MB3793-37A Fujitsu Microelectronics, Inc., MB3793-37A Datasheet - Page 11

• Manufacturer Part Number: MB3793-37A
• Description: Power Voltage Monitoring Ic With Watchdog Timer
• Manufacturer: Fujitsu Microelectronics, Inc.

5. Clock pulse input supplementation (Positive clock pulse)
1. Positive clock pulse input
See “1. Basic operation (positive clock pulse)” under “ DIAGRAM.”
2. Negative clock pulse input
See “2. Basic operation (negative clock pulse)” under “ DIAGRAM.”
The MB3793 operates in the same way whether it inputs positive or negative pulses.
3. Clock monitoring
To use the MB3793 while monitoring only one clock, connect clock pins CK1 and CK2.
Although the MB3793 operates basically in the same way as when monitoring two clocks, it monitors the clock
signal at every other input pulse.
See “3. Single-clock input monitoring (positive clock pulse)” under “ DIAGRAM.”
4. Description of Operations
The numbers given to the following items correspond to numbers (1) to (13) used in “ DIAGRAM.”
OPERATION SEQUENCE
(1) The MB3793 outputs a reset signal when the supply voltage (V
(2) If V
(3) When C
reset hold time setting capacitor C
3.79 V.
voltage (V
from “L” level).
Note:
CC
CTW
CK1
CK2
reaches or exceeds the rise-time detected voltage V
TP
The MB3793 watchdog timer monitors Clock1 (CK1) and Clock2 (CK2) pulses alternately.
When a CK2 pulse is detected after detecting a CK1 pulse, the monitoring time setting capacity (C
charging from discharging.
When two consecutive pulses occur on one side of this alternation before switching, the second pulse is ignored.
In the above figure, pulse *1 and *2 are ignored.
has been charged for a certain period of time T
th
V
V
) after the start of charging), the MB3793 cancels the reset (setting the RESET pin to “H” level
H
L
TP
. At this time, the output remains in a reset state. The V
*1
*2
PR
(until the CTP pin voltage exceeds the threshold
SH
, the MB3793 starts charging the power-on
CC
) reaches about 0.8 V (V
MB3793
TW
SH
) switches to
CCL
value is about
)
-37A
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