u3745bm ATMEL Corporation, u3745bm Datasheet - Page 7

• Manufacturer Part Number: u3745bm
• Description: Receiver
• Manufacturer: ATMEL Corporation

Figure 3. Input Matching Network with SAW Filter
Figure 4. Input Matching Network without SAW Filter
4663A–RKE–06/03
f
RF
RF
IN
= 433.92 MHz
f
RF
RF
= 433.92 MHz
8.2p
IN
C2
22p
C3
TOKO LL2012
15p
F33NJ
33n
L2
3.3p
22n
L
25n
1
2
TOKO LL2012
IN
IN_GND
25n
100p
F22NJ
8
9
C16
100p
CASE_GND
LNAGND
U3745BM
LNA_IN
B3555
3,4 7,8
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.
8
9
27n
L3
LNAGND
LNA_IN
U3745BM
TOKO LL2012
OUT_GND
F27NJ
C17
8.2p
OUT
5
6
f
RF
RF
= 315 MHz
IN
f
RF
RF
IN
= 315 MHz
33p
3.3p
10p
C2
47p
C3
39n
TOKO LL2012
F82NJ
82n
L2
TOKO LL2012
25n
100p
F39NJ
L
25n
2
1
IN
IN_GND
8
9
LNAGND
U3745BM
LNA_IN
8
9
C16
100p
CASE_GND
LNAGND
LNA_IN
U3745BM
B3551
3,4 7,8
47n
L3
TOKO LL2012
U3745BM
OUT_GND
F47NJ
C17
22p
OUT
5
6
7