BQ2007STR datasheet(8/16 Pages) TI1

8 / 16 page

VCC(VMCV). The bq2007 charges fixed-cell battery packs

of N cells. The battery voltage divider is set by the di-

vider ratio equation:

R22

=−

()

Note:

The resistor-divider network impedance

should be above 200K

Ω to protect the bq2007.

When battery temperature is monitored for maximum

and minimum allowable limits, the bq2007 requires that

the thermistor used for temperature measurement have

a negative temperature coefficient. See Figure 2.

Temperature and Voltage

Prequalifications

For charging to be initiated, the battery temperature

must fall within predetermined acceptable limits. The

voltage on the TS pin (VTS) is compared to an internal low-

temperature fault threshold (VLTF) of (0.5

∗ VCC) and the

high temperature cutoff voltage (VTCO) on the TCO pin. For

charging to be initiated, VTS must be less than VLTF and

greater than VTCO. Since VTS decreases as temperature

increases, the TCO threshold should be selected to be lower

than 0.5

∗ VCC for proper operation. If the battery

temperature is outside these limits, the bq2007 holds the

charge-pending state with a pulse trickle current until the

temperature is within limits. Temperature prequalification

and termination is disabled if VTS is greater than 0.8

∗ VCC.

See Figure 2.

The bq2007 provides undervoltage battery protection by

trickle-current conditioning of a battery that is below

the low-voltage threshold (VEDV). The battery voltage

(VCELL) is compared to the low-voltage threshold (VEDV)

and charge will be inhibited if VCELL <VEDV. The condi-

tion trickle current and fault time-out are a percentage

of the fast charge rate and maximum time-out (MTO).

Initiating Charge Action and

Discharge-Before-Charge

A charge action is initiated under control of: (1) battery

insertion or (2) power applied. Battery insertion is

detected when the voltage at the BAT pin falls from

above VMCV to below VMCV. Power applied is detected

by the rising edge of VCC when a battery is inserted.

Discharge-before-charge (see Figure 3) is initiated auto-

matically on application of power or battery insertion

when DCMD is connected to VSS. Discharge-on-demand

SLUS076A – JULY 2000

bq2007

FG200701.eps

bq2007

VCC

BAT

bq2007

VCC

SNS

BAT Voltage Connection

Thermistor Connection

NTC = negative temperature coefficient thermistor.

VSS

RSNS

VSS

RSNS

Figure 2. Voltage and Temperature Limit Measurement

bq2007

DCMD

Always Discharge

Discharge on

Command

DCMD

Figure 3. Discharge-Before-Charge

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