MAX9101ESA datasheet(7/8 Pages) MAXIM

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+1.0V Micropower SOT23 Comparators

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Open-Drain Output (MAX9101)

The MAX9101 has an open-drain output, which can be

pulled up to +6.0V above ground independent of the

supply voltage. This is typically used with an external

pullup resistor, facilitating interface between mixed logic

voltages. Alternatively, multiple open-drain comparator

outputs can be connected in a wire-OR configuration.

Applications Information

Low-Voltage Operation: VCC = 1V

The minimum operating voltage is +1.0V. At lower sup-

ply voltages, the input common-mode range remains

rail-to-rail, but the comparator’s output drive capability is

reduced and propagation delay increases (see Typical

Operating Characteristics).

Internal Hysteresis

Hysteresis increases the comparators’ noise margin by

increasing the upper threshold and decreasing the

lower threshold (Figure 1). This hysteresis prevents the

comparator from providing multiple poles when driven

with a very-slow-changing signal.

Additional Hysteresis

These comparators have 1.0mV internal hysteresis.

Additional hysteresis can be generated with two resis-

tors using positive feedback (Figure 2). Use the follow-

ing procedure to calculate resistor values:

1) Calculate the trip points of the comparator using

these formulas:

and

VTH is the threshold voltage at which the comparator

switches its output from high to low as VIN rises

above the trip point. VTL is the threshold voltage at

which the comparator switches its output from low to

high as VIN drops below the trip point.

2) The hysteresis band will be:

VHYS = VTH - VTL = VCC

3) In this example, let VCC = +5V and VREF = +2.5V:

and

4) Select R2. In this example, we will choose 1k

Ω.

5) Select VHYS. In this example, we will choose 50mV.

6) Solve for R1:

where R1

≈ 100kΩ, VTH = 2.525V, and VTL = 2.475V.

Board Layout and Bypassing

A power-supply bypass capacitor is not normally

required, but 100nF bypass capacitors can be used

when the supply impedance is high or when the supply

0 050

1000

1 1000













HYS













TL =−













25 1

TH =+

























REF

=−













REF

−

()

















THRESHOLDS

OUT

IN-

IN+

VHYST

HYSTERESIS

BAND

VIN - VHYST

VIN - +VHYST/2

GND

VCC

OUT

VIN

VREF

VCC

MAX9100

Figure 1. Threshold Hysteresis Band

Figure 2. Additional Hysteresis (MAX9100)

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