ACT8810
Active- Semi
Rev 4, 01-Oct-09
SYSTEM MANAGEMENT
FUNCTIONAL DESCRIPTION CONT’D
enable and disable REG1, REG2, and REG3,
respectively. Once the system is enabled, the
system will remain enabled until all of ON1, ON2,
and ON3 have been de-asserted. See the Control
Sequence section for more information.
ACT8810QJ1## begins its system startup
procedure by enabling REG1. When REG1 reaches
94% of its final regulation voltage, ACT8810QJ1##
automatically turns on REG4 and REG5 and
nRSTO is asserted low, holding the microprocessor
in reset for a user-selectable reset period of 260ms.
If VOUT1 is within 6% of its regulation voltage when
the reset timer expires, the nRSTO is de-asserted,
and the microprocessor can begin its power-up
sequence. Once the power-up routine is
successfully completed, the system remains
enabled after the push-button is released as long as
the microprocessor asserts any one of ON1, ON2
or ON3, and REG4, REG5 may be enabled or
disabled via the I2C interface.
Power-On Reset Output
nRSTO is an open-drain output which asserts low
upon startup or when nPBIN is driven directly to
GA, and remains asserted low until the 260ms
(default) power-on reset timer has expired. Connect
a 10kΩ or greater pull-up resistor from nRSTO to an
appropriate voltage supply.
nIRQ Output
This start-up procedure requires that the
pushbutton be held until the microprocessor
assumes control (by asserting any one of ON1,
ON2, and ON3), providing protection against
inadvertent momentary assertions of the
pushbutton. If desired, longer “push-and-hold” times
can be easily implemented by simply adding an
additional time delay before asserting ON1, ON2, or
ON3. If the microprocessor is unable to complete its
power-up routine successfully before the user lets
go of the push-button, the ACT8810QJ1##
automatically shuts itself down.
nIRQ is an open-drain output that asserts low any
time startup or an unmasked fault condition exists.
When asserted, nIRQ remains low until the
microprocessor polls the ACT8810's I2C interface.
The ACT8810 supports a variety of other fault
conditions, which may each be optionally unmasked
via the I2C interface. For more information about the
available fault conditions, refer to the appropriate
sections of this datasheet.
Connect a pull-up resistor from nIRQ to an
appropriate voltage supply. nIRQ is typically used to
drive the interrupt input of the system processor,
and is useful in a variety of software-controlled
enable/disable control routines.
Figure 3:
Sequence A
Thermal Shutdown
First Push
Button
Assert
Power-Hold
Release
Button
Second Push System
Button Shutdown
The ACT8810 integrates thermal shutdown
protection circuitry to prevent damage resulting
from excessive thermal stress, as may be
encountered under fault conditions. This circuitry
disables all regulators if the ACT8810 die
temperature exceeds 160°C, and prevents the
regulators from being enabled until the IC
temperature drops by 20°C (typ).
nPBIN
System Enable
94% of VOUT1
OUT1
ON1, ON2, ON3
OUT2, OUT3
OUT4, OUT5
Reset time Enable
nRSTO
Control Sequence
260ms
Sequence A
The ACT8810QJ1## which is set with “sequence
A“, has a system startup is initiated whenever the
following conditions occurs:
nIRQ
1) nPBIN is pushed low via 100kΩ resistance,
When ever this condition exists, the
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