BQ2000TPN datasheet(9/16 Pages) TI

9 / 16 page

A NiCd or NiMH battery pack consisting of N se-

ries-cells may benefit by the selection of the RB1 value to

be N-1 times larger than the RB2 value.

In a mixed-chemistry design, a common voltage-divider

is used as long as the maximum charge voltage of the

nickel-based pack is below that of the Li-Ion pack. Oth-

erwise, different scaling is required.

Temperature Monitoring

The bq2000T measures the temperature by the voltage

at the TS pin. This voltage is typically generated by a

negative-temperature-coefficient thermistor. The

bq2000T 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

∗ VCC

This

voltage

corresponds

the

maximum

temperature (TCO) at which fast charging is allowed.

The bq2000T terminates fast charge if the voltage on

pin TS falls below VTCO.

n High-temperature fault voltage: VHTF = 0.25

∗ VCC This

voltage corresponds to the temperature (HTF) at which

fast charging is allowed to begin.

n Low-temperature fault voltage: VLTF = 0.5

∗ VCC

This voltage corresponds to the minimum temperature

bq2000T

Parameter

Value

Maximum cell voltage (VMCV)2V

Minimum pre-charge qualification voltage (VLBAT)

950mV

High-temperature cutoff voltage (VTCO)

0.225

∗ VCC

High-temperature fault voltage (VHTF)

0.25

∗ VCC

Low-temperature fault voltage (VLTF)

0.5

∗ VCC

bq2000T fast-charge maximum time out (MTO)

RMTO

∗ CMTO ∗ 35,988

Fast-charge charging current (IMAX)

0.05/RSNS

Hold-off period

MTO/32

Top-off charging current (optional)

IMAX/16

Top-off period (optional)

MTO

Trickle-charge frequency

1Hz

Trickle-charge pulse-width

See Figure 7

Table 2. Summary of NiCd or NiMH Charging Characteristics

Parameter

Value

Maximum cell voltage (VMCV)2V

Minimum pre-charge qualification voltage (VLBAT)

950mV

High-temperature cutoff voltage (VTCO)

0.225

∗ VCC

High-temperature fault voltage (VHTF)

0.25

∗ VCC

Low-temperature fault voltage (VLTF)

0.5

∗ VCC

bq2000T fast-charge maximum time-out (MTO)

∗ RMTO ∗ CMTO ∗ 35,988

Fast-charge charging current (IMAX)

0.05/RSNS

Hold-off period

MTO/32

Minimum current (for fast-charge termination)

IMAX/14

Trickle-charge frequency (before fast charge only)

1Hz

Trickle-charge pulse-width (before fast charge only)

See Figure 7

Table 3. Summary of Li-Ion Charging Characteristics

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