Texas Instruments MSP430F2274 User Manual

Texas Instruments MSP430F2274 User Manual

Transimpedance amplifier

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MSP430F2274 Transimpedance Amplifier (TIDM-TIA)
1
Introduction
This manual describes the TIDM-TIA hardware and how to use it. The TIDM-TIA uses a MSP430F2274
microcontroller to convert the current produced by a photodiode into a voltage. The TIDM-TIA converts
current to voltage by using one of the MSP430F2274's integrated op-amps and an external feedback
resistor. This voltage is then sampled by the ADC on the MSP430F2274 and converted to a 10-bit value.
Resulting conversion values can then be used to turn the LED on or off based on simple logic. Other
GPIO pins are also available to use externally. The entire process of the TIA is indicated in
The TIDM-TIA is programmable and powered by a 4-wire JTAG connection or by an external source
through an external voltage pin.
Find more information on the
For more information on transimpedance amplifiers and their properties, see the Transimpedance
Considerations for High-Speed Amplifiers and Compensate Transimpedance Amplifiers Intuitively
resources in
Section
TIDU443 – August 2014
Submit Documentation Feedback
Figure 1. TIA Block Diagram
MSP430F2274
datasheet.
6.
MSP430F2274 Transimpedance Amplifier (TIDM-TIA) User's Guide
Copyright © 2014, Texas Instruments Incorporated
User's Guide
TIDU443 – August 2014
User's Guide
Figure
1.
1

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Summary of Contents for Texas Instruments MSP430F2274

  • Page 1 MSP430F2274’s integrated op-amps and an external feedback resistor. This voltage is then sampled by the ADC on the MSP430F2274 and converted to a 10-bit value. Resulting conversion values can then be used to turn the LED on or off based on simple logic. Other GPIO pins are also available to use externally.
  • Page 2: Hardware Description

    Blue-wire— Patch wires added to a circuit board to correct issues or change design. Hardware Description Figure 2. TIA Hardware Description MSP430F2274 Transimpedance Amplifier (TIDM-TIA) User's Guide TIDU443 – August 2014 Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated...
  • Page 3: Jtag Connector

    – I ´ photo where • is the current from the photodiode photo • is the resistance of the feedback resistor. TIDU443 – August 2014 MSP430F2274 Transimpedance Amplifier (TIDM-TIA) User's Guide Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated...
  • Page 4 R4 location on the board at the two holes. Knowing a target output voltage and measuring the current from the photodiode makes it possible to use Equation 1 to select a proper feedback resistor. MSP430F2274 Transimpedance Amplifier (TIDM-TIA) User's Guide TIDU443 – August 2014 Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated...
  • Page 5: Operational Amplifier

    Section Operational Amplifier The TIDM-TIA uses the MSP430F2274’s integrated op-amp with a feedback resistor to provide the current-to-voltage conversion. Using the op-amp is preferred to simply feeding the photodiode’s current across a resistor. A lone feedback resistor has a tradeoff between a large gain and a small response time.
  • Page 6 Input Current (A) D001 Figure 5. TIA SPICE Simulation The Tina-TI SPICE model of the op-amp is available on the MSP430F2274 product web page. Characterization data for the photodiode current versus op-amp output voltage can be seen in Figure Results are close to expected output.
  • Page 7: Analog-To-Digital Converter

    Analog-to-Digital Converter The 10-bit ADC inside the MSP430F2274 converts voltage at the output of the op-amp into a 10-bit value. Both components are connected to each other inside the MSP430F2274. By default, the ADC uses reference voltages of 0 V (GND) and 3.3 V (V ) for its samples in single-channel, single-conversion mode, which is configured in software and can be changed for the different operations of the ADC.
  • Page 8 P3.5/UCA0RXD/UCA0SOMI P4.5/TB2/A14/OA0I3 P3.6 P3.6/A6/OA0I2 P4.6/TBOUTH/A15/OA1I3 P3.7/A7/OA1I2 P4.7/TBCLK RST/NMI RST/NMI/SBWTDIO QFN PAD TEST/SBWTCK TEST/SBWTCK AVSS DVSS DVSS MSP430F2274IRHA Figure 7. TIDM-TIA Schematic MSP430F2274 Transimpedance Amplifier (TIDM-TIA) User's Guide TIDU443 – August 2014 Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated...
  • Page 9 1%, 0.1 W, 0603 External Resistor 16-bit Ultra-Low- Power Microcontroller, MSP430F2274IRHA Texas Instruments MSP430F2274IRHAT Digi-Key 296-21459-1-ND RHA0040B 32-KB Flash, 1-K RAM, RHA0040B TIDU443 – August 2014 MSP430F2274 Transimpedance Amplifier (TIDM-TIA) User's Guide Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated...
  • Page 10 3. OSRAM SFH 2701 (PDF) 4. Compensate Transimpedance Amplifiers Intuitively (SBOA055A) 5. Transimpedance Considerations for High-Speed Amplifiers (SBOA122) 6. TIDM-TIA: Design Folder MSP430F2274 Transimpedance Amplifier (TIDM-TIA) User's Guide TIDU443 – August 2014 Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated...
  • Page 11: Important Notice

    IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue.

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