5

FN6541.1

April 3, 2008

The USB_BYP and VDC_LDO stay on regardless of the

state of this pin. This ensures that the processor can be

powered up when an external source is connected to the

VDC or VUSB input pin.

PPR

Power presence indication pin. This pin is used to notify the

system processor or enable the power circuitry when a

source is connected. The pin is an open drain output pin,

which pulls low when a valid voltage (above POR) is present

at either the VDC or VUSB pin. The PPR pin is held low

regardless of the state of the EN pin. If connected to the

processor, a pull-up resistor should be connected to the

processors I/O supply. If connected to power circuitry, a

pull-up should be tied to the appropriate bypass supply.

CHG

Charge indication pin. This open-drain pin is pulled low to

indicate when the battery is being charged. If connected to

the processor, a pull-up resistor should be connected to the

processors I/O supply.

The CHG pin can also be used to drive an LED to indicate to

the user the battery is being charged.

GND

Ground pin. This provides the ground path for all internal

circuits.

Typical Application

FIGURE 1. APPLICATIONS CIRCUIT

ISL9221

VUSB

VDC

BAT

GND

VDC INPUT

USB INPUT

LDO OUTPUT

TO BATTERY

ON

OFF

USB_BYP

TO MCU

ISL9221