MICRF219 Datasheet, PDF (8/24 Pages) Micrel Semiconductor – 300MHz to 450MHz ASK Receiver with RSSI, Auto-Poll, Bit-Check and Squelch

Micrel
MICRF219
Desense
Desense is a function designed to reduce the sensitivity
of the MICRF219 receiver to a maximum of 45dB for
training the MICRF219 receiver. This is done in order to
recognize an intended transmitter. Very often, a receiver
needs to learn how to recognize a particular transmitter.
It is important for the receiver not to learn the signal of a
stray transmitter near by. The simplest solution is to turn
down the receiver gain, so the receiver only recognizes
the transmitter at close range.
The de-sense function is accessible only through serial
programming.
D0
D1
D2 MODE: Desense
0
X
X No Desense - default
1
0
0
6dB Desense
1
1
0
16dB Desense
1
0
1
30dB Desense
1
1
1
42dB Desense
Reference Control
There are 2 components in Reference and Control sub-
block: 1) Reference Oscillator and 2) Control Logic
through parallel Inputs: SEL0, SEL1, SHDN
Reference Oscillator
The reference oscillator in the MICRF219 (Figure 2.
Reference Oscillator Circuit) uses a basic Pierce crystal
oscillator configuration with MOS transconductor to
provide negative resistance. Though the MICRF219 has
build-in load capacitors for the crystal oscillator, the
external load capacitors are still required for tuning it to
the right frequency. R01 and R02 are external pins of
the MICRF219 to connect the crystal to the reference
oscillator.
Reference oscillator crystal frequency can be calculated:
F_{REF OSC} = F_RF/(32 + 1.1/12)
For 433.92 MHz, F_{REF OSC} = 13.52127 MHz.
To operate the MICRF219 with minimum offset, crystal
frequencies should be specified with 10pF loading
capacitance.
RO2
C
RO1
C
V BIAS
R
Figure 2. Reference Oscillator Circuit
January 2009
8
M9999-011509
[phone]