MB3793-42PF FUJITSU [Fujitsu Component Limited.], MB3793-42PF Datasheet - Page 4

• Manufacturer Part Number: MB3793-42PF
• Description: POWER-VOLTAGE MONITORING IC WITH WATCHDOG TIMER
• Manufacturer: FUJITSU [Fujitsu Component Limited.]

4
MB3793-42
1. Comp. S
2. Comp. O
3. Reset output buffer
4. Pulse generator
5. Watchdog timer
6. Inhibition terminal
7. Flip-flop circuit
BLOCK FUNCTIONS
Comp. S is a comparator with hysteresis to compare the reference voltage with a voltage (V
of dividing the power voltage (V
This function enables the MB3793 to detect an abnormality within 1 µs when the power is cut or falls abruptly.
Comp. O is a comparator to control the reset signal (RESET) output and compares the threshold voltage with
the voltage at the CTP terminal for setting the power-on reset hold time. When the voltage at the CTP terminal
exceeds the threshold voltage, resetting is canceled.
Since the reset (RESET) output buffer has CMOS organization, no pull-up resistor is needed.
The pulse generator generates pulses when the voltage at the CK1 and CK2 input clock terminals changes to
High from Low level (positive-edge trigger) and exceeds the threshold voltage; it sends the clock signal to the
watchdog timer.
The watchdog timer can monitor two clock pulses. Short-circuit the CK1 and CK2 clock terminals to monitor a
single clock pulse.
The inhibition (INH) terminal forces the watchdog timer on/off. When this terminal is High level, the watchdog
timer is stopped.
The flip-flop circuit RSFF1 controls charging and discharging of the power-on reset hold time setting capacity
(C
circuit only functions during resetting and does not function at power-on reset.
TP
). The flip-flop circuit RSFF2 switches the charging accelerator for charging C
CC
) by resistors R
1
and R
2
. When V
S
falls below 1.24 V, a reset signal is output.
TP
during resetting on/off. This
S
) that is the result