U3741BM Datasheet, PDF (6/32 Pages) ATMEL Corporation – UHF ASK RECEIVER IC

Figure 3. Input Matching Network with SAW Filter
8 _LNAGND
U3741BM
C3
L
9 _{LNA_IN}
22p
25n
C16
C17
f_RF = 433.92 MHz
100p
L3
27n
8.2p
TOKO LL2012
27NJ
L2
TOKO LL2012
RF_IN
C2
8.2p
F33NJ
33n
1
IN
2
IN_GND
B3555
5
OUT
OUT_GND ⁶
CASE_GND
3, 4 7, 8
Figure 4. Input Matching Network without SAW Filter
f_RF = 433.92 MHz
15p
25n
8 _LNAGND
U3741BM
9 _{LNA_IN}
RFIN
3.3p
22n
100p
TOKO LL2012
F22NJ
8
LNAGND
U3741BM
C3
L
9
LNA_IN
47p
25n
f_RF = 315 MHz
C16
C17
100p
L3
47n
22p
TOKO LL2012
F47NJ
L2
TOKO LL2012
RF_IN
F82NJ
1
IN
B3551
5
OUT
C2
82n 2
IN_GND
OUT_GND ⁶
CASE_GND
10p
3, 4 7, 8
f_RF = 315 MHz
8 _LNAGND
U3741BM
33p
25n
9 _{LNA_IN}
RF
IN
3.3p
39n
100p
TOKO LL2012
F39NJ
Please note that for all coupling conditions (see Figure 3 and Figure 4), the bond wire
inductivity of the LNA ground is compensated. C3 forms a series resonance circuit
together with the bond wire. L = 25 nH is a feed inductor to establish a DC path. Its
value is not critical but must be large enough not to detune the series resonance circuit.
For cost reduction, this inductor can be easily printed on the PCB. This configuration
improves the sensitivity of the receiver by about 1 dB to 2 dB.
6 U3741BM
4662B–RKE–10/04