ICL7665ACPA

19-0001; Rev 3; 11/15 Microprocessor Voltage Monitor with Dual Over/Undervoltage Detection The ICL7665 warns microprocessors (µPs) of overvoltage and undervoltage conditions. It draws a typical operating current of only 3µA. The trip points and hysteresis of the two voltage detectors are individually programmed 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 voltages from 1.3V to several hundred volts. The Maxim ICL7665A is an improved version with a 2%-accurate V SET1 threshold and guaranteed performance over temperature. The 3µA quiescent current of the ICL7665 makes it ideal for voltage monitoring in battery-powered systems. In both battery- and line-powered systems, the unique combination of a reference, two comparators, and hysteresis outputs reduces the size and component count of many circuits. ________________________Applications µP Voltage Monitoring Low-Battery Detection Power-Fail and Brownout Detection Battery Backup Switching Power-Supply Fault Monitoring Over/Undervoltage Protection High/Low Temperature, Pressure, Voltage Alarms ____________________________Features µP Over/Undervoltage Warning 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 ______________Ordering Information PART ICL7665CPA+ ICL7665ACPA+ TEMP. RANGE PIN-PACKAGE 0°C to +70°C 8 Plastic DIP 0°C to +70°C 8 Plastic DIP ICL7665BCPA+ 0°C to +70°C 8 Plastic DIP ICL7665CSA+ 0°C to +70°C 8 SO ICL7665ACSA+ 0°C to +70°C 8 SO ICL7665BCSA+ 0°C to +70°C 8 SO ICL7665CJA+ 0°C to +70°C 8 CERDIP ICL7665ACJA + 0°C to +70°C 8 CERDIP + ICL7665BCJA 0°C to +70°C 8 CERDIP +Denotes a lead(pb)-free/RoHS-compliant package. Ordering Information continued on last page. _________________Pin Configurations TOP VIEW __________Typical Operating Circuit VIN1 OVERVOLTAGE DETECTION V+ 1 OUT1 8 V+ 7 1 8 V+ HYST1 2 7 OUT2 6 SET2 5 HYST2 SET1 3 VIN2 OUT2 + OUT1 ICL7665 GND 4 UNDERVOLTAGE DETECTION NMI DIP/SO ICL7665 3 SET2 SET1 6 GND 4 SIMPLE THRESHOLD DETECTOR ________________________________________________________________ Maxim Integrated Products 1 ICL7665 _______________General Description ICL7665 Microprocessor Voltage Monitor with Dual Over/Undervoltage Detection 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 (Note 1)........................................(GND - 0.3V) to (V+ + 0.3V) Maximum Sink Output Current OUT1 and OUT2.............................................................25mA Maximum Source Output Current HYST1 and HYST2 ........................................................-25mA Continuous Power Dissipation (TA = +70°C) 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 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 Note 1: Due to the SCR structure inherent in the CMOS process used to fabricate these devices, connecting any terminal to voltages 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 possible, 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, TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS ICL7665 Operating Supply Voltage V+ ICL7665A ICL7665B Supply Current I+ GND ≤ VSET1, VSET2 ≤ V+, all outputs open circuit VSET TA = TMIN to TMIN 1.8 16 TA = TMIN to TMIN 2.0 16 TA = +25°C 1.6 10 TA = TMIN to TMIN 1.8 10 ICL7665, TA = +25°C; ICL7665A, TA = TMIN to TMAX V+ = 2V 2.5 10 V+ = 9V 2.6 10 V+ = 15V 2.9 15 ICL7665B, TA = +25°C V+ = 2V 2.5 10 V+ = 9V 2.6 10 ICL7665A, TA = +25°C VSET Tempco 2 MAX 16 ICL7665A, TA = TMIN to TMAX Supply Voltage Sensitivity of VSET1, VSET2 TYP 1.6 ICL7665, ICL7665B, TA = +25°C Input Trip Voltage MIN TA = +25°C ROUT1, ROUT2, RHYST1, RHYST2 = 1MΩ VSET1 1.150 1.300 1.450 VSET2 1.200 1.300 1.400 VSET1 1.275 1.300 1.325 VSET2 1.225 1.300 1.375 VSET1 1.250 1.300 1.350 VSET2 1.215 1.300 1.385 UNITS V µA V 100 ppm/°C 0.004 %/V _______________________________________________________________________________________ Microprocessor Voltage Monitor with Dual Over/Undervoltage Detection (V+ = 5V, TA = +25°C, unless otherwise noted.) SYMBOL PARAMETER Output Leakage Current IOLK, IHLK VOUT1 Saturation Voltage CONDITIONS TYP MAX All grades, VSET = 0V or VSET ≥ 2V, TA = +25°C OUT1, OUT2 10 200 HYST1, HSYT2 -10 -100 ICL7665, ICL7665A, V+ = 15V, TA = TMIN to TMAX OUT1, OUT2 2000 HYST1, HSYT2 -500 ICL7665B, V+ = 9V, TA = TMIN to TMAX OUT1, OUT2 2000 VSET1 = 2V, IOUT1 = 2mA VHYST1 Saturation Voltage VSET1 = 2V, IHYST1 = -0.5mA VOUT2 Saturation Voltage VSET2 = 0V, IOUT2 = 2mA VSET2 = 2V, IHYST2 = -0.2mA VHYST2 Saturation Voltage VSET2 = 2V, IHYST2 = -0.5mA VSET Input Leakage Current ISET MIN nA HYST1, HSYT2 -500 ICL7665, ICL7665B: V+ = 2V 0.20 ICL7665A: V+ = 2V 0.20 All grades: V+ = 5V 0.10 0.30 ICL7665, ICL7665A: V+ = 15V 0.06 0.20 ICL7665B: V+ = 9V 0.06 0.25 All grades: V+ = 2V -0.15 -0.30 All grades: V+ = 5V -0.05 -0.15 ICL7665, ICL665A: V+ = 15V -0.02 -0.10 ICL7665B: V+ = 9V -0.02 -0.15 All grades: V+ = 2V 0.20 0.50 All grades: V+ = 5V 0.15 0.30 ICL7665, ICL665A: V+ = 15V 0.11 0.25 ICL7665B: V+ = 9V 0.11 0.30 All grades: V+ = 2V -0.25 -0.80 All grades: V+ = 5V -0.43 -1.00 ICL7665: V+ = 15V -0.35 -0.80 ICL7665A: V+ = 15V -0.35 -1.00 ICL7665B: V+ = 9V -0.35 -1.00 ±0.01 ±10 GND ≤ VSET ≤ V+ VSET Input Change for Complete Output Change ∆VSET ROUT = 4.7kΩ, RHYST = 20kΩ, VOUTLO = 1% V+, VOUTHI = 99% V+ 0.1 Difference in Trip Voltage VSET1– VSET2 ROUT, RHYST = 1MΩ ±5 ROUT, RHYST = 1MΩ ±0.1 Output/Hysteresis Difference UNITS 0.50 V V V V nA mV ±50 mV mV _______________________________________________________________________________________ 3 ICL7665 ELECTRICAL CHARACTERISTICS (continued) ICL7665 Microprocessor Voltage Monitor with Dual Over/Undervoltage Detection AC OPERATING CHARACTERISTICS (V+ = 5V, TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN tSO1d tSH1d Output Delay Time, Input Going High tSO2d VSET switched from 1.0V to 1.6V, ROUT = 4.7kΩ, CL = 12pF, RHYST = 20kΩ 90 tSH1d 55 75 VSET switched from 1.6V to 1.0V, ROUT = 4.7kΩ, CL = 12pF, RHYST = 20kΩ 80 60 tO1r 0.6 tH1r VSET switched between 1.0V and 1.6V, ROUT = 4.7kΩ, CL = 12pF, RHYST = 20kΩ 0.8 0.7 tO1f Output Fall Times tH1f µs 7.5 tH2r tO2f µs 60 tSH2d tO2r Output Rise Times UNITS µs 55 tSH2d tSO2d MAX 85 tSO1d Output Delay Time, Input Going Low TYP 0.6 VSET switched between 1.0V and 1.6V, ROUT = 4.7kΩ, CL = 12pF, RHYST = 20kΩ 0.7 µs 4.0 tH2f 1.8 _______________________________________________________Switching Waveforms 1.6V INPUT VSET1,VSET2 1.0V t SO1d t SO1d V+ (5V) OUT1 t O1r t O1f HYST1 GND V+ (5V) t SH1d t H1r GND t SH1d t H1f t SO2d t SO2d V+ (5V) OUT2 t O2r HYST2 t O2f t SH2d 4 V+ (5V) GND t SH2d t H2r GND t H2f _______________________________________________________________________________________ Microprocessor Voltage Monitor with Dual Over/Undervoltage Detection SUPPLY CURRENT AS A FUNCTION OF SUPPLY VOLTAGE 0V ≤ VSET1, VSET2 ≤ V+ 4.5 V+ = 9V V+ = 15V 0.5 3.5 TA = -20°C 3.0 TA = +25°C 2.5 TA = +70°C 2.0 1.5 5 15 10 2 4 6 8 10 12 SUPPLY VOLTAGE (V) 14 16 -0.8 V+ = 9V -1.2 V+ = 2V -2.0 ICL7665-05 V+ = 15V V+ = 9V V+ = 5V -3 V+ = 2V -4 -4 HYST1 OUTPUT CURRENT (mA) 0 1.5 V+ = 2V V+ = 5V V+ = 9V V+ = 15V 1.0 0.5 0 -5 -8 60 2.0 -1 -2 0 20 40 AMBIENT TEMPERATURE (°C) OUT2 SATURATION VOLTAGE AS A FUNCTION OF OUTPUT CURRENT 0 HYST2 OUTPUT SATURATION VOLTAGE (V) ICL7665-04 V+ = 15V -12 -20 HYST2 OUTPUT SATURATION VOLTAGE vs. HYST2 OUTPUT CURRENT -0.4 -16 V+ = 2V 0 0 20 0 -20 1.5 0.5 HYST1 OUTPUT SATURATION VOLTAGE vs. HYST1 OUTPUT CURRENT V+ = 5V 2.0 0.5 IOUT OUT1 (mA) -1.6 2.5 1.0 VOLTAGE SATURATION (V) 0 3.0 1.0 0 V+ = 9V 3.5 ICL7665-06 1.0 V+ = 15V 4.0 SUPPLY CURRENT (µA) SUPPLY CURRENT (µA) V+ = 5V 0V ≤ VSET1, VSET2 ≤ V+ 4.5 4.0 1.5 0 HYST1 OUTPUT SATURATION VOLTAGE (V) 5.0 ICL7665-03 V+ = 2V VOLTAGE SATURATION (V) 5.0 ICL7665-01 2.0 SUPPLY CURRENT AS A FUNCTION OF AMBIENT TEMPERATURE ICL7665-02 OUT1 SATURATION VOLTAGE AS A FUNCTION OF OUTPUT CURRENT -5 -4 -3 -2 -1 HYST2 OUTPUT CURRENT (mA) 0 0 5 10 15 20 IOUT OUT2 (mA) _______________________________________________________________________________________ 5 ICL7665 __________________________________________Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) ICL7665 Microprocessor Voltage Monitor with Dual Over/Undervoltage Detection V+ 4.7k OUT1 HYST1 INPUT 1.6V V+ 8 OUT2 7 SET1 SET2 6 GND HSYT2 5 1 OUT1 2 HYST1 3 4 ICL7665 1.0V 4.7k OUT2 HSYT2 20k 20k 12pF 12pF 12pF 12pF Figure 1. Test Circuit _______________Detailed Description As shown in the block diagram of Figure 2, the Maxim ICL7665 combines a 1.3V reference with two comparators, two open-drain N-channel outputs, and two open-drain P-channel hysteresis outputs. The reference and comparator are very low-power linear CMOS circuits, with a total operating current of 10µA maximum, 3µA typical. The N-channel outputs can sink greater than 10mA, but are unable to source any current. These outputs are suitable for wire-OR connections and are capable of driving TTL inputs when an external pull-up resistor is added. The ICL7665 Truth Table is shown in Table 1. OUT1 is an inverting output; all other outputs are noninverting. HYST1 and HYST2 are P-channel current sources whose sources are connected to V+. OUT1 and OUT2 are N-channel current sinks with their sources connected to ground. Both OUT1 and OUT2 can drive at least one TTL load with a VOL of 0.4V. V+ SET1 HYST1 OUT1 1.3V BANDGAP REFERENCE TO V+ HYST2 SET2 OUT2 Table 1. ICL7665 Truth Table INPUT* OUTPUT HYSTERESIS VSET1 > 1.3V OUT1 = ON = LOW HYST1 = ON = HI VSET1 < 1.3V OUT1 = OFF = HI HYST1 = OFF = LOW VSET2 > 1.3V OUT2 = OFF = HI HYST2 = ON = HI VSET2 < 1.3V OUT2 = ON = LOW HYST2 = OFF = LOW 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. Figure 2. Block Diagram 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 supply current used and loading on the voltage source that is being monitored. * See Electrical Characteristics 6 _______________________________________________________________________________________ Microprocessor Voltage Monitor with Dual Over/Undervoltage Detection V+ V+ OUT1 OUT2 OUT1 VIN1 VIN2 R22 R21 OUT2 R22 ICL7665 R31 SET2 SET1 SET2 R12 R32 HYST2 HYST1 R11 VIN2 R21 ICL7665 SET1 ICL7665 VIN1 R12 R11 V+ OUT1 OUT1 VL1 VIN1 0V VU1 VIN1 VTRIP1 OUT2 V+ OUT2 VIN2 VTRIP2 0V VIN2 Figure 3. Simple Threshold Detector Basic Over/Undervoltage Detection Circuits Figures 3, 4, and 5 show the three basic voltage detection circuits. 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 VSET input is 1.3V. The external resistors form a voltage divider that attenuates the input signal. This ensures that the VSET terminal is at 1.3V when the input voltage is at the desired comparator trip point. Since the bias current of the comparator is only a fraction of a nanoamp, the current in the voltage divider can be less than one microamp without losing accuracy due to bias currents. The ICL7665A has a 2% threshold accuracy at +25°C, and a typical temperature coefficient of 100ppm/°C including comparator offset drift, eliminating the need for external potentiometers in most applications. Figure 4 adds another resistor to each voltage detector. This third resistor supplies current from the HYST output whenever the VSET input is above the 1.3V threshold. As the formulas show, this hysteresis resistor affects only the lower trip point. Hysteresis (defined as VL2 VU2 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. 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. 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 VSET / R11. R11 can typically be in the range of 10kΩ to 10MΩ. 2) Calculate R21 based on R11 and the desired trip point: ( ) ( ) VTRIP – VSET VTRIP – 1.3V R21 = R11 ——————— = R11 —————— VSET 1.3V _______________________________________________________________________________________ 7 ICL7665 Microprocessor Voltage Monitor with Dual Over/Undervoltage Detection Figure 5 1) Select a value for R11, usually between 10kΩ and 10MΩ. 2) Calculate R21: VIN R31 R32 HYST1 V+ ( R22 ICL7665 SET1 SET2 OUT1 OUT2 UNDERVOLTAGE OVERVOLTAGE GND R11 R12 OUT1 VL1 VU1 OUT2 VIN ) ) VU – VL R31 = R11 ————— VSET 4) As in the other circuits, all three resistor values may be scaled up or down in value without changing VU and VL. VU and VL depend only on the ratio of the three resistors, if the absolute values are such that the hysteresis output resistance and the leakage currents of the VSET input and hysteresis output can be ignored. Fault Monitor for a Single Supply Figure 5. Threshold Detector, VIN = V+ Figure 4 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: ) ( ) VU - VSET VU – 1.3V R21 = R11 —————— = R11 ————— VSET 1.3V 3) Calculate R31 for the desired amount of hysteresis: (R21) (V+ – 1.3V) (R21) (V+ – VSET) R31 = ————————— = ————————— VU – VL VU – VL or, if V+ = VIN: (R21) (VL – VSET) (R21) (VL – 1.3V) R31 = ————————— = ————————— VU – VL VU – VL 4) The trip voltages are not affected by the absolute 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 100kΩ to 22MΩ range. Multiplying or dividing all three resistors by the same factor will not affect the trip voltages. 8 ( ( VL – 1.3V = R11 ————— 1.3 __________Applications Information VL2 VU2 ( ) VL – VSET R21 = R11 —————— VSET 3) Calculate R31: HYST2 R21 Figure 6 shows a typical over/undervoltage fault monitor for a single supply. In this case, the upper trip points (controlling OUT1) are centered on 5.5V, with 100mV of hysteresis (VU = 5.55V, VL = 5.45V); and the lower trip points (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. Multiple-Supply Fault Monitor 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 VSET input is at 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 resistors is equal. Note that, since the voltage at the ICL7665 VSET input depends on the voltage of both supplies being monitored, there will be some interaction between the lowvoltage 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. _______________________________________________________________________________________ Microprocessor Voltage Monitor with Dual Over/Undervoltage Detection Nickel cadmium (NiCd) batteries are excellent rechargeable 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 ordinarily 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 battery, 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. Power-Fail Warning and Power-Up/Power-Down Reset Figure 9 illustrates a power-fail warning circuit that monitors raw DC input voltage to the 7805 three-terminal 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 decays at a rate of IOUT / C (in this case, 200mV/ms). Since the 7805 will continue to provide a 5V output at 1A until VIN is less than 7.3V, this circuit will give at least 3.5ms 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. 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 activate a battery-backup system. AC Power-Fail and Brownout Detector By monitoring the secondary of the transformer, the circuit in Figure 10 performs the same power-failure warning function as Figure 9. With a normal 110V AC input to the transformer, OUT1 will discharge C1 every 16.7ms when the peak transformer secondary voltage 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 discharge C1 once the power-fail warning is active. Battery Switchover Circuit The circuit in Figure 11 performs two functions: switching 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 whenever the line-powered +5V supply voltage is greater than 3.5V. The voltage drop across Q1 will only be a couple of hundred millivolts, since it will be saturated. Whenever the input voltage falls below 3.5V, OUT1 goes high, turns off Q1, and connects the 3V lithium cell to the CMOS memory. 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). 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 outside its guaranteed operating range. Simple High/Low Temperature Alarm The circuit in Figure 12 is a simple high/low temperature 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 multiplier 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 coefficient of approximately -5mV/°C. R1 is set so that the voltage at VSET2 equals the VSET2 trip voltage when the temperature of the NPN transistor reaches the level selected for the high-temperature alarm. R2 can be adjusted so that the voltage at VSET1 is 1.3V when the NPN transistor’s temperature reaches the low-temperature limit. _______________________________________________________________________________________ 9 ICL7665 Combination Low-Battery Warning and Low-Battery Disconnect ICL7665 Microprocessor Voltage Monitor with Dual Over/Undervoltage Detection +5V SUPPLY HYST1 324k 13M 5% V+ R21A 274k 100k SET2 OUT1 +15V UNDERVOLTAGE 100k DETECTOR VU ≈ 4.55V VL ≈ 4.45V OUT2 ICL7665 SET2 R21B 1.02M 100k 22M 249k 7.5M 5% ICL7665 V+ HYST1 R31 22M +5V HYST2 SET1 OVERVOLTAGE DETECTOR VU ≈ 5.55V VL ≈ 5.45V +5V HYST2 SET1 OUT2 R11 49.9k 301k OUT1 787k +5V -5V -15V POWER OK POWER OK Figure 6. Fault Monitor for a Single Supply Figure 7. Multiple-Supply Fault Monitor R31 R32 1M V+ V+ HYST1 R21 OUT2 OUT1 HYST2 SENSE R22 ICL7665 SET1 +5V, 1A OUTPUT 100Ω ICL7663 SET SHDN SET2 R11 R12 OUT1 GND OUT2 GND LOW-BATTERY WARNING LOW-BATTERY SHUTDOWN Figure 8. Low-Battery Warning and Low-Battery Disconnect UNREGULATED DC INPUT 4700µF 5V, 1A 5V, 1A OUTPUT 7805 5V REGULATOR 470µF BACK-UP BATTERY 20V CENTER TAPPED TRANS 10VAC 60Hz 7805 5V REGULATOR 4700µF +5V V+ V+ HYST1 HYST1 HYST2 ICL7665 715k SET1 ICL7665 2.2M SET1 SET2 130k 1M OUT1 R1 681k 22M 5.6M OUT2 HYST2 RESET OR WRITE ENABLE R2 1M 100k Q1 SET2 OUT2 OUT1 R3 1M C1 POWER-FAIL WARNING Figure 9. Power-Fail Warning and Power-Up/Power-Down Reset 10 Figure 10. AC Power-Fail and Brownout Detector ______________________________________________________________________________________ POWER-FAIL WARNING Microprocessor Voltage Monitor with Dual Over/Undervoltage Detection ICL7665 VCC TO CMOS MEMORY Q1 LINE-POWERED +5V INPUT 100k 1µF 1k 2N7000 2N4393 1M OUT1 V+ HYST1 HYST2 5.6M 22M ICL7665 2.4M SET1 3V LITHIUM CELL 1.15M 1% SET2 1M GND 1M 1% OUT2 220Ω Figure 11. Battery Switchover Circuit 9V V+ TEMPERATURE SENSOR (GENERAL PURPOSE NPN TRANSISTOR) HYST2 R3 470k R4 22M R6 22M ICL7665 SET2 R1, 1M HIGHTEMPERATURE LIMIT ADJUSTMENT HYST1 SET1 R5 27k OUT2 LOW-TEMPERATURE LIMIT ADJUST OUT1 R7 1.5M R2 1M ALARM SIGNAL FOR DRIVING LEDS, BELLS, ETC. Figure 12. Simple High/Low Temperature Alarm ______________________________________________________________________________________ 11 ICL7665 Microprocessor Voltage Monitor with Dual Over/Undervoltage Detection _______________________SCR Latchup Like all junction-isolated CMOS circuits, the ICL7665 has an inherent four-layer or SCR structure that can be triggered into destructive latchup under certain conditions. Avoid destructive latchup by following these precautions: 1) If either VSET terminal can be driven to a voltage greater than V+ or less than ground, limit the input current to 500µA maximum. Usually, an input voltage divider resistance can be chosen to ensure the input current remains below 500µA, even when the input voltage is applied before the ICL7665 V+ supply is connected. 2) Limit the rate-of-rise of V+ by using a bypass capacitor near the ICL7665. Rate-of-rise SCRs rarely occur unless: a) the battery has 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 linepowered systems, the rate-of-rise is usually limited by other factors and will not cause a rate-of-rise SCR action under normal circumstances. 3) Limit the maximum supply voltage (including transient spikes) to 18V. Likewise, limit the maximum voltage on OUT1 and OUT2 to +18V and the maximum voltage on HYST1 and HYST2 to 18V below V+. ___________________Chip Topography V+ OUT2 0.066" (1.42mm) OUT1 SET2 HYST2 HYST1 SET1 V- 0.084" (1.63mm) TRANSISTOR COUNT: 38 SUBSTRATE CONNECTED TO V+. _Ordering Information (continued) PART ICL7665AC/D TEMP. RANGE 0°C to +70°C PIN-PACKAGE Dice* ICL7665IPA+ -20°C to +85°C 8 Plastic DIP ICL7665IJA+ -20°C to +85°C 8 CERDIP ICL7665EPA+ -40°C to +85°C 8 Plastic DIP ICL7665AEPA+ -40°C to +85°C 8 Plastic DIP ICL7665ESA+ -40°C to +85°C 8 SO ICL7665AESA+ -40°C to +85°C 8 SO *Contact factory for dice specifications. +Denotes a lead(pb)-free/RoHS-compliant package. 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 ____________________Maxim Integrated Products, 160 Rio Robles, San Jose, CA 95134 408-601-1000 © 2015 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.