MB3793 Datasheet, PDF (11/20 Pages) Fujitsu Component Limited. – POWER-VOLTAGE MONITORING IC WITH WATCHDOG TIMER

MB3793-42/30
(7) When the voltage of the CTP pin exceeds Vth again as a result of recharging CTP, resetting is canceled and the watchdog timer restarts
monitoring.
The watchdog timer reset time (tWR) can be calculated by the following equation.
tWR (ms) ≈ D x CTP (µF)
Where, D is about 100 in the MB3793-42 and 55 in the MB3793-30.
(8) When VCC falls below the rising-edge detection voltage (VSL), the voltage of the CTP pin falls and a reset signal is output, and the
voltage at the RESET pin changes to Low level. VSL is about 4.2 V in the MB3793-42 and 3.0 V in the MB3793-30.
(9) When VCC exceeds VSH, CTP begins charging.
(10) When the voltage of the CTP pin exceeds Vth, resetting is canceled and the watchdog timer restarts.
(11) When an inhibition signal is input (INH pin is High level), the watchdog timer is halted forcibly.
In this case, VCC monitoring is continued ((8) - (9)) without the watchdog timer.
The watchdog timer does not function unless this inhibition input is canceled.
(12) When the inhibition input is canceled (INH pin is Low level), the watchdog timer restarts.
(13) When the VCC voltage falls below VSL after power-off, a reset signal is output.
Similar operation is also performed for negative clock-pulse input (Timing Chart 2).
Short-circuit the clock pins CK1 and CK2 to monitor a single clock. The basic operation is the same but the clock pulses are monitored at every
other pulse (Timing Chart 3).
s ABSOLUTE MAXIMUM RATINGS
Parameter
Power voltage*
CK1
Input voltage
CK2
INH
Reset output voltage
(direct current)
RESET
Allowable loss (Ta ≤ +85°C)
Storage temperature
Symbol
VCC
VCK1
VCK2
VINH
IOL
IOH
PD
Tstg
LImits
-0.3 to +7
-0.3 to +7
-10 to +10
200
-55 to +125
(Ta = +25°C)
Symbo
V
V
mA
mW
°C
*The power voltage is based on the ground voltage (0 V).
Note: Permanent device damage may occur if the above ABSOLUTE MAXIMUM RATINGS are exceeded. Functional operation should be
restricted to the conditions as detailed in the operational sections of this data sheet. Exposure to absolute maximum rating conditions
for extended periods may affect device reliability.
s RECOMMENDED OPERATING CONDITIONS
Parameter
Reset (RESET) output current
Power-on reset hold time setting capacity
Watchdog-timer monitoring time setting capacity
Watchdog timer monitoring time
Operating ambient temperature
Symbol
IOL
IOH
CTP
CTW
tWD
Ta
Min.
-5
0.001
0.001
0.1
-40
Limits
Typical
-
-
-
-
-
Max.
+5
10
1
1500
+85
Unit
mA
µF
µF
ms
°C
Note: These recommended operation conditions guarantee normal logic operation of an LSI circuit. The limits of the AC and DC electrical
characteristics are guaranteed within these recommended conditions.
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