LTM9005IV-AA#PBF Linear Technology, LTM9005IV-AA#PBF Datasheet - Page 14

• Manufacturer Part Number: LTM9005IV-AA#PBF
• Manufacturer: Linear Technology

Specifications of LTM9005IV-AA#PBF

• Lead Free Status / RoHS Status: Compliant

LTM9005
applicaTions inForMaTion
RF Input Port
The RF input is shown in Figure 3 and is internally matched
from 1.6GHz to 2.3GHz, requiring no external components
over this frequency range. The input return loss, shown
in Figure 4, is typically 12dB at the band edges. The input
match at the lower band edge can be optimized with a
series 3.9pF capacitor at Pin M3, which improves the
1.6GHz return loss to greater than 25dB. Likewise, the
2.3GHz match can be improved to greater than 25dB with
a series 1.5nH inductor. A series 2.7nH/2.2pF network will
simultaneously optimize the lower and upper band edges
and expand the RF input bandwidth to 1.2GHz to 2.5GHz.
Measured RF input return losses for these three cases are
also plotted in Figure 4.
14
RF
RF
IN
IN
FOR 450MHz, 900MHz
LOW-PASS MATCH
and 3.6GHz RF
L = L (mm)
–10
–15
–25
–30
–20
Z
–5
L5
O
0
C5
Figure 4. Series Reactance Matching
0.2
= 50
SERIES 3.9pF
C5
Figure 3. RF Input Schematic
0.7
1.2
3
HIGH-PASS MATCH
FOR 2.6GHz RF
AND WIDEBAND RF
NO EXT MATCH
RF
FREQUENCY (GHz)
1.7
2.2
SERIES 1.5nH
2.7
SERIES 2.7nH
AND 2.2pF
3.2
3.7
9005 F04
4.2
9005 F03
TO
MIXER
Alternatively, the input match can be shifted as low as
400MHz or up to 3800MHz by adding a shunt capacitor
(C5) to the RF input. A 450MHz input match is realizedwith
C5 = 12pF , located 6.5mm away from Pin M3 on a 50Ω
input transmission line. A 900MHz input match requires
C5 = 3.9pF , located at 1.7mm. A 3.6GHz input match is
realized with C5 = 1pF , located at 2.9mm. This series
transmission line/shunt capacitor matching topology
allows the LTM9005 to be used for multiple frequency
standards without circuit board layout modifications. The
series transmission line can also be replaced with a series
chip inductor for a more compact layout.
Input return losses for the 450MHz, 900MHz, 2.6GHz and
3.6GHz applications are plotted in Figure 5. The input return
loss with no external matching is repeated in Figure 5 for
comparison. The 2.6GHz RF input match uses the high-pass
matching network shown in Figure 3 with C5 = 3.9pF and
L5 = 3.6nH. The high-pass input matching network is also
used to create a wideband or dual-band input match. For
example, with C5 = 3.3pF and L5 = 10nH, the RF input is
matched from 800MHz to 2.2GHz, with optimum matching
in the 800MHz to 1.1GHz and 1.6GHz to 2.2GHz bands,
simultaneously.
Figure 5. RF Input Return Loss with and Without Matching
–15
–10
–20
–25
–30
–5
0
0.2
0.7
1.2
450MHz
L = 6.5mm
C5 = 12pF
900MHz
L = 1.7mm
C5 = 3.9pF
FREQUENCY (GHz)
1.7
2.2
2.7
NO EXT
MATCH
3.2
3.7
9005 F05
4.2
3.6GHz
L = 2.9mm
C5 = 1pF
2.6GHz
SERIES 3.9pF
SHUNT 3.6nH
9005p