MAX1011EVKIT

19-1335; Rev 0a; 2/98 MAX1011 Evaluation Kit Connectors for power supplies, analog inputs, and digital outputs simplify connections to the device. The PC board features an optimized layout to ensure the best possible dynamic performance. The EV kit includes a MAX1011. Component List DESIGNATION QTY C1, C3, C5 3 Features ♦ 5.85 Effective Number of Bits at 20MHz Analog Input Frequency ♦ Separate Analog and Digital Power and Ground Connections with Optimized PC Board Layout ♦ Single-Ended or Differential Analog Input ♦ Square-Pin Header for Easy Connection of Logic Analyzer to Digital Outputs ♦ User-Selectable ADC Full-Scale Gain Ranges ♦ Fully Assembled and Tested Surface-Mount Board DESCRIPTION Ordering Information 0.01µF, 10V min, 10% ceramic capacitors PART MAX1011EVKIT TEMP. RANGE 0°C to +70°C IC PACKAGE 24 QSOP C2, C7, C8 3 47pF, 10V min, 5% ceramic capacitors C4 1 0.22µF, 10V min, 10% ceramic capacitor C6 1 5pF, 10V min, 10% ceramic capacitor C9, C10 2 0.1µF, 10V min, 10% ceramic capacitors AVX (803) 946-0690 (803) 626-3123 C11, C12 2 10µF, 10V min, 20% tantalum caps AVX TAJC106K016 Coilcraft (847) 639-6400 (847) 639-1469 M/A-COM (617) 564-3100 (617) 564-3050 Sprague (603) 224-1961 (603) 224-1430 D1 1 Varactor diode M/A-COM MA4ST079CK-287, SOT23 J1 1 14-pin connector JU1, JU2, JU6 3 0Ω resistors JU3, JU4 2 2-pin headers JU5 1 3-pin header L1 1 220nH inductor Coilcraft 1008CS-221XKB R1 R2, R3 R4, R5 U1 IN+, IN- 1 2 2 1 2 10kΩ, 5% resistor 47kΩ, 5% resistors 49.9Ω, 1% resistors MAX1011CEG BNC connectors Clock Overdrive 0 Not Supplied None None 1 1 MAX1011 circuit board Shunt for JU5 Component Suppliers SUPPLIER* PHONE FAX * Please indicate that you are using the MAX1011 when contacting these component suppliers. Quick Start The MAX1011 EV kit is fully assembled and tested. Follow these steps to verify proper board operation. Do not turn on the power supplies until all connections to the EV kit are completed. 1) Connect a +5V power supply to the pad marked VCC. Connect this supply’s ground to the pad marked GND. 2) Connect a +3.3V power supply to the pad labeled VCCO. Connect the supply ground to the pad marked OGND. 3) Connect a +3.7V power supply to the pad marked VTUNE. Connect the supply ground to the GND pad. 4) Remove the shunt from jumper JU5. This sets a 250mVp-p full-scale range. ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800 For small orders, phone 408-737-7600 ext. 3468. Evaluates: MAX1011 General Description The MAX1011 evaluation kit (EV kit) simplifies evaluation of the 90Msps MAX1011 6-bit analog-to-digital converter (ADC). The kit includes the basic components necessary to operate the on-chip oscillator as a voltage-controlled oscillator (VCO). The board can also be easily modified to accommodate an external clocking source. Evaluates: MAX1011 MAX1011 Evaluation Kit 5) Connect a 250mVp-p, 20MHz sine-wave source to the analog input at BNC J3. The analog input is terminated in 50Ω (R4). 6) Connect a logic analyzer to connector J1 to monitor the digital outputs. 7) Turn on all power supplies and signal sources. Table 2. Gain-Selection Jumper JU5 Settings JU5 SETTING MAX1011 GAIN CONTROL PIN ADC GAIN RANGE GND Low-gain, 500mVp-p OPEN Mid-gain, 250mVp-p VCC High-gain, 125mVp-p JU5 1 8) Observe the digitized analog input signals with the logic analyzer. _______________Detailed Description EV Kit Jumpers The MAX1011 EV kit contains several jumpers that control board and part options. The following sections describe the different jumpers and their purposes. Table 1 lists the jumpers on the EV kit and their default positions. Table 1. EV Kit Jumpers and Default Positions JUMPER(S) FUNCTION JU1, JU2, JU6 Power-supply currentsense ports JU3, JU4 Offset-correction amplifier enabled JU5 ADC full-scale range selection DEFAULT POSITION Shorted with 0Ω resistors Open 2 3 JU5 1 2 3 JU5 1 2 3 Table 3. Typical Input-Drive Requirements for Mid-Gain INPUT DRIVE Single-Ended Noninverting Single-Ended Inverting Open Differential Analog Supply Power Requirements The MAX1011 requires a +5V at approximately 37mA for the analog VCC supply. 0Ω resistors are installed at jumper sites JU1, JU2, and JU6 and can be removed to sense device power-supply currents with an ammeter. Digital Outputs Supply The MAX1011 requires +3.3V for the VCCO supply. The current requirement from the power supply is a function of the sampling clock and analog input frequencies, as well as the capacitive loading on the digital outputs. With 15pF loads and a 20MHz analog input frequency sampled at 90Msps, the current draw is approximately 8.5mA. Analog Inputs The analog inputs to the ADC are provided through BNC connectors IN+, and IN-. The connectors are terminated with 49.9Ω to ground and are AC coupled to the converter’s analog inputs, which are internally selfbiased at 2.35V DC. A typical application circuit drives the IN+ noninverting analog input using AC-coupled signals. The nominal 20kΩ input resistance of the ana2 IN+ IN- OUTPUT CODE +125mV Open Circuit 111111 0 Open Circuit 100000 -125mV Open Circuit 000000 Open Circuit +125mV 000000 Open Circuit 0 011111 Open Circuit -125mV 111111 +62.5mV -62.5mV 111111 0 0 100000 -62.5mV +62.5mV 000000 log inputs, plus the 0.1µF AC-coupling capacitor value, sets the low-frequency corner at approximately 80Hz. You can drive the analog inputs either single-ended or differentially using AC- or DC-coupled inputs. Either the inverting or the noninverting input can be driven singleended. If the inverting input is driven, then the digital output codes are inverted (complemented). Refer to the MAX1011 data sheet for typical circuits. ADC Gain Selection The single GAIN-select pin on the MAX1011 controls the full-scale input range. Jumper JU5 is used to manually select the desired gain range as shown in Table 2. The EV kits are shipped with the mid-gain range selected (jumper pins open). Table 3 lists the possible input-drive combinations for the mid-gain (250mVp-p) full-scale range selection. Drive levels are referenced to the open-circuit, common-mode voltage of the analog inputs (typically _______________________________________________________________________________________ MAX1011 Evaluation Kit MAX1011 Fig01 105 FREQUENCY (MHz) 100 Table 4. External Clock Source EV Kit Modifications COMPONENT 95 90 85 Clock Overdrive (J2) 80 C6 DESCRIPTION Clock input BNC connector Add 5pF capacitor Remove C7, C8 47pF capacitors Replace with 0.01µF capacitors 75 70 65 60 0 1 2 3 4 5 6 7 8 L1 220nH inductor Remove R1 10kΩ resistor Remove R2, R3 47kΩ resistors Replace with 49.9Ω resistors D1 Varactor diode Remove VTUNE CONTROL VOLTAGE (V) Figure 1. MAX1011 Oscillator Frequency vs. VTUNE Control Voltage 2.35V) if DC coupled, or to ground if AC coupling is used. If the low-gain (500mVp-p) range is selected, the input-drive requirements are twice those listed in Table 3. If the high-gain (125mVp-p) range is selected, the input-drive requirements are half those listed in Table 3. Offset-Correction Amplifier The offset-correction amplifier included on the MAX1011 is usually enabled in a typical AC-coupled application circuit. For DC-coupled applications, the amplifier must be disabled by installing shorting blocks on jumpers JU3 and JU4. These jumpers short device pins OCC+ (pin 2) and OCC- (pin 3) to ground and disable the amplifier. The MAX1011 EV kit is configured with the offset-correction amplifier enabled (jumpers open) and AC-coupled analog inputs. Voltage-Controlled-Oscillator Operation The EV kit includes a voltage-controlled-oscillator (VCO) circuit to set the analog-to-digital converter (ADC) sampling rate using an external resonant tank and a varactor diode. A voltage applied to the VTUNE pad changes the varactor diode’s capacitance to adjust the tank’s resonant frequency, which sets the oscillator’s sampling frequency. VTUNE voltage can be varied from 0V to a maximum of 8V. The EV kit is designed so that a nominal VTUNE control voltage of about 3.7V sets the ADC sampling rate to 90Msps. The VTUNE control voltage should be well filtered, as any noise on the supply contributes to jitter in the internal oscillator and degrades the converter’s dynamic performance. Figure 1 shows the VTUNE control-voltage typical frequency-adjustment range for the MAX1011 EV kit (for VCO mode, refer to schematic in Figure 2). MODIFICATION External Clock Operation The MAX1011 EV kit can be converted to drive the ADC from an external clock source. This involves removing the external resonator components from the VCO circuit and adding a few new components. Table 4 lists the EV kit changes required to convert the board to accept an external clock source. The resulting schematic is shown in Figure 3. The new 49.9Ω value of R3 shown in Figure 3 provides proper termination for a 50Ω external signal generator. AC-coupling capacitor C7 couples the external clock signal to the MAX1011 oscillator circuitry at TNK+ (pin 7). R2 and C8 ensure that the impedance at both ports of the oscillator is balanced. After all modifications are complete, connect an external clock source to the BNC connector on the EV kit marked CLOCK OVERDRIVE (J2). The recommended clock amplitude is 1Vp-p; however, the ADC operates correctly with as little as 300mVp-p or up to 1.25Vp-p on CLOCK OVERDRIVE. The external clock source should have low-phase noise for best dynamic performance. A low-phase-noise sine-wave oscillator serves this purpose well. A squarewave clock source is not necessary to drive the MAX1011. The device contains sufficient gain to amplify even a low-level-input sine wave to drive the ADC comparators, while ensuring excellent dynamic performance. _______________________________________________________________________________________ 3 Evaluates: MAX1011 110 4 R1 10k BNC BNC 3 J4 J3 R2 47k D1 R3 47k 2 1 C8 47pF C6 5pF C7 47pF R5 49.9Ω (1%) R4 49.9Ω (1%) = DIGITAL GROUND (OGND) = ANALOG GROUND (GND) Figure 2. MAX1011 EV Kit Schematic (Voltage-Controlled-Oscillator Mode) _______________________________________________________________________________________ VCCO OGND GND VCC VTUNE GND PLANE RELIEVED UNDER THESE COMPONENTS VTUNE TANK IN- IN+ L1 220nH C10 0.1µF C9 0.1µF JU1 C12 10µF (10V) CUT HERE TO SEPARATE GROUNDS C11 0Ω 10µF (10V) VTUNE VCC 2 C5 0.01µF C3 0.01µF VCCO VCC C4 JU3 0.22 µF JU4 JU5 1 3 JU6 0Ω 12 11 10 9 8 7 6 5 4 3 2 1 GND VCC GND GND TNK- TNK+ VCC IN- IN+ OCC- OCC+ GAIN U1 VCCO DCLK DO D1 D2 D3 D4 D5 GND VCC N.C. OGND MAX1011 VCC 13 14 15 16 17 18 19 20 21 22 23 24 C1 0.01µF C2 47pF 0Ω JU2 J1–14 J1–12 J1–10 J1–8 J1–6 J1–4 J1–2 VCC J1–13 J1–11 J1–9 J1–7 J1–5 J1–3 J1–1 GND PLANE RELIEVED UNDER THESE COMPONENTS Evaluates: MAX1011 MAX1011 Evaluation Kit BNC J2 J4 49.9Ω (1%) R2 49.9Ω (1%) R3 = DIGITAL GROUND (OGND) VCCO OGND GND VCC VTUNE C8 0.01µF C7 0.01µF R5 49.9Ω (1%) R4 49.9Ω (1%) = ANALOG GROUND (GND) CLOCK BNC OVERDRIVE IN- BNC J3 C10 0.1µF C9 0.1µF JU1 C12 10µF (10V) CUT HERE TO SEPARATE GROUNDS C11 0Ω 10µF (10V) VTUNE VCC C5 0.01µF C3 0.01µF JU3 JU4 2 VCCO VCC C4 0.22µF JU5 1 3 GND VCC GND GND TNK- TNK+ VCC IN- IN+ OCC- OCC+ GAIN JU6 0Ω 12 11 10 9 8 7 6 5 4 3 2 1 U1 VCCO DCLK DO D1 D2 D3 D4 D5 GND VCC N.C. OGND MAX1011 VCC 13 14 15 16 17 18 19 20 21 22 23 24 C1 0.01µF C2 47pF 0Ω JU2 J1–14 J1–12 J1–10 J1–8 J1–6 J1–4 J1–2 VCC VCCO J1–13 J1–11 J1–9 J1–7 J1–5 J1–3 J1–1 GND PLANE RELIEVED UNDER THESE COMPONENTS Evaluates: MAX1011 IN+ MAX1011 Evaluation Kit Figure 3. MAX1011 EV Kit Schematic (External Clock Operation) _______________________________________________________________________________________ 5 Evaluates: MAX1011 MAX1011 Evaluation Kit Digital Outputs Bypassing The TTL/CMOS-compatible digital outputs are presented in parallel at connector J1. The data format is offset binary with the MSB as D5 and the LSB as D0. The row of pins closest to the board edge is digital output ground (OGND), while the data bits occupy the inside row. Located at the end of the connector is the pin for the output clock labeled DCLK. This signal can be used to latch the parallel-output data for capture into a logic analyzer or external DSP circuitry. The digital output is updated on DCLK’s rising edge (see the timing diagram in the MAX1011 data sheet). Proper bypassing is essential to achieve the best dynamic performance from the converter. The MAX1011 EV kit uses 10µF bypass capacitors located close to the power-supply connectors on the board to filter low-frequency supply ripple. High-frequency bypassing is accomplished with ceramic-chip capacitors located very close to the device’s supply pins. As the digital outputs toggle, transient currents in the VCCO supply can couple into sensitive analog circuitry and severely degrade the converter’s effective number of bits performance. Of particular concern is effectively bypassing VCCO to OGND. For best results, locate the bypass capacitor on the same side of the board and place it close to the device. This avoids the use of through-holes and results in lower series inductance. The capacitor size chosen for the EV kit (size 0603) keeps the layout compact. Finally, the modest value (47pF) and small size result in a high self-resonant frequency for effective high-frequency bypassing. _____________Layout Considerations The MAX1011 EV kit layout has been optimized for high-speed signals. Careful attention has been given to grounding, power-supply bypassing, and signal-path layout to minimize coupling between the analog and digital sections of the circuit. For example, the ground plane has been removed under the tank circuitry to reduce stray-capacitive loading on the relatively small capacitors required in the resonant tank formed by C6, L1, and D1. Other layout considerations are detailed in the following sections. Power Supplies and Grounding The EV kit features separate analog and digital power supplies and grounds for best dynamic performance. A thin trace located on the backside of the circuit board near the VCC power-supply connector ties the analog and output ground planes together. This trace can be cut if the power-supply grounds are referenced elsewhere. Referencing analog and digital grounds together at a single point usually avoids ground loops and corruption of sensitive analog circuitry by noise from the digital outputs. If the ground trace on the backside of the board is cut, observe the absolute maximum ratings between the two grounds. 6 __________Applications Information To achieve the full dynamic potential from the converter, minimize the capacitive loading on the digital outputs to reduce the transient currents at V CCO and OGND. The maximum capacitance per output bit should be less than 15pF. For example, the capacitance of the digital-output traces and the J1 connector on the EV kit is about 1.5pF per trace. In an applications circuit, this could be further reduced by locating the digital receiving chip very close to the MAX1011 and removing the ground plane from under the output bit traces. A logic analyzer can be connected to the J1 connector on the EV kit for evaluation purposes. The analyzer should be directly connected to the EV kit without any additional ribbon cables. Even a short length of ribbon cable can exceed the maximum recommended capacitive loading of the digital outputs. A typical high-speed logic-analyzer probe adds about another 8pF loading per digital bit, which is acceptable for good dynamic performance. _______________________________________________________________________________________ MAX1011 Evaluation Kit Evaluates: MAX1011 1.0" 1.0" Figure 4. MAX1011 EV Kit Component Placement Guide— Component Side 1.0" Figure 5. MAX1011 EV Kit Component Placement Guide— Solder Side 1.0" Figure 6. MAX1011 EV Kit PC Board Layout— Component Side Figure 7. MAX1011 EV Kit PC Board Layout— Solder Side _______________________________________________________________________________________ 7 Evaluates: MAX1011 MAX1011 Evaluation Kit NOTES Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 8 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.