bq2057, bq2057C

bq2057T, bq2057W

SLUS025F − MAY 2001 − REVISED JULY 2002

11

www.ti.com

APPLICATION INFORMATION

Figure 5. High-Side Current Sensing

Figure 6. Low-Side Current Sensing

SNS

BAT

VCC

TS

COMP

CC

VSS

STAT

bq2057

DC+

DC−

RSNS

BAT+

BAT−

SNS

BAT

VCC

TS

COMP

CC

VSS

STAT

bq2057

DC+

DC−

RSNS

BAT+

BAT−

voltage regulation phase

The voltage regulation feedback is through the BAT pin. This input is tied directly to the positive side of the

battery pack. The bq2057 monitors the battery-pack voltage between the BAT and VSS pins. The bq2057 is

offered in four fixed-voltage versions: 4.1 V, 4.2 V, 8.2 V and 8.4 V.

Other regulation voltages can be achieved by adding a voltage divider between the positive and negative

terminals of the battery pack and using bq2057T or bq2057W. The voltage divider presents scaled battery-pack

voltage to BAT input. (See Figure 7 and Figure 8.) The resistor values RB1 and RB2 for the voltage divider are

calculated by the following equation:

R

B1

R

B2

+ N

V

(CELL)

V

O(REG)

–1

Where:

N = Number of cells in series

(2)