Datasheet

hiRef

loRef

Logic

charger

control

ntc

LM3658

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SNVS328E –MAY 2005–REVISED MARCH 2007

DISABLING CHARGER (CHARGE INTERRUPT MODE)

Charging can be safely interrupted by pulling the EN_b pin high and charging can resume upon pulling the EN_b

pin low. The enable pin can be permanently tied to GND with no extra current consumption penalty during power

down mode. When the charger is disabled, timer holds its count value, and STAT1 and STAT2 are both off.

LDO MODE (AVAILABLE ONLY IN LM3658SD-B VERSION)

The LM3658SD-B version enters LDO mode when the T

pin is floating and AC wall adapter is still connected to

CHG_IN pin. In LDO mode, STAT1 and STAT2 are both on. The LM3658SD-B becomes a linear regulator

capable of delivering 1A of source current. Normally the T

pin is connected to the thermistor from the battery

pack for temperature monitoring purpose. If this pin is disconnected, the LM3658SD-B assumes that there is no

battery present and will automatically invoke the LDO mode. LDO mode allows applications to operate without a

battery provided that the AC wall adapter supplies power to the CHG_IN pin. The LDO mode is not possible in

USB mode.

For the other versions of the LM3658, floating the T

pin does not invoke LDO mode. Instead, it will go to

suspend mode. Please refer to “ Battery Temperature Monitoring” section for more detail.

5 HOUR/ 10 HOUR SELECTABLE TIMER (AVAILABLE ONLY IN LM3658SD-A VERSION)

The LM3658SD-A allows the user to select between 5 hour or 10 hour timer based on the polarity of the

USB_sel pin, in both CHG_IN mode and USBpwr mode. By pulling the USB_sel pin high, the timer is set to 5

hours. In the USBpwr mode, the polarity of the USB_sel pin determines the charge current as well as the timer.

In CHG_IN mode, the polarity of the USB_sel pin determines only the timer. The charge current is set by the

resistor at I

set

pin.

INPUT/OUTPUT BYPASS CAPACITORS

Care should be taken to support the stability of the charge system by connecting a 1 µF capacitor as close as

possible to the BATT pin. An input capacitor ranging from 1.0 µF– 10.0 µF must be connected to the CHG_IN

and USBpwr input pins. Low cost ceramic capacitors can be selected.

THERMAL PERFORMANCE OF THE WSON PACKAGE

The LM3658 is a monolithic device with integrated power FETs. For that reason, it is important to pay special

attention to the thermal impedance of the WSON package and to the PCB layout rules in order to maximize

power dissipation of the WSON package.

The WSON package is designed for enhanced thermal performance and features an exposed die attach pad at

the bottom center of the package that creates a direct path to the PCB for maximum power dissipation.

Compared to the traditional leaded packages where the die attach pad is embedded inside the molding

compound, the WSON reduces one layer in the thermal path.

Product Folder Links: LM3658