LTC5593_15 Datasheet, PDF (23/28 Pages) Linear Technology – Dual 2.3GHz to 4.5GHz High Dynamic Range Downconverting Mixer

APPLICATIONS INFORMATION
L3A (OR SHORT)
100mA
T1A
4:1
C7A
L1A
L2A
V_CCIFA
C5A
IFA
R1A
(OPTION TO
REDUCE
DC POWER)
R2A
23 _IGNDA
22
IFA⁺
21
IF A^–
20
IFBA
LTC5593
LTC5593
V_CCA
IF
AMP
4mA
BIAS
5593 F08
Figure 8. IF Amplifier Schematic with Bandpass Match
For optimum single-ended performance, the differential
IF output must be combined through an external IF
transformer or a discrete IF balun circuit. The evaluation
board (see Figures 1 and 2) uses a 4:1 IF transformer for
impedance transformation and differential to single-ended
conversion. It is also possible to eliminate the IF transformer
and drive differential filters or amplifiers directly.
The IF output impedance can be modeled as 260Ω in
parallel with 2.3pF. The equivalent small-signal model,
including bondwire inductance, is shown in Figure 9.
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.
Bandpass IF Matching
The bandpass IF matching configuration, shown in
Figures 1 and 8, is best suited for IF frequencies in the
90MHz to 600MHz range. Resistor R2A may be used to
LTC5593
22 _IFA+
0.9nH
RIF
CIF
21 _{IF A–}
0.9nH
5593 F09
Figure 9. IF Output Small-Signal Model
reduce the IF output resistance for greater bandwidth and
inductors L1A and L2A resonate with the internal IF output
capacitance at the desired IF frequency. The value of L1A,
L2A can be estimated as follows:
( ) L1A = L2A =

2πf_IF
1
2 _{• 2 • CIF}
where C_IF is the internal IF capacitance (listed in Table 3).
5593f
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