MICRF505YML Micrel Inc, MICRF505YML Datasheet - Page 22

• Manufacturer Part Number: MICRF505YML
• Description: 433/915MHZ ITRANSCEIVER, SMD, MLF32
• Manufacturer: Micrel Inc

Specifications of MICRF505YML

• Transmitting Current: 28mA
• Data Rate: 200Kbps
• Frequency Range: 850MHz To 950MHz
• Modulation Type: FSK
• Sensitivity Dbm: -111dBm
• Rf Ic Case Style: MLF
• No. Of Pins: 32
• Supply Voltage Range: 2V To 2.5V
• Output Power: 10dBm
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

MICRF505
When Modulation1 and Modulation0 is 00, the modulator
needs to be programmed properly, see “Modulator” section.
The modulation signal will now be applied directly on the
phase locked VCO. It is therefore important that the PLL
bandwidth is not too high, as this will remove the modulation.
See “PLL Filter” section on how to calculate the PLL compo-
nents. When using the modulator the modulation signal is
applied to the VCO and therefore some sort of encoding is
needed.
The level of encoding is determined by the PLL loop filter
bandwidth and data rate. Two of the most common encoding
techniques are Manchester encoding and 3B4B. Other en-
coding schemes may also be used.
Manchester encoding is when one bit is encoded in to a two-
bit word and is shown in Table 10. When using Manchester
encoding the maximum overhead is 100%. When selecting
PLL loop filter it is important to note that the min baud rate is
equal to:
M9999-051304
Frequency Modulation
Data bits
000 000 000 000 000
111 111 010 110 000
Modulation1
0000001
A6..A0
f
baud/s: Elements per second (encoded data)
f
baud_min
baud_min
0
0
1
1
Table 11. Modulation Bit Setting
: The minimum frequency of the baud rate (Hz)
=
baud / s
Modulation1 Modulation0
Modulation0
4
D7
0
1
0
1
Modulation Type
Closed loop modulation
using modulator
Not in use
FSK applied using two
sets of dividers
Not in use
Encoded words
1011 0100 1011 0100 1011
1101 0010 0011 0110 1011
D6
Table 14. Example of 3B4B encoding
D5
‘0’
PA_LDc_en
22
D4
Another much more efficient encoding type is 3B4B where
three data bits are encoded into a four-bit word. The reason
for encoding is to minimize the dc component in the modu-
lated data. To have minimum dc component each four bit
word should include two elements of “1” and two elements of
“0”. Following this guidance only 6 out of 8 word complies and
two encoded words needs special precaution. Whenever 000
and 111 data appear, the user must set/clear a flag that
indicate if last encoded word was “Word A” and select the
respective encoded word shown in Table 11.
Comments
A Flag indicates if “Word A” has been used
A Flag indicates if “Word A” has been used
Data
000
001
010
011
100
101
110
111
RSSI_en
D3
Data
Table 12. Manchester Encoding
“0”
“1”
Table 13. 3B4B Enconding
LD_en
Word A
D2
1011
1100
0011
1010
0101
1001
0110
1101
PF_FC1
D1
Word
“10”
“01”
Word B
May 13, 2004
0100
0010
PF_FC0
D0
Micrel