MCP73871-3CCISLASHML datasheet(22/40 Pages) MICROCHIP

22 / 40 page

MCP73871

DS20002090C-page 22

 2008-2013 Microchip Technology Inc.

Table 4-1 shows the chip behavior based upon the operating conditions.

TABLE 4-1:

CHIP BEHAVIOR REFERENCE TABLE

4.1

UnderVoltage Lockout (UVLO)

An internal undervoltage lockout (UVLO) circuit

monitors the input voltage and keeps the charger in

shutdown mode until the input supply rises above the

UVLO threshold.

In the event a battery is present when the input power

is applied, the input supply must rise approximately

100 mV above the battery voltage before the

MCP73871 device becomes operational.

The UVLO circuit places the device in Shutdown mode

if the input supply falls to within approximately 100 mV

of the battery voltage.

The UVLO circuit is always active. At any time the input

supply is below the UVLO threshold or falls within

approximately 100 mV of the voltage at the VBAT pin,

the MCP73871 device is placed in Shutdown mode.

During any UVLO condition, the battery reverse

discharge current is less than 2 μA.

4.2

System Load Sharing

The system load sharing feature gives the system

output pin (OUT) priority, allowing the system to power

up with deeply depleted battery packs.

With the SEL input active Low, the MCP73871 device

is designed to provide system power and Li-Ion battery

charging from a USB input while adhering to the current

limits governed by the USB specification.

With the SEL input active High, the MCP73871 device

limits the total supply current to 1.8A (system power

and charge current combined).

FIGURE 4-2:

System Load Sharing

Diagram.

4.3

Charge Qualification

For a charge cycle to begin, all UVLO conditions must

be met and a battery or output load must be present.

A charge current programming resistor must be

connected from PROG1 to VSS when SEL = High.

When SEL = Low, PROG2 needs to be tied High or

Low for proper operation.

VIN ? VBAT

VBAT ? VOUT

State

VBAT > VIN

—

Shutdown

OFF

Battery

powered

system

VIN > VBAT

—

Shutdown

OFF

VIN > VBAT

—

Shutdown

OFF

Battery

powered

system

VBAT < VOUT

Standby

OFF

VBAT > VOUT

IN + BAT

powered

system

VBAT < VOUT

IN powered,

Charge

possible

OFF

ON/OFF

VBAT > VOUT

IN + BAT

powered

system

OFF

0.2



Ideal

Diode,

Synchronous

Switch

Direction

Control

0.2



Current

Limit

Direction

Control

Charge

FET

System

Power

FET

VBAT

OUT

Charge

Control

MCP73871-3CCI/ML Datasheet(PDF) 22 Page - Microchip Technology

MCP73871-3CCI/ML Datasheet(HTML) 22 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Datasheet Download

Link URL