MCP73826(2002) Просмотр технического описания (PDF) - Microchip Technology

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MCP73826
(Rev.:2002)

Single Cell Lithium-Ion Charge Management Controller

Microchip Technology 

MCP73826

5.0 DETAILED DESCRIPTION

Refer to the typical application circuit, Figure 6-1.

5.1 Analog Circuitry

5.1.1 OUTPUT VOLTAGE INPUT (VBAT)

The MCP73826 monitors the cell voltage at the VBAT

pin. This input is tied directly to the positive terminal of

the battery. The MCP73826 is offered in two fixed-volt-

age versions for single cells with either coke or graphite

anodes: 4.1V (MCP73826-4.1) and 4.2V

(MCP73826-4.2).

5.1.2 GATE DRIVE OUTPUT (VDRV)

The MCP73826 controls the gate drive to an external

P-channel MOSFET, Q1. The P-channel MOSFET is

controlled in the linear region, regulating current and

voltage supplied to the cell. The drive output is auto-

matically turned off when the input supply falls below

the voltage sensed on the VBAT input.

5.1.3 SUPPLY VOLTAGE (VIN)

The VIN input is the input supply to the MCP73826. The

MCP73826 automatically enters a power-down mode if

the voltage on the VIN input falls below the voltage on

the VBAT pin. This feature prevents draining the battery

pack when the VIN supply is not present.

5.1.4 CURRENT SENSE INPUT (VSNS)

Fast charge current regulation is maintained by the

voltage drop developed across an external sense resis-

tor, RSENSE, applied to the VSNS input pin. The follow-

ing formula calculates the value for RSENSE:

RSENSE

=

--V---C----S--

IOUT

Where:

VCS is the current limit threshold

IOUT is the desired peak fast charge current in

amps. The preconditioning current is scaled to

approximately 43% of IOUT.

5.2 Digital Circuitry

5.2.1 SHUTDOWN INPUT (SHDN)

The shutdown input pin, SHDN, can be used to termi-

nate a charge anytime during the charge cycle, initiate

a charge cycle, or initiate a recharge cycle.

Applying a logic High input signal to the SHDN pin, or

tying it to the input source, enables the device. Apply-

ing a logic Low input signal disables the device and ter-

minates a charge cycle. In shutdown mode, the

device’s supply current is reduced to 0.5 µA, typically.

DS21705A-page 10

 2002 Microchip Technology Inc.

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