Table of Contents
1 Read This First........................................................................................................................................................................3
1.1 EVM Cleanliness Guidelines..............................................................................................................................................3
2 Overview..................................................................................................................................................................................4
2.1 Guarding and Shielding......................................................................................................................................................4
3 Getting Started........................................................................................................................................................................5
3.1 Related Documentation From Texas Instruments.............................................................................................................. 5
3.2 Electrostatic Discharge Caution......................................................................................................................................... 5
4 EVM Circuit Description.........................................................................................................................................................6
4.1 High-Impedance Amplifier Circuit.......................................................................................................................................6
4.2 Transimpedance Amplifier Circuit...................................................................................................................................... 7
5 Cleaning the EVM..................................................................................................................................................................13
5.1 Ultrasonic Wash............................................................................................................................................................... 13
5.2 Manual Cleaning Procedure.............................................................................................................................................13
6 Schematic, PCB Layout, and Bill of Materials................................................................................................................... 13
6.1 EVM Schematic................................................................................................................................................................14
6.2 PCB Layout...................................................................................................................................................................... 16
6.3 Bill of Materials.................................................................................................................................................................20
List of Figures
Figure 4-1. HI-Z Circuit Schematic (Simplified)............................................................................................................................6
Figure 4-2. TIA Circuit Schematic (Simplified).............................................................................................................................7
Figure 4-3. T-Switch Timing Diagram.......................................................................................................................................... 9
Figure 4-4. T-Switch Logic Low (Normal Operation)..................................................................................................................10
Figure 4-5. T-Switch Logic Low Equivalent Circuit (Normal Operation).....................................................................................10
Figure 4-6. T-Switch Logic High (Discharge Feedback).............................................................................................................11
Figure 4-7. T-Switch Logic High Equivalent Circuit (Discharge Feedback)................................................................................11
Figure 4-8. Guarded Diode Limiter............................................................................................................................................ 12
Figure 6-1. OPA928EVM Hi-Z Schematic..................................................................................................................................14
Figure 6-2. OPA928EVM TIA Schematic................................................................................................................................... 15
Figure 6-3. Top Overlay............................................................................................................................................................. 16
Figure 6-4. Top Solder Mask......................................................................................................................................................16
Figure 6-5. Top Layer PCB Layout............................................................................................................................................ 17
Figure 6-6. Internal Power Layer PCB Layout........................................................................................................................... 17
Figure 6-7. Internal Guard Layer PCB Layout........................................................................................................................... 18
Figure 6-8. Bottom Layer PCB Layout.......................................................................................................................................18
Figure 6-9. Bottom Solder Mask................................................................................................................................................ 19
Figure 6-10. Bottom Overlay......................................................................................................................................................19
List of Tables
Table 4-1. TIA Jumper Block Connections...................................................................................................................................8
Table 4-2. TIA Pin Socket Configurations.................................................................................................................................... 8
Table 6-1. OPA928EVM Bill of Materials....................................................................................................................................20
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2OPA928 Evaluation Module SBOU282A – DECEMBER 2022 – REVISED MARCH 2023
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