EVK-ACT8945AQJ303-T Datasheet, PDF (27/42 Pages) Active-Semi, Inc – Advanced PMU for Atmel SAMA5D3 Series & SAM9 Series Processors

ACT8945A
Rev 2, 11-Feb-14
SYSTEM CONTROL INFORMATION
Control Signals
Enable Inputs
The ACT8945A features a variety of control inputs,
which are used to enable and disable outputs
depending upon the desired mode of operation.
PWRHLD is a logic input, while nPBIN is a unique,
multi-function input.
nPBIN Multi-Function Input
ACT8945A features the nPBIN multi-function pin,
which combines system enable/disable control with
a hardware reset function. Select either of the two
pin functions by asserting this pin, either through a
direct connection to GA, or through a 50kΩ resistor
to GA, as shown in Figure 2.
Figure 2:
nPBIN Input
Push-Button
Manual
Reset
OUT3
VSYS
nPBIN
Manual
Reset
Detect
Push-
Button
Detect
automatically shuts down.
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
interrupt 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 OUT3) through a 10kΩ or greater resistor.
nRSTO Output
nRSTO is an open-drain output which asserts low
upon startup or when manual reset is asserted via
the nPBIN input. When asserted on startup, nRSTO
remains low until reset time-out period expires after
OUT1 reaches its power-OK threshold. When
asserted due to manual-reset, nRSTO immediately
asserts low, then remains asserted low until the
nPBIN input is de-asserted and the reset time-out
period expires.
Connect a 10kΩ or greater pull-up resistor from
nRSTO to an appropriate voltage supply (typically
OUT3).
To CPU
nPBSTAT
ACT8945A
Warm/Cold Manual Reset Function
The second major function of the nPBIN input is to
provide warm and cold manual reset function. To
manually reset the processor, drive nPBIN directly
to GA through a low impedance (less than 2.5kΩ).
An internal timer detects the duration of the manual
reset event.
Short Press/Warm Reset
When the manual reset button is pressed for less
than 130ms, ACT8945A commences a warm reset
operation where nRSTO immediately asserts low,
then remains asserted low until the manual reset
button is released for 64ms.
Long Press / Cold Reset (Power Cycle)
When the manual reset button is pressed for more
than 130ms, ACT8945A commences a power cycle
routine in which case all regulators are turned off
and then turned back on after reset button is
released with all the registers reloaded to default
values. When the ACT8945A turns on again, it
stays enabled for 128ms, the PWRHLD need to be
asserted during this time so that the system
remains powered, otherwise the ACT8945A
nIRQ Output
nIRQ is an open-drain output that asserts low any
time an interrupt is generated. Connect a 10kΩ or
greater pull-up resistor from nIRQ to an appropriate
voltage supply. nIRQ is typically used to drive the
interrupt input of the system processor.
Many of the ACT8945A's functions support
interrupt-generation as a result of various
conditions. These are typically masked by default,
but may be unmasked via the I²C interface. For
more information about the available fault
conditions, refer to the appropriate sections of this
datasheet.
Note that under some conditions a false interrupt
may be generated upon initial startup. For this
reason, it is recommended that the interrupt service
routine check and validate nSYSLEVMSK[-] and
nFLTMSK[-] bits before processing an interrupt
generated by these bits. These interrupts may be
validated by nSYSSTAT[-], OK[-] bits.
Push-Button Control
The ACT8945A is designed to initiate a system
enable sequence when the nPBIN multi-function
input is asserted. Once this occurs, a power-on
sequence commences, as described below. The
power-on sequence must complete and the
microprocessor must take control (by asserting
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