MCP73837-AMISLASHMF datasheet(19/36 Pages) MICROCHIP

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DS20002071C-page 19

MCP73837/8

5.2

Digital Circuitry

5.2.1

STATUS INDICATORS AND POWER

GOOD (PG) OPTION

The charge status outputs have two different states:

Low (L), and High Impedance (Hi-Z). The charge status

outputs can be used to illuminate LEDs. Optionally, the

charge status outputs can be used as an interface to a

host microcontroller. Table 5-1 summarizes the state of

the status outputs during a charge cycle.

5.2.2

USB PORT CURRENT

REGULATION SELECT (PROG2)

For the MCP73837/8, driving the PROG2 input to a

logic Low selects the low charge current setting

(maximum 100 mA). Driving the PROG2 input to a logic

High selects the high charge current setting (maximum

500 mA).

The Precondition current and Termination current are

percentages of the charge current selected by the

PROG2 level. The percentage is based on the selected

part number of the device.

5.2.3

POWER GOOD (PG) OPTION

The power good (PG) option is a pseudo open-drain

output. It is only available on the MCP73837. The PG

output can sink current, but not source current. How-

ever, there is a diode path back to the input, and as

such, the output should be pulled up only to the input.

The PG output is low whenever the input to the

MCP73837 is above the UVLO threshold and greater

than the battery voltage. If the supply voltage is above

the UVLO, but below VREG(typical)+0.3V, the

MCP73837 will pulse the PG output as the device

determines if a battery is present.

5.2.4

TIMER ENABLE (TE) OPTION

The timer enable (TE) input option is used to enable or

disable the internal timer. It is only available on the

MCP73838. A low signal on this pin enables the inter-

nal timer and a high signal disables the internal timer.

The TE input can be used to disable the timer when the

charger is supplying current to charge the battery and

power the system load. The TE input is compatible with

1.8V logic.

5.2.5

DEVICE DISABLE (PROG1/2)

The current regulation set input pin (PROG1/2) can be

used to terminate a charge at any time during the

charge cycle, as well as to initiate a charge cycle or to

initiate a recharge cycle.

Placing a programming resistor from the PROG1/2

input to VSS enables the device. Allowing the PROG1/2

input to float or applying a logic-high input signal to

PROG1 disables the device and terminates a charge

cycle. When disabled, the device’s supply current is

reduced to 75 µA, typically.

TABLE 5-1:

STATUS OUTPUTS

Charge Cycle State

STAT1

STAT2

Shutdown

High Z

High-Z

Standby

High-Z

High Z

Preconditioning

High Z

Constant Current

High Z

Constant Voltage

High Z

Charge Complete – Standby

High Z

Temperature Fault

High Z

Timer Fault

High Z

System Test Mode

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