BQ2003 datasheet(4/20 Pages) TI2

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Discharge-Before-Charge

The DCMD input is used to command discharge-before-

charge via the DIS output. Once activated, DIS becomes

active (high) until VCELL falls below VEDV, at which time

DIS goes low and a new fast charge cycle begins. See

Table 1 for the conditions that initiate discharge-before-

charge.

Discharge-before-charge is qualified by the

same voltage and temperature conditions that qualify a

new charge cycle start (see below). If a discharge is ini-

tiated but the pack voltage or temperature is out of

range, the chip enters the charge pending mode and

trickle charges the battery until the voltage and tem-

perature qualification conditions are met, and then

starts to discharge.

Starting A Charge Cycle

The stimulus required to start a new charge cycle is de-

termined by the configuration of the CCMD and DCMD

inputs.

If CCMD and DCMD are both pulled up or

pulled down, then a new charge cycle is started by (see

Figure 2):

VCC rising above 4.5V

VCELL falling through the maximum cell voltage,

VMCV.VMCV is the voltage presented at the MCV

input pin, and is configured by the user with a re-

sistor divider between VCC and ground.

The al-

lowed range is 0.2 to 0.4

∗ VCC.

A rising edge on CCMD if it is pulled down, or a fal-

ling edge on CCMD if it is pulled up.

Starting a new charge cycle may be limited to a push-

button or logical pulse input only by pulling one member

of the DCMD and CCMD pair up while pulling the other

input down. In this configuration a new charge cycle

will be started only by a falling edge on CCMD if it is

pulled up, and by a falling edge on CCMD if it is pulled

down. See Table 1.

If the battery is within the configured temperature and

voltage limits, the IC begins fast charge. The valid bat-

tery voltage range is VEDV <VBAT <VMCV where:

VEDV = 0.2

∗ VCC ± 30mV

The valid temperature range is VHTF <VTEMP <VLTF,

where:

VLTF = 0.4

∗ VCC ± 30mV

VHTF = [(1/8

∗ VLTF) + (7/8 ∗ VTCO)] ± 30mV

VTCO is the voltage presented at the TCO input pin, and is

configured by the user with a resistor divider between VCC

and ground. The allowed range is 0.2 to 0.4

∗ VCC.

If the temperature of the battery is out of range, or the

voltage is too low, the chip enters the charge pending

state and waits for both conditions to fall within their

allowed limits.

There is no time limit on the charge

pending state; the charger remains in this state as long

as the voltage or temperature conditons are outside of

bq2003

Fast Charging

Top-Off

(Optional)

34 sec.

TD200301a.eps

Discharge

(Optional)

Charge

Pending

DIS

MOD Switch-Mode Configuration

MOD External Regulation

(SNS Grounded)

CHG Status Output

TEMP Status Output

Charge cycle start.

Battery outside temperature limits.

Battery within temperature limits.

Battery discharged to 0.2

VCC.

sec.

Figure 2. Charge Cycle Phases

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