BAT+

Q1

FMMT718

D2

ZHCS1000

L1

47 H

m

C9

1000PF

R12

120OHMS

Q2

MMBT3904LT1

C6

47 F

m

D5

MMSD914LT

D3

MMSD914LT

D4

S1A

DC-

R10

1KW

D1

RED

R2

2KW

C3

10 F

m

D6

BZT52-C5V1

R1

100KW

RC 6

LED

3

BAT

4

VSS

2

TS

5

VCC 7

SNS

1

MOD 8

U1

bq2000

C4

0.0022 F

m

R4

12.4K

VCC

C7

4.7PF

C8

0.33 F

m

Q3

MMBT3904LT1

R11

220 W

R6

210KW

C5

10 F

m

BAT-

THERM

CHEMISTRY

R7

200KW

R9

221KW

R5

20KW

C1

0.1

R8

6.81KW

C2

0.1

NOTES:

1.ForLi-Ion,theCHEMISTRY isleftfloating.

ForNiCd/NiMH,theCHEMISTRY istiedtoBAT-

2.DCinputvoltage:9–16V

4.L1:3L GlobalP/NPKSMD-1005-470K-1A

3.Chargecurrent:1A

R13

1.1K

R3

0.05 W

DC+

bq2000

SLUS138D – JANUARY 2008 – REVISED DECEMBER 2009

www.ti.com

Figure 7. Single-Cell Li-Ion, 3-Cell NiCd/NiMH 1A Charger

Minimum Current (Li-Ion Only)

The bq2000 monitors the charging current during the voltage-regulation phase of Li-Ion batteries. Fast charge is

terminated when the current is tapered off to 14% of the maximum charging current.

Once constant-current fast charge has ended, the bq2000 either measures the value of the CMTO capacitor (in

the case of Nickel batteries) and then proceeds to either top-off or trickle maintenance charge or simply

completes the constant-voltage stage of fast charge (in the case of a Li-Ion cell).

Top-Off and Pulse-Trickle Maintenance Charge

An optional top-off charge is available for NiCd or NiMH batteries. Top-off may be desirable on batteries that

have a tendency to terminate charge before reaching full capacity. To enable this option, the capacitance value

of CMTO connected between the RC pin and VCC (Figure 5) should be greater than 0.13µF, and the value of the

resistor connected to this pin should be less than 250k

Ω. To disable top-off, the capacitance value should be less

than 0.07µF. The tolerance of the capacitor needs to be taken into account in component selection.

Once top-off is started, the timer is reset and top-off proceeds until the timer expires, VMCV is reached, or there is

a temperature fault. During top-off, current is delivered to the battery in pulses that occur each second. The fixed

pulse width allows an average current of 1/16 of the fast charge current to be delivered to the battery every

second. The LED is always off during top-off and trickle maintenance charge.

10

Submit Documentation Feedback

Copyright © 2008–2009, Texas Instruments Incorporated

Product Folder Link(s): bq2000