BQ24070 datasheet(17/26 Pages) TI

17 / 26 page

www.ti.com

bq24070

LTF

HTF

BATTERY

PACK

PACK+

PACK−

NTC

TEMP

ITS

VLTF

VHTF

RT1

RT2

UDG

−04086

bq24070

LTF

HTF

BATTERY

PACK

PACK+

PACK−

NTC

ITS

VLTF

VHTF

UDG

−04085

Battery Pre-Conditioning

O (PRECHG) +

(PRECHG)

(SET)

SET

(3)

Battery Charge Current

O (OUT) +

(SET)

SET

(4)

bq24070

SLUS694A – MARCH 2006 – REVISED MARCH 2006

FUNCTIONAL DESCRIPTIONS (continued)

pins. An internal current source provides the bias for most-common 10 k

Ω negative-temperature coefficient

thermistors (NTC) (see Figure 9). The device compares the voltage on the TS pin against the internal V(LTF) and

V(HTF) thresholds to determine if charging is allowed. Once a temperature outside the V(LTF) and V(HTF) thresholds

is detected, the device immediately suspends the charge. The device suspends charge by turning off the power

FET and holding the timer value (i.e., timers are not reset). Charge is resumed when the temperature returns to

the normal range. The allowed temperature range for 103AT-type thermistor is 0°C to 45°C. However, the user

may increase the range by adding two external resistors. See Figure 10.

Figure 9. TS Pin Configuration

Figure 10. TS Pin Thresholds

During a charge cycle, if the battery voltage is below the V(LOWV) threshold, the bq24070 applies a precharge

current, IO(PRECHG), to the battery. This feature revives deeply discharged cells. The resistor connected between

the ISET1 and VSS, RSET, determines the precharge rate. The V(PRECHG) and K(SET) parameters are specified in

the specifications table. Note that this applies to both AC-mode and USB-mode charging.

The bq24070 activates a safety timer, t(PRECHG), during the conditioning phase. If V(LOWV) threshold is not

reached within the timer period, the bq24070 turns off the charger and enunciates FAULT on the STAT1 and

STAT2 pins. The timeout is extended if the charge current is reduced by DPPM or thermal regulation. See the

Timer Fault Recovery section for additional details.

The bq24070 offers on-chip current regulation with programmable set point. The resistor connected between the

ISET1 and VSS, RSET, determines the charge level. The charge level may be reduced to give the system priority

on input current (see DPPM). The V(SET) and K(SET) parameters are specified in the specifications table.

When powered from a USB port, the input current available (0.1 A/0.5 A) is typically less than the programmed

(ISET1) charging current, and therefore, the DPPM feature attempts to keep the output from being pulled down

by reducing the charging current.

The charge level, during AC mode operation only (Mode = High), can be changed by a factor of 2 by setting the

ISET2 pin high (full charge) or low (half charge). The voltage on the ISET1 pin, VSET1, is divided by 2 when in

the half constant current charge mode. Note that with Mode low, the ISET2 pin controls only the 0.1 A/0.5 A

USB current level.

See the section titled Power-Path Management for additional details.

Submit Documentation Feedback

BQ24070 Datasheet(PDF) 17 Page - Texas Instruments

BQ24070 Datasheet(HTML) 17 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

Datasheet Download

Link URL