AAT3532 Datasheet, PDF (5/8 Pages) Advanced Analogic Technologies – MicroPower™ Microprocessor Reset Circuit

AAT3532
MicroPower™ Microprocessor Reset Circuit
Functional Block Diagram
VCC
TOL
VCC
Tolerance
Select
VREF
Reset
Generator
RST
RST
PBRST
ST
TD
De-Bounce
Circuit
Watchdog
Timer
Detector
Watchdog
Timer
GND
Applications Information
Power Monitor
The reset function monitors the V_CC supply to ensure
a microprocessor is correctly reset and is powered
up into a known condition following a power supply
failure. RST and RST will remain valid for V_CC volt-
ages down to 1.4V.
The RST and RST pins are asserted whenever V_CC
drops below the reset threshold voltage. This volt-
age can be set by programming the TOL pin.
Connecting TOL to V_CC sets the 10% tolerance of
the V_CC supply (typically 4.37V for V_CC = 5V).
Connecting TOL to GND sets the 5% tolerance of
the V_CC supply (typically 4.62V for V_CC = 5V). The
reset pin is guaranteed to remain asserted for a
minimum period of 250ms after V_CC has risen
above the reset threshold voltage. (See Figure 1.)
RST output is an open drain output. For correct
operation, a pull-up resistor of 10kΩ should be con-
nected between this output and V_CC.
VCC
0V
RESET Output Delay (VCC Rising)
tRPU
RST
+5V
+4.75V (5% Trip Point)
+4.50V (10% Trip Point)
RESET Output Delay (VCC Falling)
tRPD
RST
Figure 1: Reset Output Delay.
3532.2005.12.1.2
5