MB3793-27A Datasheet, PDF (5/30 Pages) Fujitsu Component Limited. – Power Voltage Monitoring IC with Watchdog Timer

MB3793-27A
4. Block Description
1. Comp. S
Comp. S is a comparator with hysteresis to compare the reference voltage with a voltage (V_S) that is the result of dividing the power
voltage (V_CC) by resistors 1 and 2. When V_S falls below 1.24 V, a reset signal is output.
This function enables the MB3793 to detect an abnormality within 1 s when the power is cut or falls abruptly.
2. Output circuit
The output circuit contains a RESET output control comparator that compares the voltage at the CTP pin to the threshold voltage to
release the RESET output if the CTP pin voltage exceeds the threshold value.
Since the reset (RESET) output buffer has CMOS organization, no pull-up resistor is needed.
3. Pulse generator
The pulse generator generates pulses when the voltage at the CK1 and CK2 clock pins changes to High from Low level
(positive-edge trigger) and exceeds the threshold voltage; it sends the clock signal to the watchdog timer.
4. Watchdog timer
The watchdog timer can monitor two clock pulses. Short-circuit the CK1 and CK2 clock pins to monitor a single clock pulse.
5. Inhibition pin
The inhibition (INH) pin forces the watchdog timer on/off. When this pin is High level, the watchdog timer is stopped.
6. Logic circuit
The logic circuit contains flip-flops.
Flip-flop RSFF1 controls the charging and discharging of the power-on reset hold time setting capacitor (C_TP).
Flip-flop RSFF2 turns on/off the circuit that accelerates charging of the power-on reset hold time setting capacitor
(C_TP) at a reset. The RSFF2 operates only at a reset; it does not operate at a power-on reset when the power is turned on.
5. Absolute Maximum Ratings
Parameter
Symbol
Power supply voltage*
V_CC
CK1
V_CK1
Input voltage*
CK2
V_CK2
Reset output current
INH
I_INH
RESET
I_OL
I_OH
Power dissipation
P_D
Storage temperature
Tstg
: The voltage is based on the ground voltage (0 V).
Conditions
—
—
—
—
—
Ta  +85C
—
Rating
Min
Max
–0.3
+7
–0.3
+7
–10
+10
—
200
–55
+125
Unit
V
V
mA
mW
C
WARNING:
1. Semiconductor devices may be permanently damaged by application of stress (including, without limitation,
voltage, current or temperature) in excess of absolute maximum ratings.Do not exceed any of these ratings.
Document Number: 002-08550 Rev. *A
Page 5 of 30