MICRF008YM TR Micrel Inc, MICRF008YM TR Datasheet - Page 11

• Manufacturer Part Number: MICRF008YM TR
• Manufacturer: Micrel Inc

Specifications of MICRF008YM TR

• Operating Band Frequency: 300 to 440MHz
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 3.94mm
• Product Height (mm): 1.48mm
• Operating Supply Voltage (min): 4.75V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Lead Free Status / Rohs Status: Compliant

C
In order to calculate the right value for the C
the data format needs to have a preamble that
resembles the data pattern, that is it has the same
period and duty cycle. (See “Application Hint 42”) If the
data pattern has no preamble, a large capacitor value
should be used, such as 1μF to 2.2μF. However, if the
data pattern has a preamble, the C
calculated and should be used instead of a large
capacitor. This will guarantee a stable and reliable
performance for the receiver. If the data pattern has
variable data rates, the C
calculated for the lowest data rate and optimized in
range tests. To find the C
procedure below:
where:
REFOSC is the reference oscillator frequency in MHz.
Bit period is given in seconds and is the inverse of the
baud rate for Manchester encoding.
The result obtained is in farads.
It follows the C
frequencies mentioned above in the Table 4. Again, as
mentioned before, the data pattern needs preamble.
C
The function of the C
ripple on the AGC control voltage by using a sufficiently
large capacitor. It is suggested a value between 1μF to
10μF depending on data dead time, noise, and recovery
time from strong to low RF signals. Large capacitor
values can be connected to V
required (C2). When connected to V
Frequency
Micrel, Inc.
August 2008
TH
AGC
433.93
(MHz)
1. Find the data period or bit period, and the
2. The C
Capacitor
315
390
418
Capacitor
Table 4. Recommended C
reference oscillator frequency. The reference
oscillator frequency is the RF carrier frequency
divided by 129. The bit period is the elapsed
time from one high and one low of the data
pattern.
C
TH
=
TH
5
capacitor is calculated by:
×
TH
100nF
120nF
120nF
1000
82nF
bit
C
TH
144.55
capacitor value for the common
period
AGC
TH
capacitor is to minimize the
Baud Rate (Hz)
×
×
10
REFOSC
capacitor value follow the
TH
TH
DD
3
2400
39nF
47nF
47nF
47nF
C
Capacitor Values
capacitor should be
if fast charge time is
TH
TH
DD
, it will charge 10
capacitor can be
[ ]
F
TH
capacitor,
4800
18nF
22nF
22nF
22nF
C
TH
11
times faster. The drawback is the ripple noise from AGC
pin being thrown into the V
is current-based, with an attack current of 15μA, and a
decay current of 1.5μA. It is suggested the following
values for the C
be further optimized during receiver range tests.
Reference Oscillator Frequency
A Colpitts oscillator inside the chip generates the
reference oscillator frequency. It requires a resonator of
some kind connected to the REFOSC pin. Either a
ceramic resonator or a crystal can be used. A resonator
is chosen due to its lower cost and because the
MICRF008YM is running in sweep mode, which does not
require the precision of a crystal. Resonators found in
the market normally have a precision of 0.5%. This
precision is sufficient for the MICRF008YM. The
reference oscillator frequency can also be generated by
an external source through connector J1 and capacitor
C1. The maximum level should not exceed 0.5V
reference oscillator frequency is calculated by the
following equation and Table 6 shows the resonator
frequency for the most common used frequencies:
where:
For a list of ceramic resonator manufactures, see
“Application Hint 35.”
•
•
Frequency (MHz)
Baud Rate (Hz)
REFOSC is the reference oscillator frequency in
MHz.
fc is the RF received carrier frequency of interest
in MHz.
REFOSC =
Table 6. Reference Oscillator Frequency
Table 5. Recommended Values for C
433.92
1000
2400
4800
315
390
418
AGC
capacitors in the Table 5. Values can
129
fc
DD
line. The signal on this pin
REFOSC (MHz)
C
2.2 to 4.7
4.7 to 10
1 to 2.2
AGC
2.44
3.02
3.24
3.36
M9999-080108
(µF)
MICRF008
AGC
RMS
. The