U6808BMFPG3 Atmel, U6808BMFPG3 Datasheet - Page 6

• Manufacturer Part Number: U6808BMFPG3
• Manufacturer: Atmel

Specifications of U6808BMFPG3

• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (min): 4.5V
• Operating Supply Voltage (max): 5.5V
• Operating Temp Range: -40C to 125C
• Operating Temperature Classification: Automotive
• Package Type: SOIC
• Mounting: Surface Mount
• Pin Count: 8
• Lead Free Status / Rohs Status: Not Compliant

5.9
5.9.1
5.9.2
5.9.3
5.9.3.1
5.9.3.2
Figure 5-3.
5.9.3.3
6
Time/s
Update rate is too
fast
Watchdog Window Calculation
U6808B
Example with Recommended Values
RC Oscillator
Watchdog WDI
WDI Pulse Width for Fault Detection after 3 Pulses
WDI Dropouts for Immediate Fault Detection
Reset Delay
79/f
Watchdog Timing Diagram with Tolerances
WDC
Update rate is
either too fast or
good
C
R
t
f
f
t
f
Upper watchdog window
Minimum: 169/f
Maximum: 170/f
Lower watchdog window
Minimum: 79/f
Maximum: 80/f
Minimum:
Maximum:
The duration of the over or undervoltage pulses determines the enable and reset output. A pulse
duration shorter than the debounce time has no effect on the outputs. A pulse longer than the
debounce time results in the first reset delay. If a pulse appears during this delay, a second
delay time is triggered. Therefore, the total reset delay time can be longer than specified in the
data sheet.
WDC
WDC
WDI
WDC
WDI
osc
osc
(Hz) =0.01
= 100 Hz
(s) = 10
(Hz) = 1/(t
= 39 k (may be 5%, R
= 3.3 nF (should be preferably 10%, NPO)
= 100 µs
80/f
Watchdog window
update rate is good
WDC
-3
250/f
251/f
WDC
WDC
WDC
WDC
WDC
[C
t
f
f
WDI
WDC
WDC
)
= 7.9 ms
WDC
WDC
osc
= 8.0 ms
= 16.9 ms
= 17.0 ms
= 10 ms
(nF)
= 10 kHz
= 25 ms
= 25.1 ms
169/f
osc
Update rate is
either too slow or
good
[(0.00078
WDC
f
< 100 k due to leakage current and humidity)
WDC
f
WDC
f
WDC
f
WDC
/79 = 126.6 Hz
/80 = 125.0 Hz
/169 = 59.1 Hz
/170 = 58.8 Hz
R
170/f
osc
Update rate is too
slow
(k )) + 0.0005]]
WDC
250/f
Update rate is
either too slow or
pulse has
dropped out
WDC
Pulse has
dropped out
4707B–AUTO–10/05
251/f
WDC