ACT4910QW
Rev 1.0, 15-Sept-2017
startup delay time, and current limit thresholds. Any
changes to these registers are lost when power is
recycled. The default values can be modified at the
factory to optimize IC functionality for specific
applications. Please consult sales@active-semi.com for
custom options and minimum order quantities.
The NORMAL state is the normal operating state after
startup with no faults. The eFuse is fully on, VOUT =
VIN, and the IC provides full operating current. Note that
the IC charges the storage capacitors to their
programmed value at the beginning of NORMAL state.
HEALTH CHECK State
When modifying only certain bits within a register, take
care to not inadvertently change other bits.
Inadvertently changing register contents can lead to
unexpected device behavior.
The HEALTH CHECK state can be considered a sub-
state of NORMAL. The IC operates identical to the
NORMAL state with the addition of activating the
circuitry that check the storage capacitor health. The IC
automatically enters HEALTH STATE every four
minutes. The user may also manually enter this state by
writing a 1 into the FORCE_HLTHCHK bit which is bit 1
in register 0x0Ah. This bit automatically resets to 0 after
the health check routine completes. The IC
automatically exits HEALTH CHECK and enters
SUPPLEMENT state in a fault condition.
State Machine
ACT4910 contains an internal state machine with seven
internal states: UV/POR, SOFT-START, NORMAL,
HEALTH CHECK, SUPPLEMENT, SHUTDOWN1, and
SHUTDOWN2.
UV/POR State
SUPPLEMENT State
The IC enters the UV/POR state on power up. It also
enters UV/POR from SUPPLEMENT state in the
following conditions:
The IC enters SUPPLEMENT state when it detects a
fault condition. It opens the eFuse to bi-directionally
disconnect the input from the output. It automatically
turn on the buck converter to power the output from the
storage capacitors. The following five conditions move
the IC into SUPPLEMENT state.
1. When the input voltage drops below the EN_UV
threshold.
2. When the storage capacitor voltage drops
below 3.6V.
1. EN voltage below UV threshold
2. EN voltage above the OV threshold
3. Input voltage above the OV threshold
4. eFuse current above the OC threshold
5. VIN – VOUT > 560mV
3. When the buck converter output voltage goes
OV or UV.
The user may force the IC into UV/POR by writing a 1
into the FORCE_PWROFF bit, register 0x0Ah, bit 0.
When entering UV/POR from power up, all registers
reset to their default state. The registers retain their
existing values when the IC enters from SUPPLEMENT
state or from SHUTDOWN2 EFUSE. The IC transitions
to the SOFT-START state when EN pin is above 0.64V
and the input voltage is above UVLO.
SHUTDOWN1 State
SHUTDOWN1 protects against over temperature
(145 °C), internal LDO failure, or boot capacitor failure.
The eFuse remains on and continues to provide power
to the output, but the boost converter is disabled. The
ADC remains on and I2C functionality is still operational.
The IC transitions to SHUTDOWN2 state if the die
temperature increases to 155°C. If transitions back to
the NORMAL state if the fault conditions go away.
SOFTSTART State
In the SOFTSTART state, the IC slowly turns on the
eFuse to minimize inrush currents. The output voltage
dV/dt ramp rate is controlled by the SS pin. The SS pin
directly controls the maximum output voltage dV/dt
while the ILIM pin indirectly controls it by limiting the
current into the output capacitance. The IC stays in the
SOFTSTART state until VIN-VOUT < 200mV and a
10ms timer times out. Note that the output voltage may
be fully charged up to VIN even though the IC in still in
the SOFTSTART state. The storage caps charge up to
the output voltage in this state.
NORMAL State
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