lt5527euf-trpbf Linear Technology Corporation, lt5527euf-trpbf Datasheet - Page 11

• Manufacturer Part Number: lt5527euf-trpbf
• Description: 400mhz To 3.7ghz High Signal Level Downconverting Mixer
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
0dBm LO drive is recommended for optimum noise figure,
although –3dBm will still deliver good conversion gain
and linearity.
Custom matching networks can be designed using the
port impedance data listed in Table 2. This data is refer-
enced to the LO pin with no external matching.
Table 2. LO Input Impedance vs Frequency
IF Output Port
The IF outputs, IF
collectors of the mixer switching transistors (see Fig-
ure 7). Both pins must be biased at the supply voltage,
which can be applied through the center tap of a trans-
former or through matching inductors. Each IF pin draws
26mA of supply current (52mA total). For optimum single-
ended performance, these differential outputs should be
combined externally through an IF transformer or a
discrete IF balun circuit. The standard evaluation board
(see Figure 1) includes an IF transformer for impedance
transformation and differential to single-ended transfor-
mation. A second evaluation board (see Figure 2) realizes
the same functionality with a discrete IF balun circuit.
The IF output impedance can be modeled as 415Ω in
parallel with 2.5pF at low frequencies. An equivalent
small-signal model (including bondwire inductance) is
shown in Figure 8. Frequency-dependent differential IF
FREQUENCY
(MHz)
1200
1500
1850
2150
2450
2650
3000
3500
4000
5000
300
450
600
900
50
+
30.4 – j355.7
and IF
IMPEDANCE
U
19.7 + j12.8
34.3 + j24.3
49.8 + j21.3
49.0 + j12.0
8.7 – j52.2
9.4 – j25.4
11.5 – j8.9
53.8 + j8.9
50.4 + j3.2
45.1 + j0.3
41.1 + j2.4
41.9 + j8.1
55.4 + j8.6
33.2 + j8.7
INPUT
–
U
, are internally connected to the
W
0.977
0.847
0.740
0.635
0.463
0.330
0.209
0.093
0.032
0.052
0.101
0.124
0.120
0.096
0.226
MAG
S11
U
ANGLE
–124.8
–158.7
–15.9
–86.7
146.7
106.9
176.5
163.1
129.8
146.7
78.5
61.7
80.5
87.9
53.2
output impedance is listed in Table 3. This data is refer-
enced to the package pins (with no external components)
and includes the effects of IC and package parasitics. The
IF output can be matched for IF frequencies as low as
several kHz or as high as 600MHz.
Table 3. IF Output Impedance vs Frequency
The following three methods of differential to single-
ended IF matching will be described:
• Direct 8:1 transformer
• Lowpass matching + 4:1 transformer
• Discrete IF balun
FREQUENCY (MHz)
Figure 7. IF Output with External Matching
Figure 8. IF Output Small-Signal Model
140
240
300
380
450
500
10
70
1
V
CC
R
415Ω
S
IF
IF
+
–
2.5pF
0.7nH
0.7nH
11
10
5527 F07
DIFFERENTIAL OUTPUT
IMPEDANCE (R
IF
IF
L1
L2
+
–
C3
415||-j6.4k
11
10
415||-j64k
415||-j909
413||-j453
407||-j264
403||-j211
395||-j165
387||-j138
381||-j124
5527 F08
V
LT5527
CC
IF
|| X
4:1
11
IF
)
IF
50Ω
5527f
OUT