AN332
Rev. 0.8
165
Property 0x3702. AM_AGC_ATTACK_RATE
Sets the AGC attack rate. Large values provide slower attack, and smaller values provide faster attack. The CTS
bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
POWERUP mode. The default is 4 (approximately 1400 dB/s).
Nominal "5600" is based on Silabs' AM antenna dummy and Si474xEVB reference design and may vary with
source impedance and design changes. In most systems, an exact value is not important. However, to calculate for
a different source impedance and/or design:
1. Drive antenna input with desired source impedance (via antenna or antenna dummy).
2. Increase RF level until AGC index changes from 19 to 20. Record last RF level with index equal 19.
3. Increase RF level until AGC index reaches 39. Record RF level with index equal 39.
4. Replace “5600” in rate equation with “(RF39 – RF19)/0.00667”.
Available in: Si4740/41/42/43/44/45
Default: 0x0004
Step: 4
Range: 4–248
Notes:
1.
Was property 0x4102 in FW2.C.
2.
For FW2.E, attack rate may be faster than programmed depending on initial and final RF levels.
Bit
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
Name
0
0
0
0
0
0
0
0
ATTACK [7:0]
AGC Attack Rate (dB/s)
5600
ATTACK 7:0
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