ADP1055ACPZ-R7 datasheet(17/140 Pages) AD

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Data Sheet

ADP1055

Rev. A | Page 17 of 140

START-UP AND POWER-DOWN SEQUENCING

VDD AND VCORE PINS

The proper amount of decoupling capacitance must be placed

between the VDD and AGND pins, as close as possible to the

device to minimize the trace length. It is recommended that the

VCORE pin not be loaded in any way.

POWER-UP AND POWER-DOWN COMMANDS

The PMBus commands OPERATION (Register 0x01) and

ON_OFF_CONFIG (Register 0x02) control the power-up and

power-down behavior of the ADP1055.

Figure 20. OPERATION (Register 0x01) and ON_OFF_CONFIG

(Register 0x02)

POWER SEQUENCING

Power sequencing is controlled using Register 0x60 through

0x60, TON_DELAY) and the turn-off command (Register 0x64,

TOFF_DELAY) can each be programmed from 0 ms to 1024 ms

in steps of 1 ms.

The soft start ramp-up time (Register 0x61, TON_RISE) and

the ramp-down time (Register 0x65, TOFF_FALL) can be

programmed from 0 ms to 100 ms in steps of 1 ms.

All values are rounded to the nearest available value. If a value is

programmed outside the allowed range, it is forced to the nearest

legal value.

POWER-UP AND SOFT START ROUTINE

When VDD is applied to the device, a certain time elapses

before the ADP1055 can regulate the power supply.

When VDD is above UVLO and VCORE reaches above

VCORE POR through an internal regulator, the ADP1055

downloads the user settings from Page 1 of the EEPROM

into the internal registers.

After the EEPROM download, the ADP1055 determines its

address, programmed by the ADD pin and the I2C slave

base address (Register 0xD0, SLV_ADDR_SELECT).

The ADP1055 waits for an idle time, after which the device

is ready for normal operation. If the black box must erase a

page to precondition the EEPROM for storing, the idle

time is extended by ~35 ms (see the Black Box Timing

section).

If the ADP1055 is programmed to power up at this time

(OPERATION is enabled), the soft start ramp begins.

Otherwise, the ADP1055 waits for the OPERATION

command.

The outputs start switching, depending on the configuration of

the OPERATION command (Register 0x01) and the ON_OFF_

CONFIG command (Register 0x02).

If the ADP1055 is programmed to be always on (Register

0x02[4] = 0), the device begins the soft start ramp. Figure 21

shows the entire soft start process.

Figure 21. Example of Soft Start and Soft Stop Settings in the GUI

The soft start proceeds as follows.

Upon power-up, the ADP1055 waits for the programmed

TON_DELAY (Register 0x60) and ramps to the regulation

voltage according to the time programmed in TON_RISE

(Register 0x61).

The soft start begins to ramp up the internal digital

reference. The total duration of the soft start ramp is

programmable using the TON_RISE command. The

TON_MAX command specifies the maximum on time

before which the output voltage must exceed the

VOUT_UV_FAULT_LIMIT (Register 0x44). If the

VOUT_UV_FAULT_LIMIT is set to 0, the TON_MAX

value is ignored.

If the soft start from precharge function is enabled

(Register 0xFE51[0] = 1), the soft start ramp starts from the

current value of the output voltage sensed on VS± and,

therefore, the soft start ramp time is reduced proportionally.

SOFT STOP ROUTINE

The soft stop process occurs in a manner similar to the soft start

process, using the TOFF_DELAY, TOFF_MAX, and TOFF_FALL

commands. These commands are the counterparts of the

TON_DELAY, TON_MAX, and TON_RISE commands used

for soft start. For more information about soft stop, see the Soft

Stop section.

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