FEATURES
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LT5554
Broadband Ultra Low
Distortion 7-Bit Digitally
Controlled VGA
DESCRIPTION
The LT
®
5554 is a 7-bit digitally controlled programmable
gain (PG) amplifier with 16dB gain control range. It
consists of a 50Ω input variable attenuator, followed by
a high linearity variable transconductance amplifier. The
coarse 4dB input attenuator step is implemented via 2-bits
of digital control (PG5, PG6). The fine transconductance
amplifier 0.125dB step within 3.875dB gain control range
is set via 5-bits digital control (PG0 to PG4). The LT5554
gain control inputs (PGx) and the STROBE input can be
directly coupled to TTL or ECL drivers. The seven parallel
gain control inputs time skew can be eliminated by using
the STROBE input positive transition.
The internal output resistor R
O
= 400Ω limits the maxi-
mum overall gain to 36dB for open outputs. The internal
circuitry of open output collectors enables the LT5554 to
be unconditionally stable over any loading conditions (in-
cluding external SAW filters) and provides –80dB reverse
isolation at 300MHz.
The LT5554 is internally protected during overdrive and
has an on-chip power supply regulator.
With 0.125dB step resolution and 5ns settling time, the
LT5554 is suitable in applications where continuous gain
control is required.
1GHz Bandwidth at all Gains
48dBm OIP3 at 200MHz, 2V
P-P
into 50Ω,
R
OUT
= 100Ω
–88dBc IMD3 at 200MHz, 2V
P-P
into 50Ω,
R
OUT
= 100Ω
1.4nV/√Hz Input-Referred-Noise (RTI)
20dBm Output P1dB at 70MHz, R
OUT
= 130Ω
2dB to 18dB Gain Range (R
OUT
= 50Ω)
0.125dB Gain Step Size
30ps Group Delay Variation
5ns Fast Gain Settling Time
5ns Fast Overdrive Recovery
–80dB Reverse Isolation
APPLICATIONS
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Differential ADC Driver
IF Sampling Receivers
VGA IF Power Amplifier
50Ω Driver
Instrumentation
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
TYPICAL APPLICATION
OIP3 and SFDR vs Frequency
132
5V
V
CC
0.1μF
SFDR (dBm/Hz)
IN
+
RF
INPUT
LO
IF
BPF
IF
AMPLIFIER
DEC
IN
–
0.1μF
C
DEC
0.1μF
MODE
130
46
OIP3 (dBm)
R
OUT
= 50Ω
49
–
LT5554
BPF
ADC
OIP3
+
7 BITS
PGx GAIN CONTROL
STROBE
5554 TA01
128
SFDR
43
126
0
50
100
150
FREQUENCY (MHz)
40
200
5554 TA01b
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LT5554
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
PIN CONFIGURATION
TOP VIEW
GND
GND
GND
GND
GND
24 V
CC
23 ENB
22 GND
33
21 OUT
–
20 OUT
+
19 GND
18 MODE
17 V
CC
9 10 11 12 13 14 15 16
PG5
GND
PG6
PG0
GND
STROBE
GND
PG1
PG2
PG3
PG4
32 31 30 29 28 27 26 25
GND
GND
DEC
IN
+
IN
–
DEC
GND
GND
1
2
3
4
5
6
7
8
Supply Voltage
V
CC
..........................................................................6V
Pin Voltages and Currents
OUT
+
, OUT
–
............................................................7V
STROBE, PGx..........................................–0.5V to V
CC
ENB, MODE.............................................–0.5V to V
CC
IN
+
, IN
–
, DEC ........................................... –0.5V to 4V
Operating Ambient Temperature Range
LT5554 ............................................... –40°C to +85°C
Junction Temperature ........................................... 125°C
Storage Temperature Range................. –65°C to +150°C
UH PACKAGE
32-LEAD (5mm 5mm) PLASTIC QFN
T
JMAX
= 150°C,
θ
JA
= 34°C/W,
θ
JC
= 3°C/W
EXPOSED PAD (PIN 33) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT5554IUH#PBF
TAPE AND REEL
LT5554IUH#TRPBF
PART MARKING
5554
PACKAGE DESCRIPTION
32-Lead (5mm
×
5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
5554f
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LT5554
AC ELECTRICAL CHARACTERISTICS
SYMBOL
BW
OP1dB
G
M
CMRR
S12
PARAMETER
Large Signal –3dB Bandwidth
Output 1dB Compression Point
Amplifier Transconductance at G
MAX
Common Mode Gain to Single-Ended
Output
Reverse Isolation
Overdrive Recovery Time
IIP3
OIP3
IMD3
OIP3
OIP3
HD3
V
ONOISE
NF
RTI
SFDR
Input Third Order Intercept Point
Output Third Order Intercept Point for
Max-Gain
Intermodulation Product for Max-Gain
Output Third Order Intercept Point for
–3.875dB STEP
Output Third Order Intercept Point
Third Harmonic Distortion
Output Noise Noise Spectral Density
Noise Figure
Input Referred Noise Spectral Density
(RMS) (Note 5)
Spurious Free Dynamic Range in 1Hz
BW.
Maximum Voltage and Power Gain
Minimum Voltage and Power Gain
Gain Step Size (Note 9)
Group Delay Step Accuracy
Input Resistance
Input Capacitance
Output Resistance
Output Capacitance
CONDITIONS
All Gain Settings (Note 7)
All Gain Settings, R
OUT
= 130Ω, 70MHz
F
IN
= 100MHz
F
IN
= 100MHz, Figure 19
F
IN
= 100MHz
F
IN
= 400MHz
5ns Input Pulse, V
OUT
within ±10%
G
MAX
, F
IN
= 200MHz
G
MAX
–3.875dB, F
IN
= 200MHz
F
IN
= 100MHz
F
IN
= 200MHz
F
IN
= 100MHz
F
IN
= 200MHz
F
IN
= 100MHz
F
IN
= 200MHz
G
MAX
, F1 = 88MHz, F2 = 112MHz
G
MAX
–3.875dB, F1 = 88MHz, F2 = 112MHz
Pout = 10dBm, F
IN
= 100MHz, G
MAX
G
MAX
, F
IN
= 200MHz
G
MAX
–3.875dB, F
IN
= 200MHz
G
MAX
, F
IN
= 200MHz
G
MAX
–3.875dB, F
IN
= 200MHz
G
MAX
, F
IN
= 200MHz
G
MAX
–3.875dB, F
IN
= 200MHz
G
MAX
, F
IN
= 200MHz
G
MAX
–3.875dB, F
IN
= 200MHz
F
IN
= 112MHz
F
IN
= 100MHz
Except For –4dB, –8dB, –12dB Steps
For –4dB, –8dB, –12dB Steps
F
IN
= 100MHz
F
IN
= 100MHz, G
MAX
to G
MAX
–3.875dB
F
IN
= 100MHz, G
MAX
–4dB to G
MIN
F
IN
= 100MHz
F
IN
= 100MHz
F
IN
= 100MHz
15.3
40.5
38
Dynamic Performance
LF – 1000
20
0.15
–6
–86
–78
5
27
30
45
46
–82
–84
44
40
47
44
–62
10.7
7.3
10
10.5
1.34
1.42
128
129
17.6
1.725
0.125
10
43
47
2.8
400
1.9
0.25
0.35
19.7
MHz
dBm
S
dB
dB
dB
ns
dBm
dBm
dBm
dBm
dBc
dBc
dBm
dBm
dBm
dBm
dBc
nV/√Hz
nV/√Hz
dB
dB
nV/√Hz
nV/√Hz
dBm/Hz
dBm/Hz
dB
dB
dB
dB
ps
Ω
Ω
pF
Ω
pF
(R
OUT
= 50Ω) Specifications are at T
A
= 25°C. V
CC
= 5V, V
CCO
= 5V,
ENB = 3V, MODE = 5V, STROBE = 2.2V, V
IH
= 2.2V, V
IL
= 0.6V, maximum gain (Notes 3, 6), (Test circuits shown in Figure 16), unless
otherwise noted.
MIN
TYP
MAX
UNIT
Noise/Linearity Performance Two Tones, P
OUT
= 4dBm/Tone (2V
P-P
into 50Ω), Δf = 200kHz
Amplifier Voltage Gain and Gain Step
G
MAX
G
MIN
G
STEP
GD
ERROR
R
IN
C
IN
R
O
C
O
AMPLIFIER I/O Differential IMPEDANCE
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LT5554
AC ELECTRICAL CHARACTERISTICS
SYMBOL
IIP3
OIP3
IMD3
V
ONOISE
NF
RTI
SFDR
G
VMAX
G
PMAX
PARAMETER
Input Third Order Intercept Point
Output Third Order Intercept Point for
Max-Gain
Intermodulation Product for Max-Gain
Output Noise Noise Spectral Density
Noise Figure
Input Referred Noise Spectral Density
(RMS) (Note 5)
Spurious Free Dynamic Range in
1Hz BW.
Maximum Voltage Gain
Maximum Power Gain
CONDITIONS
G
MAX
, F
IN
= 200MHz
G
MAX
–3.875dB, F
IN
= 200MHz
F
IN
= 100MHz
F
IN
= 200MHz
F
IN
= 100MHz
F
IN
= 200MHz
G
MAX
, F
IN
= 200MHz
G
MAX
–3.875dB, F
IN
= 200MHz
G
MAX
, F
IN
= 200MHz
G
MAX
–3.875dB, F
IN
= 200MHz
G
MAX
, F
IN
= 200MHz
G
MAX
–3.875dB, F
IN
= 200MHz
G
MAX
, F
IN
= 200MHz
F
IN
= 100MHz
F
IN
= 100MHz
(R
OUT
= 100Ω) Specifications are at T
A
= 25°C. V
CC
= 5V, V
CCO
= 5V,
ENB = 3V, MODE = 5V, STROBE = 2.2V, V
IH
= 2.2V, V
IL
= 0.6V, maximum gain (Notes 3, 8), (Test circuits shown in Figure 16), unless
otherwise noted.
MIN
TYP
27
27
48
48
–88
–88
21.4
14.5
10
10.5
1.34
1.42
128
23.6
20.6
MAX
UNIT
dBm
dBm
dBm
dBm
dBc
dBc
nV/√Hz
nV/√Hz
dB
dB
nV/√Hz
nV/√Hz
dBm/Hz
dB
dB
Noise/Linearity Performance Two Tones, P
OUT
= 4dBm/Tone (2V
P-P
into 50Ω), Δf = 200kHz
AC ELECTRICAL CHARACTERISTICS (Timing Diagram)
SYMBOL
T
SU
T
HOLD
T
PW
T
R
T
LATENCY
T
GLITCH
A
GLITCH
PARAMETER
Setup Time PGx vs STROBE
Hold Time PGx vs STROBE
STROBE Pulse Width
STROBE Period
Latency Time of the Previous Gain State
Time Between Previous Stable Gain State
to Next Stable State
Max Glitch Amplitude
Output Settles within 1%
Output Settles within 1%
V
IN
= 0 (No Signal or STROBE Transition During
Output Signal Zero Crossing)
STROBE Transition when Output Power is at
Peak + 10dBm Power
CONDITIONS
PGx and Strobe Timing Characteristics
(R
OUT
= 50Ω) Specifications are
at T
A
= 25°C. V
CC
= 5V, V
CCO
= 5V, ENB = 3V, MODE = 5V, STROBE = 3V, V
IH
= 2.2V, V
IL
= 0.6V, maximum gain (Test circuit shown in
Figure 16), unless otherwise noted.
MIN
TYP
0
1
2
4
4
5
1
3
MAX
UNIT
ns
ns
ns
ns
ns
ns
mV
dB
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LT5554
AC ELECTRICAL CHARACTERISTICS (Timing Diagram)
Timing Diagram
PG0, 1, 2, 3, 4, 5, 6
INPUTS
T
SU
T
HOLD
T
PW
STROBE
INPUTS
DATA
TRANSPARENT
DATA
LATCH
T
GLITCH
T
LATENCY
OUT SIGNAL
STATE (i)
STATE (i + 1)
STATE (i + 2)
5554 TD01
DC ELECTRICAL CHARACTERISTICS
SYMBOL
V
CC
V
CCO
PARAMETER
Supply Voltage
OUT
+
, OUT
–
Output Pin DC Common Mode (Note 4)
Voltage
DEC, IN
+
, IN
–
Bias Voltage
PGx, STR Input Current
PGx, STR Input Current
OUT
+
, OUT
–
Current
V
CC
Supply Current
ENB Input LOW Voltage
ENB Input HIGH Voltage
ENB Input Current
ENB Input Current
ENB Input Current
Disable
Enable
V
IN
= 0.6V
V
IN
= 3V
V
IN
= 5V
V
IN
= 0.6V
V
IN
= 5V
Normal Operating Conditions
Specifications are at T
A
= 25°C. V
CC
= 5V, V
CCO
= 5V, ENB = 3V,
MODE = 5V, unless otherwise noted. (Note 3) (Test circuit shown in Figure 16), unless otherwise noted.
CONDITIONS
MIN
4.75
TYP
5
5
MAX
5.25
6
UNIT
V
V
Shutdown DC Characteristics, ENB = 0.6V
V
IN(BIAS)
I
IL(PG)
I
IH(PG)
I
OUT
I
CC
V
IL(EN)
V
IH(EN)
I
IL(EN)
I
IH(EN)
I
IH(EN)
2
0
210
20
4
5.1
0.6
3
70
220
300
V
CC
20
2.15
V
μA
μA
μA
mA
V
V
μA
μA
μA
Enable Input DC Characteristics
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