LMH6518 Datasheet, PDF (1/8 Pages) National Semiconductor (TI) – 825 MHz, Digital Controlled, Variable Gain Amplifier

PRELIMINARY
May 30, 2008
LMH6518
825 MHz, Digital Controlled, Variable Gain Amplifier
General Description
The LMH6518 is a digitally controlled variable gain amplifier
whose total gain can be varied from −1.16 dB to 38.84 dB for
a 40 dB range in 2 dB steps. The −3 dB bandwidth is 825 MHz
at all gains. Gain accuracy at each setting is typically 0.1 dB.
When used in conjunction with a National Semiconductor
Gsample/second (Gsps) ADC with adjustable full scale (FS)
range, the LMH6518 gain adjustment will accommodate full
scale input signals from 6.8 mV_PP to 920 mV_PP.
The LMH6518 gain is programmed via a SPI-1 serial bus. A
signal path combined gain resolution of 8.5 mdB can be
achieved when the LMH6518’s gain and the Gsps ADC’s FS
input are both manipulated. Propagation Delay variation
across gain settings is typically 100 ps. 2^nd/3rd order har-
monic distortion is −50/−53 dBc at 100 MHz.
Inputs and outputs are dc-coupled. The outputs are differen-
tial with individual Common Mode (CM) voltage control (for
Main and Auxiliary outputs) and have a selectable bandwidth
limiting circuitry (common to both Main & Auxiliary) of 20, 100,
200, 350, 650 MHz, 750 MHz or full bandwidth. The Auxiliary
output (“OUT PA” and “OUT NA”) follows the Main output and
is intended for use in Oscilloscope trigger function circuitry but
may have other uses in other applications.
Features
■ ^{Gain range}
■ ^{Gain step size}
■ ^{Combined gain resolution with}
Gsample/second ADC’s
■ ^{Min gain}
■ ^{Max gain}
■ ^{−3 dB BW}
■ ^{Rise/fall time}
■ ^{Recovery time}
■ ^{Propagation delay variation}
■ ^{HD2 @ 100 MHz}
■ ^{HD3 @ 100 MHz}
■ ^{Input-referred noise (max gain)}
■ ^{Power consumption}
40 dB
2 dB
8.5 mdB
−1.16 dB
38.84 dB
825 MHz
500 ps
5 ns
100 ps
−50 dBc
−53 dBc
0.93 nV/√Hz
1.1W
Applications
■ ^{Oscilloscope programmable gain amplifier}
■ ^{Differential ADC drivers}
■ ^{High frequency single ended input to differential}
conversion
■ ^{Precision gain control applications}
■ ^{Medical applications}
■ ^{RF/ IF applications}
Functional Block Diagram
LMH™ is a trademark of National Semiconductor Corporation.
© 2008 National Semiconductor Corporation 300688
30068801
www.national.com