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User's Guide

SNOA553B–October 2010–Revised May 2013

AN-2081 LMH6517EVAL-R1 Evaluation Board

Figure 1. LMH6517EVAL-R1 Evaluation Board

1 General Description

The LMH6517EVAL-R1 evaluation board is designed to aid in the characterization of Texas Instruments'

High Speed LMH6517 Digital Controlled Variable Gain Amplifier (DVGA).

The evaluation board is used as a guide for high frequency layout and as a tool to aid in device testing

and characterization.

2 Basic Operation

The LMH6517 DVGA has differential inputs and differential outputs. To aid evaluation with 50Ω, single

ended test equipment the LMH6517EVAL-R1 evaluation board is shipped with transformers on both the

input and output signal paths. The single ended signal path uses the IN+ and OUT+ marked connectors.

The IN− and OUT− signal paths are grounded and the SMA connectors are not installed.

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SNOA553B–October 2010–Revised May 2013 AN-2081 LMH6517EVAL-R1 Evaluation Board

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Summary of content (14 pages)

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User's Guide SNOA553B – October 2010 – Revised May 2013 AN-2081 LMH6517EVAL-R1 Evaluation Board Figure 1. LMH6517EVAL-R1 Evaluation Board 1 General Description The LMH6517EVAL-R1 evaluation board is designed to aid in the characterization of Texas Instruments' High Speed LMH6517 Digital Controlled Variable Gain Amplifier (DVGA). The evaluation board is used as a guide for high frequency layout and as a tool to aid in device testing and characterization.
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Basic Operation www.ti.com The input and output pins of the LMH6517 will self bias to approximately mid supply (2.5V). The LMH6517EVAL-R1 board has been designed with AC coupling on both input and output signal paths to protect test equipment and to ensure proper operation of the LMH6517 DVGA. Any modifications to the board should preserve the operating points of the DVGA and protect sensitive test equipment.
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Basic Operation www.ti.com Figure 2.
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Using with Different Sources or Loads www.ti.com Figure 3. Input Schematic The board was designed to be very flexible for many different configurations. Zoomed in portions of the input and output schematics are shown above in Figure 2 and Figure 3. The evaluation board, as shipped, has been optimized for ease of use with single ended 50 Ohm test equipment. This configuration may not emulate the most common application circuits. The signal path schematic is shown in Figure 8 and the full schematic in .
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Additional Design Tools www.ti.com Near the power connector are a number of 0.1” pitch headers. The header labeled J1 provides off board access to the LMH6517 digital control pins. The J1 pins and functions are described below. The jack labeled J10 is normally loaded with a shorting jumper, it provides power to a 3.3V power supply used to provide 3.3V logic signals to the digital pins. The jack labeled J11 is also loaded with a shorting block and it provides the 5V power to the LMH6517.
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Serial Mode www.ti.com The dip switches that are used to control gain in parallel mode have different functions in Pulse mode. SWA, which controls the A channel should be set with the A4, A3, ENA and LATA positions in the OFF setting. The positions marked A5 and A0 need to be in the ON position. The positions marked A2 and A1 are used to set the DVGA gain step size. Table 1.
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Serial Mode www.ti.com Once the SPUSI2 board drivers and TinyI2CSPI software are installed, the appropriate pins on the LMH6517 board need to be connected to the SPUSI2 board. Soldering jumpers is one easy method. Connect the CLK, SDI and CS pins as well as a ground wire to the SPUSI2 board. The board software should be set to SPI mode and the CS adn CKPOL columns should be set to 1. The CKPHA column needs to be set to 1and the number of bits should be set to 16.
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Serial Mode www.ti.com Figure 4.
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Serial Mode www.ti.com Figure 5.
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Serial Mode www.ti.com Figure 6.
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Serial Mode www.ti.com Figure 7.
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Serial Mode www.ti.com Figure 8.
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Serial Mode www.ti.com Figure 9.
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IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.