MCP2140A Microchip Technology, MCP2140A Datasheet - Page 15

• Manufacturer Part Number: MCP2140A
• Description: IrDA Standard Protocol Stack Controller With Fixed 9600 Baud Communication Rate
• Manufacturer: Microchip Technology

2.8
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
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
© 2007 Microchip Technology Inc.
Minimizing Power
(Parameter
D010A).
2.8.1
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 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
oscillator is shut down and the PHACT pin will be low
(Parameter
Table 2-3
specified in
TABLE 2-3:
2.8.2
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
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.
PHACT = H 407 µA IR communications is
PHACT = L
Note:
Note:
Mode
PHACT Signal
shows the MCP2140A current. These are
AUTOMATIC LOW POWER MODE
Additional system current is from the
Receiver/Transmitter and the RXPDREF
voltage reference circuitry.
RETURNING TO DEVICE
OPERATION
For proper operation, the device oscillator
must be within oscillator specification in
the time frame specified in
IR140.
D010B).
Parameter D010A
Current
23 µA
DEVICE MAXIMUM
OPERATING CURRENT
occurring (or waiting for
timeout).
No IR communications.
MCP2140A
and
Comment
Parameter
DS22050A-page 15
Parameter
D010B.