LT5514
Ultralow Distortion IF
Amplifier/ADC Driver with
Digitally Controlled Gain
FEATURES
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
DESCRIPTIO
Output IP3 at 100MHz: 47dBm
Maximum Output Power: 21dBm
Bandwidth: LF to 850MHz
Propagation Delay: 0.8ns
Maximum Gain: 33dB
Noise Figure: 7.3dB (Max Gain)
Gain Control Range: 22.5dB
Gain Control Step: 1.5dB
Gain Control Settling Time: 500ns
Output Noise Floor: 鈥?34dBm/Hz (Max Gain)
Reverse Isolation: 鈥?0dB
Single Supply: 4.75V to 5.25V
Low Power Mode
Shutdown Mode
Enable/Disable Time: 1碌s
Differential I/O Interface
20-Lead TSSOP Package
The LT
廬
5514 is a programmable gain amplifier (PGA) with
bandwidth extending from low frequency (LF) to 850MHz.
It consists of a digitally controlled variable attenuator,
followed by a high linearity amplifier. The amplifier is
configured with two identical transconductance amplifi-
ers, hard wired in parallel with individual dedicated enable
pins. When both amplifiers are enabled (Standard mode),
the LT5514 offers an OIP3 of +47dBm (at 100MHz).
Power dissipation can be reduced when a single amplifier
is enabled (Low Power mode). Four parallel digital inputs
control the gain over a 22.5dB range with 1.5dB step
resolution. An on-chip power supply regulator/filter helps
isolate the amplifier signal path from external noise sources.
The LT5514鈥檚 open-loop architecture offers stable opera-
tion for any practical load conditions, including peaking-
free AC response when driving capacitive loads, and
excellent reverse isolation.
The LT5514 may be operated broadband, where the out-
put differential RC time constant sets the bandwidth, or it
may be used as a narrowband driver with the appropriate
output filter.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
s
High Linearity ADC Driver
IF Sampling Receivers
VGA IF Power Amplifier
50鈩?Driver
Instrumentation Applications
TYPICAL APPLICATIO
56
5V
53
CHOKE
0.1碌F
RF
INPUT
LO
IF
BPF
IF
AMP
0.1碌F
4 LINES
CHOKE
0.1碌F
OIP3 (dBm)
50
R
OUT
= 200鈩?/div>
47
R
OUT
= 100鈩?/div>
44
41
38
35
0
50
100
FREQUENCY (MHz)
150
200
5514 TA02
LT5514
100鈩?/div>
0.1碌F
GAIN CONTROL
ADC
5514 TA01
U
Output IP3 vs Frequency
(Standard Mode)
5514f
U
U
1
next