5

LTC4410

sn4410 4410fs

OPERATIO

The LTC4410 manages the total current consumption

between a battery charger and a USB portable device. In

a system using the LTC4410, a battery charger can be set

up to charge at the maximum available current from the

USB port without any need to reserve current for the

device load. As the USB device current increases, the

LTC4410 decreases the battery charge current so as not

to exceed the maximum allowable current from the USB

port. This allows for simultaneous battery charging and

device operation. The LTC4410 can only reduce the bat-

tery charge current to zero. It is the responsibility of the

USB device load to not exceed the USB power limits.

The LTC4410 uses an internal power MOSFET to sense

of ±6%. This current can be summed into the PROG node

of a battery charger to reduce the charge current. The

LTC4410 is primarily designed to interface with battery

chargers that use a program pin to set the maximum

charge current, with a charge current to program pin

current ratio of 1000:1. The voltage on CHP can be

externally monitored to signal overcurrent conditions.

forces the USBP pin high. This signal can be used to detect

when the USB voltage is present and drive an external

switch to connect or disconnect a battery from the USB

peripheral.

The MODE pin controls the state of an internal 370µA

primary function of the current reference is to offset the

battery charger charge current for 100mA mode. When

MODE is high, the current reference is disabled. The total

MODE controlled current offset makes it possible to con-

figure the battery charger and the LTC4410 to support the

USB specification 1.0 and 2.0 required 100mA and 500mA

modes of operation.

The low quiescent current (80µA, when MODE is high) of

the LTC4410 makes the system easily compliant with the

USB specifications 1.0 and 2.0 SUSPEND MODE current

consumption requirements.

mode, draining 1µA (typical) from the Lithium-Ion battery.

This condition occurs when the USB device is operating

off of its internal battery and not connected to the USB

port.