MM1145 查看數據表（PDF） - Mitsumi
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MM1145 Datasheet PDF : 7 Pages
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MITSUMI
System Reset (with built-in watchdog timer) MM1145
6. Operation is as follows if either clock CK1 or CK2 ceases (the figure shows CK1).
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Output goes to reset state (RESET goes low) when CT voltage reaches reset ON threshold value VT1
(.=. 1.4V).
The formula for CT charging time (TWD : watchdog timer monitoring time) until reset is output is as follows.
TWD (ms) .=. 2500 CT (µF)
7. Watchdog timer reset time TWR is the discharge time until CT voltage drops to reset OFF threshold value
VT2 from reset ON threshold value VT1. The formula is as follows.
TWR (ms) .=. 500 CT (µF)
After reset OFF threshold value is reached, output reset is released and CT starts charging. Thereafter,
steps 4 and 5 are repeated if a normal clock is input, and when one of the clocks ceases, 6 and 7 are
repeated.
In the same way, 6 and 7 are repeated if both clocks CK1 and CK2 cease.
8. Reset is output when VCC drops to VSL (.=. 4.2V). CT is charged simultaneously.
9. CT charging starts when VCC rises to VSH.
When VCC drops momentarily, CT charging begins after the charge is first discharged, if the time from VCC
dropping below VSL until it rises to VSH is longer than the VCC input pulse width standard value TPI.
10.Output reset is released after VCC goes above VSH and after TPR, and the watchdog timer starts.
11.Watchdog timer operation can be stopped by switching RCT voltage from high to low. (Clocks CK1 and
CK2 are invalid. Regardless of status, TC pin voltage discharges quickly and goes to 0V.) This operation
can be applied from any timing. In this state the IC functions as a reset IC with power ON reset.
12.Watchdog timer operation re-starts when RCT voltage switches to high.
13.When power is OFF, reset is output if VCC goes below VSL.
14.When Vcc drops to 0V, reset output is held until VCC reaches 0.8V.
Measuring Circuit
Measuring Circuit 1
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