MAX9075 Datasheet, PDF (6/8 Pages) Maxim Integrated Products – Low-Cost, Ultra-Small, 3μA Single-Supply Comparators

Low-Cost, Ultra-Small, 3µA
Single-Supply Comparators
PIN
MAX9075
MAX9077
SOT23-5 SC70-5
SO
SOT23-8
1
1
—
—
—
—
1
1
2
2
4
2
3
3
—
—
—
—
3
4
4
4
—
—
—
—
2
3
5
5
8
8
—
—
5
5
—
—
6
6
—
—
7
7
NAME
OUT
OUTA
GND
IN+
INA+
IN-
INA-
VCC
INB+
INB-
OUTB
Pin Description
FUNCTION
Comparator Output
Output of Comparator A
Ground
Noninverting Comparator Input
Noninverting Input of Comparator A
Inverting Comparator Input
Inverting Input of Comparator A
Positive Supply Voltage
Noninverting Input of Comparator B
Inverting Input of Comparator B
Output of Comparator B
Detailed Description
The MAX9075/MAX9077 feature a 580ns propagation
delay from an ultra-low supply current of only 3µA per
comparator. These devices are capable of single-sup-
ply operation in the +2.1V to +5.5V range. Large inter-
nal output drivers allow rail-to-rail output swing with up
to 2mA loads. Both comparators offer a push-pull out-
put that sinks and sources current.
Comparator Output
The MAX9075/MAX9077 are designed to maintain a
low supply current during repeated transitions by limit-
ing the shoot-through current.
Noise Considerations, Comparator Input
The input common-mode voltage range for these
devices extends from -0.2V to VCC - 1.2V. Unlike many
other comparators, the MAX9075/MAX9077 can oper-
ate at any differential input voltage within these limits.
Input bias current is typically -5nA if the input voltage is
between the supply rails.
Although the comparators have a very high gain, useful
gain is limited by noise. The comparator has a wide-
band peak-to-peak noise of approximately 70µV.
Applications Information
Adding Hysteresis
Hysteresis extends the comparator’s noise margin by
increasing the upper threshold and decreasing the
lower threshold. A voltage divider from the output of the
comparator sets the trip voltage. Therefore, the trip
voltage is related to the output voltage. Set the hystere-
sis with three resistors using positive feedback, as
shown in Figure 1.
The design procedure is as follows:
1) Choose R3. The leakage current of IN+ may cause a
small error; however, the current through R3 can be
approximately 500nA and still maintain accuracy.
The added supply current due to the circuit at the
trip point is VCC/R3; 10MΩ is a good practical value
for R3, as this keeps the current well below the sup-
ply current of the chip.
2) Choose the hysteresis voltage (VHYS), which is the
voltage between the upper and lower thresholds. In
this example, choose VHYS = 50mV and assume
VREF = 1.2V and VCC = 5V.
3) Calculate R1 as follows:
R1 = R3 · VHYS / VCC = 10MΩ · 0.05 / 5 = 100kΩ
6 _______________________________________________________________________________________