MRF24WG0MA_12 Datasheet, PDF (13/38 Pages) Microchip Technology – MRF24WG0MA/MB Data Sheet 2.4 GHz IEEE 802.11b/g™

MRF24WG0MA/MB
2.3 Power States
The MRF24WG0MA/MB has several power states.
These are Hibernate, Sleep and Active (two sub-
states), as shown in Figure 2-3. The selection of power
state directly affects system behavior, and overall
power consumption or battery life. There is also a
“Stand-by” state that is not user-controlled.
2.3.1 HIBERNATE STATE
An “Off” state is defined as no power applied to the
device. The Hibernate mode is the closest to controlled
off that the module can approach. It is controlled
through the HIBERNATE pin (high input puts the
module into Hibernate). When in Hibernate, the module
only consumes leakage current, but does not maintain
state. Hibernate has to be fully controlled by the PIC
MCU.
The module contains about 70 µF of internal bulk
capacitance. Supplies should be provisioned to supply
sufficient charge on release of hibernate for desired
start time or sufficient delay must be provided in
software after hibernate release and before releasing
reset.
This state provides the best battery life for embedded
products. Entering Hibernate for intervals of less than 1
minute is not likely to save power.
2.3.2 POWER SAVE (PS) MODE
The PS mode is a low-power dynamic state that
automatically implements the 802.11 Power Save
feature. In this mode, if enabled, the module will enter
PS mode when all activity is complete.
The module will wake autonomously to any PIC
intervention so it can check DTIM beacons from the
Access Point. If any traffic is listed as queued for the
module, then it will awake and get the data from the
Access Point on the next possible opportunity. When
data is acquired, the module will interrupt the PIC
microcontroller on a normal “data available” indication.
If no data is available on a DTIM check, the module
reenters the Power Save state until the next DTIM. The
DTIM interval is programmed at the Access Point. This
state can provide “as if on” behavior of the radio with a
significant power savings versus “always on”. The
battery life expectation of this mode is several days to
several weeks. This mode is characterized by a very
low latency (as low as 200 ms) to begin data transfer
from the state.
2.3.3 ACTIVE STATE
The Active state is identified as one of two states where
the radio circuitry is fully on. The two active states are
the Receive state (RX ON) and the Transmit state (TX
ON).
2.3.4 STAND-BY STATE
The Stand-by state is not user-controlled but is noted
as it helps identify and track certain operations of the
module during power tracing.
TABLE 2-1:
State
Off
Hibernate
Power Save
RX ON
TX ON
Stand-by
MRF24WG0MA/MB POWER STATE DEFINITIONS
VDD
0V
3.3V
3.3V
3.3V
3.3V
3.3V
CS
0V
3.3V
0V
0V
0V
0V
Description
Power is completely disconnected
All internal power regulators are OFF – enabled by HIBERNATE pin
Enabled by TCP/IP driver
Receive circuits are on and receiving
Transmit circuits are on and transmitting
State machine transition state only – not user controlled
 2012 Microchip Technology Inc.
Preliminary Information
DS70686B-page 13