mb3793-27apnf Fujitsu Microelectronics, Inc., mb3793-27apnf Datasheet - Page 12

• Manufacturer Part Number: mb3793-27apnf
• Description: Power-voltage Monitoring Ic With Watchdog Timer
• Manufacturer: Fujitsu Microelectronics, Inc.

12
MB3793
(3) When C
(4) When the voltage at the watchdog timer monitor time setting pin C
(5) If the CK2 pin inputs a clock pulse (positive edge trigger) when the C
(6) If no clock pulse is fed to the CK1 or CK2 pin within the watchdog timer monitor time t
(7) When a certain period of time t
(8) If V
(9) When V
(10) When the CTP pin voltage reaches or exceeds V
(11) Making the inhibit pin active (setting the INH pin to “H” from “L”) forces the watchdog timer to stop operation.
(12) Canceling the inhibit input (setting the INH pin to “L” from “H”) restarts the watchdog timer.
(13) The reset signal is output when the power supply is turned off to set V
voltage (V
from “L” level).
The V
The power-on reset hold timer monitor time t
t
The value of A is about 750 with V
charging the watchdog timer monitor time setting capacitor (C
V
The value of V
order or simultaneously, the C
The MB3793 repeats operations (4) and (5) as long as the CK1/CK2 pin inputs clock pulses with the system
logic circuit operating normally.
with the system logic circuit, the CTW pin is set to the “L” level threshold voltage V
outputs a reset signal (setting the RESET pin to “L” level from “H” level).
The value of V
The watchdog timer monitor time t
t
The value of B is hardly affected by the power supply voltage; it is about 1600 with V
recharging the C
The watchdog timer monitor reset time t
t
The value of D is 55 with V
The MB3793 repeats operations (4) and (5) as long as the CK1/CK2 pin inputs clock pulses. If no clock
pulse is input, the MB3793 repeats operations (6) and (7).
MB3793 outputs a reset signal (setting the RESET pin to “L” level from “H” level).
The value of V
the watchdog timer. It repeats operations (4) and (5) as long as the CK1/CK2 pin inputs clock pulses.
This stops only the watchdog timer, leaving the MB3793 monitoring V
The watchdog timer remains inactive unless the inhibit input is canceled.
PR
WD
WR
H
, the C
(ms)
(ms)
(ms)
CC
is lowered to the fall-time detected voltage (V
th
value is about 2.4 V with V
TP
CC
.
. =
.
. =
.
. =
TW
-27A
has been charged for a certain period of time T
th
A
reaches or exceeds V
B
D x C
) after the start of charging), the MB3793 cancels the reset (setting the RESET pin to “H” level
switches from the charge state to the discharge state.
C
H
L
SL
C
is always about 0.24 V regardless of the detected voltage.
TP
is always about 1.24 V regardless of the detected voltage.
TW
TP
TP
is 2.7 V
( F)
), the MB3793 cancels the reset signal and starts operating the watchdog timer.
( F)
( F)
CC
TW
= 3.3 V and about 50 with V
WR
SH
switches from the discharge state to the charge state.
has passed (until the CTP pin voltage reaches or exceeds Vth again after
CC
WD
CC
again, the MB3793 starts charging the C
= 3.3 V and about 700 with V
= 3.3 V
is set with the following equation:
WR
is set with the following equation:
PR
is set with the following equation:
th
, the MB3793 cancels the reset and restarts operating
SL
) or less, the CTP pin voltage decreases and the
PR
(until the CTP pin voltage exceeds the threshold
CC
= 3.0 V.
TW
).
TW
CC
reaches the “H” level threshold voltage
TW
= 3.0 V. The MB3793 also starts
CC
is being discharged in the CK1-CK2
CC
(operations (8) to (10)).
to V
TP
SL
.
or less.
L
or less and the MB3793
WD
due to some problem
CC
= 3.0 V to 3.3 V.