1
POWER-FAIL
WARNING
POWER-FAIL WARNING
Figure 9. Power-Fail Warning and Power-Up/Power-Down Reset
Figure 10. AC Power-Fail and Brownout Detector
10 ______________________________________________________________________________________
Mic ro p ro c e s s o r Vo lt a g e Mo n it o r w it h
Du a l Ove r/Un d e rvo lt a g e De t e c t io n
ICL765
V
CMOS
MEMORY
TO
Q1
CC
LINE-POWERED
+5V INPUT
100k
1µF
1k
2N7000
2N4393
1M
OUT1
V+
HYST1
HYST2
3V
LITHIUM
CELL
5.6M
1M
22M
1.15M
1%
ICL7665
2.4M
SET1
GND
SET2
OUT2
1M
1%
220Ω
Figure 11. Battery Switchover Circuit
9V
V+
TEMPERATURE
SENSOR
(GENERAL
PURPOSE NPN
TRANSISTOR)
HYST2
HYST1
R3
470k
R4
22M
R6
22M
LOW-TEMPERATURE
LIMIT ADJUST
ICL7665
SET2
SET1
OUT1
R5
27k
R1, 1M
HIGH-
TEMPERATURE
LIMIT
R2
R7
1.5M
OUT2
1M
ALARM
SIGNAL FOR
DRIVING LEDS,
BELLS, ETC.
ADJUSTMENT
Figure 12. Simple High/Low Temperature Alarm
______________________________________________________________________________________ 11
Mic ro p ro c e s s o r Vo lt a g e Mo n it o r w it h
Du a l Ove r/Un d e rvo lt a g e De t e c t io n
_______________________S CR La t c h u p
___________________Ch ip To p o g ra p h y
Like all junction-isolated CMOS circuits, the ICL7665 has
a n inhe re nt four-la ye r or SCR s truc ture tha t c a n b e
triggered into destructive latchup under certain con-
ditions. Avoid destructive latchup by following these
precautions:
V+
OUT2
1) If either V
terminal can be driven to a voltage
SET
ICL765
greater than V+ or less than ground, limit the input
current to 500µA maximum. Usually, an input volt-
age divider resistance can be chosen to ensure
the inp ut c urre nt re ma ins b e low 500µA, e ve n
whe n the inp ut volta g e is a p p lie d b e fore the
ICL7665 V+ supply is connected.
0. 066"
(1. 42mm)
OUT1
SET2
HYST2
2) Limit the ra te -of-ris e of V+ b y us ing a b yp a s s
capacitor near the ICL7665. Rate-of-rise SCRs
ra re ly oc c ur unle s s : a ) the b a tte ry ha s a low
impedance—as is the case with NiCd and lead
acid batteries; b) the battery is connected directly
to the ICL7665 or is switched on via a mechanical
switch with low resistance; or c) there is little or no
input filter capacitance near the ICL7665. In line-
powered systems, the rate-of-rise is usually limited
by other factors and will not cause a rate-of-rise
SCR action under normal circumstances.
HYST1
SET1
V-
0. 084"
(1. 63mm)
TRANSISTOR COUNT: 38
SUBSTRATE CONNECTED TO V+.
3) Limit the maximum supply voltage (including tran-
sient spikes) to 18V. Likewise, limit the maximum volt-
age on OUT1 and OUT2 to +18V and the maxi-
mum voltage on HYST1 and HYST2 to 18V below V+.
_Ord e rin g In fo rm a t io n (c o n t in u e d )
PART
TEMP. RANGE
0°C to +70°C
PIN-PACKAGE
8 TO-99
ICL7665CTV
ICL7665ACTV
ICL7665BCTV
ICL7665AC/D
ICL7665IPA
ICL7665IJA
0°C to +70°C
8 TO-99
0°C to +70°C
8 TO-99
0°C to +70°C
Dice*
-20°C to +85°C
-20°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
8 Plastic DIP
8 CERDIP
8 Plastic DIP
8 Plastic DIP
8 SO
ICL7665EPA
ICL7665AEPA
ICL7665ESA
ICL7665AESA
8 SO
*Contact factory for dice specifications.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 ____________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 4 0 8 -7 3 7 -7 6 0 0
© 1997 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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