m5295a Renesas Electronics Corporation., m5295a Datasheet - Page 6

• Manufacturer Part Number: m5295a
• Description: Watchdog Timer
• Manufacturer: Renesas Electronics Corporation.

M5295AL/AP/AFP
• Pin (1) (WD pin) input requirements
3. Relationship between input pulse width and input capacitance Cin
REJ03D0780-0200 Rev.2.00 Jun 15, 2007
Page 6 of 12
Q
RST1 is output when t
(1) Connect capacitor between WD pin and voltage input. (refer to section 3)
(2) Input cycle: t
(3) Input pulse width t
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.
1
is off when voltage at pin (1) is 1.5V or less.
V
t
1.1 ⋅ C ⋅ R
3
IN
= Cin ⋅ 5 × 10
Cin
1
1
1
< f
WD
30k
4
or less (discharge should start before voltage at WD pin reaches 4 V.)
20k
⋅ ln
4
WDIN
is longer than t
Vin
1.5
: t
2
C = 103
or less
Q
100µs
1
50µs
C = 104
WD
1ms
0.5
ms
.
t
Discharge Voltage x(V)
When t
as shown above. Set t
[t
(t
2
WDIN
2
Figure 4
Figure 5
: Discharge time during normal input)
(3µs) or more] but not to exceed t
3
3
is too long, TC pin output waveform frequency changes
RST1
WD
V
(1)
TC
(2)
(3)
IN
4
1.5V
Cin: 10000pF, t
Cin: 1000pF, t
Cin: 100pF, t
t
1
Vin
Vin
3
V
R
t
to be sufficiently long to turn on Q
3
CC
1
= 10kΩ
t
2
= 5V
3
3
= 6µs
t
3
= 60µs
WD
= 0.6ms
t
4
2
(discharge time).
4V
2V
t
t
t
t
1