SBOU268 November   2021 OPA593

 

  1.   Trademarks
  2. 1Overview
    1. 1.1 Getting Started
      1. 1.1.1 Related Documentation From Texas Instruments
    2. 1.2 High-Voltage Warning and Safe Use
    3. 1.3 Electrostatic Discharge Caution
  3. 2Operation
    1. 2.1 Jumper Blocks, Jacks, and Test Points
    2. 2.2 Inputs
    3. 2.3 Outputs
    4. 2.4 Enable or Disable
    5. 2.5 Status Flags
      1. 2.5.1 Circuit Protection
  4. 3Application Circuits
    1. 3.1 Setting Dual-Supply or Single-Supply Operation
      1. 3.1.1 Dual-Supply Operation Configuration
      2. 3.1.2 Single-Supply Operation Configuration
    2. 3.2 Common Op-Amp Configurations
      1. 3.2.1 Inverting Gain of –10 V/V
        1. 3.2.1.1 External Connections for –10 V/V Inverting Gain Configuration
        2. 3.2.1.2 Inverting Gain of –10 V/V Configuration Electrical Performance
      2. 3.2.2 Noninverting Gain of +2 V/V
        1. 3.2.2.1 External Connections to OPA593EVM for Noninverting Gain Configuration
        2. 3.2.2.2 Noninverting Gain Configuration Electrical Performance
      3. 3.2.3 Gain of +10 V/V Difference Amplifier
        1. 3.2.3.1 Jumper Shunt Locations for Difference-Amplifier Configuration
        2. 3.2.3.2 Gain of 10 V/V Difference Amplifier Configuration Electrical Performance
      4. 3.2.4 Improved Howland Current Pump
        1. 3.2.4.1 Jumper Shunt Locations for Improved Howland Current Pump Configuration
  5. 4Schematic, PCB Layout, and Bill of Materials
    1. 4.1 EVM Schematic
      1. 4.1.1 EVM Default Configuration
    2. 4.2 PCB Layout
    3. 4.3 Bill of Materials

3.2.4 Improved Howland Current Pump

The OPA593EVM can be configured as an improved Howland current pump that provides a transconductance amplifier function, sometimes called a V‑to‑I converter. Configuring the V‑to‑I converter with the EVM requires that one resistor, Riso2 (a wide 2512 size), be changed on the EVM PCB from 0 Ω to 49.9 Ω (2 W). If a different output current range is required, this resistor may need to be a different value. Equation 4 shows the Riso2 relationship to the output current.

Additionally, Rhcp1 (a 0805-size, 10-kΩ resistor) must be installed at that location on the PCB. Rhcp1 resides just above C12, and up and to the right of the current-limit set resistor shorting blocks JP12 through JP16.

Connect jumper shunts as listed in Table 3-4 to configure the OPA593 as an improved Howland current pump. The jumper shunt installations are illustrated in Figure 3-4. The jumper shunts are designated in the BOM as a shunt and have an SH-J# part designator. The jumper shunts appear in the schematic as the red jumpers connected across the various JP# jumper blocks.

Table 3-4 Jumper Shunt Connections for an Improved Howland Current Pump
Jumper Number Jumper Shunt Connects Notes
JP1 VIN– J5 to OPA593 –IN pin, through Ri1 (10 kΩ)
JP6 VIN+ J9 to OPA593 noninverting input through R4 (10 kΩ)
JP9 R8 (10 kΩ) from OPA593 noninverting input to GND
JP11 Open Enabled mode
JP13 Sets current limit to 100 mA
JP17 E/D Com pin E/D Com pin selection GND
JP18 RF1 (10 kΩ) inserted in OPA593 feedback path
JP21 Open IOUT flows through external load
Figure 3-4 OPA593EVM Jumper Shunt Locations for an Improved Howland Current Pump