BQ2002DSLASHT datasheet(4/21 Pages) TI2

4 / 21 page

Note: This resistor-divider network input impedance to

end-to-end should be at least 200k

Ω and less than 1 MΩ.

A ground-referenced negative temperature coefficient ther-

mistor placed in proximity to the battery may be used as a

low-cost temperature-to-voltage transducer. The tempera-

ture sense voltage input at TS is developed using a

resistor-thermistor network between VCC and VSS.

See

Figure 1.

Starting A Charge Cycle

Either of two events starts a charge cycle (see Figure 5):

1. Application of power to VCC or

2. Voltage at the BAT pin falling through the maximum

cell voltage where

VMCV =2V

±5%

If the battery is within the configured temperature and

voltage limits, the IC begins fast charge. The valid bat-

tery voltage range is VBAT <VMCV. The valid tempera-

ture range is VHTF <VTS <VLTF for the bq2002T and

VHTF <VTS for the bq2002D where

VLTF = 0.4

∗ VCC ±5%

VHTF = 0.25

∗ VCC ±5% (bq2002T only)

If the battery voltage or temperature is outside of these

limits, the IC pulse-trickle charges until the tempera-

ture falls within the allowed fast charge range or a new

charge cycle is started.

Fast charge continues until termination by one or more of

the four possible termination conditions:

n Rate of temperature rise

n Maximum voltage

n Maximum temperature

n Maximum time

T/ t Termination

The bq2002D/T samples at the voltage at the TS pin ev-

ery 19s and compares it to the value measured three

samples earlier.

If the voltage has fallen 25.6mV or

more, fast charge is terminated. The

∆T/∆t termination

test is valid only when VTCO <VTS <VLTF for the

bq2002T and VTCO <VTS for the bq2002D.

Temperature Sampling

A sample is taken by averaging together 16 measure-

ments taken 570

µs apart. The resulting sample period

(18.18ms) filters out harmonics around 55Hz. This tech-

bq2002D/T

OSC

LED

VCC

VSS

BAT

INH

Clock

Phase

Generator

Timing

Control

Sample

History

A to D

Converter

MCV

Check

Power

Down

Bd2002TD.eps

Voltage

Reference

Power-On

Reset

TCO

Check

HTF/

LTF

Check

Charge-Control

State Machine

T/ t

ALU

Figure 4. Block Diagram

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