LT5527 LINER [Linear Technology], LT5527 Datasheet - Page 11

• Manufacturer Part Number: LT5527
• Description: 400MHz to 3.7GHz 5V High Signal Level Downconverting Mixer
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
0dBm LO drive is recommended for optimum noise fi gure,
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 referenced
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 Figure 7).
Both pins must be biased at the supply voltage, which
can be applied through the center tap of a transformer or
through matching inductors. Each IF pin draws 26mA of
supply current (52mA total). For optimum single-ended
performance, these differential outputs should be com-
bined externally through an IF transformer or a discrete IF
balun circuit. The standard evaluation board (see Figure
1) includes an IF transformer for impedance transforma-
tion and differential to single-ended transformation. 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
FREQUENCY
(MHz)
1200
1500
1850
2150
2450
2650
3000
3500
4000
5000
300
450
600
900
50
30.4 – j355.7
IMPEDANCE
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
and IF
–
, are internally connected to the
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
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
8. Frequency-dependent differential IF output impedance
is listed in Table 3. This data is referenced to the package
pins (with no external components) and includes the ef-
fects 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 (RIF || XIF)
IF
IF
L1
L2
+
–
C3
11
10
415||-j6.4k
415||-j909
413||-j453
407||-j264
403||-j211
395||-j165
387||-j138
381||-j124
415||-j64k
5527 F08
LT5527
V
CC
4:1
11
5527fa
IF
50Ω
OUT