LTC5540IUH#PBF Linear Technology, LTC5540IUH#PBF Datasheet - Page 13

• Manufacturer Part Number: LTC5540IUH#PBF
• Description: IC, DOWN CONVERTING MIXER 1.3GHZ, QFN-20
• Manufacturer: Linear Technology

Specifications of LTC5540IUH#PBF

• Frequency Range: 600MHz To 1.3GHz
• Supply Voltage Range: 3.1V To 3.5V
• Rf Ic Case Style: QFN
• No. Of Pins: 20
• Operating Temperature Range: -40°C To +85°C
• Rf Type: GSM, LTE, WCDMA, WiMax
• Operating Supply Voltage: 3.3V
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

applicaTions inForMaTion
Bandpass IF Matching
The IF output can be matched for IF frequencies as low
as 70MHz or as high as 500MHz using the bandpass
IF matching shown in Figure 1 and Figure 7. L1 and L2
resonate with the internal IF output capacitance at the
desired IF frequency. The value of L1, L2 is calculated
as follows:
where C
Values of L1 and L2 are tabulated in Figure 1 for various IF
frequencies. For IF frequencies below 70MHz, the values
of L1, L2 become unreasonably high and the lowpass
topology shown in Figure 9 is preferred. Measured IF
output return loss for bandpass IF matching is plotted
in Figure 10.
Table 4. IF Output Impedance vs Frequency
Lowpass IF Matching
An alternative IF matching network shown in Figure 9 uses
a lowpass topology, which provides excellent RF to IF
and LO to IF isolation. V
center tap of the 4:1 transformer. A lowpass impedance
transformation is realized by shunt elements R2 and
C13 (in parallel with the internal R
inductors L1 and L2. Resistor R2 is used to reduce the
IF output resistance, or it can be deleted for the highest
conversion gain. The final impedance transformation to
50Ω is realized by transformer T1. The matching element
values shown in Figure 9 are optimized for a wideband
30MHz-150MHz IF match. The demo board (see Figure 2)
has been laid out to accommodate this matching topology
with very few modifications.
L1 = L2 = 1/[(2 π f
FREQUENCY (MHz)
IF
is the internal IF capacitance (listed in Table 4).
140
190
240
300
380
450
70
IF
)
2
• 2 • C
CCIF
IMPEDANCE (R
IF
is supplied through the
]
DIFFERENTIAL OUTPUT
IF
584 || -j316 (2.1pF)
561 || -j253 (2.1pF)
532 || -j182 (2.3pF)
511 || -j154 (2.3pF)
674 || -j1137 (2pF)
628 || -j569 (2pF)
606 || -j419 (2pF)
and C
IF
IF
), and series
|| X
IF
(C
IF
))
IF Amplifier Bias
The IF amplifier delivers excellent performance with
V
to be common. With V
P1dB increases by almost 3dB, at the expense of higher
power consumption. Mixer performance at 900MHz is
shown in Table 5 with V
conversion gain, high-Q wire-wound chip inductors are
recommended for L1 and L2, especially when using
V
substituted, with a slight reduction in conversion gain.
Table 5. Performance Comparison with V
(RF = 900MHz, High-Side LO, IF = 190MHz)
CCIF
CCIF
V
3.3V
5V
CCIF
Figure 10. IF Output Return Loss - Bandpass Matching
= 3.3V. Low-cost multilayer chip inductors may be
= 3.3V, which allows the V
3.1-5.3V
–10
–15
–20
Figure 9. IF Output with Lowpass Matching
–5
V
0
CCIF
50
270nH
I
CCIF
96
99
100 150 200 250 300 350
C9
1µF
150nH
19
L1
82nH
IF
100nH
T1
+
FREQUENCY (MHz)
7.9
7.9
G
CCIF
CCIF
C
LTC5540
1.5pF
C13
4:1
R2
1k
33nH
= 3.3V and 5V. For the highest
increased to 5V, the RF input
C8
22pF
P1dB
14.5
11
400 450
CC
18
CCIF
L2
82nH
IF
and V
5540 F10
–
LTC5540
= 3.3V and 5V
IF
50
30MHz TO 150MHz
500
OUT
25.9
25.9
IIP3
CCIF
5540 F09
supplies

10.0
9.9
NF
5540f