u3741bm ATMEL Corporation, u3741bm Datasheet - Page 6

• Manufacturer Part Number: u3741bm
• Description: Uhf Ask Receiver Ic
• Manufacturer: ATMEL Corporation

Figure 3. Input Matching Network with SAW Filter
Figure 4. Input Matching Network without SAW Filter
6
RF
f
RF
IN
= 433.92 MHz
f
RF
RF
= 433.92 MHz
U3741BM
IN
8.2p
C2
22p
C3
15p
TOKO LL2012
3.3p
F33NJ
L2
33n
22n
L
25n
1
2
TOKO LL2012
25n
100p
IN
F22NJ
IN_GND
8
9
C16
100p
CASE_GND
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.
3, 4
LNAGND
U3741BM
LNA_IN
8
9
B3555
LNAGND
LNA_IN
27n
U3741BM
L3
7, 8
TOKO LL2012
OUT_GND
27NJ
C17
8.2p
OUT
5
6
f
RF
RF
= 315 MHz
IN
RF
f
RF
IN
= 315 MHz
33p
3.3p
10p
C2
47p
39n
C3
TOKO LL2012
F82NJ
TOKO LL2012
25n
L2
82n
100p
F39NJ
L
25n
1
2
IN
IN_GND
8
9
LNAGND
LNA_IN
U3741BM
8
9
100p
C16
CASE_GND
LNAGND
U3741BM
LNA_IN
3, 4 7, 8
B3551
47n
L3
TOKO LL2012
OUT_GND
C17
F47NJ
22p
4662B–RKE–10/04
OUT
6
5