BQ2000 Datasheet, PDF(9/18 Page) Texas Instruments – Programmable Multi-Chemistry Fast-Charge Management IC

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BQ2000 Datasheet, PDF (9/18 Pages) Texas Instruments – Programmable Multi-Chemistry Fast-Charge Management IC

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bq2000

Table 2. Summary of NiCd or NiMH Charging Characteristics

Parameter

Maximum cell voltage (VMCV)

Minimum pre-charge qualification voltage (VLBAT)

High-temperature cutoff voltage (VTCO)

High-temperature fault voltage (VHTF)

Low-temperature fault voltage (VLTF)

bq2000 fast-charge maximum time out (MTO)

Fast-charge charging current (IMAX)

Hold-off period

Top-off charging current (optional)

Top-off period (optional)

Trickle-charge frequency

Trickle-charge pulse-width

Value*

950mV

0.225 â VCC

0.25 â VCC

0.5 â VCC

RMTO â CMTO â 35,988

0.05/RSNS

MTO/32

IMAX/16

MTO

1Hz

See Figure 7

*Please refer to DC Thresholds Specification for details.

SNS voltage is less than VSNSLO or greater than VSNSHI,

the bq2000 switches the MOD output low to shut off

charging current to the battery. Figure 8 shows a typical

multi-chemistry charge circuit.

Temperature Monitoring

The bq2000 measures the temperature by the voltage at

the TS pin. This voltage is typically generated by a neg-

ative-temperature-coefficient thermistor. The bq2000

compares this voltage against its internal threshold

voltages to determine if charging is safe. These

thresholds are the following:

n High-temperature cutoff voltage: VTCO = 0.225 â VCC

This voltage corresponds to the maximum

temperature (TCO) at which fast charging is allowed.

The bq2000 terminates fast charge if the voltage on

pin TS falls below VTCO.

Table 3. Summary of Li-Ion Charging Characteristics