LMH6518 Datasheet | National Semiconductor

LMH6518 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 d B to 38.84 d B for a 40 d B range in 2 d B steps. The - 3 d B bandwidth is 825 MHz at all gains. Gain accuracy at each setting is typically 0.1 d B. When used in conjunction with a National Semiconductor Gsample/second (Gsps) ADC with adjustable full scale (FS) range, the LMH6518 gain adjustment will acmodate full scale input signals from 6.8 m VPP to 920 m VPP. The LMH6518 gain is programmed via a SPI-1 serial bus. A signal path bined gain resolution of 8.5 md B 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 d Bc at 100 MHz. Inputs and outputs are dc-coupled. The outputs are differential with individual mon Mode (CM) voltage control (for Main and Auxiliary outputs) and have a selectable bandwidth limiting circuitry (mon 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 - bined gain resolution with - - - - - - - - - - Gsample/second ADC’s Min gain Max gain - 3 d B BW Rise/fall time Recovery time Propagation delay variation HD2 @ 100 MHz HD3 @ 100 MHz Input-referred noise (max gain) Power consumption 40 d B 2 d B 8.5 md B - 1.16 d B 38.84 d B 825 MHz 500 ps 5 ns 100 ps - 50 d Bc - 53 d Bc 0.93 n V/√Hz 1.1W Applications - Oscilloscope programmable gain amplifier - Differential ADC drivers - High frequency single ended input to differential conversion - Precision gain control...