LMH6514

LMH6514 600 MHz, Digital Controlled, Variable Gain Amplifier January 24, 2008 LMH6514 600 MHz, Digital Controlled, Variable Gain Amplifier General Description The LMH6514 is a high performance, digitally controlled variable gain amplifier (DVGA). It combines precision gain control with a low noise, ultra-linear, differential amplifier. Typically, the LMH6514 drives a high performance ADC in a broad range of mixed signal and digital communication applications such as mobile radio and cellular base stations where automatic gain control (AGC) is required to increase system dynamic range. When used in conjunction with a high speed ADC, system dynamic range can be extended by up to 42 dB. The LMH6514 has a differential input and output allowing large signal swings on a single 5V supply. It is designed to accept signals from RF elements and maintain a terminated impedance environment. The input impedance is 200Ω resistive. The output impedance is either 200Ω or 400Ω and is user selectable. A unique internal architecture allows use with both single ended and differential input signals. Input signals to the LMH6514 are scaled by a highly linear, digitally controlled attenuator with seven accurate 6 dB steps. The attenuator output provides the input signal for a high gain, ultra linear differential transconductor. The transconductor differential output current can be converted into a voltage by using the on-chip 200Ω or 400Ω loads. The transconductance gain is 0.1 Amp/Volt resulting in a maximum voltage gain of +32 dB when driving a 200Ω load, or 38 dB when driving the 400Ω load. On chip digital latches are provided for local storage of the gain setting. The gain step settling time is 5 ns and care has been taken to reduce the sensitivity of bandwidth and phase to gain setting. The LMH6514 operates over the industrial temperature range of −40°C to +85°C. The LMH6514 is available in a 16-Pin, thermally enhanced, LLP package. Features ■ ■ ■ ■ ■ ■ ■ ■ Adjustable gain with a 42 dB range Precise 6.02 dB gain steps Parallel 3 bit gain control On chip register gain setting Fully differential signal path Single ended to differential capable 200Ω input impedance Small footprint (4 mm x 4 mm) LLP package Key Specifications ■ ■ ■ ■ ■ ■ ■ 600 MHz bandwidth at 100Ω load 39 dBm OIP3 at 75 MHz, 200Ω load 26 dB to 38 dB maximum gain Selectable output impedance of 200Ω or 400Ω. 8.3 dB noise figure 5 ns gain step switching time 100 mA supply current Applications ■ ■ ■ ■ ■ ■ Cellular base stations IF sampling receivers Instrumentation Modems Imaging Differential line receiver Typical Application 30042901 LMH™ is a trademark of National Semiconductor Corporation. © 2008 National Semiconductor Corporation 300429 www.national.com LMH6514 Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance (Note 2) Human Body Model Machine Model Positive Supply Voltage (Pin 3) Output Voltage (Pin 14,15) Differential Voltage between Any Two Grounds Analog Input Voltage Range Digital Input Voltage Range Output Short Circuit Duration (one pin to ground) Junction Temperature 2 kV 150V −0.6V to 5.5V −0.6V to 6.8V