M5295AP datasheet(6/13 Pages) RENESAS

6 / 13 page

M5295AL/AP/AFP

REJ03D0780-0200 Rev.2.00 Jun 15, 2007

Page 6 of 12

• Pin (1) (WD pin) input requirements

(1) Connect capacitor between WD pin and voltage input. (refer to section 3)

(2) Input cycle: tWD or less (discharge should start before voltage at WD pin reaches 4 V.)

1.1

⋅ C ⋅ R1

< f

(3) Input pulse width tWDIN: t2 or less

234

0.5

C = 104

1ms

µs

C = 103

100

µs

VCC = 5V

R1 = 10kΩ

Discharge Voltage x(V)

Figure 4

3. Relationship between input pulse width and input capacitance Cin

When input to pin (1) is 1.5 V or more, TC pin discharges electricity. Determine pulse width and input capacitance

Cin with reference to the diagram shown in figure 5.

t3 = Cin ⋅ 5 × 10

4 ⋅ ln

RST1 is output when t4 is longer than tWD.

Vin

1.5

Q1 is off when voltage at pin (1) is 1.5V or less.

VIN

1Q1

30k

Cin

20k

tWD

Cin: 10000pF, t3 = 0.6ms

Cin: 1000pF, t3 = 60µs

Cin: 100pF, t3 = 6µs

VIN

(1)

Vin

1.5V

(2)

RST1

(3)

When t3 is too long, TC pin output waveform frequency changes

as shown above. Set t3 to be sufficiently long to turn on Q1

[tWDIN(3µs) or more] but not to exceed t2 (discharge time).

(t2: Discharge time during normal input)

Figure 5

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