BQ2007STR datasheet(9/16 Pages) TI1

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is initiated by a negative-going pulse on the DCMD pin

regardless of charging activity. The DCMD pin is inter-

nally pulled up to VCC; therefore, not connecting this pin

results in disabling the discharge-before-charge func-

tion. When the discharge begins, the DIS output goes

high to activate an external transistor that connects a

load to the battery. The bq2007 terminates discharge-

before-charge by detecting when the battery cell voltage

is less than or equal to the end-of-discharge voltage

(VEDV).

Charge State Actions

Once the required discharge is completed and temperature

and voltage prequalifications are met, the charge state is

initiated. The charge state is configured by the VSEL,

FAST, and TM input pins. The FAST input selects between

Fast and Standard charge rates. The Standard charge rate

is 14 of the Fast charge rate, which is accomplished by dis-

abling the regulator for a period of 286

µs of every 1144µs

(25% duty cycle). In addition to throttling back the charge

current, time-out and hold-off safety time are increased ac-

cordingly. See Table 4.

The VSEL input selects the voltage termination method.

The termination mode sets the top-off state and trickle

charge current rates.

The TM input selects the Fast

charge rate, the Standard rate, and the corresponding

charge times. Once charging begins at the Fast or Stan-

dard rate, it continues until terminated by any of the fol-

lowing conditions:

Negative delta voltage (-

∆ V)

Peak voltage detect (PVD)

Maximum temperature cutoff (TCO)

Maximum time-out (MTO)

Maximum cutoff voltage (MCV)

Voltage Termination Hold-off

To prevent early termination due to an initial false peak

battery voltage, the -

∆ V and PVD terminations are

disabled during a short “hold-off” period at the start of

charge. During the hold-off period when fast charge is

selected (FAST = 1), the bq2007 will top off charge to

prevent excessive overcharging of a fully charged

battery. Once past the initial charge hold-off time, the

termination is enabled. TCO and MCV terminations are

not affected by the hold-off time.

∆V or PVD Termination

Table 5 summarizes the two modes for full-charge

voltage termination detection. When VSEL =VSS,

negative delta voltage detection occurs when the voltage

seen on the BAT pin falls 12mV (typical) below the

maximum sampled value. VSEL =VCC selects peak

voltage detect termination and the top-off charge state.

PVD termination occurs when the BAT pin voltage falls

6mV per cell below the maximum sampled value. When

charging a battery pack with a fixed number of cells, the

∆ V and PVD termination thresholds are -6mV and 0 to

-3mV per cell, respectively.

The valid battery voltage

range on VBAT for -

∆ V or PVD termination is from

0.262

∗ VCC to 0.8 ∗ VCC.

SLUS076A – JULY 2000

bq2007

VSEL

Detection

Method

Top-Off

Pulse Trickle

Rate

VSS

∆ V

Disabled

VCC

PVD

Enabled

Table 5. VSEL Configuration

FAST

Input

State

Input

State

Time-out

Period

(min)

MOD

Duty

Cycle

Hold-off

period

(sec)

Trickle

Rep Rate

∆ V C 32

Trickle

Rep Rate

PVD C 64

VSS

Float

640 (C8)

25%

2400

219Hz

109Hz

VSS

320 (C4)

25%

1200

109Hz

55Hz

VSS

VCC

160 (C2)

25%

600

55Hz

27Hz

VCC

Float

160 (C2)

100%

600

219Hz

109Hz

VCC

VSS

80 (C)

100%

300

109Hz

55Hz

VCC

40 (2C)

100%

150

55Hz

27Hz

Table 4. bq2007 Charge Action Control Summary

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