M5295AFP データシートの表示（PDF） - Renesas Electronics

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M5295AFP

Watchdog Timer

Renesas Electronics 

M5295AL/AP/AFP

Operating Description

VCC

VTH2(H)

VTH1

0V

VTH3(H)

TC VTH3(L)

0V

VTH2(L)

VTH1

VIN

0V

RST1

0V

RST2

0V

tRST(1)

tWD

(1)(2)(3) (4) (5)

tRST(2)

(6)

(7) (8)

(9)(10)(11)

(1): The VCC rises up to 0.8 V, then RST1 and RST2 generates low output, and rising up to 4.25 V,

charge of C1 begins.

(2): The VCC rises up to 4.7 V, then RST2 generates high.

(3), (4): The voltage at TC pin is 2 V, then RST2 generates high, when 4 V, C1 is discharged and RST1

generates low.

(5): The voltage at TC pin falls to 2 V, then RST1 generates high unless normal clock signal is entered

to WD pin, RST1 repeats this operation.

(6), (7): Before the voltage at TC pin reaches 4 V, if normal clock signal is entered to WD pin, low RST1 is

canceled.

(8), (9): In the case of entrance of abnormal signal input, as the waveform of TC pin repeats charge and

discharge of RST1 alternatively from 2 V to 4 V, the RST1 repeats high and low output operation.

(10): The VCC falls to 4.6 V, then RST2 generates low, this detective voltage has a 100 mV hysteresis.

(11): When VCC goes down to 4.25 V(VTH1), the status of TC pin is switched to discharge. When the

potentional at TC pin is detected being VTH3(H) or VTH3(L), the status of RST1 becomes "low".

Terminology

tRST(1): Time required for TC pin potential to rise from 0 V VTH3(L) when VCC is being applied.

tWD : Time required for TC pin potential to rise from VTH3(L) to VTH3(H).

tRST(2): Time required for TC pin potential to go down from VTH3(H) to VTH3(L).

Figure 1 Operating Waveform

REJ03D0780-0200 Rev.2.00 Jun 15, 2007

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