APR3021/2/3
Application Information
VCC
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
VCC
RESET
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.
100K
GND
Figure 1. Ensuring RESET Valid to VCC = 0 V
Reset Output
+3.3V
+5.0V
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.
V
CC
V
CC
APR3023
RESET
100k
RESET 5V
INPUT System
GND
GND
Figure 2. APR3023 Open Drain Output with Multiple
Supplies
Copyright ANPEC Electronics Corp.
Rev. A.2 - Oct., 2003
9
www.anpec.com.tw
ANPEC [ ANPEC ELECTRONICS COROPRATION ]
