MCP2140AT-ISLASHSS datasheet(15/60 Pages) MICROCHIP

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DS22050A-page 15

MCP2140A

2.8

Minimizing Power

During IR communication between a Primary Device

and the MCP2140A, the MCP2140A is in an opera-

tional mode. In this mode, the MCP2140A consumes

the operational current (Parameter D010A).

For many applications, the time that IR communication

is occurring is a small percentage of the applications

operational time. The ability for the IR controller to be

in a low power mode during this time will save on the

applications power consumption. The MCP2140A will

automatically enter a low power mode once IR activity

has stopped and will return to operational mode once

IR activity is detected on the RXPD and RXPDREF

pins. The PHACT pin indicates if the Protocol Handler

is Active or inactive (low power mode).

Another way to minimize system power is to use an I/O

pin of the Host Controller to enable power to the IR

circuity

2.8.1

AUTOMATIC LOW POWER MODE

The Automatic Low Power mode allows the system to

achieve the lowest possible operating current.

When the IR link has been “closed”, the protocol

handler

state

machine

returns

the

Normal

Disconnect Mode (NDM). During NDM, if no IR activity

occurs for about 10 seconds, the device is disabled and

enters into Low Power mode. In this mode, the device

oscillator is shut down and the PHACT pin will be low

(Parameter D010B).

Table 2-3 shows the MCP2140A current. These are

specified in Parameter D010A and Parameter D010B.

TABLE 2-3:

DEVICE MAXIMUM

OPERATING CURRENT

2.8.2

RETURNING TO DEVICE

OPERATION

The device will exit the Low Power mode when the

RXPD pin voltage crosses the REPDREF pin reference

voltage.

A device reset will also cause the MCP2140A to exit

Low Power mode. After device initialization, if no IR

activity occurs for about 10 seconds, the device returns

to the Low Power mode.

2.9

PHACT Signal

The PHACT signal indicates that the MCP2140 Proto-

col Handler is active. This output pin is an open

collector, so when interfacing to the Host Controller, a

pull-up resistor is required.

Mode

Current

Comment

PHACT = H

407 µA

IR communications is

occurring (or waiting for

timeout).

PHACT = L

23 µA

No IR communications.

Note:

Additional system current is from the

Receiver/Transmitter and the RXPDREF

voltage reference circuitry.

Note:

For proper operation, the device oscillator

must be within oscillator specification in

the time frame specified in Parameter

IR140.

MCP2140AT-I/SS Datasheet(PDF) 15 Page - Microchip Technology

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