ACT4921 datasheet(19/35 Pages) QORVO

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Data Sheet Rev. B, January 2020 | Subject to change without notice

19 of 35

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ACT4921

Power Loss Protection with 6A eFuse

VIN

VOUT

VSTR

PLI

nIRQ

EN_UV

Buck_UV

Soft Start

Boost On

Supplement

Mode

10ms

Delay

9ms Delay

Figure 4: Operation State

Pin Functions

VIN

VIN is the input the eFuse. Connect a 0.1uF ceramic

capacitor between VIN and PGND. VIN is directly

connected to VOUT in normal operation. The eFuse

disconnects VIN from VOUT when the IC enters

supplement mode.

The EN pin provides a digital input to turn the IC on or

off. When EN is low when input power is applied, the IC

remains disabled. Pulling EN high moves the IC into the

SOFTSTART state. When EN is pulled low while input

power

valid,

the

immediately

enters

SUPPLEMENT mode. After the storage capacitor is

depleted, the IC is disabled.

VINS

The

VINS

provides

both

overvoltage

and

undervoltage protection thresholds. The VINS pin

contains two precision comparators with hysteresis. It

can be directly driven from a digital input to turn the

eFuse on and off. The EN pin is typically used with a

resistor divider from VIN to AGND to program an eFuse

startup voltage higher than the IC’s UVLO value. The

eFuse turns on when the input EN is high and the VINS

voltage goes above the VINS_UV_REF threshold.

Once the eFuse is on, it turns off and enters supplement

mode if the VINS pin goes above the VINS_OV_REF

threshold or below the VINS_UV_REF threshold.

The VINS pin should not be left floating. It can be driven

from standard logic signals greater than VINS_UV_REF.

It can also be driven with open-drain logic to provide.

When driving it with an open-drain, ensure that the

pullup voltage is not higher than the VINS_OV_REF

setting.

VINS_UV_REF is fixed at 0.64V. However, the

VINS_OV_REF can be programmed by I2C bits

VINS_OV_REF [2:0].

The default VINS_OV_REF

voltage is set by the IC’s CMI.

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