lt5560 Linear Technology Corporation, lt5560 Datasheet - Page 15

• Manufacturer Part Number: lt5560
• Description: 0.01mhz To 4ghz Low Power Active Mixer
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
The LT5560 consists of a double-balanced mixer, a com-
mon-base input buffer amplifi er, and bias/enable circuits.
The IC has been designed for frequency conversion applica-
tions up to 4GHz, though operation over a wider frequency
range may be possible with reduced performance. For best
performance, the input and output should be connected
differentially. The LO input can be driven by a single-ended
source with either low side or high side LO operation. The
LT5560 is characterized and production tested using a
single-ended LO drive.
The quiescent DC current of the LT5560 can be adjusted
from less than 4mA to approximately 13.5mA through
the use of an external resistor. This functionality gives the
user the ability to make application dependent trade-offs
between IIP3 performance and DC current.
Three demo boards, as described in Table 1, are available
depending on the desired application. The listed input
and output frequency ranges are based on measured
12dB return loss bandwidths and the LO port frequency
ranges are based on 10dB return loss bandwidths. The
general circuit topologies are shown in Figures 1, 2 and
3 for DC963B, DC991A and DC1027A, respectively. The
board layouts are shown in Figures 23, 24 and 25. The
low frequency board, DC1027A, can be reconfi gured for
upconverting applications.
Table 1. LT5560 Demo Board Descriptions
Upconverting,
Cellular Band
Downconverting
Cellular Band
Downconverting,
VHF Band
Note: Consult factory for demo boards for UMTS, WLAN and other bands.
Signal Input Port
Figure 4 shows a simplifi ed schematic of the differential
input signal port and an example topology for the external
impedance matching circuit. Pins 3 and 4 each source
up to 6mA of DC current. This current can be reduced by
the addition of resistor R1 (adjustable mixer current is
discussed in a later section). The DC ground path can be
DESCRIPTION
MIXER
NUMBER
DC1027A
DC963B
DC991A
BOARD
DEMO
U
U
710-1300
115-295
50-190
INPUT
FREQ.
(MHz)
W
OUTPUT
850-940
110-170
FREQ.
(MHz)
3-60
U
530-930
530-930
180-310
FREQ.
(MHz)
LO
provided through the center-tap of an input transformer,
as shown, or through matching inductors or chokes con-
nected from pins 3 and 4 to ground.
INPUT
The lowpass impedance matching topology shown may
be used to transform the differential input impedance
at pins 3 and 4 to match that of the signal source. The
differential input impedances for several frequencies are
listed in Table 2.
Table 2. Input Signal Port Differential Impedance
FREQUENCY
(MHz)
1500
1900
2150
2450
3600
140
240
360
450
750
900
70
T1
IMPEDANCE
Figure 4. Input Port with Lowpass
External Matching Topology
29.1 + j16.3
29.4 + j20.8
29.6 + j23.6
29.9 + j27.0
31.7 + j42.1
28.5 + j0.8
28.5 + j1.6
28.6 + j2.7
28.6 + j4.0
28.6 + j4.9
28.8 + j8.2
28.8 + j9.8
INPUT
(Ω)
R1
C1
REFLECTION COEFFICIENT (Z
L1
L2
0.274
0.274
0.275
0.276
0.278
0.287
0.294
0.328
0.357
0.376
0.399
0.499
MAG
3
4
IN
IN
–
+
LT5560
ANGLE (DEG.)
86.2
177
174
171
167
163
153
148
138
120
114
107
O
15
= 50Ω)
V
LT5560
BIAS
5560 F04
5560f