MRF39RA Datasheet, PDF (20/72 Pages) Microchip Technology – Low-Power, Integrated UHF Receiver

MRF39RA
3.0 OPERATING MODES
3.1 Basic Modes
The circuit is set in four different basic modes as
described in Table 3-1.
By default when switching from one mode to another,
the sub-blocks wakes up according to a pre-defined
and optimized sequence. Alternatively, these operating
modes can be selected directly by disabling the
automatic sequencer (SequencerOff in RegOpMode =
1).
TABLE 3-1: BASIC RECEIVER MODES
ListenOn
in RegOpMode
Mode in
RegOpMode
Selected mode
0
000
Sleep mode
0
001
Stand-by mode
0
010
FS mode
0
100
Receive mode
1
x
Listen mode
Enabled blocks
None
Top regulator and crystal oscillator
Frequency synthesizer
Frequency synthesizer and receiver
See Section 3.3 “Listen Mode”
3.2 Automatic Sequencer and
Wake-up Times
By default when switching from one operating mode to
another, the circuit takes care of the sequence of
events in a manner that the transition timing is
optimized. For example, when switching from Sleep
mode to Receive mode, the MRF39RA first goes to
Standby mode (XO started), then to Frequency
Synthesizer mode, and finally, when the PLL has
locked, to Receive mode.
The crystal oscillator wake-up time, TS_OSC, is
directly related to the time for the crystal oscillator to
reach its steady state. This depends notably on the
crystal characteristics.
The frequency synthesizer wake-up time, TS_FS, is
directly related to the time needed by the PLL to reach
its steady state. The PLL_LOCK signal, provided on an
external pin, gives an indication of the lock status. It
goes high when the PLL reaches its locking range.
Three specific cases can be highlighted:
• Receiver wake-up time from Sleep mode =
TS_OSC + TS_FS + TS_RE
• Receiver wake-up time from Sleep mode,
AGC enabled = TS_OSC + TS_FS + TS_RE_AGC
• Receiver wake-up time from Sleep mode,
AGC and AFC enabled = TS_OSC + TS_FS +
TS_RE_AGC&AFC.
These timings are detailed in Section 3.2.1 “Receiver
Start-up Time”.
In applications where the target average power
consumption, or the target start-up time do not require
setting the MRF39RA in the lowest power modes
(Sleep or Standby), the respective TS_OSC and
TS_FS timings in the equations above can be omitted.
DS40001778B-page 20
 2015 Microchip Technology Inc.