TMP89FW24ADFG Datasheet, PDF (105/548 Pages) Toshiba Semiconductor – 8 Bit Microcontroller TLCS-870/C1 Series

TMP89FW24A
6. Power-on Reset Circuit
The power-on reset circuit generates a reset when the power is turned on. When the supply voltage is lower
than the detection voltage of the power-on reset circuit, a power-on reset signal is generated.
6.1 Configuration
The power-on reset circuit consists of a reference voltage generation circuit and a comparator.
The supply voltage divided by ladder resistor is compared with the voltage generated by the reference voltage gen-
eration circuit by the comparator.
VDD
Comparator
Power-on reset signal
Reference voltage
generation circuit
Figure 6-1 Power-on Reset Circuit
6.2 Function
When power supply voltage goes on, if the supply voltage is equal to or lower than the releasing voltage of the
power-on reset circuit, a power-on reset signal is generated and if it is higher than the releasing voltage of the power-
on reset circuit, a power-on reset signal is released.
Until the power-on reset signal is generated, a warm-up circuit and a CPU is reset.
When the power-on reset signal is released, the warm-up circuit is activated. The reset of the CPU and peripher-
al circuits is released after the warm-up time that follows reset release has elapsed.
Increase the supply voltage into the operating range during the period from detection of the power-on reset re-
lease voltage until the end of the warm-up time that follows reset release. If the supply voltage has not reached
the operating range by the end of the warm-up time that follows reset release, the TMP89FW24A cannot operate
properly.
For voltage drop detection, use the voltage detection circuit. For details, refer to the chapter on the voltage detec-
tion circuit.
RA000
Page 89
2012/5/18