ACT5880
Rev 2, 03-Sep-13
reset timer expires, nRSTO is de-asserted. If the
equipment system pulls the PWRHLD (or any of the
HFPWR, ACOK or RTC alarm wake-up) to a logic
high before the push-button is released, the enable
state of the ACT5880 is kept. If this does not
happen, the ACT5880 goes back to the disable
state. The Figure 3 shows the states of the
ACT5880 and its power rails. The ACT5880 has 2
programmable reset timeout, which is optional on
default setting and programmable in operation.
Push-button Inputs
The nPBIN features dual-functions input, by
detecting if it is directly shorted to ground or pulled
to ground through a resistor of around 50kꢀ (good
in range of 24kꢀ to 82kꢀ). See the Figure 2 for the
external connection, the push-button that directly
grounds the nPBIN input is namely the "Reset Key",
is identified as a manual reset request by the
ACT5880 when it is pressed; The other push-button
is namely the "Enable Key", is identified as a device
enable request when it is pressed.
When "Enable Key" is pressed in ACT5880 enable
state, the response depends on if the OUT1 outputs
is normal at the moment.
When either "Reset Key" or "Enable Key" is
pressed, the nPBSTAT asserts low; In both cases
the ACT5880 may assert interrupt to the application
system if it is programmed so, by pulling the nIRQ
low.
Figure 3:
Power Rail Sequence
Figure 2:
The External Circuit for The Push button Input
When OUT1 is already enabled, the push button
event only asserts nPBSTAT (and the nIRQ if it is
programmed so). When the OUT1 is disabled, the
push button event starts OUT1 and pulls the nRSTO
low until the reset time-out expires after the OUT1 is
in regulation, also asserts nPBSTAT (and nIRQ if it is
programmed so), while no change to other
rails.Figure 4 shows the "Enable Key" push button
event when OUT1 is disabled.
ACT5880
nPBSTAT Output
nPBSTAT is an open-drain output that reflects the
state of the nPBIN input; nPBSTAT is asserted low
whenever nPBIN is asserted, and is high-Z
otherwise. This output is typically used as an push
button status signal to the processor, to initiate a
software-programmable routine such as operating
mode selection or to open a menu. Connect
nPBSTAT to an appropriate supply voltage
(typically IO voltage) through a 10kꢀ or greater
resistor.
Figure 4:
REG1 to nRSTO Sequence
Control Sequences
Power Output Sequence
A typical enable sequence initiates as a result of
pressing “Enable Key”, which is one of the 5 events
mentioned in the "Device Power States", and it
turns ACT5880 into the power-on default state or
last powered state before being turned off by
removing all the 5 events. When REG1 reaches its
power-OK threshold, nRSTO is asserted low. If
REG1 is above its power-OK threshold when the
See Figure 4 for illustration of pressing of "Enable
Key" when OUT1 does not output. When OUT1 is in
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