ADP8860ACBZ-R7 datasheet(14/52 Pages) AD

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ADP8860

Rev. 0 | Page 14 of 52

NOTES

1. VDMAX IS THE CALCULATED GAIN DOWN TRANSITION POINT.

WAIT

100µs (TYP)

MIN (VD1:D7) < VHR(UP)

STATUP:

CHARGE

VIN TO VOUT

EXIT STBY

VOU T > VOUT(START)

WAIT

100µs (TYP)

WAIT

100µs (TYP)

MIN (VD1:D7) < VHR(UP)

MIN (VD1:D7) > VDMAX

MIN (VD1:D7) < VDMAX

G = 2

G = 3/2

EXIT

STARTUP

G = 1

STBY

Figure 27. State Diagram for Automatic Gain Selection

Soft Start Feature

At startup (either from UVLO activation or fault/standby

recovery), the output is first charged by ISS (3.75 mA typical)

until it reaches about 92% of VIN. This soft start feature reduces

the inrush current that is otherwise present when the output

capacitance is initially charged to VIN. When this point is

reached, the controller enters 1× mode. If the output voltage is

not sufficient, then the automatic gain selection determines the

optimal point as defined in the Automatic Gain Selection section.

OPERATING MODES

There are four different operating modes: active, standby,

shutdown, and reset.

Active Mode

In active mode, all circuits are powered up and in a fully

operational state. This mode is entered when nSTBY (in

Standby Mode

Standby mode disables all circuitry except for the I2C receivers.

Current consumption is reduced to less than 1 μA. This mode is

entered when nSTBY is set to 0 or when the nRST pin is held

low for more than 100 μs (maximum). When standby is exited,

a soft start sequence is performed.

Shutdown Mode

Shutdown mode disables all circuitry, including the I2C receivers.

Shutdown occurs when VIN is below the undervoltage thresholds.

When VIN rises above VIN(START) (2.05 V typical), all registers are

reset and the part is placed into standby mode.

Reset Mode

In reset mode, all registers are set to their default values and the

part is placed into standby. There are two ways to reset the part:

power-on reset (POR) and the nRST pin. POR is activated any-

time that the part exits shutdown mode. After a POR sequence

is complete, the part automatically enters standby mode.

After startup, the part can be reset by pulling the nRST pin low.

As long as the nRST pin is low, the part is held in a standby state

but no I2C commands are acknowledged (all registers are kept

at their default values). After releasing the nRST pin, all registers

remain at their default values, and the part remains in standby;

however, the part does accept I2C commands.

The nRST pin has a 50 μs (typical) noise filter to prevent inad-

vertent activation of the reset function. The nRST pin must be

held low for this entire time to activate reset.

The operating modes function according to the timing diagram

in Figure 28.

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