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Precharge and 0-V Charging—Theory of Operation

SLEEP Control Input (SLEEP)

Power Modes

bq29312A

SLUS629A – JANUARY 2005 – REVISED AUGUST 2005

FUNCTIONAL DESCRIPTION (continued)

The default-state of the CHG and DSG FET drive is off, when PMS = GND. A host can control the FET drive by

programming OUTPUT CTL (b3...b1) where b1 is used to control the discharge FET, b2 is used to control the

charge FET, and b3 is used to control the ZVCHG FET. These controls are only valid when not in the initialized

state. The CHG drive FET can be powered by PACK and the DSG FET can be powered by BAT.

The bq29312A supports both a charger that has a precharge mode and one that does not. The bq29312A also

supports charging even when the battery falls to 0 V. Detail is described in the application section.

The SLEEP input is pulled-up internally to REG. When SLEEP is pulled to REG, the bq29312A enters the

SLEEP mode. The SLEEP mode disables all the FET outputs and the OL, SC, and watchdog faults are also

disabled. The RAM configuration is still valid on exit of the SLEEP mode. The host can force the bq29312A into

SLEEP mode via register control also.

Table 1. SLEEP Control Input

SLEEP

ITEM

EXIT SLEEP

FUNCTION

Active

REG Output

Active

External pin control:

CHG, DSG, ZVCHG, TOUT, OD

OC and SC protection:

Write is available,

Last pre-sleep entry configuration is valid. (If

SCD, SCC and OCD

but read is disabled

change configuration, latest write data is valid.)

CELL Translation

Disabled

PACKOUT, VMEN

Cell Balancing:

CB[3:0]

Watchdog: WDDIS

The bq29312A has three power modes, Normal, Sleep, and Ship. The following table outlines the operational

functions during these power modes.

Table 2. Power Modes

POWER

TO EXIT POWER

TO ENTER POWER MODE

MODE DESCRIPTION

MODE

MODE

The battery is in normal operation with protection, power

management, and battery monitoring functions available and

SLEEP = GND and

operating.

Normal

STATE CTL( b0) = 0 and

STATE CTL( b1) = 0

The supply current of this mode varies as the host can enable

and disable various power management features.

{SLEEP = REG (floating) or

On entry to this mode, all registers are masked off keeping

SLEEP = GND and

Sleep

STATE CTL( b0) = 1 } and

their state.

STATE CTL( b0) = 0

STATE CTL( b1) = 0

interface, but reading data is disabled until exit of Sleep mode.

STATE CTL( b1) = 1

The bq29312A is completely shut down as in the sleep mode.

Supply voltage to

Ship

And supply at the PACK pin is

PACK

removed

powered down, and memory is not valid.

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