BQ24030 Datasheet, PDF(13/20 Page) Texas Instruments – SINGLE-CHIP CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC (bqTINYI)

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BQ24030 Datasheet, PDF (13/20 Pages) Texas Instruments – SINGLE-CHIP CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC (bqTINYI)

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bq24030, bq24032, bq24035

www.ti.com

Case 2: USB (PSEL = Low)

SLUS618 â AUGUST 2004

System Power

In this case, the system load is powered directly from the USB port through the internal switch Q3 (see Figure 5

). Note in this case Q3 regulates the total current to the 100 mA or 500 mA level, as selected on the ISET2 input.

Switch Q1 is turned off in this mode. If the system and battery load is less than the selected regulated limit, then

Q3 is fully on and VOUT is approximately (VUSB-VUSB-DO). The systemâs power management is responsible for

keeping its system load below the USB current level selected (if the battery is critically low or missing), otherwise

the output drops to the battery voltage. Therefore, the system should have a low power mode for USB power

application. The DPPM feature keeps the output from dropping below its programmed threshold, due to the

battery charging current, by reducing the charging current.

Charge Control

When USB is present and selected, Q3 regulates the input current to the value selected by the ISET2 pin

(0.1/0.5A). The charge current to the battery is set by the ISET1 resistor (typically > 0.5A). Since the charge

current typically is programmed for more current than Q3 allows, the output voltage drops to the battery voltage

or DPPM voltage, which ever is higher. If the DPPM threshold is reached first, the charge current is reduced as

described below.

Dynamic Power Path Management (DPPM)

The theory of operation is the same as described above, in CASE 1, except that Q3 restricts the amount of input

current delivered to the output and battery instead of the input supply.

Note that the DPPM voltage, V(DPPM), is programmed as follows:

V(DPPM) + I(DPPM) R(DPPM) SF

(2)

where

â¢ RDPPM is the external resistor connected between the DPPM and VSS pins

â¢ I(DPPM) is the internal current source

â¢ SF is the scale factor as specified in the specification table

Battery Temperature Monitoring

The bqTINY-III continuously monitors battery temperature by measuring the voltage between the TS and VSS

pins. An internal current source provides the bias for most-common 10 kâ¦ negative-temperature coefficient

thermistors (NTC) (see Figure 5). 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

powerFET 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 0Â°C to 45Â°C. However

the user may increase the range by adding two external resistors. See Figure 6.

bqTINYIII

LTF

HTF

VLTF

VHTF

PACK+

ITS

PACKâ

NTC

BATTERY

PACK

Figure 5. TS Pin Configuration

UDGâ04085