Datasheet MAX9075, MAX9077 (Maxim) - 6

MAX9075/MAX9077 Low-Cost, Ultra-Small, 3µA Single-Supply Comparators Pin Description PIN MAX9075 MAX9077 NAME FUNCTION SOT23 SC70 µMAX/SO SOT23
1 1 — — OUT Comparator Output — — 1 1 OUTA Output of Comparator A 2 2 4 2 GND Ground 3 3 — — IN+ Noninverting Comparator Input — — 3 4 INA+ Noninverting Input of Comparator A 4 4 — — IN- Inverting Comparator Input — — 2 3 INA- Inverting Input of Comparator A 5 5 8 8 VCC Positive Supply Voltage — — 5 5 INB+ Noninverting Input of Comparator B — — 6 6 INB- Inverting Input of Comparator B — — 7 7 OUTB Output of Comparator B
Detailed Description Applications Information
The MAX9075/MAX9077 feature a 580ns propagation
Adding Hysteresis
delay from an ultra-low supply current of only 3µA per Hysteresis extends the comparator’s noise margin by comparator. These devices are capable of single-sup- increasing the upper threshold and decreasing the ply operation in the 2.1V to 5.5V range. Large internal lower threshold. A voltage divider from the output of the output drivers allow rail-to-rail output swing with up to comparator sets the trip voltage. Therefore, the trip 2mA loads. Both comparators offer a push-pull output voltage is related to the output voltage. Set the hystere- that sinks and sources current. sis with three resistors using positive feedback, as
Comparator Output
shown in Figure 1. The MAX9075/MAX9077 are designed to maintain a The design procedure is as follows: low-supply current during repeated transitions by limit- 1) Choose R3. The leakage current of IN+ may cause a ing the shoot-through current. small error; however, the current through R3 can be
Noise Considerations, Comparator Input
approximately 500nA and still maintain accuracy. The input common-mode voltage range for these The added supply current due to the circuit at the devices extends from 0V to V trip point is VCC/R3; 10MΩ is a good practical value CC - 1.2V. Unlike many other comparators, the MAX9075/MAX9077 can oper- for R3, as this keeps the current well below the sup- ate at any differential input voltage within these limits. ply current of the chip. Input bias current is typically -5nA if the input voltage is 2) Choose the hysteresis voltage (VHYS), which is the between the supply rails. voltage between the upper and lower thresholds. In Although the comparators have a very high gain, useful this example, choose VHYS = 50mV and assume gain is limited by noise. The comparator has a wide- VREF = 1.2V and VCC = 5V. band peak-to-peak noise of approximately 70µV. 3) Calculate R1 as follows: R1 = R3 x VHYS/VCC = 10MΩ x 0.05/5 = 100kΩ 6 Maxim Integrated