MB3793-45 Fujitsu Media Devices, MB3793-45 Datasheet - Page 11

• Manufacturer Part Number: MB3793-45
• Description: Power Voltage Monitoring IC with Watchdog Timer
• Manufacturer: Fujitsu Media Devices

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4
5. Clock pulse input supplementation (Positive clock pulse)
1. Positive clock pulse input
2. Negative clock pulse input
3. Clock monitoring
4. Description of Operations
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OPERATION SEQUENCE
See “1. Basic operation (positive clock pulse)” under “ DIAGRAM”.
See “2. Basic operation (negative clock pulse)” under “ DIAGRAM”.
The MB3793 operates in the same way whether it inputs positive or negative pulses.
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”.
The numbers given to the following items correspond to numbers (1) to (13) used in “ DIAGRAM”.
(1) The MB3793 outputs a reset signal when the supply voltage (V
(2) If V
(3) When C
set hold time setting capacitor C
4.60 V.
old voltage (V
level from “L” level).
Note: The MB3793 watchdog timer monitors Clock1 (CK1) and Clock2 (CK2) pulses alternately.
CC
CTW
CK1
CK2
reaches or exceeds the rise-time detected voltage V
TP
When a CK2 pulse is detected after detecting a CK1 pulse, the monitoring time setting capacity
(C
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.
V
has been charged for a certain period of time T
V
H
TW
L
th
) switches to charging from discharging.
) after the start of charging), the MB3793 cancels the reset (setting the RESET pin to “H”
TP
. At this time, the output remains in a reset state. The V
*1
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*2
PR
SH
, the MB3793 starts charging the power-on re-
(until the CTP pin voltage exceeds the thresh-
CC
) reaches about 0.8 V (V
MB3793-45
SH
CCL
value is about
)
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