LTC5542IUH#PBF Linear Technology, LTC5542IUH#PBF Datasheet - Page 10

• Manufacturer Part Number: LTC5542IUH#PBF
• Description: IC, DOWN CONVERTING MIXER 2.7GHZ, QFN-20
• Manufacturer: Linear Technology

Specifications of LTC5542IUH#PBF

• Frequency Range: 1.6GHz To 2.7GHz
• Supply Voltage Range: 3.3V To 5V
• Rf Ic Case Style: QFN
• No. Of Pins: 20
• Operating Temperature Range: -40°C To +85°C
• Rf Type: CDMA, GSM, TD-SCDMA, WCDMA
• 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
LTC5542
Introduction
The LTC5542 consists of a high linearity passive double-
balanced mixer core, IF buffer amplifi er, high speed single-
pole double-throw (SPDT) LO switch, LO buffer amplifi er
and bias/shutdown circuits. See Block Diagram section for
a description of each pin function. The RF and LO inputs
are single-ended. The IF output is differential. Low-side or
high-side LO injection can be used. The evaluation circuit,
shown in Figure 1, utilizes bandpass IF output matching and
an IF transformer to realize a 50Ω single-ended IF output.
The evaluation board layout is shown in Figure 2.
RF Input
The mixer’s RF input, shown in Figure 3, is connected to
the primary winding of an integrated transformer. A 50Ω
match is realized when a series capacitor C1 and shunt
capacitor C11, are connected to the RF input. C1 is also
needed for DC blocking if the RF source has DC voltage
present, since the primary side of the RF transformer is
DC-grounded internally. The DC resistance of the primary
is approximately 3.6Ω.
The secondary winding of the RF transformer is internally
connected to the passive mixer. The center-tap of the
transformer secondary is connected to pin 3 (CT) to allow
the connection of bypass capacitor, C2. The value of C2
10
Figure 2. Evaluation Board Layout
5541 F02
5542 F02
is LO frequency-dependent and is not required for most
applications. When used, C2 should be located within
2mm of pin 3 for proper high-frequency decoupling. The
nominal DC voltage on the CT pin is 1.2V.
For the RF input to be matched, the selected LO input must
be driven. The measured RF input return loss is shown
in Figure 4 for LO frequencies of 1.7GHz, 2.1GHz and
2.5GHz. These LO frequencies correspond to the lower,
middle and upper values of the LO range. As shown in
Figure 4, the RF input impedance is somewhat dependent
on LO frequency.
RF
IN
C1
–10
–15
–20
–25
–30
–5
0
1.2
Figure 4. RF Input Return Loss
Figure 3. RF Input Schematic
C11
C2
2
3
1.7
RF
CT
LO = 2.5GHz
LO = 2.1GHz
FREQUENCY (GHz)
LO = 1.75GHz
2.2
2.7
C11 = 0.7pF
C1 = 22pF
TO MIXER
LTC5542
5542 F04
3.2
5542 F03
5542f