Datasheet

Input
Preamp
Ladder
Attenuator
Output Amp
Common Mode
Control
Bandwidth
Limiting
Circuitry
Aux Amp
Overvoltage
Clamp
GND
5,8
V
CC
3,4
V
CM_Aux
16
Serial Peripheral
Interface
12
V
DD
Hi Gain
or
Low Gain
10 Step
2 dB/Step
+IN
-IN
6
7
10
9
11
SDIO
CS
SCLK
13
V
CM
15
14
1
2
-OUT Aux
+OUT Aux
-OUT
+OUT
AUXILIARY
OUTPUT
MAIN OUT
72µ$'&¶
LMH6518
50:
50:
50:
50:
Overvoltage
Clamp
Overvoltage
Clamp
LMH6518
www.ti.com SNOSB21C –MAY 2008–REVISED JULY 2013
LMH6518 900 MHz, Digitally Controlled, Variable Gain Amplifier
Check for Samples: LMH6518
1
FEATURES
DESCRIPTION
The LMH6518 is a digitally controlled variable gain
2
• Gain Range 40 dB
amplifier whose total gain can be varied from −1.16
• Gain Step Size 2 dB
dB to 38.8 dB for a 40 dB range in 2 dB steps. The
• Combined Gain Resolution with
−3 dB bandwidth is 900 MHz at all gains. Gain
Gsample/Second ADC’s 8.5 mdB
accuracy at each setting is typically 0.1 dB. When
used in conjunction with a Texas Instruments
• Min Gain −1.16 dB
Gsample/second (Gsps) ADC with adjustable full
• Max Gain 38.8 dB
scale (FS) range, the LMH6518 gain adjustment will
• −3 dB BW 900 MHz
accommodate full scale input signals from 6.8 mV
PP
to 920 mV
PP
to get 700 mV
PP
nominal at the ADC
• Rise/Fall Time <500 ps
input. The Auxiliary output (“+OUT Aux” and “−OUT
• Recovery Time <5 ns
Aux”) follows the Main output and is intended for use
• Propagation Delay Variation 100 ps
in Oscilloscope trigger function circuitry but may have
other uses in other applications.
• HD2 @ 100 MHz −50 dBc
• HD3 @ 100 MHz −53 dBc
The LMH6518 gain is programmed via a SPI-1
compatible serial bus. A signal path combined gain
• Input-Referred Noise (Max Gain) 0.98 nV/√Hz
resolution of 8.5 mdB can be achieved when the
• Over-Voltage Clamps for Fast Recovery
LMH6518’s gain and the Gsps ADC’s FS input are
• Power Consumption — Auxiliary Turned Off
both manipulated. Inputs and outputs are DC-
1.1W0.75W
coupled. The outputs are differential with individual
Common Mode (CM) voltage control (for Main and
Auxiliary outputs) and have a selectable bandwidth
APPLICATIONS
limiting circuitry (common to both Main and Auxiliary)
• Oscilloscope Programmable Gain Amplifier
of 20, 100, 200, 350, 650, 750 MHz or full bandwidth.
• Differential ADC Drivers
• High Frequency Single-Ended Input to
Differential Conversion
• Precision Gain Control Applications
• Medical Applications
• RF/IF Applications
Functional Block Diagram
1
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Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Copyright © 2008–2013, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.