SC803 datasheet(6/17 Pages) SEMTECH

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SC803

POWER MANAGEMENT

Monitor Mode

In the monitor mode the voltage of the battery will be

monitored against the programmed voltage. This will oc-

cur after a battery has been fully charged and the device

has shut off. If the voltage of the battery falls below the

recharge threshold (specified at 200mV) the charger will

activate and charge the battery to its programmed volt-

age. This means that it will enter the full charging se-

quence from fast-charge to terminating the charging cycle

when the programmed termination current is reached.

The maximum current drain of the battery during moni-

tor mode will be no more than 1uA over temperature.

LDO Mode

One of the nice features of the SC803 is its ability to

work with or without a battery. If the battery is not in

place the device can enter the LDO mode. In this mode

the SC803 will act like a low dropout regulator. The out-

put voltage is set to 4.1V, 4.2V or externally set by a

resistor divider. See the section titled “Configuring the

Output Voltage to the Battery” for setting an output volt-

age other than 4.1V or 4.2V. The input pin BIP (Battery

In Place) is used to switch the SC803 from charger mode

to LDO mode. If this pin is logic high the device will be in

charger mode, if it is logic low it will be in the LDO mode.

During LDO mode the device will regulate the output volt-

age with a current limit set by the resistor tied to the

IPRGM pin. The BIP pin can be tied to the CP pin to place

the device in charge mode whenever the adaptor is in

place. The maximum voltage on the BIP input pin is 6V,

so do not tie it to the VCC input since this voltage can

exceed 6V in some conditions. The BIP pin should never

be left floating, but instead, should be tied through pull-

up/pull-down resistors when connected to a high imped-

ance control pin, otherwise it can be connected directly

to the CP pin or GND. The equation for setting the cur-

rent limit in the LDO mode will be:

1000

1.5

ILDO

PRGM

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LED Flags

There are three LED drivers on the SC803: OVP (Over

Voltage), STAT (Status) and CP (Charger Present). Each

output can drive an LED directly without a current limit

resistor. In addition, each output can be monitored by a

microprocessor for change in their status. The following

table defines each LED output.

Applications Information

Pre-Charge Mode

Pre-charge mode is automatically enabled whenever the

battery voltage is below 2.8V. It is primarily used to limit

the power dissipation of the battery and the SC803 de-

vice whenever the battery is undercharged. As the bat-

tery begins to charge in this mode, the voltage of the

battery will rise and when the 2.8V limit is reached, the

SC803 will switch to the fast charge mode. The pre-

charge current value is selected by the termination re-

sistor on the ITERM pin. The maximum range of the pre-

charge current is from 10mA to 125mA. Whenever the

charger is in pre-charge or fast-charge the status LED

will light indicating that the battery is being charged. The

equation to select the pre-charge current is given by:

2.8

PCI

TERM

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Fast-Charge Mode

The fast-charge mode exists while the battery voltage is

above 2.8V and the battery is not fully charged. The fast-

charge current can be set to a maximum of 1.5A and is

selected by the program resistor on the IPRGM pin. In

fact, the voltage on this pin will represent the current

through the battery enabling a microprocessor or ana-

log-to-digital converter (ADC), to monitor battery current

by sensing the voltage on the IPRGM pin. The equation

to set the fast-charge current is given by:

1000

1.5

FCI

PRGM

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

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Note that for a given program resistor the current through

the battery can be determined by replacing 1.5 with the

actual voltage on the IPRGM pin in the above equation.

Termination Current

Once the battery reaches the program voltage of 4.1V,

4.2V or externally set voltage, the device will transition

from a constant current source to a constant voltage

source, as the current through the battery begins to de-

crease while the voltage remains constant. During this

time when the current falls below the programmed ter-

mination current set by the termination resistor on the

ITERM pin, the SC803 will turn off and the end of charge

will be indicated by the status LED turning off. The equa-

tion to set the termination current is given by:

1.5

ITERM

TERM

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