APR3021 datasheet(9/15 Pages) ANPEC

9 / 15 page

 ANPEC Electronics Corp.

Rev. A.2 - Oct., 2003

APR3021/2/3

www.anpec.com.tw

Application Information

VCC Transient Rejection

The APR3021/2/3 have the function to reject the tran-

sient glitches from the power line. The Maximum Tran-

sient Duration vs. Reset Threshold Overdrive shows

at Typical Characteristics.The transient voltage with

the duration under the curve will not generate a reset

signal, e.g. a transient of 100mV below the reset

threshold voltage have the duration more than 35us, it

will generate a reset signal. Connect a 0.1uF bypass

capacitor to the VCC pin can improve the transient

immunity.

Reset Output

The APR3021/2/3 have 3 output stage versions:

APR3001 is an active low push-pull output, when the

VCC drops below the reset threshold, the RESET out-

put generates a low signal. APR3022 is an active high

push-pull output, when the VCC drops below the reset

threshold, the RESET output generates a high signal

(see Timing Chart). APR3023 is an active low open

drain output, the RESET output must be connected a

pull-up resistor to a supply voltage that is lower than

6V, it suits to use in multiple voltage systems (see

Figure 2). The APR3021 RESET output is valid until

the VCC=1.2V, below 1.2V the IC is shutdown, and

the output becomes a floating state. If it is a trouble, a

resistor should be connected from reset output to

ground to keep the reset output low (see Figure 1).

For The APR3022, a pull-up resistor to VCC is required

to keep the valid reset output for VCC below 1.2V.

RESET

VCC

GND

VCC

100K

Figure 1. Ensuring RESET Valid to VCC = 0 V

VCC

APR3023

RESET

GND

+3.3V

+5.0V

VCC

GND

RESET

INPUT

System

100k

Figure 2. APR3023 Open Drain Output with Multiple

Supplies

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