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LMH6515
600 MHz, Digital Controlled, Variable Gain Amplifier
General Description
Features
The LMH6515 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 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 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 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 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 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 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 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.
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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
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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
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Cellular base stations
IF sampling receivers
Instrumentation
Modems
Imaging
Differential line receiver
Typical Application
20214301
LMH™ is a trademark of National Semiconductor Corporation.
© 2007 National Semiconductor Corporation
202143
www.national.com
LMH6515 600 MHz, Digital Controlled, Variable Gain Amplifier
October 2007
LMH6515
Storage Temperature Range
Soldering Information
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
Infrared or Convection (20 sec)
Wave Soldering (10 sec)
Operating Ratings
2 kV
150V
−0.6V to 5.5V
−0.6V to 6.8V
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