LMH6518

LMH6518 825 MHz, Digital Controlled, Variable Gain Amplifier www.DataSheet4U.com 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 mVPP to 920 mVPP. 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. 2nd/3rd order harmonic distortion is −50/−53 dBc at 100 MHz. Inputs and outputs are dc-coupled. The outputs are differential 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 ■ Combi...