ACT8846
Rev 4, 25-May-16
microprocessor must assert PWRHLD (GPIO6_B0)
to ensure that the system remains powered after
nPBIN is released. Once the power-up routine is
completed, the system remains enabled after the
push-button is released as long as PWRHLD is
asserted high. If the processor does not assert
PWRHLD before the user releases the push-button,
the boot-up sequence is terminated and all
regulators are disabled. This provides protection
against "false-enable", when the push-button is
accidentally depressed, and also ensures that the
system remains enabled only if the processor
successfully completes the boot-up sequence.
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.
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 10kꢀ or greater pull-up resistor from
nRSTO to an appropriate voltage supply.
nIRQ Output
As with the enable sequence, a typical disable
sequence is initiated when the user presses the
push-button, which interrupts the processor via the
nPBSTAT output. After system is turned on, the
processor may shut down the system by setting
OFFSYSCLR[ ] to 1 then setting OFFSYS[ ] to 1, or
by pulling PWRHLD to logic low. The user could
force shut down ACT8846 anytime by pressing the
power on push-button for 10 seconds even when
software crashes.
nIRQ is an open-drain output that asserts low any
time an interrupt is generated. Connect a 10kꢀ 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 ACT8846'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.
SLEEP Mode Sequence
The ACT8846 supports RK31x8 processor’s
SLEEP mode operation. Once a successful power-
up routine has been completed, SLEEP mode may
be initiated through a variety of software-controlled
mechanisms.
Push-Button Control
The ACT8846 is designed to initiate a system
enable sequence when the nPBIN multi-function
input is asserted for 32ms. 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
PWRHLD) before nPBIN is de-asserted. If the
microprocessor is unable to complete its power-up
routine successfully before the user releases the
push-button, the ACT8846 automatically shuts the
system down. This provides protection against
accidental or momentary assertions of the push-
button. If desired, longer “push-and-hold” times can
be implemented by simply adding an additional time
delay before asserting PWRHLD.
SLEEP mode is typically initiated when the user
presses the push-button during normal operation.
Pressing the push-button asserts the nPBIN input,
which asserts the nPBSTAT output, which
interrupts the processor. In response to this
interrupt the processor should disable REG6,
REG7, REG8, REG9, REG10 and REG12 via I2C,
then de-assert PWREN(GPIO6_B1), disabling
REG3. PWRHLD should remain asserted during
SLEEP mode so that REG1, REG2, REG4, REG5,
and REG11 remain enabled.
The ACT8846 wakes up from SLEEP mode when
either the push-button and/or PWREN (GPIO6_B1)
is asserted. In either case, REG3 is enable which
allow the system to resume normal operation.
Control Sequences
The ACT8846 features
a
variety of control
sequences that are optimized for supporting system
enable and disable, as well as SLEEP mode of the
Rockchip RK31x8 processors.
Enabling/Disabling Sequence
A typical enable sequence is initiated whenever the
nPBIN is asserted low for 32ms via 50Kꢀ
resistance. The power control diagram is shown in
Figure 3. During the boot sequence, the
: Only for ACT8846QM468.
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