BROADBAND ULTRA LOW DISTORTION 7-BIT DIGITALLY CONTROLLED VGA
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1150A
LT5554
DESCRIPTION
Demonstration circuit 1150A 1150A is a featuring the
LTC5554 IC, a 7-bit programmable gain amplifier. It in-
corporates a variety of passive components to support
configurations for varied applications.
The LT5554 is a differential input and output precision
programmable gain amplifier with 16dB gain range and
0.125dB gain step.
The seven LT5554 gain control inputs (PGx, x=0,2,..6)
and the STROBE input can be coupled to TTL (DC-
coupling type) or ECL and (low-voltage) CMOS drivers
(AC-coupling type) without external components. The 3-
state MODE pin allows the selection of the coupling type.
The LT5554 gain state can be updated asynchronously
when STROBE is HIGH or synchronously using the
STROBE input positive transition. In the latter STROBED-
MODE, the external control logic time skew is eliminated
and synchronization with the ADC clock is possible.
With 0.125dB step resolution and 5ns settling time, the
LT5554 may be suited in quasi-continuous gain control
applications
.
The LT5554 power and voltage gain for Maximum Gain
is 18dB when application R
out
=50•. Application gain can
be changed with different R
out
selections.
The LT5554 amplifier is unconditionally stable. Conse-
quently, LC-filters or SAW filters can be connected to the
LT5554 I/O pins without padding.
Lacking global feed-back, the LT5554 has -80dB reverse
isolation @ 400MHz (package limited).
Design files for this circuit board are available. Call
the LTC factory.
PowerPath is a trademark of Linear Technology Corporation
1
BROADBAND ULTRA LOW DISTORTION 7-BIT DIGITALLY CONTROLLED VGA
Table 1. Typical DEMO BOARD Performance Summary [T
A
= 25°C, VCC = 5V, VccO = 5V, ENB = 3V, MODE = 5v, STROBE = 2.2V, HIH =
2.2V, MAXIMUM GAIN, POUT = 4dBm/Tone (2VP-P into 50Ω),
∆
f = 200KHz]
Ω
SYMBOL
V
CC
V
CC
O
I
CC
I
ODC
R
IN
C
IN
R
O
C
O
HD2
HD3
PARAMETER
Supply Voltage
OUT± Output Pin DC Common Mode Voltage
V
CC
Supply Current
OUT± Quiescent Current
Input Resistance
Input Capacitance
Output Resistance
Output Capacitance
Second Harmonic Distortion
Third Harmonic Distortion
(For more detail, Please see Note 4 of
data sheet)
V
CC = 5V
OUT± Voltages = 5V
F
IN
=100MHz
F
IN
=100MHz
F
IN
=100MHz
F
IN
=100MHz
Pout=10dBm (Single Tone),
F
IN
=100MHz, R
OUT
= 50Ω
Pout=10dBm (Single Tone),
F
IN
=100MHz, R
OUT
= 50Ω
CONDITIONS
TYPICAL PERFORMANCE
4.75 to 5.25
3.5 to 6
100
96
45
2.8
400
1.9
-76
-62
R
OUT
50Ω
Ω
G
VMAX
G
PMAX
IIP3
OIP3
IMD3
V
ONOISE
NF
RTI
SFDR
Maximum Voltage Gain
Maximum Power Gain
Input Third Order Intercept Point
Output Third Order Intercept Point
Intermodulation Product
Output Noise Noise Spectral Density
Noise Figure
Input Referred Noise Spectral Density
Spurious Free Dynamic Range
F
IN
=200MHz
F
IN
=200MHz
F
IN
=200MHz
F
IN
=200MHz
F
IN
=200MHz
F
IN
=200MHz
F
IN
=200MHz
F
IN
=200MHz
F
IN
=200MHz
13.7
13.6
27.8
41.5
-84
10.7
10
1.34
128
100Ω
Ω
19.6
16.6
27
44
-88
21.4
10
1.34
128
dB
dB
dBm
dBm
dBc
nV/√Hz
dB
nV/√Hz
dBm/Hz
UNIT
V
V
mA
mA
Ω
P
F
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1150A
Ω
P
F
dBc
dBc
Table 2. DC1150A Board I/O Description
CONNECTOR
J1
J3
VCC
VCCO
VPG
ENABLE
FUNCTION
Singe-Ended Input
Singe-Ended Output
LT5554 VCC pin.
Output bias voltage
Bias STROBE and all PGx via
10KΩ resistors.
Enable/Shut-down
COMMENTS
50Ω
Signal source, no external termination necessary
50Ω
matched, can drive network/spectrum analyzer input
Connect to power supply 5V.
Connect to power supply 5V.
Connect to power supply in 3 to 5V range for Maximum Gain state. Connect to GROUND for Mini-
mum Gain state.
Connect to 5V to enable LT5554, or connect to GND for shut-down.
2
BROADBAND ULTRA LOW DISTORTION 7-BIT DIGITALLY CONTROLLED VGA
MODE
STROBE
Selects STROBE and PGx in-
put type
VGA gain update mode
Connect to 5V for gain control inputs DC-coupled TTL levels. (consult tables 1 and 2 on page 19 of
datasheet for other settings)
STROBE=H
STROBE=L
: gain is asynchronously set by PGx transitions.
: gain is not changed by PGx transitions.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1150A
STROBE=signal : gain is synchronously set by the PGx state strobed by the STROBE pin positive
transitions.
PG0 … PG6
VGA control inputs
Biased by default from VPG via 10kΩ resistors when left open.
Apply the desired level to corresponding PGx Turret or J5 connector pin to change the gain state.
VDEC
Input common-mode voltage
test point
Self-biasing within LT5554, normally open. When voltage is applied, the internal bias buffer source
and sink currents can be measured.
Table 3. DC1150A Board I/O Optional Features
CONNECTOR
J5
J2
J4
J6
J7
FUNCTION
External LT5554 state control
PG1/PG2
PG3/PG4
PG5/PG6
STROBE
COMMENTS
Board Edge Connector can be used instead of board mounted turrets to control the LT5554 state.
Timing evaluation. 50Ω matched SMA connector
Timing evaluation. 50Ω matched SMA connector
Timing evaluation. 50Ω matched SMA connector
Timing and full speed up to 200MHz evaluation. 50Ω matched SMA connector
Table 4. DC1150A Board I/O Optional circuits
INPUT PORT
OUTPUT PORT
COMMENTS
Single-Ended Input and Output with transformers. (Standard Demo Board is shipped with
this configuration.) Simplified Input and Output circuits is shown on page 4.
Differential Capacitively-Coupled input and Output with transformer. Circuit modification is
shown on page 5.
Single-Ended with trans- Differential outputs converted to
former coupled to differ- Single-Ended with transformer
ential source
Differential Inputs with
Differential outputs converted to
Capacitively-Coupled to a Single-Ended with transformer
Differential Source
Single-Ended with trans- Differential wide band Decoupling Single-Ended transformer Input and differential 100 decoupling capacitors outputs. Circuit
former coupled to differ- capacitors Outputs
modification is shown on page 6.
ential source
Single-Ended with trans- Differential 50 Outputs with
former coupled to differ- transformer
ential source
Single-Ended transformer Input and Differential 50 outputs with transformer. Circuit modi-
fication is shown on page 7.
Table 5. DC1150A Board different Rout Impedance
ROUT ***
Rout=50•
Rout=75•
Rout=100•
FUNCTION
50• Single-ended output(J3)
50• Single-ended output(J3)
50• Single-ended output(J3)
COMMENTS
R5 and R6 = 68.1•. T2 =TC2-1T. (Standard Demo Board installed with these components values)
Replace R5 and R6 from 68.1• to 124•. T2(TC2-1T) replace with TC3-1T(Mini-Circuit)
Replace R5 and R6 from 68.1• to 205•. T2(TC2-1T) replace with TC4-1W(Mini-Circuit)
3
BROADBAND ULTRA LOW DISTORTION 7-BIT DIGITALLY CONTROLLED VGA
NOTE:
***
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1150A
Consult Tables 3, 4 page 23, 24 respectively of datasheet for others Rout Options.
LT5554 STANDARD DEMO BOARD WITH SINGLE-ENDED INPUT AND OUTPUT TRANSFORMERS
VCCO
VCCO
Demo Boards with simplified Input and Output Circuits
0
J1
1
C20
2.7pF
5
T1
1:1
3
2
4
ETC1-1-13
R1
0
0
C2
C1
DEC
C5
1uF
25
C3
0.1uF
E1
R5
68.1
C19
4.7uF
IN+
25
Ro
400
OUT-
VCCO
3
2
1
TC2-1T
T2
OUT-
J3
4
5
R2
0
LT5554
IN-
OUT+
R6
68.1
C9
0.1uF
C18
0.1uF
Demo Board’s Silk Screen
4
BROADBAND ULTRA LOW DISTORTION 7-BIT DIGITALLY CONTROLLED VGA
MODIFICATION FOR 50 SINGLE-ENDED TRANSFORMER INPUT TO DIFFERENTIAL INPUT
VCCO
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1150A
VCCO
Demo Boards with simplified Input and Output Circuits
0
J1
1
C20
2.7pF
5
T1
1:1
3
2
4
ETC1-1-13
R1
0
0
C2
C1
DEC
C5
1uF
25
C3
0.1uF
E1
R5
68.1
C19
4.7uF
IN+
25
Ro
400
OUT-
VCCO
3
2
1
TC2-1T
T2
OUT-
J3
4
5
R2
0
LT5554
IN-
OUT+
R6
68.1
C9
0.1uF
C18
0.1uF
1) Remove T1 and bypass with 0 resistors.
(Connecting transformer footprint 1 to 3
and pin 5 to 4)
2) Install decoupling capacitors C1 and C2.
3) Install J11 connector.
4) Remove C20 and R1.
MODIFIED INPUT CIRCUIT
VCCO
VCCO
Differential Capacitively-Coupled Input
J1
IN-
0
1
5
J11
T1
1:1
3
2
4
ETC1-1-13
0
C2
C1
DEC
C5
1uF
25
C3
0.1uF
E1
R5
68.1
C19
4.7uF
IN+
25
Ro
400
OUT-
VCCO
3
2
1
TC2-1T
T2
OUT-
J3
4
5
R2
0
LT5554
IN+
IN-
OUT+
R6
68.1
C9
0.1uF
C18
0.1uF
5
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