Datasheet

200 ms
DELAY
100 ms
0.3 ms
WD_EN
WD
_ _
_
10 - 6 5000 1/
= 3
1/
1/ 2
WD OSC OSC
WD HOLD WD OUT
WD OUT OSC
CW OW WD
t x R x f
t x t
t f
t t t
= =
=
= =
500KHz
ROSC
250KHz
25KHz
Setup www.ti.com
nRST is test point to monitor the reset output pin. It is going to a high-level after power-up and the set
DELAY, and is only triggered for a low-pulse in case of an undervoltage-condition on Vout.
DELAY Jumper allows selection of the reset delay timer using an external capacitor (CDLY) to ground.
Connecting more jumpers adds the respective delay times.
Figure 2. Delay Jumper
WD_EN This Jumper enables the watchdog. With the Jumper installed it is disabled, open is enabled.
Figure 3. Watchdog-Enable Jumper
WD is the Service pin to provide a trigger signal to the Watchdog-timer. The left pin is connected to GND,
the right pin can be connected to a signal generator.
Figure 4. Watchdog-Service Pin
The Watchdog needs to get serviced with a frequency calculated per Equation 2:
(2)
Where
t
WD
= width of watchdog window
R
OSC
= resistor connected at ROSC pin
t
WD_OUT
= width of fault output
f
OSC
= frequency of internal oscillator
t
CW
= width of close window
t
OW
= width of open window
Figure 5. Watchdog-Oscillator Jumper
The frequency set by the ROSC represents the internal clocking of the watchdog. The service frequency
needs to be ~3500 times lower. If all jumpers are left open, the device defaults to approximately 30kHz.
2
TPS7A63xxEVM Evaluation Module SLVU477– June 2011
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