BQ2007 datasheet(2/16 Pages) TI

2 / 16 page

The acceptable battery temperature range is set by an

internal low-temperature threshold and an external

high-temperature cutoff threshold. The absolute tem-

perature is monitored as a voltage on the TS pin with

the external thermistor network shown in Figure 2.

The bq2007 provides for undervoltage battery protection

from high-current charging if the battery voltage is less

than the normal end-of-discharge value. In the case of a

deeply discharged battery, the bq2007 enters the

charge-pending state and attempts trickle-current condi-

tioning of the battery until the voltage increases. Should

the battery voltage fail to increase above the discharge

value during the undervoltage time-out period, a fault

condition is indicated.

Discharge-before-charge may be selected to automatically

discharge the battery pack on battery insertion or with a

push-button switch. Discharge-before-charge on demand

provides conditioning services that are useful to correct or

prevent the NiCd voltage depression, or “memory” effect,

and also provide a zero capacity reference for accurate

capacity monitoring.

After prequalification and any required discharge-

before-charge operations, charge action begins until one of

the full-charge termination conditions is detected. The

bq2007 terminates charging by any of the following methods:

Negative delta voltage (-

∆V)

Peak voltage detect (PVD)

Maximum absolute temperature

Maximum battery voltage

Maximum charge time-out

The bq2007 may be programmed for negative delta

voltage (-

∆V) or peak voltage detect (PVD) charge

termination algorithms. The VSEL input pin selects -

∆V

or PVD termination to match the charge rate and

battery characteristics.

To provide maximum safety for battery and system,

charging terminates based on maximum temperature

cutoff (TCO), maximum cutoff voltage (MCV), and

maximum time-out (MTO). The TCO threshold is the

maximum battery temperature limit for charging. TCO

terminates charge action when the temperature sense

input voltage on the TS pin drops below the TCO pin

voltage threshold. MCV provides battery overvoltage

protection by detecting when the battery cell voltage

(VCELL =VBAT -VSNS) exceeds the VMCV value and ter-

minates fast charge, standard charge, or top-off charge.

The maximum time-out (MTO) termination occurs when

the charger safety timer has completed during the active

charge state.

The bq2007 indicates charge state status with an audio

alarm output option and two dedicated output pins with pro-

grammable display options. The DSEL1–2 inputs can select

one of the three display modes for the LED1–2 outputs.

Charger status is indicated for:

Charge pending

Charge in progress

Charge complete

Fault condition

Pin Descriptions

SEGA–G

Display output segments A–G

State-of-charge monitoring outputs. QDSEL

input selects the bargraph or BCD digit dis-

play mode. See Table 3.

MSEL

Display driver mode select

Soft-programmed input selects LED or LCD

driver configuration at initialization.

When

MSEL is pulled up to VCC, outputs SEGA–G are

LED interface levels; when MSEL is pulled

down to VSS, outputs SEGA–G are LCD levels.

DSEL1–

DSEL2

Display mode select 1–2

Soft-programmed inputs control the LED1—2

charger status display modes at initialization.

See Table 2.

MULT

Fixed-cell pack select

Soft-programmed input is pulled up to VCC

when charging multi-cell packs and is pulled

down to VSS for charging packs with a fixed

number of cells.

QDSEL

State-of-charge display select

The QDSEL input controls the SEGA–G

state-of-charge display modes. See Table 3.

LED1–

LED2

Charger status outputs 1–2

Charger status output drivers for direct

drive of LED displays.

Display modes are

selected by the DSEL input. See Table 2.

INH

Charge inhibit input

When low, the bq2007 suspends all charge ac-

tions, drives all outputs to high impedance, and

assumes a low-power operational state. When

transitioning from low to high, a charge

cycle is initiated. See page 10 for details.

bq2007

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