DEM-ADS9xxE ® EVALUATION FIXTURE FEATURES DESCRIPTION ● PROVIDES FAST AND EASY PERFORMANCE TESTING FOR ADS900/ADS901 AND ADS930/ADS931 The DEM-ADS9xxE evaluation fixture is designed for ease of use when evaluating the high speed analogto-digital converter of the ADS9xx family. It was designed to be the common evalution platform for four of the models within the ADS9xxE family. The board will acommodate the ADS900 and ADS930, converters with internal references, as well as the ADS901 and ADS931, which require the external references. Because of its flexible design, the user can evaluate the converter in many different configurations; either with DC-coupled or AC-coupled input, or singleended or differential inputs. ● AC- AND DC-COUPLED INPUTS ● ON-BOARD REFERENCE ● ON-BOARD CLOCK ● ON-BOARD REGULATOR FOR +3V AND +5V OPERATION Furthermore, the board can be operated with the onboard crystal clock or with an external clock. The onboard reference circuit is adjustable, and the data outputs from the ADS9xx converter are decoupled from the connector via the TTL-buffer. International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111 Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 © 1997 Burr-Brown Corporation LI-488A Printed in U.S.A. January, 1997 INITIAL CONFIGURATION AND QUICK START throughout a wide frequency range. The level shift should be set to 0V at pin 5 of the OPA2650 by adjusting RV2, which will produce a ground-centered signal swing at the output of the op amp. In order to implement the correct commonmode voltage for the A/D converter, resistor R30 must be added. The value is not critical but should be between 1kΩ and 5kΩ. Through the use of the solder switches the demonstration board, DEM-ADS9xxE, can be adjusted in a variety of configurations to accommodate a specific model or function. Before starting evalution, the user should decide on the configuration and make the appropriate connections. The following list is a guideline for an inital setup: • The clock source is the on-board crystal. Close switch ‘CCLK’ and ‘DIV2’ to activate the clock and operate with a divider ratio of ÷2. Alternatively, a single-ended-to-differential input interface can be implemented using a RF transformer. Note that only the ADS900 and ADS930 feature the differential inputs. For setting it up, remove resistor R22 and add resistors R28 and R29, which should have a value of 24.9Ω. Remove resistors R27 and R30, if used, and close solder switch ‘MID’. To establish symmetrical inputs, capacitor C26 should equal capacitor C31, typically 22pF. The footprint of the transformer was selected to accommodate RF-transformer case style KK81, similar to T1-6T by Mini-Circuits. • The DC-coupled input is activated through connecter J2, ‘–VIN BUF’. CLOCK • The supply voltage should be +3V for the A/D converter; close switch ‘ADC/REF’ at the +3V side. If the board is equipped with HC541 buffers, select switch ‘U9/U10’ on the +5V side. If LCX541s are used, select the +3V side. Note that the LCX series will provide logic levels compatible for 3V logic. • The external references are not applied to the converter; solder switches ‘REFT’ and ‘REFB’ are open. On-Board Clock The ADS9xxE demonstration board is equipped with a crystal oscillator and D-type Flip-Flops (U7), which allow two different divider ratios (÷2 and ÷4) for the clock. The selection of the divider ratio can be done using the solder switched labeled ‘DIV2’ and ‘DIV4’. When using the onboard clock make sure that solder switch ‘CCLK’ is closed and ‘ECLK’ is open. The DEM-ADS9xxE comes with a 40MHz crystal which supports the full sampling speed of the ADS900 and ADS901. To evaluate the ADS930 and ADS931 at its maximum sampling speed of 30MHz, the crystal must be replaced with a 60MHz type. The replacement is easily done since the crystal is socketed. • The power-down function is disabled. The evaluation board typically requies a ±5V supply unit. The negative supply is necessary to appropriately power the op amp used in the interface circuit. Reconfiguring the demonstration board for AC-coupled input, in combination with the crystal clock, makes it possible to operate the board on a single +5V supply. INPUTS DC-Coupled The standard configuration of the evaluation board uses the dual high-speed op amp OPA2650, a voltage feedback type op amp. In order to implement level shifting into the DCcoupled circuit, op amp U3:B operates in an inverting mode, with the level shifting voltage applied its noninverting input. To offer a high impedance input to this interface circuit, the second op amp, U3:A, buffers the inverting gain stage. This provides a terminated 50Ω input to the demonstration board through connector J2, ‘–VIN BUF’. Besides using op amp U3:A as a buffer, it can be reconfigured for gain by changing the resistor values for R9 and R3. If it is desired to evaluate the circuit with only one op amp in the signal path, the second input, J1, can be used which requires some additional components to be soldered to the board. Note that in this case, the input impedance to the board is also determined by the input resistor value, R10, and an appropriate termination resistor, R1, value must be selected. A desired commonmode voltage can be set by adjusting potentiometer RV2. External Clock In addition to the on-board clock, the A/D converter can be driven by an external clock. For this, a low-jitter sine wave generator may be used. Apply the generator to SMA connector J3 (‘EXT CLK’). The ECL to TTL translator IC (U4) will transform the sine wave into a logic signal with a 50% duty cycle. When operating in this external clock mode, open solder switch ‘CCLK’ and close ‘ECLK’. Note that the external clock passes the divider as well. EXTERNAL REFERENCE While the ADS900 and ADS930 have references on-chip, the ADS901 and ADS931 require two external reference voltages; a top reference (REFT) and a bottom reference (REFB). Both references are available by the on-board reference circuit consisting of the micropower reference IC, REF-1004, and a general purpose single-supply op amp. This reference circuit is designed to operate on +5V and +3V. This supply voltage can be selected via the solder switches ‘ADC/REF’. The REF-1004 produces a stable +1.2V. With potentiometer RV 1 (REFT/B), this voltage can be adjusted between approximately +1.24V and +0.4V, and will affect both reference levels at the AC-Coupled The DC-coupled circuit previously discussed can also be reconfigured for AC-coupling. To do so, resistor R17 (0Ω) must be taken out and capacitors C20 and C22 assembled. The purpose of using two capacitors, one ceramic and one tantalum type, in parallel, is to assure a constant impedance ® DEM-ADS9xx 2 PC BOARD LAYOUT same time. The default configuration for the bottom reference driver (U5:B) is a unity gain stage, but can easily be modified by changing resistors R12 and R18. The top reference driver (U5:A) employs gain, which can be adjusted through potentiometer RV3. The gain range is from approximately 1.3V/V to 3V/V. If the ADS901 or ADS931 are to be used on the demonstration board, solder switches ‘REFB’ and ‘REFT’ must be closed. The voltage set for the references on these models determines the full-scale input signal range of the converter. For example, with REFT = +2V and REFB = +1V, the input range for an ADS901 will be 1Vp-p. The DEM-ADS9xxE demonstration board is made as a fourlayer PC board. To achieve the highest level of performance, surface-mount components are used wherever possible. This reduces the trace length and minimizes the effects of parasitic capacitance and inductance. The A/D converter is treated like an analog component therefore, the demonstration board has a consistent ground plane. Keep in mind that this approach may not yield optimum performance results when designing the ADS9xx into different individual applications. In any case, thoroughly bypassing the supply and reference pins of the converter, as shown on the demonstration board, is strongly recommended. Alternatively, a very simple way of setting up the reference voltages is by deriving them from the power supply. Using resistors R25 and R26 will allow a current flow from the supply through the A/D’s internal resistor ladder. In this case, solder switches ‘+VS’ and ‘GND’ must be closed and ‘REFT’ and ‘REFB’ open. SUPPLY VOLTAGE SETTING The ADS9xx converter family consists of models that operate on +3V or +5V supplies. To allow the evaluation of each converter in its typical environment, a voltage regulator was added to the demonstration board. The factory configuration uses the REG1117-3, a fixed +3V voltage regulator. Through a set of four solder switches, the two circuit blocks—the A/ D plus the reference, and the output buffer, can be tied independently to either the +3V or +5V supply. The respective labels of the solder switches are ‘ADC/REF’ and ‘U9/ U10’. If desired, the REG1117-3 can be replaced with models producing other output voltages, such as +2.85V or +3.3V, or the adjustable output model. Refer to the REG1117 data sheet for details. Depending on the model and its specified supply voltage, it may be necessary to reconfigure the reference circuit to obtain the recommended reference voltages (see the individual data sheets for details). Resistors R23 and R24 are used to establish the level shift voltage (common-mode voltage, VCM) needed for the DC-coupled input circuit. This voltage will track if adjustments are made to the reference voltages. DATA OUTPUT The data output is provided at CMOS logic levels. All ADS9xx converters use straight offset binary coding. The data output pins of the converter are buffered from the connector, P3, by two CMOS octal buffers (HC541). As an alternative, the HC type can be replaced with the new LCX541 (available from Motorola or National Semiconductor). These devices are designed for +3V operation and offer 5V tolerant inputs. ADS900/ADS930 SETTINGS The ADS900 and ADS930 are 10- and 8-bit converters, respectively, and operate with sampling frequencies up to 20MHz. Both models have internal references, therefore, the solder switches ‘REFT’ and ‘REFB’ must be open. Resistor R27 (0Ω) and R30 (3kΩ) should be installed. For the ADS900, the supply voltage must be set to +3V, whereas the ADS930 can operate with either +3V or +5V. ADS901/ADS931 SETTINGS The ADS901 and ADS931 are 10-and 8-bit converters, respectively, and operate with sampling frequencies up to 30MHz. These models do not have an internal reference and the connection to the on-board reference circuit is required. Also, resistor R27 must be removed. ® 3 DEM-ADS9xx R16 402Ω R10(1) J1 –VIN R1(1) C20(1) 0.1µF U3:A OPA2650U J2 –VIN BUF 3 4 1 U3:B OPA2650U R11 402Ω 6 7 2 R2 49.9Ω R22 24.9Ω R17 0Ω 5 R9(1) 8 C15 0.1µF R5 24.9Ω R3 Open C22(1) 2.2µF + C23(1) 0.1µF U3, 8 U3, 4 –5V + –5V C1 2.2µF RV2 5kΩ +5V C3 0.1µF +5V C5 0.1µF + C8 2.2µF VCM NOTE: (1) Part Not Assembled. FIGURE 1. DEM-ADS9xxE Analog Input Circuit. ® DEM-ADS9xx 4 FIGURE 2. DEM-ADS9xxE Reference Circuit. 5 ® DEM-ADS9xx 7 6 5 2 3 4 NOTE: (1) Part Not Assembled. 8 1 U8 REF1004C-1.2 ADC/REF R7 3kΩ RV1 5kΩ R6 10kΩ C11 0.1µF C12 0.1µF R13 3kΩ R13 Open C19(1) 0.1µF RV3 5kΩ 3 2 7 4 1 U5:B MC34072D 8 U5:A MC34072D 5 6 C18(1) 0.1µF R21 24.9Ω R20 1kΩ R19 24.9Ω R18 0Ω SS1 +5V VCM R25(1) R24 1kΩ R23 1kΩ SS11 +VS SS10 REFT R26(1) SS9 GND SS8 REFB C28 0.1µF Pin 22, U1 Pin 24, U1 FIGURE 3. DEM-ADS9xxE DUT and Digital Outputs. ® DEM-ADS9xx 6 SS10 REFT SS8 REFB R22 XFRM IN J4 R31(1) ADC/Ref T1(1) C24 0.1µF R27 0Ω R29(1) + C25 2.2µF C26 22pF SS7 MID PWRDN SS12 C30 0.1µF C27 0.1µF R30 3kΩ R28(1) C31 22pF CLK U7 C34 0.1µF + DD GND GND (MSB) B1 B2 B3 B4 B5 B6 B7 B8 B9 14 13 2 12 5 9 3 6 8 11 7 7 4 8 10 9 19 1 2 3 4 5 6 7 8 9 6 C36 0.1µF CLK 1 19 5 4 3 +VS 1 2 LV C35 2.2µF (LSB) B10 U1 ADS9xxE 28 +V S 27 IN 26 CM 25 LnBY 24 REFB/IN 23 NC 22 REFT 21 LpBY 20 GND 19 GND 18 +V S 17 PWRDN 16 OE 15 CLK C32 2.2µF + ADC/Ref R34 10kΩ R33 10kΩ R32 10kΩ Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7 A0 A1 A2 A3 A4 A5 A6 A7 OE2 OE1 Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7 U10 74HCX541 A0 A1 A2 A3 A4 A5 A6 A7 OE2 OE1 U9 74HCX541 18 17 16 15 14 13 12 11 18 17 16 15 14 13 12 11 P3:1 P3:3 P3:5 P3:7 P3:9 B1 B2 B3 B4 B5 P3:11 B6 P3:13 B7 P3:15 B8 U9/U10 C38 0.1µF P3:17 B9 P3:19 B10 P3:33 DV U9/U10 C37 0.1µF P3:39 OE FIGURE 4. DEM-ADS9xxE Clock and Power Supply Circuit. 7 ® DEM-ADS9xx P2:1 P2:2 P2:3 +5 GND –5 EXT CLK P1:2 GND J3 P1:1 +5V C2 0.1µF C4 0.1µF –5V +5V + C6 10µF C7 10µF R4 49.9Ω C10 0.1µF –5V + 3 C14 0.1µF + C13(1) 10µF 1 Gnd 4 3 2 1 VOUT R15(1) R14(1) + VBB GND NC Q0 D0 D0 VCC VEE U4 MC100ELT25D 2 4 NOTE: (1) Part is not assembled. R8 49.9Ω –5V + C9 10µF +5V VIN U2 REG1117-3 5 6 7 8 C17 0.1µF C16 10µF +5V C21 0.1µF +5V +5V SS4 +3V SS3 +3V SS2 +5V SS1 4 40MHz GND NC CCLK SS6 ECLK SS5 U6 OUT +V U9/U10 ADC/REF 2 1 R25 CLR D CLK PRE Q Q 3 2 CLR D CLK PRE 5 6 P3:28 GND P3:30 GND P3:32 GND P3:34 GND P3:36 GND P3:38 GND P3:40 GND P3:23 GND P3:25 GND P3:27 GND P3:29 GND P3:31 GND P3:35 GND P3:37 GND GND GND GND GND P3:20 GND P3:18 GND P3:16 GND P3:14 GND P3:12 GND P3:10 GND P3:8 P3:6 P3:4 P3:26 GND P3:2 P3:24 GND SS14 DIV4 Clock P3:22 GND +5V Q Q SS13 DIV2 P3:21 GND C33 0.1µF 10 9 8 7 U7:B 74AC11074D 12 13 14 1 U7:A 74AC11074D Pin 15, U1 FIGURE 5. Top-Layer (component side) with Silkscreen; DEM-ADS9xxE. FIGURE 6. Power Plane; DEM-ADS9xxE. ® DEM-ADS9xx 8 FIGURE 7. Bottom Layer with Silkscreen; DEM-ADS9xxE. ® 9 DEM-ADS9xx COMPONENT LIST REFERENCE QTY COMPONENT DESCRIPTION MANUFACTURER U1 1 ADS9xxE High-Speed ADC, 28-Pin SSOP Burr-Brown U2 1 REG1117-3 3V Fixed Regulator Burr-Brown U3 1 OPA2650U Dual VFA Op Amp, SO-8 Burr-Brown U4 1 MC100ELT25D ECL to TTL Translator, SO-8 Motorola U5 1 MC34072D Dual, Single-Supply Op Amp, SO-8 Motorola U6 1 F3000 Crystal, 40MHz/60MHz Fox U7 1 74AC11074D Dual D-Type Flip-Flop, SO-14 Texas Instruments U8 1 REF1004C-1.2 1.2V Reference, SO-8 Burr-Brown U9, U10 2 MC74LCX541DW 3V Octal Buffer, 20-Pin SOIC Motorola U9, U10 2 74HC541 5V Octal Buffer, 20-Pin SOIC div. R15, R17, R18 3 CRCW1206ZEROF 0Ω, MF 1206 Chip Resistor, 1% Dale R5, R19, R21, R22 4 CRCW120624R9F 24.9Ω, MF 1206 Chip Resistor, 1% Dale R2, R4, R8 3 CRCW120649R9F 49.9Ω, MF 1206 Chip Resistor, 1% Dale R11, R16 2 CRCW12064020F 402Ω, MF 1206 Chip Resistor, 1% Dale R20, R23, R24 3 CRCW12061001F 1kΩ, MF 1206 Chip Resistor, 1% Dale R7, R13, R30 3 CRCW12063001F 3kΩ, MF 1206 Chip Resistor, 1% Dale R6, R32, R33, R34 4 CRCW12061002 10kΩ, MF 1206 Chip Resistor, 1% Dale RV1, RV2, RV3 3 RJ26FW-502 5kΩ, 1/4" 10-Turn Pot Bourns C6, C7, C9, C16 4 ECE-V1CV100SR 10µF/16V, Surface-Mount Polar, Alu Capacitor Panasonic C1, C8, C25, C32, C35 C2, C3, C4, C5, C10, C11, C12, C14, C15, C17, C21, C24, C27, C28, C29 5 TAJR225006 2.2µF/10V, 3216 Tantalum Capacitor AVX C30, C33, C34, C36, C37, C38 22 12065C104KAT 0.1µF/50V, X7R 1206 Ceramic Capacitor AVX C26, C31 2 12065C220KAT 22pF/50V, NP0 1206 Ceramic Capacitor AVX P1 1 ED555/2DS 2-Pin Term Block On-Shore Technology P2 1 ED555/3DS 3-Pin Term Block On-Shore Technology P3 1 IDH-40LP-S3-TG 20x2 Dual-Row Shrouded Header Robinson-Nugent J2, J3 2 142-0701-201 Straight SMA PCB Connector EF Johnson Sockets for U6 4 #701C Flush Mount Pins McKenzie Technology 4 1-SJ5003-0-N Rubber Feet, Black, 0.44x0.2 Digi-Key 1 PCBA 2161 PC Board A2161, Rev. A Burr-Brown ® DEM-ADS9xx 10