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dc1033bf
DEMO MANUAL DC1033B
ONT/OFFT PROGRAMMING
Additional pushbutton turn on and off de-bounce time
can be set by attaching a capacitor from the ONT and
OFFT pins to GND and can be done through JP3 and
JP4, respectively, on the DC1033B. Select OPEN for the
Internal Default Time of the LTC2952 only or choose CAP
for additional timing. See figures 2, 3, 4 and 5 for timing
differences. The additional timing can be calculated using
the following equations:
t
ONT
= C
ONT
[F] • 9.3 x 106 [Ω]
t
OFFT
= C
OFFT
[F] • 9.3 x 106 [Ω]
INT/KILL
The INT pin can be tied to the KILL pin through JP5
to immediately shutdown when INT pulls low during a
turn off sequence. When the pins are untied, the INT pin
becomes open collector for the interrupt period before
power is turned off.
OPERATING PRINCIPLES
VOLTAGE MONITORS PFI AND VM
Voltage monitoring is also provided by the Power Fail
Input (PFI) and Voltage Monitor (VM) pins. If the voltage
at PFI falls below its threshold, a signal is given at PFO
and shown with an LED. If the voltage at VM falls below
its threshold, a signal is given at RST and also shown
with an LED. RST is typically connected to the Reset of a
microcontroller to reset the device and halt operation until
the supply voltage is above a specified voltage.
WATCHDOG AND EXTEND FUNCTION WITH WDE
During a shutdown process after the INT pin goes high
impedance, a rising or falling edge on the WDE pin within
a 500ms period extends the waiting period before the EN
line is set low. See figure 6 and 7 for timing comparison.
The WDE pin can also be used with the VM pin to provide
a watchdog timer.
Figure 2. Pushbutton Turn ON with No Additional Timing
