LT6600-20 Linear Technology, LT6600-20 Datasheet

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LT6600-20

Manufacturer Part Number
LT6600-20
Description
Very Low Noise Differential Amplifier and 20MHz Lowpass Filter
Manufacturer
Linear Technology
Datasheet
FEATURES
TYPICAL APPLICATIO
APPLICATIO S
V
IN
, LTC and LT are registered trademarks of Linear Technology Corporation.
Programmable Differential Gain via Two External
Resistors
Adjustable Output Common Mode Voltage
Operates and Specified with 3V, 5V, 5V Supplies
0.5dB Ripple 4th Order Lowpass Filter with 20MHz
Cutoff
76dB S/N with 3V Supply and 2V
Low Distortion, 2V
Fully Differential Inputs and Outputs
SO-8 Package
Compatible with Popular Differential Amplifier
Pinouts
High Speed ADC Antialiasing and DAC Smoothing in
Networking or Cellular Base Station Applications
High Speed Test and Measurement Equipment
Medical Imaging
Drop-in Replacement for Differential Amplifiers
0.01 F
402
2.5MHz: 83dBc 2nd, 88dBc 3rd
20MHz: 63dBc 2nd, 64dBc 3rd
R
IN
402
R
IN
GAIN = 402 /R
1
7
2
8
LT6600-20
V
V
+
MID
OCM
3
6
5V
+
0.1 F
U
4
5
IN
P-P
, 800 Load
49.9
49.9
U
18pF
P-P
Output
A
+
IN
V
CM
LTC1748
A/D
5V
1 F
V
D
+
V
Amplifier and 20MHz Lowpass Filter
OUT
66002 TA01a
DESCRIPTIO
The LT
with a 4th order 20MHz lowpass filter approximating a
Chebyshev frequency response. Most differential amplifi-
ers require many precision external components to tailor
gain and bandwidth. In contrast, with the LT6600-20, two
external resistors program differential gain, and the filter’s
20MHz cutoff frequency and passband ripple are internally
set. The LT6600-20 also provides the necessary level
shifting to set its output common mode voltage to accom-
modate the reference voltage requirements of A/Ds.
Using a proprietary internal architecture, the LT6600-20
integrates an antialiasing filter and a differential amplifier/
driver without compromising distortion or low noise
performance. At unity gain the measured in band
signal-to-noise ratio is an impressive 76dB. At higher
gains the input referred noise decreases so the part can
process smaller input differential signals without signifi-
cantly degrading the output signal-to-noise ratio.
The LT6600-20 also features low voltage operation. The
differential design provides outstanding performance for
a 2V
supply.
The LT6600-20 is packaged in an SO-8 and is pin compat-
ible with stand alone differential amplifiers.
P-P
Very Low Noise, Differential
®
signal level while the part operates with a single 3V
6600-20 combines a fully differential amplifier
–120
–100
–110
–30
–40
–50
–10
–20
–60
–70
–80
–90
0
0
U
An 8192 Point FFT Spectrum
10
FREQUENCY (MHz)
20
www.DataSheet4U.com
INPUT 5.9MHz
2V
f
SAMPLE
P-P
LT6600-20
30
= 80MHz
66002 TA01b
40
66002f
1

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LT6600-20 Summary of contents

Page 1

... The LT6600-20 also features low voltage operation. The differential design provides outstanding performance for a 2V signal level while the part operates with a single 3V P-P supply. The LT6600-20 is packaged in an SO-8 and is pin compat- ible with stand alone differential amplifiers. A/D LTC1748 ...

Page 2

... LT6600- ABSOLUTE AXI U RATI GS (Note 1) Total Supply Voltage ................................................ 11V Operating Temperature Range (Note 6) ...– Specified Temperature Range (Note 7) ....– Junction Temperature ........................................... 150 C Storage Temperature Range ................. – 150 C Lead Temperature (Soldering, 10 sec).................. 300 C ELECTRICAL CHARACTERISTICS range, otherwise specifications are at T ...

Page 3

... Note 7: The LT6600C-20 is guaranteed to meet specifications and is designed, characterized and expected to meet the extended temperature limits, but is not tested at –40 C and 85 C. The LT6600I-20 is guaranteed to meet specified performance from – LT6600-20 www.DataSheet4U.com + – = 5V, V ...

Page 4

... LT6600- TYPICAL PERFOR A CE CHARACTERISTICS Amplitude Response 10 0 –10 –20 –30 –40 –50 –60 – GAIN = 1 – –90 0 100 FREQUENCY (MHz) 66002 G01 Passband Gain and Group Delay GAIN 12 GAIN = GROUP ...

Page 5

... VOLTAGE PIN 2 TO PIN 7 (V) 66002 G13 50mV/DIV –40 C DIFFERENTIAL A INPUT 200mV/DIV 66002 G14 LT6600-20 www.DataSheet4U.com Distortion vs Input Common Mode Level –40 2ND HARMONIC 3RD HARMONIC, – 2ND HARMONIC, – 3RD HARMONIC – ...

Page 6

... LT6600- CTIO S – and IN (Pins 1, 8): Input Pins. Signals can be applied to either or both input pins through identical external resistors The DC gain from differential inputs to the IN differential outputs is 402 / (Pin 2): Is the DC Common Mode Reference Voltage OCM for the 2nd Filter Stage. Its value programs the common mode voltage of the differential output of the filter ...

Page 7

... V is the common mode input voltage Similarly, the voltages V and V OUT OUT 4 and 5 of the LT6600-20 are the filter outputs. The + difference between V and V OUT OUT output voltage. The average of V OUT common mode output voltage. Figure 1 illustrates the LT6600-20 operating with a single 3.3V supply and unity passband gain ...

Page 8

... LT6600- APPLICATIO S I FOR ATIO In Figure 3 the LT6600-20 is providing 12dB of gain. The gain resistor has an optional 62pF in parallel to improve the passband flatness near 20MHz. The common mode output voltage is set to 2V. Use Figure 4 to determine the interface between the LT6600-20 and a current output DAC. The gain, or “trans- impedance,” ...

Page 9

... Pin 7 – the voltage of Pin 7 + 2V. Pin high impedance input The LT6600-20 was designed to process a variety of input 1MHz 25 C signals including signals centered around the mid-supply voltage and signals that swing between ground and a positive voltage in a single supply system (Figure 1). The ...

Page 10

... The LT6600-20 amplifiers combine high speed with large- signal currents in a small package. There is a need to ensure that the die junction temperature does not exceed 150 C. The LT6600-20 package has Pin 6 fused to the lead frame to enhance thermal conduction when connecting to INPUT REFERRED a ground plane or a large metal trace ...

Page 11

... U U APPLICATIO S I FOR ATIO Table 2. LT6600-20 SO-8 Package Thermal Resistance COPPER AREA TOPSIDE BACKSIDE BOARD AREA (mm ) (mm ) (mm ) 1100 1100 2500 330 330 2500 35 35 2500 35 0 2500 0 0 2500 Junction temperature calculated from the ambient J temperature and power dissipation, P ...

Page 12

... McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com A 5th Order, 20MHz Lowpass Filter + V 0 – – OUT OUT LT6600- – OUT OUT + + 0 • R • 20MHz 66002 TA02a 402 – ...

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