19-0194; Rev 1; 2/97 Ultra Low-Power, Low-Cost Comparators with 2% Reference ____________________________Features ♦ Ultra-Low 4µA Max Quiescent Current Over Extended Temp. Range (MAX931) Ideal for 3V or 5V single-supply applications, the MAX931-MAX934 operate from a single +2.5V to +11V supply (or a ±1.25V to ±5V dual supply), and each comparator’s input voltage range extends from the negative supply rail to within 1.3V of the positive supply. ♦ Internal 1.182V ±2% Bandgap Reference The MAX931-MAX934’s unique output stage continuously sources as much as 40mA. And by eliminating powersupply glitches that commonly occur when comparators change logic states, the MAX931-MAX934 minimize parasitic feedback, which makes them easier to use. ♦ No Switching Crowbar Current ♦ Power Supplies: Single +2.5V to +11V Dual ±1.25V to ±5.5V ♦ Input Voltage Range Includes Negative Supply ♦ Adjustable Hysteresis ♦ TTL-/CMOS-Compatible Outputs ♦ 12µs Propagation Delay (10mV Overdrive) ♦ 40mA Continuous Source Current ♦ Available in Space-Saving µMAX Package The single MAX931 and dual MAX932/MAX933 provide a unique and simple method for adding hysteresis without feedback and complicated equations, using the HYST pin and two resistors. ______________Ordering Information MAX931CPA 0°C to +70°C 8 Plastic DIP For applications that require increased precision with similar power requirements, see the MAX921-MAX924 data sheet. These devices include a 1% precision reference. MAX931CSA MAX931CUA MAX931EPA MAX931ESA 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C 8 SO 8 µMAX 8 Plastic DIP 8 SO INTERNAL COMPARATORS INTERNAL 2% PER HYSTERESIS REFERENCE PACKAGE PART PACKAGE MAX931 Yes 1 Yes 8-Pin DIP/SO/ µMAX MAX932 Yes 2 Yes 8-Pin DIP/SO/ µMAX MAX933 Yes 2 Yes 8-Pin DIP/SO/ µMAX MAX934 Yes 4 No 16-Pin DIP/SO PART TEMP. RANGE PIN-PACKAGE Ordering Information continued on last page. For similar devices guaranteed over the military temp. range, see the MAX921-MAX924 data sheet. The MAX931, MAX933, and MAX934 are pin-compatible with the 1% accurate MAX921, MAX923, and MAX924, respectively. The MAX932 and MAX922 are not pin-compatible. __________Typical Operating Circuit VIN 7 V+ 3 IN+ OUT 8 4 IN- ________________________Applications Battery-Powered Systems Threshold Detectors 5 HYST 6 REF MAX931 Window Comparators Oscillator Circuits Alarm Circuits V2 GND 1 THRESHOLD DETECTOR ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800 MAX931-MAX934 _______________General Description The MAX931-MAX934 single, dual, and quad micropower, low-voltage comparators plus an on-board 2% accurate reference feature the lowest power consumption available. These comparators draw less than 4µA supply current over temperature (MAX931), and include an internal 1.182V ±2% voltage reference, programmable hysteresis, and TTL/CMOS outputs that sink and source current. MAX931-MAX934 Ultra Low-Power, Low-Cost Comparators with 2% Reference ABSOLUTE MAXIMUM RATINGS V+ to V-, V+ to GND, GND to V-................................-0.3V, +12V Inputs Current, IN_+, IN_-, HYST...............................................20mA Voltage, IN_+, IN_-, HYST................(V+ + 0.3V) to (V- – 0.3V) Outputs Current, REF....................................................................20mA Current, OUT_ .................................................................50mA Voltage, REF ....................................(V+ + 0.3V) to (V- – 0.3V) Voltage, OUT_ (MAX931/934) .....(V+ + 0.3V) to (GND – 0.3V) Voltage, OUT_ (MAX932/933)..........(V+ + 0.3V) to (V- – 0.3V) OUT_ Short-Circuit Duration (V+ ≤ 5.5V) ...............Continuous Continuous Power Dissipation (TA = +70°C) 8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) ...727mW 8-Pin SO (derate 5.88mW/°C above +70°C)................471mW 8-Pin µMAX (derate 4.1mW/°C above +70°C) .............330mW 16-Pin Plastic DIP (derate 10.53mW/°C above +70°C)..842mW 16-Pin SO (derate 8.70mW/°C above +70°C) ................696mW Operating Temperature Ranges: MAX93_C_ _ .......................................................0°C to +70°C MAX93_E_ _.....................................................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10sec) .............................+300°C 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—5V Operation (V+ = 5V, V- = GND = 0V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS 11 V POWER REQUIREMENTS Supply Voltage Range (Note 1) 2.5 MAX931, HYST = REF MAX932, HYST = REF Supply Current TA = +25°C 2.5 C/E temp. ranges 3.2 4 TA = +25°C 3.1 C/E temp. ranges 4.5 6 IN+ = IN- + 100mV µA MAX933, HYST = REF TA = +25°C 3.1 C/E temp. ranges 4.5 6 TA = +25°C 5.5 6.5 MAX934 C/E temp. ranges 8.5 COMPARATOR Input Offset Voltage VCM = 2.5V Input Leakage Current (IN-, IN+) IN+ = IN- = 2.5V, C/E temp. ranges ±0.01 Input Leakage Current (HYST) Input Common-Mode Voltage Range Common-Mode Rejection Ratio Power-Supply Rejection Ratio Voltage Noise Hysteresis Input Voltage Range MAX931, MAX932, MAX933 ±0.02 Response Time 2 VV- to (V+ – 1.3V) V+ = 2.5V to 11V 100Hz to 100kHz MAX931, MAX932, MAX933 TA = +25°C, 100pF load 0.1 0.1 20 REF – 0.05 Overdrive = 10mV Overdrive = 100mV ±10 mV ±5 nA V+ – 1.3 1.0 1.0 REF 12 4 _______________________________________________________________________________________ nA V mV/V mV/V µVRMS V µs Ultra Low-Power, Low-Cost Comparators with 2% Reference MAX931-MAX934 ELECTRICAL CHARACTERISTICS—5V Operation (continued) (V+ = 5V, V- = GND = 0V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER CONDITIONS Output High Voltage C/E temp. ranges, IOUT = 17mA Output Low Voltage C/E temp. ranges, IOUT = 1.8mA MIN TYP MAX V+ – 0.4 UNITS V MAX932, MAX933 V- + 0.4 MAX931, MAX934 GND + 0.4 V REFERENCE X C temp. range 1.158 E temp. range 1.147 1.182 1.206 Reference Voltage V TA = +25°C 15 C/E temp. ranges 6 TA = +25°C 8 C/E temp. ranges 4 1.217 25 Source Current µA 15 Sink Current µA Voltage Noise 100Hz to 100kHz 100 µVRMS Note 1: MAX934 comparators work below 2.5V, see Low-Voltage Operation section for more details. ELECTRICAL CHARACTERISTICS—3V Operation (V+ = 3V, V- = GND = 0V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX 2.4 3.0 UNITS POWER REQUIREMENTS MAX931, HYST = REF MAX932, HYST = REF Supply Current TA = +25°C C/E temp. ranges TA = +25°C 3.8 3.4 C/E temp. ranges 4.3 5.8 IN+ = (IN- + 100mV) µA MAX933, HYST = REF TA = +25°C 3.4 C/E temp. ranges TA = +25°C 4.3 5.8 5.2 6.2 MAX934 C/E temp. ranges COMPARATOR Input Offset Voltage Input Leakage Current (IN-, IN+) Input Leakage Current (HYST) VCM = 1.5V IN+ = IN- = 1.5V, C/E temp. ranges MAX931, MAX932, MAX933 8.0 ±0.01 ±0.02 ±10 ±1 mV nA nA _______________________________________________________________________________________ 3 MAX931-MAX934 Ultra Low-Power, Low-Cost Comparators with 2% Reference ELECTRICAL CHARACTERISTICS—3V Operation (continued) (V+ = 3V, V- = GND = 0V, TA = TMIN to TMAX, unless otherwise noted.) CONDITIONS PARAMETER MIN Input Common-Mode Voltage Range TYP MAX V- V+ – 1.3 Common-Mode Rejection Ratio V- to (V+ – 1.3V) 0.2 1 Power-Supply Rejection Ratio V+ = 2.5V to 11V 0.1 1 Voltage Noise 100Hz to 100kHz 20 Hysteresis Input Voltage Range MAX931, MAX932, MAX933 Response Time TA = +25°C, 100pF load Output High Voltage C/E temp. ranges, IOUT = 10mA Output Low Voltage C/E temp. ranges, IOUT = 0.8mA V mV/V mV/V µVRMS REF – 0.05 Overdrive = 10mV Overdrive = 100mV UNITS REF 14 5 V µs V+ – 0.4 V MAX932, MAX933 V- + 0.4 MAX931 GND + 0.4 V REFERENCE C temp. range 1.158 E temp. range 1.147 1.182 1.206 Reference Voltage V TA = +25°C 15 C/E temp. ranges 6 TA = +25°C 8 C/E temp. ranges 4 1.217 25 Source Current µA 15 Sink Current Voltage Noise 4 µA 100Hz to 100kHz 100 _______________________________________________________________________________________ µVRMS Ultra Low-Power, Low-Cost Comparators with 2% Reference 4.5 4.0 VOH (V) 1.5 1.0 3.5 3.0 2.5 V+ = 3V 0.5 2.0 0.0 12 16 20 0 10 LOAD CURRENT (mA) 30 40 1.165 V+ = 5V OR V+ = 3V 1.160 0 50 MAX921/924-TOC4 EXTENDED TEMP. RANGE COMMERCIAL TEMP. RANGE 1.18 1.17 1.16 IN+ = IN- + 100mV 4.0 IN+ = IN- +100mV 4.5 3.0 V+ = 3V, V- = 0V 2.5 V+ = 5V, V- = 0V 3.5 3.0 2.5 V+ = 3V, V- = 0V 2.0 2.0 -60 -20 MAX933 SUPPLY CURRENT vs. TEMPERATURE SUPPLY CURRENT (µA) 4.5 4.0 V+ = 5V, V- = 0V 3.5 3.0 2.5 60 100 140 -20 20 100 60 TEMPERATURE (°C) MAX934 SUPPLY CURRENT vs. TEMPERATURE MAX934 SUPPLY CURRENT vs. LOW SUPPLY VOLTAGES 10 IN+ = (IN- + 100mV) 9 8 7 -60 V+ = 5V, V- = -5V 6 V+ = 5V, V- = 0V 5 4 10 MAX921/924-TOC8 MAX921/924-TOC7 IN+ = IN- +100mV SUPPLY CURRENT (µA) 5.0 20 TEMPERATURE (°C) TEMPERATURE (°C) IN+ = IN- +100mV SUPPLY CURRENT (µA) 20 40 60 80 100 120 140 30 4.0 V+ = 5V, V- = 0V -60 -40 -20 0 25 20 5.0 1.15 1.14 15 10 MAX932 SUPPLY CURRENT vs. TEMPERATURE V+ = 5V, V- = - 5V 3.5 5 OUTPUT LOAD CURRENT (µA) 4.5 SUPPLY CURRENT (µA) 1.21 REFERENCE VOLTAGE (V) 1.170 MAX931 SUPPLY CURRENT vs. TEMPERATURE 1.22 1.19 SOURCE 1.175 LOAD CURRENT (mA) REFERENCE VOLTAGE vs. TEMPERATURE 1.20 20 MAX921/924-TOC5 8 SUPPLY CURRENT (µA) 4 1.180 1.155 1.5 0 SINK 1.185 MAX921/924-TOC6 V+ = 3V VOL (V) 1.190 140 MAX921/924-TOC9 2.0 V+ = 5V REFERENCE OUTPUT VOLTAGE (V) V+ = 5V MAX921/924-TOC2 5.0 MAX921/4-TOC1 2.5 REFERENCE OUTPUT VOLTAGE vs. OUTPUT LOAD CURRENT OUTPUT VOLTAGE HIGH vs. LOAD CURRENT MAX921/924-TOC3 OUTPUT VOLTAGE LOW vs. LOAD CURRENT 1 0.1 V+ = 3V, V- = 0V V+ = 3V, V- = 0V 3 2.0 -60 -20 20 60 TEMPERATURE (°C) 100 140 0.01 -60 -20 20 60 TEMPERATURE (°C) 100 140 1.0 1.5 2.0 2.5 SINGLE-SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 5 MAX931-MAX934 __________________________________________Typical Operating Characteristics (V+ = 5V, V- = GND, TA = +25°C, unless otherwise noted.) ____________________________Typical Operating Characteristics (continued) (V+ = 5V, V- = GND, TA = +25°C, unless otherwise noted.) HYSTERESIS CONTROL -20 -40 2.5 2.0 1.5 10 20 30 40 50 RESPONSE TIME FOR VARIOUS INPUT OVERDRIVES 2 50mV 1 10mV 0 0 -2 2 6 10 14 18 RESPONSE TIME (µs) 10mV 100mV 2 20mV 1 50mV 100 1 80 100 1 ±20mV OVERDRIVE 0.1 ±100mV OVERDRIVE 0.01 -2 2 6 10 14 18 1.0 2.0 1.5 RESPONSE TIME (µs) SINGLE-SUPPLY VOLTAGE (V) SHORT-CIRCUIT SOURCE CURRENT vs. SUPPLY VOLTAGE SHORT-CIRCUIT SINK CURRENT vs. SUPPLY VOLTAGE 200 OUT CONNECTED TO V- 160 OUT CONNECTED TO V+ GND CONNECTED TO VSINK CURRENT (mA) MAX921/924-TOC16 10 60 40 10 0 180 SOURCE CURRENT (mA) SOURCE CURRENT INTO 0.75V LOAD 20 MAX934 RESPONSE TIME AT LOW SUPPLY VOLTAGES MAX921/924-TOC14 4 3 MAX934 OUTPUT DRIVE AT LOW SUPPLY VOLTAGES 100 VOLH 6 LOAD CAPACITANCE (nF) 5 0 100 8 0 RESPONSE TIME (ms) 20mV 10 0.3 MAX121/124-TOC17 MAX921/924-TOC13 RESPONSE TIME FOR VARIOUS INPUT OVERDRIVES OUTPUT VOLTAGE (V) VREF -VHYST (mV) 100mV VOHL 12 2 -0.3 INPUT VOLTAGE (mV) 4 3 14 4 0.1 0.2 -0.2 -0.1 0 IN+ INPUT VOLTAGE (mV) 5 MAX921/924 TOC12 MAX921/924-TOC11 3.0 0 0 OUTPUT VOLTAGE (V) 3.5 0.5 -80 INPUT VOLTAGE (mV) 16 1.0 OUTPUT LOW -60 V0 10µF MAX921/924-TOC15 NO CHANGE 18 140 120 100 80 60 20 2.5 MAX121/124-TOC18 20 100k 4.0 OUTPUT VOLTAGE (V) 40 4.5 RESPONSE TIME (µs) OUTPUT HIGH IN+ – IN- (V) 5.0 MAX921/924 TOC10 60 0 RESPONSE TIME vs. LOAD CAPACITANCE TRANSFER FUNCTION 80 CURRENT (mA) MAX931-MAX934 Ultra Low-Power, Low-Cost Comparators with 2% Reference 10 40 20 SINK CURRENT AT VOUT = 0.4V 0 0.1 1.0 1.5 2.0 SINGLE-SUPPLY VOLTAGE (V) 6 2.5 0 0 1.0 2.0 3.0 4.0 TOTAL SUPPLY VOLTAGE (V) 5.0 0 5 TOTAL SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 10 Ultra Low-Power, Low-Cost Comparators with 2% Reference PIN NAME MAX931 MAX932 MAX933 1 – – GND – 1 1 OUTA 2 2 2 V- FUNCTION Ground. Connect to V- for single-supply operation. Output swings from V+ to GND. Comparator A output. Sinks and sources current. Swings from V+ to V-. Negative supply. Connect to ground for single-supply operation (MAX931). 3 – – IN+ – 3 3 INA+ 4 – – IN- – 4 – INB+ Noninverting input of comparator B – – 4 INB- Inverting input of comparator B 5 5 5 HYST Hysteresis input. Connect to REF if not used. Input voltage range is from VREF to VREF - 50mV. 6 6 6 REF Reference output. 1.182V with respect to V-. 7 7 7 V+ Positive supply 8 – – OUT Comparator output. Sinks and sources current. Swings from V+ to GND. – 8 8 OUTB Comparator B output. Sinks and sources current. Swings from V+ to V-. PIN MAX934 Noninverting comparator input Noninverting input of comparator A Inverting comparator input NAME FUNCTION 1 OUTB Comparator B output. Sinks and sources current. Swings from V+ to GND. 2 OUTA Comparator A output. Sinks and sources current. Swings from V+ to GND. 3 V+ 4 INA- Inverting input of comparator A 5 INA+ Noninverting input of comparator A 6 INB- Inverting input of comparator B 7 INB+ Noninverting input of comparator B 8 REF Reference output. 1.182V with respect to V-. 9 V- 10 INC- Inverting input of comparator C 11 INC+ Noninverting input of comparator C 12 IND- Inverting input of comparator D 13 IND+ Noninverting input of comparator D 14 GND Ground. Connect to V- for single-supply operation. 15 OUTD Comparator D output. Sinks and sources current. Swings from V+ to GND. 16 OUTC Comparator C output. Sinks and sources current. Swings from V+ to GND. Positive supply Negative supply. Connect to ground for single-supply operation. _______________________________________________________________________________________ 7 MAX931-MAX934 ____________________________________________________________Pin Descriptions MAX931-MAX934 Ultra Low-Power, Low-Cost Comparators with 2% Reference _______________Detailed Description The MAX931-MAX934 comprise various combinations of a micropower 1.182V reference and a micropower comparator. The Typical Operating Circuit shows the MAX931 configuration, and Figures 1a-1c show the MAX932/MAX933/MAX934 configurations. Each comparator continuously sources up to 40mA, and the unique output stage eliminates crowbar glitches during output transitions. This makes them immune to parasitic feedback (which can cause instability) and provides excellent performance, even when circuitboard layout is not optimal. Internal hysteresis in the MAX931/MAX932/MAX933 provides the easiest method for implementing hysteresis. It also produces faster hysteresis action and consumes much less current than circuits using external positive feedback. Power-Supply and Input Signal Ranges This family of devices operates from a single +2.5V to +11V power supply. The MAX931 and MAX934 have 1 OUTA 2 MAX932 OUTB a separate ground for the output driver, allowing operation with dual supplies ranging from ±1.25V to ±5.5V. Connect V- to GND when operating the MAX931 and the MAX934 from a single supply. The maximum supply voltage in this case is still 11V. For proper comparator operation, the input signal can be driven from the negative supply (V-) to within one volt of the positive supply (V+ - 1V). The guaranteed common-mode input voltage range extends from V- to (V+ - 1.3V). The inputs can be taken above and below the supply rails by up to 300mV without damage. Operating the MAX931 and MAX934 at ±5V provides TTL/CMOS compatibility when monitoring bipolar input signals. TTL compatibility for the MAX932 and MAX933 is achieved by operation from a single +5V supply. Low-Voltage Operation: V+ = 1V (MAX934 Only) The guaranteed minimum operating voltage is 2.5V (or ±1.25V). As the total supply voltage is reduced below 2.5V, the performance degrades and the supply 8 MAX934 V+ 7 V- 1 REF 3 INA+ 6 2 4 HYST INB+ 5 3 OUTB OUTC OUTA OUTD V+ V4 Figure 1a. MAX932 Functional Diagram 5 1 OUTA 2 MAX933 OUTB REF INB- HYST IND- INB+ INC- REF V- 6 5 V- Figure 1b. MAX933 Functional Diagram 8 13 12 C INC+ 8 4 INA+ 6 INB7 3 INA+ IND+ B 15 GND 14 INA- 8 V+ 7 V- D A 16 Figure 1c. MAX934 Functional Diagram _______________________________________________________________________________________ 11 10 9 Ultra Low-Power, Low-Cost Comparators with 2% Reference As the input voltage approaches the comparator's offset, the output begins to bounce back and forth; this peaks when VIN = VOS. (The lowpass filter shown on the graph averages out the bouncing, making the transfer function easy to observe.) Consequently, the comparator has an effective wideband peak-to-peak noise of around 0.3mV. The voltage reference has peak-to peak noise approaching 1mV. Thus, when a comparator is used with the reference, the combined peak-to-peak noise is about 1mV. This, of course, is much higher than the RMS noise of the individual components. Care should be taken in the layout to avoid capacitive coupling from any output to the reference pin. Crosstalk can significantly increase the actual noise of the reference. __________Applications Information Comparator Output With 100mV of overdrive, propagation delay is typically 3µs. The Typical Operating Characteristics show the propagation delay for various overdrive levels. The MAX931 and MAX934 output swings from V+ to GND, so TTL compatibility is assured by using a +5V ±10% supply. The negative supply does not affect the output swing, and can range from 0V to -5V ±10%. The MAX932 and MAX933 do not have a GND pin, and their outputs swing from V+ to V-. Connect V- to ground and V+ to a +5V supply to achieve TTL compatibility. The MAX931-MAX934’s unique design achieves an output source current of more than 40mA and a sink current of over 5mA, while keeping quiescent currents in the microampere range. The output can source 100mA (at V+ = 5V) for short pulses, as long as the package's maximum power dissipation is not exceeded. The output stage does not generate crowbar switching currents during transitions, which minimizes feedback through the supplies and helps ensure stability without bypassing. Hysteresis Hysteresis increases the comparators’ noise margin by increasing the upper threshold and decreasing the lower threshold (see Figure 2). Hysteresis (MAX931/MAX932/MAX933) To add hysteresis to the MAX931/MAX932/MAX933, connect resistor R1 between REF and HYST, and connect resistor R2 between HYST and V- (Figure 3). If no hysteresis is required, connect HYST to REF. When hysteresis is added, the upper threshold increases by the same amount that the lower threshold decreases. The hysteresis band (the difference between the upper and lower thresholds, VHB) is approximately equal to twice the voltage between REF and HYST. The HYST input can be adjusted to a maximum voltage of REF and to a minimum voltage of (REF - 50mV). The THRESHOLDS IN+ Voltage Reference The internal bandgap voltage reference has an output of 1.182V above V-. Note that the REF voltage is referenced to V-, not to GND. Its accuracy is ±2% in the range 0°C to +70°C. The REF output is typically capable of sourcing 15µA and sinking 8µA. Do not bypass the REF output. For applications that require a 1% precision reference, see the MAX921-MAX924 data sheet. INVREF - VHYST HYSTERESIS VHB BAND OUT Noise Considerations Although the comparators have a very high gain, useful gain is limited by noise. This is shown in the Transfer Function graph (see Typical Operating Characteristics). Figure 2. Threshold Hysteresis Band _______________________________________________________________________________________ 9 MAX931-MAX934 current falls. The reference will not function below about 2.2V, although the comparators will continue to operate with a total supply voltage as low as 1V. While the MAX934 has comparators that may be used at supply voltages below 2V, the MAX931, MAX932, and MAX933 may not be used with supply voltages significantly below 2.5V. At low supply voltages, the comparators’ output drive is reduced and the propagation delay increases (see Typical Operating Characteristics ). The useful input voltage range extends from the negative supply to a little under 1V below the positive supply, which is slightly closer to the positive rail than the device operating from higher supply voltages. Test your prototype over the full temperature and supply-voltage range if operation below 2.5V is anticipated. MAX931-MAX934 Ultra Low-Power, Low-Cost Comparators with 2% Reference maximum difference between REF and HYST (50mV) will therefore produce a 100mV max hysteresis band. Use the following equations to determine R1 and R2: VHB R1 = × 2 ( IREF ) VHB 1.182 – 2 R2 = IREF Where I REF (the current sourced by the reference) should not exceed the REF source capability, and should be significantly larger than the HYST input current. I REF values between 0.1µA and 4µA are usually appropriate. If 2.4MΩ is chosen for R2 (IREF = 0.5µA), the equation for R1 and VHB can be approximated as: R1 (kΩ) = VHB (mV) When hysteresis is obtained in this manner for the MAX932/MAX933, the same hysteresis applies to both comparators. Hysteresis (MAX934) Hysteresis can be set with two resistors using positive feedback, as shown in Figure 4. This circuit generally draws more current than the circuits using the HYST pin on the MAX931/MAX932/MAX933, and the high feedback impedance slows hysteresis. The design procedure is as follows: 1. Choose R3. The leakage current of IN+ is under 1nA (up to +85°C), so the current through R3 can be around 100nA and still maintain good accuracy. The current through R3 at the trip point is VREF/R3, or 100nA for R3 = 11.8MΩ. 10MΩ is a good practical value. 2. Choose the hysteresis voltage (V HB), the voltage between the upper and lower thresholds. In this example, choose VHB = 50mV. 3. Calculate R1. V R1 = R3 × HB V+ 0.05 = 10M × 5 = 100kΩ 4. Choose the threshold voltage for VIN rising (VTHR). In this example, choose VTHR = 3V. 5. Calculate R2. 1 R2 = 1 VTHR 1 − − (VREF × R1) R1 R3 1 = 3 1 1 − − (1.182 × 100k) 100k 10M = 65.44kΩ A 1% preferred value is 64.9kΩ. 6. Verify the threshold voltages with these formulas: VIN rising : 1 1 1 + + VTHR = VREF × R1 × R1 R2 R3 VIN falling : VTHF = VTHR − (R1 × V +) R3 2.5V TO 11V IREF 5 REF R1 MAX931 MAX932 MAX933 V+ R2 MAX934 VGND HYST V- VREF 2 Figure 3. Programming the HYST Pin 10 R3 V+ VIN R1 R2 V+ 7 6 Figure 4. External Hysteresis ______________________________________________________________________________________ OUT Ultra Low-Power, Low-Cost Comparators with 2% Reference _______________Typical Applications Auto-Off Power Source Figure 5 shows the schematic for a 40mA power supply that has a timed auto power-off function. The comparator output is the switched power-supply output. With a 10mA load, it typically provides a voltage of (VBATT - 0.12V), but draws only 3.5µA quiescent current. This circuit takes advantage of the four key features of the MAX931: 2.5µA supply current, an internal reference, hysteresis, and high current output. Using the component values shown, the three-resistor voltage divider programs the maximum ±50mV of hysteresis and sets the IN- voltage at 100mV. This gives an IN+ trip threshold of approximately 50mV for IN+ falling. The RC time constant determines the maximum poweron time of the OUT pin before power-down occurs. This period can be approximated by: R x C x 4.6sec For example: 2MΩ x 10µF x 4.6 = 92sec. The actual time will vary with both the leakage current of the capacitor and the voltage applied to the circuit. Window Detector The MAX933 is ideal for making window detectors (undervoltage/overvoltage detectors). The schematic is shown in Figure 6, with component values selected for an 4.5V undervoltage threshold, and a 5.5V overvoltage threshold. Choose different thresholds by changing the values of R1, R2, and R3. To prevent chatter at the output when the supply voltage is close to a threshold, hysteresis has been added using R4 and R5. OUTA provides an active-low undervoltage indication, and OUTB gives an active-low overvoltage indication. ANDing the two outputs provides an activehigh, power-good signal. The design procedure is as follows: 1. Choose the required hysteresis level and calculate values for R4 and R5 according to the formulas in the Hysteresis (MAX931/MAX932/MAX933) section. In this example, ±5mV of hysteresis has been added at the comparator input (VH = VHB/2). This means that the hysteresis apparent at V IN will be larger because of the input resistor divider. 2. Select R1. The leakage current into INB- is normally under 1nA, so the current through R1 should exceed MOMENTARY SWITCH VIN 4.5V TO 6.0V 7 V+ +5V VOTH = 5.5V VUTH = 4.5V R3 V+ INA+ 6 MAX931 IN+ REF OUTA 3 47k 5 R2 HYST OUT 1.1M 4 HYST R C IN- POWER GOOD R5 10k 8 V2 REF OUTB VBATT -0.15V 10mA 100k UNDERVOLTAGE OVERVOLTAGE INB- GND 1 Figure 5. Auto-off power switch operates on 2.5µA quiescent current. R1 R4 2.4M V- MAX933 Figure 6. Window Detector ______________________________________________________________________________________ 11 MAX931-MAX934 Board Layout and Bypassing Power-supply bypass capacitors are not needed if the supply impedance is low, but 100nF bypass capacitors should be used when the supply impedance is high or when the supply leads are long. Minimize signal lead lengths to reduce stray capacitance between the input and output that might cause instability. Do not bypass the reference output. MAX931-MAX934 Ultra Low-Power, Low-Cost Comparators with 2% Reference 100nA for the thresholds to be accurate. R1 values up to about 10MΩ can be used, but values in the 100kΩ to 1MΩ range are usually easier to deal with. In this example, choose R1 = 294kΩ. 3. Calculate R2 + R3. The overvoltage threshold should be 5.5V when V IN is rising. The design equation is as follows: VOTH R2 + R3 = R1 × − 1 VREF + VH 5.5 = 294k × − 1 (1.182 + 0.005) = 1.068MΩ 4. Calculate R2. The undervoltage threshold should be 4.5V when VIN is falling. The design equation is as follows: The full-scale threshold (all LEDs on) is given by VIN = (R1 + R2)/R1 volts. The other thresholds are at 3/4 full scale, 1/2 full scale, and 1/4 full scale. The output resistors limit the current into the LEDs. Level Shifter Figure 8 shows a circuit to shift from bipolar ±5V inputs to TTL signals. The 10kΩ resistors protect the comparator inputs, and do not materially affect the operation of the circuit. Two-Stage Low-Voltage Detector Figure 9 shows the MAX932 monitoring an input voltage in two steps. When VIN is higher than the LOW and FAIL thresholds, outputs are high. Threshold calculations are similar to those for the windowdetector application. (VREF − VH ) − R1 VUTH (1.182 − 0.005) = (294k + 1.068M) × − 294k 4.5 = 62.2kΩ Choose R2 = 61.9kΩ (1% standard value). 5. Calculate R3. R3 = (R2 + R3) − R2 = 1.068M − 61.9k V IN +5V 3 V+ 1.182V 182k 5 1V 250k Bar-Graph Level Gauge 12 INA+ 9 2 4 INA- 7 INB+ 330Ω 1 OUTB 750mV 250k 6 INB- 11 INC+ 330Ω 16 OUTC 500mV 250k 10 INC- 13 IND+ 330Ω OUTD 250mV 250k The high output source capability of the MAX931 series is useful for driving LEDs. An example of this is the simple four-stage level detector shown in Figure 7. REF OUTA Undervoltage threshold : (R1 + R2 + R3) VUTH = (VREF − VH ) × (R1 + R2) = 4.484V, R5 . where the hysteresis voltage VH = VREF × R4 MAX934 8 V- = 1.006MΩ Choose R3 = 1MΩ (1% standard value). 6. Verify the resistor values. The equations are as follows, evaluated for the above example. Overvoltage threshold : (R1 + R2 + R3) VOTH = (VREF + VH ) × R1 = 5.474V. R2 R1 R2 = (R1 + R2 + R3) × 15 12 IND- 330Ω GND 14 Figure 7. Bar-Graph Level Gauge ______________________________________________________________________________________ Ultra Low-Power, Low-Cost Comparators with 2% Reference MAX931-MAX934 +5V V+ 10k VINA MAX934 INA+ OUTA VIN 0 FOR VINA < 0V 1 FOR VINB > 0V +5V R3 INA- V+ INA+ 10k VINB INPUT VOLTAGE FAIL REF INB+ R2 OUTB R5 HYST INB- R4 10k VINC INC+ INPUT VOLTAGE LOW INB+ OUTC INCR1 MAX932 V- 10k VIND IND+ OUTD INDREF GND N.C. V- -5V Figure 8. Level Shifter: ±5V Input to CMOS Output Figure 9. Two-Stage Low-Voltage Detector ______________________________________________________________________________________ 13 MAX931-MAX934 Ultra Low-Power, Low-Cost Comparators with 2% Reference _________________Pin Configurations _Ordering Information (continued) PART TOP VIEW GND 1 V- 2 IN+ 3 MAX931 IN- 4 V+ 6 REF 5 HYST MAX933CSA MAX933CUA MAX933EPA MAX933ESA MAX934CPE 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C 0°C to +70°C 8 SO 8 µMAX 8 Plastic DIP 8 SO 16 Plastic DIP MAX934CSE MAX934EPE MAX934ESE 0°C to +70°C -40°C to +85°C -40°C to +85°C 16 Narrow SO 16 Plastic DIP 16 Narrow SO OUTB V- 2 7 V+ 6 REF 5 HYST DIP/SO/µMAX OUTA 1 8 OUTB V- 2 7 V+ 6 REF 5 HYST MAX933 INB- 4 8 SO 8 µMAX 8 Plastic DIP 8 SO 8 Plastic DIP 7 8 INA+ 3 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C 0°C to +70°C MAX932CSA MAX932CUA MAX932EPA MAX932ESA MAX933CPA 1 INB+ 4 8 Plastic DIP OUT OUTA MAX932 For similar devices guaranteed over the military temp. range, see the MAX921-MAX924 data sheet. The MAX931, MAX933, and MAX934 are pin-compatible with the 1% accurate MAX921, MAX923, and MAX924, respectively. The MAX932 and MAX922 are not pin-compatible. DIP/SO/µMAX OUTB 1 16 OUTC OUTA 2 15 OUTD V+ 3 INA- 4 14 GND MAX934 13 IND+ INA+ 5 12 IND- INB- 6 11 INC+ INB+ 7 10 INC- REF 8 9 V- DIP/Narrow SO 14 PIN-PACKAGE 0°C to +70°C 8 DIP/SO/µMAX INA+ 3 TEMP. RANGE MAX932CPA ______________________________________________________________________________________ Ultra Low-Power, Low-Cost Comparators with 2% Reference PDIPN.EPS SOICN.EPS ______________________________________________________________________________________ 15 MAX931-MAX934 ________________________________________________________Package Information __________________________________________Package Information (continued) 8LUMAXD.EPS MAX931-MAX934 Ultra Low-Power, Low-Cost Comparators with 2% Reference 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. 16 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.