AAT3603 datasheet(25/35 Pages) ANALOGICTECH

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AAT3603178

Total Power Solution for Portable Applications

PRODUCT DATASHEET

3603.2008.06.1.0

www .analogictech.com

Reverse Battery Leakage

The AAT3603 includes internal circuitry that eliminates

the need for series blocking diodes, reducing solution

size and cost as well as dropout voltage relative to con-

ventional battery chargers. When the input supply is

removed or when CHGIN goes below the AAT3603’s

under voltage-lockout (UVLO) voltage, or when CHGIN

drops below VBAT, the AAT3603 automatically reconfig-

ures its power switches to minimize current drain from

the battery.

Adapter Power Indicator (ADPP)

This is an open drain output which will pull low when

VCHGIN > 4.5V. When this happens the charge current will

be reset to the default ISET values or I2C programmed

values.

Charge Status Output (STAT)

The AAT3603 provides battery charging status via a sta-

tus pin. This pin is a buffered output with a supply level

up to the LDO1 output (PowerDigital). The status pin can

indicate the following conditions:

Event Description

STAT

No battery charging activity

Low (to GND)

Battery charging

High (to VOUT1)

Charging completed

Low (to GND)

Table 2: Charge Status Output (STAT).

CHGIN Bypass Capacitor Selection

CHGIN is the power input for the AAT3603 battery char-

ger. The battery charger is automatically enabled when-

ever a valid voltage is present on CHGIN. In most appli-

cations, CHGIN is connected to either a wall adapter or

USB port. Under normal operation, the input of the char-

ger will often be “hot-plugged” directly to a powered USB

or wall adapter cable, and supply voltage ringing and

overshoot may appear at the CHGIN pin. A high quality

capacitor connected from CHGIN to G, placed as close as

possible to the IC, is sufficient to absorb the energy.

Wall-adapter powered applications provide flexibility in

input capacitor selection, but the USB specification pres-

ents limitations to input capacitance selection. In order

to meet both the USB 2.0 and USB OTG (On The Go)

specifications while avoiding USB supply under-voltage

conditions resulting from the current limit slew rate

(100mA/μs) limitations of the USB bus, the CHGIN

bypass capacitance value must be between 1μF and

4.7μF. Ceramic capacitors are often preferred for bypass-

ing due to their small size and good surge current rat-

ings, but care must be taken in applications that can

encounter hot plug conditions as their very low ESR, in

combination with the inductance of the cable, can create

a high-Q filter that induces excessive ringing at the

CHGIN pin. This ringing can couple to the output and be

mistaken as loop instability, or the ringing may be large

enough to damage the input itself. Although the CHGIN

pin is designed for maximum robustness and an absolute

Constant Current Mode Charge Current

vs. ISET Resistor

(VIN = 5V; VBAT = 3.6V)

ISET Resistor (k

Ω)

200

400

600

800

1000

1200

1400

0.1

100

ISET Voltage vs. Battery Voltage

(CHGIN = 5.0V, RISET = 1.24k

Ω)

Battery Voltage (V)

0.2

0.4

0.6

0.8

1.2

1.4

2.5

2.9

3.3

3.7

4.1

4.5

Figure 5: Constant Current Mode Charge ICH_CC Setting vs. ISET Resistor

and ISET Voltage vs. Battery Voltage.

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