lt5524 Linear Technology Corporation, lt5524 Datasheet - Page 13

• Manufacturer Part Number: lt5524
• Description: Low Distortion If Amplifier/adc Driver With Digitally Controlled Gain
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
In fixed gain applications, the LT5524 can be set to 3dB
attenuation relative to maximum gain. As shown in the
Typical Performance Characteristics, this gives a 2dB
reduction in the output noise floor with no loss of linearity.
In general, the output noise floor can be reduced by
decreasing R
reduced OIP3.
LT5524 Characterization
The LT5524’s typical performance data are based on the
test circuits shown in Figures 9 and 10. Figure 9 does not
necessarily reflect the use of the LT5524 in an actual
application. (For that, see the Application Boards section.)
V
TRANSFORMER DEMO BOARD
CC
R
50Ω
IN
IF
SRC
V
SRC
OUT
0.33µF
J1
0Ω
(and hence power gain), at the cost of
C1
1:1
T1
ETC-1-
U
1-13
PGA0 PGA1 PGA2 PGA3
1:2
TC2-1T
T1
V
47nF
CC
C7
U
R9
35.7Ω
47nF
Figure 10. Output Transformer Application Board (Simplified Schematic)
C8
C1
0.47µF
C2
0.1µF
ATT =
7.7dB
R10
35.7Ω
Figure 9. Characterization Board (Simplified Schematic)
W
35.7Ω
35.7Ω
PGA0
R7
R8
PGA1
EN
C2
0.1µF
10
1
2
3
4
5
6
7
8
9
IN
IN
+
–
EN
V
GND
GND
IN
IN
GND
GND
PGA0
PGA1
DUT
CC1
–
+
–
+
U
LT5524
LT5524
51k
R5
51k
MONITOR
PGA3
PGA2
OUT
OUT
R6
V
GND
GND
GND
GND
CC2
V
NC
CCO
–
+
(OPT)
(OPT)
20
19
18
17
16
15
14
13
12
11
C
C
R
PGA2 PGA3
OUT
OUT
OUT
NC
Rather, it represents a compromise that most accurately
measures the actual operation of the part by itself,
undistorted by the artifacts of the impedance transformation
network, or by external bandwidth limiting factors. Balun
transformers are used to interface with single-ended test
equipment. Input and output resistive attenuators (not
shown) provide broadband I/O impedance control. The
L1, L2 inductors are selected for maximally flat AC output
response. C
capacitive loading when this is specified as a
characterization variable. The V
setting the output DC level (5V typical) by adjusting
voltage V
(OPT)
(OPT)
100Ω
R
L1
L2
OUT
100Ω
200Ω
R
OUT
OSUP
37.4Ω
37.4Ω
OUT
R3, R4
37.4Ω
87.4Ω
R3
R4
25Ω
R1
.
(normally open) shows the placement of
R
255Ω
MATCH
25Ω
12dB
ATT
9dB
R2
L1, L2
33nH
47nF
0Ω
C5
47nF
C6
C4
0.1µF
C4
0.1µF
TC4-1W
•
•
ETC-1-
4:1
T2
1-13
CCO
1:1
T1
•
C3
4.7µF
C3
4.7µF
monitor pin allows
R
J2
0Ω
50Ω
LOAD
V
5524 F09
OSUP
LT5524
V
OUT
OSUP
IF
R
50Ω
5524 F10
LOAD
13
5524f