MCP73827-4.2VUA Просмотр технического описания (PDF) - Microchip Technology

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MCP73827-4.2VUA

Single Cell Lithium-Ion Charge Management Controller with Mode Indicator and Charge Current Monitor

Microchip Technology 

4.0 DEVICE OVERVIEW

The MCP73827 is a linear charge management con-

troller. Refer to the functional block diagram on page 2

and the typical application circuit, Figure 6-1.

4.1 Charge Qualification and

Preconditioning

Upon insertion of a battery or application of an external

supply, the MCP73827 verifies the state of the SHDN

pin. The SHDN pin must be above the logic High level.

If the SHDN pin is above the logic High level, the

MCP73827 initiates a charge cycle. The charge status

output, MODE, is pulled low throughout throughout the

preconditioning and controlled current phases (see

Table 5-1 for charge status outputs). If the cell is below

the preconditioning threshold, 2.4V typically, the

MCP73827 preconditions the cell with a scaled back

current. The preconditioning current is set to approxi-

mately 43% of the fast charge peak current. The pre-

conditioning safely replenishes deeply depleted cells

and minimizes heat dissipation in the external pass

transistor during the initial charge cycle.

4.2 Controlled Current Regulation - Fast

Charge

Preconditioning ends and fast charging begins when

the cell voltage exceeds the preconditioning threshold.

Fast charge utilizes a foldback current scheme based

on the voltage at the VSNS input developed by the drop

across an external sense resistor, RSENSE, and the out-

put voltage, VBAT. Fast charge continues until the cell

voltage reaches the regulation voltage, VREG.

MCP73827

4.3 Constant Voltage Regulation

When the cell voltage reaches the regulation voltage,

VREG, constant voltage regulation begins. The

MCP73827 monitors the cell voltage at the VBAT pin.

This input is tied directly to the positive terminal of the

battery. The MCP73827 is offered in two fixed-voltage

versions for battery packs with either coke or graphite

anodes: 4.1V (MCP73827-4.1) and 4.2V

(MCP73827-4.2).

4.4 Charge Cycle Completion

The charge cycle can be terminated by a host micro-

controller when the output of the charge current moni-

tor, IMON, has diminished below approximately 10% of

the peak output voltage level. Alternatively, the transi-

tion of the charge status output, MODE, can be used to

initialize a timer to terminate the charge. The charge is

terminated by pulling the shutdown pin, SHDN, to a

logic Low Level.

© 2007 Microchip Technology Inc.

DS21704B-page 9

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