ACT4910QW
Rev 1.0, 15-Sept-2017
FUNCTIONAL DESCRIPTION
General
I2C Serial Interface
ACT4910 provides protection, control, and supple-
mental storage for power failure prevention systems.
This functionality goes by many names: Power Loss
Protection (PLP), Power Loss Imminent (PLI) and
Power Failure Protection (PFP). It provides a system
with additional run time after a power failure to all the
system to save critical data before shutting down. Typi-
cal applications include solid state disk drives (SSD)
and servers. In normal operation when input power is
good, the IC connects the input to the output through
the eFuse. This powers the system load from the sys-
tem input power. If an input voltage fault occurs, the IC
disconnects the input from the output and enters sup-
plement mode, where output power comes from the
high voltage storage capacitor power. The internal buck
converter efficiently converts the storage voltage down
to the regulated output voltage. All startup, storage ca-
pacitor charging, and switching between normal and
supplement mode operation is autonomous and does
not require user intervention.
To ensure compatibility with a wide range of systems,
the ACT4910 uses standard I2C commands. The
ACT4910 operates as a slave device, and can be fac-
tory configured to one of three 7-bit slave addresses.
The 7-bit slave address is followed by an eighth bit,
which indicates whether the transaction is a read-oper-
ation or a write-operation. Refer to each specific CMI for
the IC’s slave address
7-Bit Slave Address
8-Bit Write
Address
0x34h
0x74h
0xB4h
8-Bit Read
Address
0x35h
0x75h
0xB5h
0x1Ah
0x3Ah
0x5Ah
001 1010b
011 1010b
101 1010b
The I2C packet processing state machine does not have
a timeout function, however, any time the I2C state ma-
chine receives a start bit command, it immediately re-
sets the packet processing, even if it is in the middle of
a valid packet. The I2C functionality is operational in all
states except RESET.
During start up, the ACT4910 limits the output voltage
dV/dt to minimize system level inrush currents. After
softstart is complete, the IC charges the storage capac-
itors with the internal boost converter. The IC automati-
cally recharges the storage capacitors as needed. The
IC contains extensive protection circuitry to protect
against input voltage overvoltage and undervoltage,
output voltage overload and short circuit, degraded stor-
age capacitors, and thermal overload.
I2C commands are communicated using the SCL and
SDA pins. SCL is the I2C serial clock input. SDA is the
data input and output. SDA is open drain and must have
a pull-up resistor. Signals on these pins must meet
timing requirements in the Electrical Characteristics
Table.
I2C Registers
The IC communicates with the host processor via I2C
and GPIOs. The nIRQ pin indicates general faults which
can be read by the host processor via I2C. A dedicated
power failure pin, PLI, automatically and immediately
goes low to indicate a power loss condition. This gives
the system advanced warning to complete all active
tasks and shutdown. See the Pin Function section for
additional PLI pin functionality.
TheACT4910 contains an array of internal registers that
contain the IC’s basic instructions for setting up the IC
configuration, output voltages, sequencing, fault
thresholds, fault masks, etc. These registers are what
give the IC its operating flexibility. The two types of
registers are described below.
Basic Volatile – These are R/W (Read and Write) and
RO (Read only). After the IC is powered, the user can
modify the R/W register values to change IC
functionality. Changes in functionality include things like
masking certain faults. The RO registers communicate
IC status such as fault conditions. Any changes to these
registers are lost when power is recycled. The default
values are fixed and cannot be changed by the factory
or the end user.
The ACT4910 is highly flexible and contains many I2C
configurable functions. The IC’s default functionality is
defined by its default CMI (Code Matrix Index), but
much of this functionality can be changed via I2C. I2C
functionality includes storage voltage setting, OV and
UV fault thresholds, switching frequencies, ADC control
and automatic fault thresholds, PLI pin functionality,
health check settings, and current limits. The CMI Op-
tions section shows the default settings for each availa-
ble CMI option. Contact sales@active-semi.com for ad-
ditional information about other configurations.
Basic Non-Volatile – These are R/W and RO. After the
IC is powered, the user can modify the R/W register
values to change IC functionality. Changes in
functionality include things like output voltage settings,
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