MCP2140 データシートの表示（PDF） - Microchip Technology

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MCP2140

IrDA® Standard Protocol Stack Controller With Fixed 9600 Baud Communication Rate

Microchip Technology 

MCP2140

2.8 Minimizing Power

During IR communication between a Primary Device

and the MCP2140, the MCP2140 is in an operational

mode. In this mode, the MCP2140 consumes the

operational current (Parameter D010).

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 MCP2140 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.

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 han-

dler state machine returns to 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 oscilla-

tor is shut down and the PHACT pin will be low

(Parameter D010A).

Table 2-3 shows the MCP2140 current. These are

specified in Parameter D010 and Parameter D010A.

TABLE 2-3: DEVICE MAXIMUM

OPERATING CURRENT

Mode Current

Comment

PHACT = H 2.2 mA IR communications is

occurring.

PHACT = L 60 µA No IR communications.

Note: Additional system current is from the

Receiver/Transmitter circuitry.

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 MCP2140 to exit Low

Power mode. After device initialization, if no IR activity

occurs for about 10 seconds, the device is disabled and

returns into the Low Power mode.

Note:

For proper operation, the device oscillator

must be within oscillator specification in

the time frame specified in

Parameter IR140.

2.9 PHACT Signal

The PHACT signal indicates that the MCP2140 Proto-

col Handler is active. This output pin is an open collec-

tor, so when interfacing to the Host Controller, a pull-up

resistor is required.

DS21790A-page 14

Preliminary

 2003 Microchip Technology Inc.

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