LMP2021MAEVAL

User's Guide SNOA537A – December 2008 – Revised April 2013 AN–1932 LMP2021MAEVAL - Bridge Sensor Instrumentation Amplifier Evaluation Board 1 Introduction The LMP2021MAEVAL instrumentation amplifier evaluation board is configured as a differential-in, differential-out amplifier using the LMP2021. Also included is a precision reference and buffer to drive a bridge sensor. The board is set up to be used with the ADC141S626 evaluation board (part number: ADC141S626EB). 2 Power J3 J4 J5 J7 3 Connect to the positive supply. Connect to ground. If using dual supplies connect to the negative supply. If using a single supply short J5 to ground. Pin 1 of J2 can be used to power the ADC141S626EB evaluation board, which requires +5 V. If J3 is +5 V, JP3 can be shorted to provide +5 V to the ADC141S626EB evaluation board. If J3 is not +5 V, leave JP3 open and connect +5 V to J7. Input Signal and Bridge Excitation J1 is used to power the bridge sensor and input the signal from the bridge to the amplifier. The LM4120 (U4) provides a precision +5 V reference. This is buffered by the LMP7741 (U5) and supplied on pin 1 of J1 to power the bridge sensor. The bottom of the bridge sensor can be connected to pin 2, which is connected to ground. The outputs of the bridge sensor can be connected to pins 3 and 5 of J1. 4 Output Signal The output of the amplifier is available on pins 3 and 5 of J2. This connector is pin-to-pin compatible with the input connector of the ADC141S626EB evaluation board. 5 Amplifier Gain The gain of the amplifier is set using R1, R10, R11, and R12. If R11 = R12, the gain of the amplifier is 1 + (2R11)/(R1||R10). All trademarks are the property of their respective owners. SNOA537A – December 2008 – Revised April 2013 Submit Documentation Feedback AN–1932 LMP2021MAEVAL - Bridge Sensor Instrumentation Amplifier Evaluation Board Copyright © 2008–2013, Texas Instruments Incorporated 1 Amplifier Gain www.ti.com V- 0.1 PF Vref + V- 1k R2 6 LMP2021 C8 C9 0.1 PF 0.1 PF 2 OUT U4 IN 0.47 PF 0 7 LM4120AIM5-5.0 C7 4 C16 U2 V+ - 5 REF 0.1 PF 4 3 GND R6 EN 3 C17 0.1 PF 2 J6 SMA C6 1 V+ C5 0.1 PF V+ V+ R11 C1 J1 1 Vb 2 5 GND + V V +CM -CM 3 V+ - 10k C18 R10 150 J2 VADC 1 VADC 0.1 PF 2 C19 3 4 GND IN+ 1 4 LMP7741 U1 GND - R1 NC C2 0.1 PF 0.1 PF 5 V- + 3 2 6 R7 Vref 4 C12 NC 0.1 PF R12 GND 5 IN- 0 GND V+ 10k C4 0.1 PF C10 C24 6 J8 SMA LMP2021 R17 3 + + C20 0 6.8 PF C11 0.1 PF 0.1 PF 0.1 PF 0.1 PF C14 C22 0.1 PF 4 C21 C25 JP3 R3 U3 V- 1k C13 1 C23 0.1 PF J5 V- 6.8 PF C3 0.1 PF C15 + V+ 1 7 - J4 GND + 2 J3 V+ 1 J7 +5V 0.1 PF 1 V- 6.8 PF 0.1 PF VADC V- V+ V- Figure 1. Schematic 2 AN–1932 LMP2021MAEVAL - Bridge Sensor Instrumentation Amplifier Evaluation Board SNOA537A – December 2008 – Revised April 2013 Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Amplifier Gain www.ti.com Figure 2. PCB Top Figure 3. PCB Bottom SNOA537A – December 2008 – Revised April 2013 Submit Documentation Feedback AN–1932 LMP2021MAEVAL - Bridge Sensor Instrumentation Amplifier Evaluation Board Copyright © 2008–2013, Texas Instruments Incorporated 3 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. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 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