High-Voltage, Dual-Input, USB/AC

Adapter Chargers in 2mm x 3mm TDFN

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Soft-Start

The soft-start circuitry activates when entering fast-

charge mode. In the MAX8804Y, soft-start is entered

directly after being enabled, and the charging current

ramps up in 250µs from 0 to 500mA (95mA in USB

mode). This reduces the inrush current on the input

supply. Note that the MAX8804V/MAX8804W/

MAX8804Z has a prequalification state and the charg-

ing current ramps up when the prequalification state is

Thermal Regulation Control

The thermal-regulation loop limits the MAX8804V/

MAX8804W/MAX8804Y/MAX8804Z die temperature to

+105°C by reducing the charge current as necessary.

This feature not only protects the ICs from overheating,

but also allows a higher charge current at room temper-

ature without risking damage to the system.

Charging-Status Output (CHG)

CHG is an open-drain output that indicates charger sta-

tus. CHG goes low during charge cycles where the

MAX8804V/MAX8804W/MAX8804Y/MAX8804Z are in

prequalification or fast-charge mode. CHG goes high

impedance when the charge current reaches the top-

off threshold for more than 4ms, indicating charging is

done. The CHG status is latched after the top-off

threshold is reached. The latch is reset by toggling the

SET input, recycling input power, or increasing the

charging current to the top-off threshold plus 57mA

(typ).

When the MAX8804V/MAX8804W/MAX8804Y/MAX8804Z

are used in conjunction with a microprocessor (µP), con-

nect a pullup resistor between CHG and the logic I/O

voltage to indicate charge status to the µP. Alternatively,

CHG can sink up to 5mA for an LED charge indicator.

Power-OK Monitor (POK)

The MAX8804V/MAX8804W/MAX8804Y/MAX8804Z con-

tain an open-drain POK output that goes low when a

valid input source is detected at either DC or USB. A

valid input source is one whose voltage is greater than

4.15V and exceeds the battery voltage by 250mV. After a

valid input has been established, charging is sustained

with inputs as low as 3.5V as long as the input voltage

remains above the battery voltage by at least 40mV. POK

status is maintained regardless of SET status.

When the MAX8804V/MAX8804W/MAX8804Y/MAX8804Z

are used in conjunction with a µP, connect a pullup resis-

tor between POK and the logic I/O voltage to indicate

power-OK to the µP. Alternatively, POK can sink up to

5mA for an LED power-OK indicator.

USB Power Status Output (USBPWR)

(MAX8804Y/MAX8804Z Only)

ance. USBPWR indicates the USB input presence

regardless of SET status and charger status.

When the MAX8804Y/MAX8804Z are used in conjunction

with a µP, connect a pullup resistor between USBPWR

and the logic I/O voltage to indicate USB power status

to the µP. Alternatively, USBPWR can sink up to 5mA

for an LED USB power status indicator.

Battery Pack Dectection Input

(DETBAT, MAX8804V/MAX8804W Only)

DETBAT is pulled up to an internal 3V supply through a

63k

Ω resistor. Driving DETBAT low or connecting it to

GND allows SET to control the charger. When DETBAT

is left unconnected, the MAX8804V/MAX8804W enters

shutdown.

Applications Information

Capacitor Selection

Connect a 2.2µF ceramic capacitor from BAT to GND for

proper stability. Connect a 1µF ceramic capacitor from

DC to GND. If using the USB input, bypass USB to GND

with a 1µF ceramic capacitor. Use a larger input bypass

capacitor for high charging currents to reduce supply

noise. All capacitors should be X5R dielectric or better.

Be aware that some capacitors have large voltage and

temperature coefficients and should be avoided.

Thermal Considerations

The MAX8804V/MAX8804W/MAX8804Y/MAX8804Z are

available in a thermally enhanced TDFN package with

an exposed paddle. Connect the exposed paddle to a

large copper ground plane to provide a thermal contact

between the device and the PCB for increased power

dissipation. The exposed paddle transfers heat away

from the device, allowing the IC to charge the battery

with maximum current, while minimizing the die temper-

ature increase.

Input Sources

The MAX8804V/MAX8804W/MAX8804Y/MAX8804Z

operate from well-regulated input sources. The operat-

ing input voltage range is 4.15V to 7V. The device sur-

vives DC input supply voltages up to 30V and USB

input source voltages up to 16V without damage to the

IC. If the input voltage is greater than 7.5V (typ), the IC

stops charging. An appropriate power supply must pro-

vide at least 4.2V plus the voltage drop across the

internal pass transistor when sourcing the desired max-

imum charging current: