LP28501 datasheet(7/10 Pages) POWER

7 / 10 page

LP28501-02

Mar.-2017

Email: marketing@lowpowersemi.com

www.lowpowersemi.com

Page 7 of 10

Preliminary Datasheet

LP28501

Application Information

The LP28501 is an easy controlled power path

management device and a single cell Li-Ion battery

charger. It integrates the input reverse-blocking FET,

high-side switching FET, low-side switching FET,

and BATFET between system and battery. The

device also integrates the bootstrap diode for the

high-side gate drive.

Device Power Up from Battery without DC Source

If only battery is present and the voltage is above

depletion threshold, the BATFET turns on and

connects battery to system. The REG LDO stays off

to minimize the quiescent current. The low RDSON in

BATFET and the low quiescent current on BAT

minimize the conduction loss and maximize the

battery run time.

Power Up from DC Source

When the DC source plugs in, the LP28501 checks

the input source voltage to turn on REG LDO and all

the bias circuits. It also checks the input current limit

before starts the buck converter.

Input Source Qualification

After REG LDO powers up, the LP28501 checks the

current capability of the input source. The input

source has to meet the following requirements to

start the buck converter.

1. VBUS voltage below 16V

2. VREG voltage above 2.43V

Once the input source passes all the conditions

above, the permit signal is asserted to the chip.

Input Current Limit Detection

The USB ports on personal computers are

convenient charging source for portable devices

(PDs). If the portable device is attached to a USB

host, the USB specification requires the portable

device to draw limited current. If the portable device

is attached to a charging port, it is allowed to draw up

to the maximum current form the USB host by two

parts limit：

1. VREG voltage above 2.43V

2. The maximum input current < ILIMIT

VSYS and Narrow VDC Architecture

The device deploys Narrow VDC architecture (NVDC)

with BATFET separating system from battery. The

minimum system voltage is set by battery voltage.

With a not fully depleted battery, the system is

regulated (RBATFET×I(BAT,SYS))V less than the battery

voltage. And a selectable VSYS could be set by

SYSSEL when battery is fully depleted and adapter

is applied to VBUS.

Charge state indication

As showed below, the STAT and FULL LED respond

to this six STATES.

STATE

STAT

FULL

Without Battery

Flicker

Light On

Charging

Light On

Light Off

Charge complete

Light Off

Light On

Battery overheat

Flicker

Light Off

Time out

Flicker

Light Off

VREG < VREG(th)

Light On

Light Off

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