LT6600-2.5_09 Datasheet, PDF (1/16 Pages) Linear Technology – Very Low Noise, Differential Amplifi er and 2.5MHz Lowpass Filter

LT6600-2.5
Very Low Noise, Differential
Amplifier and 2.5MHz Lowpass Filter
FEATURES
n _{±0.6dB (Max) Ripple 4th Order Lowpass Filter with}
2.5MHz Cutoff
n _{Programmable Differential Gain via Two External}
Resistors
n _{Adjustable Output Common Mode Voltage}
n _{Operates and Specified with 3V, 5V, ±5V Supplies}
n _{86dB S/N with 3V Supply and 1VRMS Output}
n _{Low Distortion, 1VRMS, 800Ω Load}
1MHz: 95dBc 2nd, 88dBc 3rd
n _{Fully Differential Inputs and Outputs}
n _{Compatible with Popular Differential Amplifier}
Pinouts
n _{SO-8 and DFN-12 Packages}
APPLICATIONS
n _{High Speed ADC Antialiasing and DAC Smoothing in}
Networking or Cellular Base Station Applications
n _{High Speed Test and Measurement Equipment}
n _{Medical Imaging}
n _{Drop-in Replacement for Differential Amplifiers}
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
DESCRIPTION
The LT^®6600-2.5 combines a fully differential amplifier
with a 4th order 2.5MHz lowpass filter approximating a
Chebyshev frequency response. Most differential ampli-
fiers require many precision external components to tail
or gain and bandwidth. In contrast, with the LT6600-2.5,
two external resistors program differential gain, and the
filter’s 2.5MHz cutoff frequency and passband ripple are
internally set. The LT6600-2.5 also provides the necessary
level shifting to set its output common mode voltage to ac-
commodate the reference voltage requirements of A/Ds.
Using a proprietary internal architecture, the LT6600-2.5
integrates an antialiasing filter and a differential ampli-
fier/driver without compromising distortion or low noise
performance. At unity gain the measured in band signal-
to-noise ratio is an impressive 86dB. At higher gains the
input referred noise decreases so the part can process
smaller input differential signals without significantly
degrading the output signal-to-noise ratio.
The LT6600-2.5 also features low voltage operation. The
differential design provides outstanding performance for a
4V_P-P signal level while the part operates with a single 3V
supply. The LT6600-2.5 is available in SO-8 and DFN-12
packages.
For similar devices with higher cutoff frequency, refer
to the LT6600-5, LT6600-10, LT6600-15 and LT6600-20
data sheets.
TYPICAL APPLICATION (S8 Pin Numbers Shown)
16 BIT 4kHz to 2.5MHz
DISCRETE MULTI-TONE
SIGNAL AT 50MSPS
DAC Output Filter
5V
LADCOM
I_{OUT A}
LTC1668
I_{OUT B}
CLK
–5V 50MHz
52.3Ω
52.3Ω
5V
0.1μF
1580Ω _{1 –}
7
3
+⁴
2 ^LT6600-2.5
8₊
1580Ω
–₅
6
0.1μF
V_OUT+
V_OUT–
–5V
660025 TA01a
DAC Output Spectrum
0
–10
–20 _{BASEBAND SIGNAL}
–30
–40
–50
DAC OUTPUT IMAGE
–60
–70
–80
–90
0 12 24 36 48 60 72 84 96 108 120
FREQUENCY (MHz)
660025 TA01b
LT6600-2.5 Output Spectrum
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
0 12 24 36 48 60 72 84 96 108 120
FREQUENCY (MHz)
660025 TA01c
660025fb
1