MCP73844 datasheet(14/26 Pages) MICROCHIP

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MCP73841/2/3/4

DS21823D-page 14

 2003-2013 Microchip Technology Inc.

5.1.6

BATTERY VOLTAGE SENSE (VBAT)

The MCP7384X monitors the battery voltage at the

VBAT pin. This input is tied directly to the positive

terminal of the battery. The MCP7384X is offered in

four fixed-voltage versions for single or dual series cell

battery packs, with either coke or graphite anodes:

- 4.1V (MCP73841-4.1, MCP73843-4.1)

- 4.2V (MCP73841-4.2, MCP73843-4.2)

- 8.2V (MCP73842-8.2, MCP73844-8.2)

- 8.4V (MCP73842-8.4, MCP73844-8.4)

5.1.7

DRIVE OUTPUT (DRV)

The MCP7384X controls the gate drive to an external

P-channel MOSFET. The P-channel MOSFET is

controlled in the linear region regulating current and

voltage supplied to the cell. The drive output is

automatically turned off when the voltage on the VDD

input falls below the undervoltage lockout voltage

(VSTOP).

5.2

Digital Circuitry

5.2.1

CHARGE STATUS OUTPUT (STAT1)

A status output provides information on the state-of-

charge. The current-limited, open-drain output can be

used to illuminate an external LED. Optionally, a pull-up

resistor can be used on the output for communication

with a host microcontroller. Table 5-1 summarizes the

state of the status output during a charge cycle.

TABLE 5-1:

STATUS OUTPUTS

The flashing rate (1 Hz) is based off a timer capacitor

(CTIMER) of 0.1 µF. The rate will vary based on the

value of the timer capacitor.

5.2.2

LOGIC ENABLE (EN)

The logic-enable input pin (EN) can be used to

terminate a charge anytime during the charge cycle,

initiate a charge cycle or initiate a recharge cycle.

Applying a logic-high input signal to the EN pin, or tying

it to the input source, enables the device. Applying a

logic-low

input

signal

disables

the

device

and

terminates a charge cycle. When disabled, the device’s

supply current is reduced to 0.25 µA, typically.

Charge Cycle State

Stat1

Qualification

OFF

Preconditioning

Constant-Current Fast

Charge

Constant-Voltage

Charge Complete

OFF

Safety Timer Fault

Flashing

(1 Hz, 50% duty cycle)

Cell Temperature Invalid

Flashing

(1 Hz, 50% duty cycle)

Disabled - Sleep mode

OFF

Battery Disconnected

OFF

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