FUSE

160

1 k

Si 1406

1

OUT 8

0.1 F

2

VDD 7

260

3

6

4

CD

GND 5

0.1

F

100

0.33 F

PWR PAD

0.1 F

VC1_ CB

VC1

VC 2

CB_ EN

100

PACK+

PACK±

CELL2

CELL1

13

bq29200, bq29209

www.ti.com

SLUSA52C – SEPTEMBER 2010 – REVISED MARCH 2016

Product Folder Links: bq29200 bq29209

Submit Documentation Feedback

Copyright © 2010–2016, Texas Instruments Incorporated

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

9.1 Application Information

The bq2920x is designed to be used in 2-series Li-Ion battery packs and with the option to include voltage-based

cell balancing. The number of parallel cells or the overall capacity of the battery only affects the cell balancing

circuit due to the level of potential imbalance that needs to be corrected.

9.2 Typical Applications

9.2.1 Battery Connection

Figure 9 shows the configuration for the 2-series cell battery connection with cell balancing enabled.

Figure 9. 2-Series Cell Configuration

9.2.1.1 Design Requirements

For this design example, use the parameters listed in Table 1.

Table 1. Design Parameters

DESIGN PARAMETER

Input voltage range

4 V to 10 V

Overvoltage Protection (OVT)

4.35 V

Overvoltage detection delay time

3 s

Overvoltage detection delay timer capacitor

0.33 µF

Cell Balancing Enabled

Yes

Cell Balancing Current, ICB1 and ICB2

10 mA

Cell Balancing Resistors, RCB, RCB1, RCB2 and RVD

RCB = 100

Ω, RCB1 = 260 Ω, RCB2 = 160 Ω, RVD = 100 Ω

9.2.1.2 Detailed Design Procedure

The bq2920x has limited features but there are some key calculations to be made when selecting external

component values.

•

Calculate the required CCD capacitor value for the voltage protection delay time. Care should be taken to

evaluate the tolerances of the capacitor and the bq2920x to ensure system specifications are met.

•

Calculate the cell balancing resistor values to provide a suitable level of balancing current that will, at a

minimum, counter act an increase in imbalance during normal operation of the battery. Care should be taken

to ensure any connectivity resistance is also considered as this will also reduce the balancing current level.