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19-1335; Rev 0a; 2/98
MAX1011 Evaluation Kit
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. 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.
Features
o 5.85 Effective Number of Bits at 20MHz Analog Input Frequency o Separate Analog and Digital Power and Ground Connections with Optimized PC Board Layout o Single-Ended or Differential Analog Input o Square-Pin Header for Easy Connection of Logic Analyzer to Digital Outputs o User-Selectable ADC Full-Scale Gain Ranges o Fully Assembled and Tested Surface-Mount Board
Evaluates: MAX1011
Component List
DESIGNATION QTY C1, C3, C5 C2, C7, C8 C4 C6 C9, C10 C11, C12 D1 J1 JU1, JU2, JU6 JU3, JU4 JU5 L1 R1 R2, R3 R4, R5 U1 IN+, INClock Overdrive None None 3 3 1 1 2 2 1 1 3 2 1 1 1 2 2 1 2 0 1 1 DESCRIPTION 0.01F, 10V min, 10% ceramic capacitors 47pF, 10V min, 5% ceramic capacitors 0.22F, 10V min, 10% ceramic capacitor 5pF, 10V min, 10% ceramic capacitor 0.1F, 10V min, 10% ceramic capacitors 10F, 10V min, 20% tantalum caps AVX TAJC106K016 Varactor diode M/A-COM MA4ST079CK-287, SOT23 14-pin connector 0 resistors 2-pin headers 3-pin header 220nH inductor Coilcraft 1008CS-221XKB 10k, 5% resistor 47k, 5% resistors 49.9, 1% resistors MAX1011CEG BNC connectors Not Supplied MAX1011 circuit board Shunt for JU5
Ordering Information
PART MAX1011EVKIT TEMP. RANGE 0C to +70C IC PACKAGE 24 QSOP
Component Suppliers
SUPPLIER* AVX Coilcraft M/A-COM Sprague PHONE (803) 946-0690 (847) 639-6400 (617) 564-3100 (603) 224-1961 FAX (803) 626-3123 (847) 639-1469 (617) 564-3050 (603) 224-1430
* 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.
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MAX1011 Evaluation Kit Evaluates: MAX1011
5) Connect a 250mVp-p, 20MHz sine-wave source to the analog input at BNC J3. The analog input is terminated in 50 (R4). 6) Connect a logic analyzer to connector J1 to monitor the digital outputs. 7) Turn on all power supplies and signal sources. 8) Observe the digitized analog input signals with the logic analyzer.
Table 2. Gain-Selection Jumper JU5 Settings
JU5 SETTING
JU5
1 2 3
MAX1011 GAIN CONTROL PIN GND
ADC GAIN RANGE
Low-gain, 500mVp-p
_______________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.
JU5
1 2 3
OPEN
Mid-gain, 250mVp-p
JU5
1 2 3
VCC
High-gain, 125mVp-p
Table 1. EV Kit Jumpers and Default Positions
JUMPER(S) JU1, JU2, JU6 JU3, JU4 JU5 FUNCTION Power-supply currentsense ports Offset-correction amplifier enabled ADC full-scale range selection DEFAULT POSITION Shorted with 0 resistors Open Open
Table 3. Typical Input-Drive Requirements for Mid-Gain
INPUT DRIVE Single-Ended Noninverting IN+ +125mV 0 -125mV Open Circuit Single-Ended Inverting Open Circuit Open Circuit +62.5mV Differential 0 -62.5mV INOpen Circuit Open Circuit Open Circuit +125mV 0 -125mV -62.5mV 0 +62.5mV OUTPUT CODE 111111 100000 000000 000000 011111 111111 111111 100000 000000
Analog Supply Power Requirements
The MAX1011 requires a +5V at approximately 37mA for the analog VCC supply. 0 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.
log inputs, plus the 0.1F 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
Analog Inputs
The analog inputs to the ADC are provided through BNC connectors IN+, and IN-. The connectors are terminated with 49.9 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 20k input resistance of the ana2
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MAX1011 Evaluation Kit
MAX1011 Fig01
110 105 100 FREQUENCY (MHz) 95 90 85 80 75 70 65 60 0 1 2 3 4 5 6 7 8 VTUNE CONTROL VOLTAGE (V)
Table 4. External Clock Source EV Kit Modifications
COMPONENT Clock Overdrive (J2) C6 C7, C8 L1 R1 R2, R3 D1 DESCRIPTION Clock input BNC connector 5pF capacitor 47pF capacitors 220nH inductor 10k resistor 47k resistors Varactor diode MODIFICATION Add Remove Replace with 0.01F capacitors Remove Remove Replace with 49.9 resistors Remove
Evaluates: MAX1011
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.
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 49.9 value of R3 shown in Figure 3 provides proper termination for a 50 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.
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).
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Evaluates: MAX1011
MAX1011 Evaluation Kit
Figure 2. MAX1011 EV Kit Schematic (Voltage-Controlled-Oscillator Mode)
C9 0.1F 1 JU5 VCC 2 3 R4 49.9 (1%)
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U1 MAX1011
1 GAIN D5 D4 D3 D2 D1 DO DCLK VCCO OGND GND VCC GND N.C. VCC GND JU6 0 VCC VTUNE JU1 VCC C11 0 10F (10V) GND CUT HERE TO SEPARATE GROUNDS C12 10F (10V) VCCO VCCO VCC VTUNE J1-2 J1-4 J1-6 J1-8 J1-10 J1-12 J1-14 17 16 15 14 13 C1 0.01F VCC 18 19 20 21 22 23 OCC+ OCCIN+ INVCC TNK+ TNKGND 24 JU4 2 3 4 C7 47pF L1 220nH 6 7 C6 5pF 8 9 C8 47pF 11 12 C5 0.01F C3 0.01F 10 5 1 C4 JU3 0.22 F J1-1 J1-3 J1-5 J1-7 J1-9 J1-11 J1-13 C2 47pF GND PLANE RELIEVED UNDER THESE COMPONENTS C10 0.1F R5 49.9 (1%) 2 0 JU2 OGND
IN+
J3
BNC
IN-
J4
BNC
TANK
R3 47k
D1
VTUNE
R1 10k
3
R2 47k
GND PLANE RELIEVED UNDER THESE COMPONENTS
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= ANALOG GROUND (GND)
= DIGITAL GROUND (OGND)
IN+
J3
C9 0.1F
BNC 2 3 VCC
1 JU5
IN-
J4
R4 49.9 (1%)
BNC C10 0.1F
U1 MAX1011
1 GAIN D5 D4 D3 D2 D1 DO DCLK 18 JU2 VCCO OGND N.C. VCC GND JU6 0 17 16 15 14 13 C1 0.01F VCC VCCO C2 47pF 0 19 20 21 22 23 OCC+ OCCIN+ INVCC TNK+ TNKGND GND VCC GND 24 J1-1 J1-3 J1-5 J1-7 J1-9 J1-11 J1-13 GND PLANE RELIEVED UNDER THESE COMPONENTS
J2 JU4 2 C4 0.22F 3 4 49.9 (1%) C7 0.01F 5 6 7 C8 0.01F 8 9 R2 10 C3 0.01F 12 C5 0.01F 11 JU3
R5 49.9 (1%)
CLOCK BNC OVERDRIVE R3
Figure 3. MAX1011 EV Kit Schematic (External Clock Operation)
J1-2 J1-4 J1-6 JU1 VCC C11 0 10F (10V) GND CUT HERE TO SEPARATE GROUNDS C12 10F (10V) VCCO VCCO VCC J1-8 J1-10 J1-12 J1-14 VCC VTUNE VTUNE OGND
49.9 (1%)
= ANALOG GROUND (GND)
Evaluates: MAX1011
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= DIGITAL GROUND (OGND)
MAX1011 Evaluation Kit
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MAX1011 Evaluation Kit Evaluates: MAX1011
Digital Outputs
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).
Bypassing
Proper bypassing is essential to achieve the best dynamic performance from the converter. The MAX1011 EV kit uses 10F 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.
__________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.
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.
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MAX1011 Evaluation Kit Evaluates: MAX1011
1.0"
1.0"
Figure 4. MAX1011 EV Kit Component Placement Guide-- Component Side
Figure 5. MAX1011 EV Kit Component Placement Guide-- Solder Side
1.0"
1.0"
Figure 6. MAX1011 EV Kit PC Board Layout-- Component Side
Figure 7. MAX1011 EV Kit PC Board Layout-- Solder Side
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MAX1011 Evaluation Kit Evaluates: MAX1011
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 (c) 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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