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EVALUATING THE HMCAD1511/HMCAD1520 ANALOG-TO-DIGITAL CONVERTERS

Preface

This user guide describes the HMCAD1520-EBZ and HMCAD1511-EBZ evaluation boards, which provide the support circuitry required to operate the HMCAD1520 and HMCAD1511 in its various modes and configurations. The application software used to interface with the device is also described.

This guide shows how HMCAD15XX-EBZ works with the SDP-H1 (EVAL-SDP-CH1Z) controller board developed by Analog Devices. Link to the previous user guide document is provided for customers who still have the old evaluation system developed by Hittite which uses the Xilinx SP-601 controller board.

Typical Setup

Figure 1. HMCAD15xx-EBZ (left) and EVAL-SDP-CH1Z (right) Setup

Tip: Click on any picture in this guide to open an enlarged version.

Helpful Files

Previous User Guide for EVAL01-HMCAD15xx Evaluation Board
HMCAD1520 and HMCAD1511 Datasheet
HMCAD15xx-EBZ Schematic
HMCAD15xx-EBZ BOM
PCB Layout
PCB Gerber Files
HMCAD15xx-EBZ Interleaving Spurs Calculator

Software Needed:

Hardware Needed:

HMCAD1520-EBZ/HMCAD1511-EBZ Evaluation Board
SDP-H1 (EVAL-SDP-CH1Z) Board
12Vdc 1A Wall Adapter for SDP-H1
PC with ACE and Visual Analog Software Applications
(2) High-Frequency Continuous Wave Generator (Clock and Analog Input Source)
(2) SMA Cables
USB A to USB Mini Cables

Evaluation Board Hardware

Analog Inputs

HMCAD1520-EBZ /HMCAD1511-EBZ evaluation board has four input channels that supports single-ended to differential conversion with the use of a balun. By default, all input channels 1-4 (SMAs J3, J5, J6 and J7) are balun-coupled. Alternatively, input channel 1 (SMAs J3 and J4) can be configured to differential to differential conversion, and input channel 2 (SMA J5) can be configured to single-ended to differential conversion using the onboard LTC6419 high-speed differential ADC driver.

Refer to the table below for the optional amplifier configuration.

Analog Input Channel Number	Default Input Driver, AC/DC coupling	Signal type on Input/Output	Install	Uninstall
1	LTC6419, DC coupling, Unity Gain	Differential/Differential	R23, R24, R41, R42, R45, R60, R61	R56, R57
2	LTC6419, DC coupling, Unity Gain	Single-Ended/Differential	R23, R24, R46, R58, R59	C53, R54, R55

Analog Input Vcm

The HMCAD1520/HMCAD1511 supplies the common-mode voltage at half-supply (0.9V) for all the analog input channels. No external supply is needed for the input Vcm.

Clocking

The HMCAD1520-EBZ evaluation board uses an external clock source on SMA J1 as default.

On the other hand, the HMCAD1511-EBZ evaluation board has an on-board 1GHz crystal for clocking the HMCAD1511. The user can also configure the board to use an external clock source for the HMCAD1511-EBZ board.

Refer to the table below for alternative clock configuration

Clock Configuration	Install	Uninstall
Onboard	R13	R12
External	R12	R13

Power Supply

Both the HMCAD1520 and HMCAD1511 were being supplied by ADM7154 with 1.8V. The board can be modified to bypass the LDO so the HMCAD1520 and HMCAD1511 are directly supplied by the LTM8078 DC-DC regulator. To do this, change components C3 to 100uF, R6 to 200k, and install a ferrite bead to R9.

The supply rails for other components on the board (crystal, amplifier, etc) are isolated to the HMCAD1520 and HMCAD1511 supply rail. Refer to the board schematics for more info.

Quick Start Guide

The following procedure below shows how to setup the evaluation board to capture 70MHz input signal at 1GSPS sampling rate:

Attach the HMCAD1520-EBZ/HMCAD1511-EBZ evaluation board to the SDP-H1 FMC connector thru the P1 port.
Connect the SDP-H1 to PC via USB and to a 12V 1A power supply. Refer to Figure 1.
Open ACE, The board will automatically be recognized by the software. Otherwise, install the plugin for HMCAD1511/20 evaluation board.
Double click the HMCAD1520 evaluation system and then double click the HMCAD1520 blue chip. The onboard LED should light up, indicating power is already supplied.

Figure 2. HMCAD1520-EBZ ACE Window
Apply the configuration wizard settings shown in Figure 3. For HMCAD1520-EBZ, select External Clock as clock source and input 1GHz on the CLKIN.

Figure 3. Wizard Settings
Connect a continuous wave generator as an input signal on SMA J7. Use a bandpass filter in between the signal source and the SMA connector.
Set the frequency to 71MHz.
For HMCAD1520-EBZ, connect a continuous wave generator as the ADC clock. Set the clock frequency to 1GHz and 5dBm output level.
Click the Proceed to Analysis and click on the FFT Tab. Click Run Once to capture an FFT plot.
Observe the fundamental frequency and power. Adjust the signal source to obtain -1dBFS fundamental power at 71MHz.

Figure 4. HMCAD1520-EBZ FFT Window
For the manual input of interleaving spurs, go to the Analysis Tab and click the Dynamic Settings.
Proceed to the FFT Spurs Section and click the “+” button on the side and input the following frequencies provided from the spur calculator (refer to the tip below). Then, click OK. Figure 5 shows the FFT spurs section of the Quad Mode for 160 MSPS and 70 MHz input.

Figure 5. HMCAD1520-EBZ FFT Spurs Section for Quad Mode (Fs =160MSPS and Fin = 70MHz)
Lastly, click the Rerun Analysis.

For your reference on what frequencies to include in the section, you can download the HMCAD15xx-Interleaving Spurs Calculator in the Helpful Files, and input both the sampling and input frequencies on the yellow boxes provided. The calculator will provide the spur frequencies depending on the selected mode.

Note: In case the HMCAD1511-EBZ is operating at maximum sampling frequency Fsmax and no data capture is shown, try the following steps below:

When using external clock, decrease the sampling frequency of HMCAD1511 less than the Fsmax of 250MHz/500MHz/1000MHz for quad/dual/single mode.
When using on-board clock, adjust the clock divider making the sampling frequency of HMCAD1511 less than the fsmax of 250MHz/500MHz/1000MHz for quad/dual/single mode.

Visual Analog Export for Interleaving Spurs on Noise Calculation

The HMCAD1520 and HMCAD1511 have interleaving spurs that can be observed at the output. To obtain the AC performance measurements as seen on the typical specification on the datasheet, follow these procedures.

On the Results tab of the Analysis window at ACE, click Export. Make sure to export 1 data set at a time to avoid editing the csv file on Visual Analog. To do this, only select 1 channel at the Display Channels at the top.

Figure 6. HMCAD1520-EBZ ACE Data Export
Install Visual Analog and install the appropriate canvas for the specific channel mode. These are AD9230 VA canvas that is modified to accommodate the HMCAD15xx device. Download the canvas here: hmcad15xx_visualanalog_canvas.zip
On the Browse button, open the _RawSamples.csv file exported from the ACE software. Indicate the correct sampling frequency on the Pattern Loader block, and the correct resolution at the Input Formatter block. The Resolution and Alignment value should be the same.

Figure 7. Visual Analog Settings
Click Run button on the top left part.
The FFT plot on the left includes the interleaving spurs on the calculations (which is the same with the ACE Results), while the FFT plot on the right excludes the interleaving spurs on the calculations.

Figure 8. Visual Analog FFT Plots

Troubleshooting Tips

If the FFT window remains blank after Running Once in ACE, do the following:

Make sure there is a clock signal going to the ADC.
Check the 1.8V supply rails of the ADC. The onboard yellow LED indicates 12V is being supplied to the board.
Check if there's no error messages in ACE. If there is any, power cycle the board and restart the ACE software.
Make sure the SDP-H1 board is powered up and connected to the PC via USB.

If the FFT plot appears abnormal, do the following:

Make sure that the input signal is not overdriving the ADC. Limit the fundamental frequency to -1dBFS.
Check for the Vcm at the analog input path. The Vcm should be around 0.9V.
Make sure that the correct encoding is set in ACE. The default setting is Twos complement.
Check for any loose connections between the input SMA and the signal source. Same with the clock source if using an external clock.
If using the LTC6419 as the ADC driver, check the 5V supply rail and the 0.9V common mode voltage.
Make sure the correct resolution and channel configuration are set correctly on ACE.

If the FFT plot appears normal but performance is poor, do the following:

Make sure that an appropriate analog filter is used on the input signal.
Make sure that the fundamental frequency is set to -1dBFS.
Make sure that the signal generators for the clock and the analog input are clean (low phase noise).
Make sure the correct resolution and channel configuration are set correctly on ACE.

If the ACE cannot detect the board or prompts an error message during data capture, do the following:

Make sure the SDP-H1 is powered correctly and connected to the PC via USB.
Make sure that the HMCAD1520-EBZ /HMCAD1511-EBZ is attached properly on the P1 port of the SDP-H1.
Make sure that the yellow LED on the HMCAD1520-EBZ /HMCAD1511-EBZ evalboard is lit up.
Power cycle both the HMCAD1520-EBZ /HMCAD1511-EBZ and the SDP-H1, and restart the ACE software.

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