MAX9015(2003) 데이터 시트보기 (PDF) - Maxim Integrated

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MAX9015
(Rev.:2003)

SOT23, Dual, Precision, 1.8V, Nanopower Comparators With/Without Reference

Maxim Integrated 

SOT23, Dual, Precision, 1.8V, Nanopower

Comparators With/Without Reference

Board Layout and Bypassing

The MAX9015–MAX9020 ultra-low supply current typi-

cally requires no power-supply bypass capacitors.

However, when the supply has high output impedance,

long lead lengths or excessive noise, or fast transients,

bypass VCC to VEE with a 0.1µF capacitor placed as

close to the VCC pin as possible. Minimize signal trace

lengths to reduce stray capacitance. Use a ground

plane and surface-mount components for best perfor-

mance. If REF is decoupled, use a low-leakage ceram-

ic capacitor.

Window Detector

The MAX9018 is ideal for window detectors (undervolt-

age/overvoltage detectors). Figure 4 shows a window

detector circuit for a single-cell Li+ battery with a 2.9V

end-of-life charge, a peak charge of 4.2V, and a nomi-

nal value of 3.6V. Choose different thresholds by

changing the values of R1, R2, and R3. OUTA provides

an active-low undervoltage indication, and OUTB pro-

vides an active-low overvoltage indication. ANDing the

two open-drain outputs provides an active-high, power-

good signal.

The design procedure is as follows:

1) Select R1. The input bias current into INB- is nor-

mally less than 2nA, so the current through R1

should exceed 100nA for the thresholds to be accu-

rate. In this example, choose R1 = 1.24MΩ

(1.24V/1µA).

2) Calculate R2 + R3. The overvoltage threshold

should be 4.2V when VIN is rising. The design

equation is as follows:

R2

+

R3

=

R1 x





VOTH

VREF + VHB





−



1



= 1.24MΩ

x

 4.2V 

 1.24V + 0.004



− 1



=2.95MΩ

3) Calculate R2. The undervoltage threshold should

be 2.9V when VIN is falling. The design equation is

as follows:

R2

=

(R1 +

R2

+

R3)

x



VREF − VHB

VUTH



−

R1

= (1.24MΩ + 2.95MΩ) x (1.236) −1.24MΩ

2.9

= 546kΩ

VIN VOTH = 4.2V

VUTH = 2.9V

R3

INA+

REF/INA-

REF

R2

1.24V

VEE

INB+

INB-

5V

VCC

OUTA

MAX9018

OUTB

POWER-

GOOD

R1

VEE

Figure 4. Window Detector Circuit

For this example, choose a 499kΩ standard value 1%

resistor.

4) Calculate R3:

R3 = (R2 + R3) - R2

= 2.95MΩ - 546kΩ

= 240MΩ

5) Verify the resistor values. The equations are as fol-

lows, evaluated for the above example:

Overvoltage threshold:

VOTH

=

(VREF

+

VHB )

x

(R1 +

R2

R1

+ R3)

= 4.20V

Undervoltage threshold:

VUTH

=

(VREF

−

VHB )

x

(R1 + R2 + R3)

(R1 + R2)

= 2.97V

where the internal hysteresis band, VHB, is 4mV.

Zero-Crossing Detector

Figure 5 shows a zero-crossing detector application.

The MAX9015/MAX9016/MAX9019/MAX9020s’ invert-

ing input is connected to ground, and its noninverting

input is connected to a 100mVP-P signal source. As the

signal at the noninverting input crosses zero, the com-

parator’s output changes state.

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