ADS7883EVM, ADS7884EVM, ADS7885EVM, ADS7886EVM, ADS7887EVM, ADS7888EVM User's Guide Literature Number: SLAU166B October 2005 – Revised August 2008
SLAU166B – October 2005 – Revised August 2008 Submit Documentation Feedback
Contents 1 EVM Overview ..................................................................................................................... 5 1.1 2 3 4 5 6 7 8 9 Features .................................................................................................................... 5 Introduction......................................................................................................................... 6 Analog Interface..............................................................
www.ti.com List of Figures 1 2 3 4 5 Input Buffer Circuit ........................................................................................................... 7 Top: Layer 1................................................................................................................. 14 Ground Plane: Layer 2 .................................................................................................... 14 Power Plane: Layer 3 ..................................................................
User's Guide SLAU166B – October 2005 – Revised August 2008 ADS788xEVM This user's guide describes the characteristics, operation, and use of the evaluation module (EVM). A complete circuit description as well as schematic diagrams and bill of materials are included for Revision B of the EVMs. This user's guide describes the characteristics, operation, and use of the ADS7883EVM, ADS7884EVM, ADS7885EVM, ADS7886EVM, ADS7887EVM, and the ADS7888EVM (ADS788xEVM).
Introduction 2 www.ti.com Introduction The ADS7883 is a 12-bit, 3-MSPS serial-interface ADC. The ADS7884 is a 10-bit, 3-MSPS serial-interface ADC. The ADS7885 is an 8-bit, 3-MSPS serial-interface ADC. The ADS7886 is a 12-bit, 1-MSPS serial-interface ADC. The ADS7887 is a 10-bit, 1.25-MSPS serial-interface ADC. The ADS7888 is an 8-bit, 1.25-MSPS ADC. These devices include a capacitor-based successive approximation register (SAR) ADC with inherent sample-and-hold stages.
Analog Interface www.ti.com 3 Analog Interface The ADS788x ADC has one analog input pin. A signal for the input pin can be applied at connector P1, pin 2 (as shown in Table 2), or applied to the center pin of SMA connector J1. The input range of the converter set by the power-supply voltage applied at pin 1. For example, if VDD = 2.35 V, then VI can range from 0 V up to 2.35 V or 2.35 VPP. Table 2. Analog Input Connector 3.
Analog Interface www.ti.com The 15-Ω series resistor works with the capacitor, C20, to filter the input signal and isolates the amplifier from the capacitive load. The 680-pF capacitor to ground at the ADC input works with the series resistor to filter the input signal, behaving as a charge reservoir. It provides a short to ground for high-frequency noise and kickback currents when the device switches from hold to sample mode.
Digital Interface www.ti.com 4 Digital Interface The ADS788xEVM is designed for easy interfacing to multiple platforms. Samtec part numbers SSW-110-22-F-D-VS-K and TSM-110-01-T-DV-P provide a convenient dual row header/socket combination at P1 and P2. Consult Samtec at www.samtec.com or 1-800-SAMTEC-9 for a variety of mating connector options.
Power Supplies 5 www.ti.com Power Supplies The EVM accepts four power supplies. • A dual ±VS dc supply for the dual-supply operational amplifers. Recommended: ±6 VDC. • A single 5-V dc supply for the analog section of the board (ADC + reference). • A single 5-V or 3.3-V dc supply for the digital section of the board (output buffers U6). There are two ways to provide these voltages. 1. Wire in voltages at test points on the EVM. See Table 5. Table 5.
www.ti.com 6 Using the EVM Using the EVM The ADS788xEVM serves three functions: 1. As a reference design 2. As a prototype board; and 3. As software test platform 6.1 As a Reference Board As a reference design, the ADS788xEVM contains the essential circuitry to showcase the ADC. This essential circuitry includes the input amplifier, reference circuit, and buffers.
ADS788xEVM BOM 7 www.ti.com ADS788xEVM BOM Table 7 contains a complete bill of materials for the ADS788xEVM . Schematic diagrams are also provided for reference. Contact the Product Information Center or e-mail dataconvapps@list.ti.com for questions regarding this EVM. Table 7. ADS788xEVM Bill of Materials Item No.
ADS788xEVM BOM www.ti.com Table 7.
ADS788xEVM LAYOUT 8 www.ti.com ADS788xEVM LAYOUT This section contains the layout drawings for revision B of the ADS788xEVM PCB. Figure 2. Top: Layer 1 Figure 3.
ADS788xEVM LAYOUT www.ti.com Figure 4. Power Plane: Layer 3 Figure 5.
ADS788xEVM Schematics 9 www.ti.
1 2 3 4 5 6 Revision History REV ECN Number Approved D D J1 P1 1 3 5 7 9 11 13 15 17 19 2 4 6 8 10 12 14 16 18 20 +IN EXT_REF W1 CS Analog Input P2 SCLK C FS TP1 +VA +VA B_SDO TP2 J2 +VA +AVCC DGND +3.3VD 1 3 5 7 9 2 4 6 8 10 -VA -VA CS SCLK -VA B_SDO 1 3 5 7 9 11 13 15 17 19 2 4 6 8 10 12 14 16 18 20 C Serial Control AGND +5VD Power Supply TP3 W2 +VDD +AVCC +AVCC TP4 Circuits B B ti A A 12500 TI Boulevard.
1 2 3 4 5 6 Revision History REV R4 ECN Number Approved +VA NI U3 0.47uF +5VCC GND_F GND_S ENABLE C2 R6 OUT_F OUT_S IN D 1uF 6 5 4 0 7 1 2 3 C8 R12 R3 REF3225 5 D U2 3 NI 0 R9 6 2 1 OPA735 0 R1 4 NI R2 +IOVDD 2 NI 1 3 SJP1 W3 -VA TP15 R18 C4 1uF 10k +5VCC W4 R15 CS 100 C10 +VCC C14 NI NI R14 C1 1k NI C 1 C TP5 C13 10nF R13 2 10k C9 1uF 0 +IOVDD +VA U5 1 2 3 C3 3 R5 C17 2.
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