Datasheet

MAX9021/MAX9022/MAX9024
Micropower, Ultra-Small, Single/Dual/Quad,
Single-Supply Comparators
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Detailed Description
The MAX9021/MAX9022/MAX9024 are single/dual/
quad, low-cost, low-power comparators that consume
only 2.8µA and provide a propagation delay, t
PD
, typi-
cally 3µs. They have an operating-supply voltage from
2.5V to 5.5V when operating from a single supply and
from ±1.25V to ±2.75V when operating from dual power
supplies. Their common-mode input voltage range
extends from the negative supply to within 1.1V of the
positive supply. Internal hysteresis ensures clean out-
put switching, even with slow-moving input signals.
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 compara-
tor’s output sets the trip voltage. Therefore, the trip volt-
age is related to the output voltage.
These comparators have 4mV internal hysteresis.
Additional hysteresis can be generated with two resis-
tors, using positive feedback (Figure 1). Use the follow-
ing procedure to calculate resistor values:
1) Find the trip points of the comparator using these for-
mulas:
V
TH
= V
REF
+ ((V
DD
- V
REF
)R2) / (R1 + R2)
V
TL
= V
REF
(1 - (R2 / (R1 + R2))
where V
TH
is the threshold voltage at which the com-
parator switches its output from high to low as V
IN
rises above the trip point. V
TL
is the threshold volt-
age at which the comparator switches its output from
low to high as V
IN
drops below the trip point.
Pin Description
PIN
M A X9 0 2 1
M A X9 0 2 2
M A X9 0 2 4
NAME FUNCTION
1— — IN+ Comparator Noninverting Input
2411V
SS
Negative Supply Voltage
3— — IN- Comparator Inverting Input
4— — OUT Comparator Output
58 4 V
DD
Positive Supply Voltage. Bypass with a 0.1µF capacitor to GND.
—1 1OUTA Comparator A Output
—2 2 INA- Comparator A Inverting Input
—3 3 INA+ Comparator A Noninverting Input
—5 5 INB+ Comparator B Noninverting Input
—6 6 INB- Comparator B Inverting Input
—7 7OUTB Comparator B Output
—— 8 OUTC Comparator C Output
—— 9 INC- Comparator C Inverting Input
—— 10 INC+ Comparator C Noninverting Input
—— 12 IND+ Comparator D Noninverting Input
—— 13 IND- Comparator D Inverting Input
—— 14 OUTD Comparator D Output