LMH6515 Datasheet, PDF (1/18 Pages) National Semiconductor (TI) – 600 MHz, Digital Controlled, Variable Gain Amplifier

October 2007
LMH6515
600 MHz, Digital Controlled, Variable Gain Amplifier
General Description
The LMH6515 is a high performance, digitally controlled vari-
able gain amplifier (DVGA). It combines precision gain control
with a low noise, ultra-linear, differential amplifier. Typically,
the LMH6515 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 auto-
matic gain control (AGC) is required to increase system dy-
namic range. When used in conjunction with a high speed
ADC, system dynamic range can be extended by up to 32 dB.
The LMH6515 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 re-
sistive. 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 LMH6515 are scaled by a highly linear,
digitally controlled attenuator with 31 accurate 1 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
+26 dB when driving a 200Ω load, or 32 dB when driving the
400Ω load. On chip digital latches are provided for local stor-
age 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 LMH6515 operates over the industrial temperature range
of −40°C to +85°C. The LMH6515 is available in a 16-Pin,
thermally enhanced, LLP package.
Features
■ ^{Adjustable gain with a 31 dB range}
■ ^{Precise 1 dB gain steps}
■ ^{Parallel 5-bit gain control}
■ ^{On chip register stores 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 @ 100Ω load}
■ ^{40 dBm OIP3 @ 75 MHz, 200Ω load}
■ ^{20 dB to 30 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
LMH™ is a trademark of National Semiconductor Corporation.
© 2007 National Semiconductor Corporation 202143
20214301
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