High-Voltage, Dual-Input, USB/AC

Adapter Chargers in 2mm x 3mm TDFN

8

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Detailed Description

The MAX8804W/MAX8804Y/MAX8804Z dual-input linear

battery chargers use voltage, current, and thermal-con-

trol loops to charge and protect a single Li+ battery.

When a Li+ battery with a cell voltage below 2.5V is

inserted, the MAX8804W/MAX8804Z chargers enter the

prequalification stage where they precharge that cell

with 95mA (Figure 2). The CHG indicator output is dri-

ven low to indicate entry into the prequalification state.

When battery voltage exceeds 2.5V, the charger soft-

starts as it enters the fast-charge stage. The MAX8804Y

eliminates the prequalification state and enters fast-

charge when the battery is inserted. The fast-charge cur-

rent level is programmed by a simple single-wire

interface. As the battery voltage approaches 4.2V, the

charging current is reduced. If the battery current drops

below the top-off current threshold, the CHG indicator

goes high impedance, signaling that the battery is fully

charged. The ICs then enter a constant voltage-regula-

tion mode to maintain the battery at full charge.

The MAX8804W/MAX8804Y/MAX8804Z automatically

select between either a USB or AC adapter input source.

The AC adapter charge current is programmable from

400mA to 700mA in 50mA steps through a simple single-

wire interface (see Tables 2 and 3). The USB charge cur-

rent is programmable to 95mA, 380mA, or 475mA

through the same interface (see Tables 4 and 5).

DC AND USB OUTPUT CONTROL

LOGIC

CONTROL

DC

USB

BAT

SET

POK

CHG

<USBPWR>

4.15V TO 30V

4.15V TO 16V

TEMP

SENSOR

+105

°C

VOLTAGE

LOOP

BIAS

CIRCUIT

REF

GND

OVERVOLTAGE

PROTECTION

Li+

MAX8804Y

MAX8804Z

DC

POK

USB

POK

(DETBAT)

NOTE: ( ) FOR MAX8804W ONLY

< > FOR MAX8804Y/MAX8804Z ONLY

Figure 1. Functional Diagram