XRP7725 Datasheet, PDF (31/34 Pages) Exar Corporation – Power Management System

XRP7725
Intel Node Manager Compatible Programmable
Power Management System
Short duration Enable pin toggled low
Short duration shutdown pulses to the
ENABLE pin of the XRP7725, which do not
provide sufficient time for the LDO5 voltage
to fall below 3.5V, can result in significant
delay in re-enabling of the device. Some
examples below show LDO5 and ENABLE
pins:
For users that wish to create their own
programming procedure so they can re-
program Flash in-circuit using their system
software, please contact Exar for a list of I²C
Flash Commands needed.
ENABLING XRP7725
XRP7725 has a weak internal pull-up ensuring
it gets enabled as soon as internal voltage
supplies have ramped up and are in
regulation.
Driving the Enable pin low externally will keep
the controller in the shut-down mode. A
simple open drain pull down is the
recommended way to shut XRP7725 down.
If the Enable pin is driven high externally to
control XRP7725 coming out of the shut-down
mode, care must be taken in such a scenario
to ensure the Enable pin is driven high after
V_CC gets supplied to the controller.
In the configuration when V_CC = LDO5 =
4.75V to 5.5V, disabling the device by
grounding the Enable pin is not
recommended. At this time we recommend
leaving the Enable pin floating and placing the
controller in the “Standby Mode” instead in
this scenario. The standby mode is defined as
the state when all switching channels and
LDO3.3 are disabled, all GPIO/PSIOs are
programmed as inputs, and system clock is
disabled. In this state chip consumes 440uA
typical.
No load on LDO5, blue trace. Recovery time
after ENABLE logic high is approximately
40ms.
Adding a 200 ohm load on LDO5 pulls voltage
below 3.5V and restart is short.
Note that as V_CC increases, the restart time
falls as well. 5.5V input is shown as the worst
case.
Since the ENABLE pin has an internal current
source, a simple open drain pull down is the
recommended way to shut down the
© 2014 Exar Corporation
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Rev. 1.0.0