SBOS850 December 2017 OPA192-Q1 , OPA2192-Q1
PRODUCTION DATA.
- 1 Features
- 2 Applications
- 3 Description
- 4 Revision History
- 5 Pin Configuration and Functions
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6 Specifications
- 6.1 Absolute Maximum Ratings
- 6.2 ESD Ratings
- 6.3 Recommended Operating Conditions
- 6.4 Thermal Information: OPA192-Q1
- 6.5 Thermal Information: OPA2192-Q1
- 6.6 Electrical Characteristics: VS = ±4 V to ±18 V (VS = 8 V to 36 V)
- 6.7 Electrical Characteristics: VS = ±2.25 V to ±4 V (VS = 4.5 V to 8 V)
- 6.8 Typical Characteristics
- 6.9 Typical Characteristics
- 7 Parameter Measurement Information
- 8 Detailed Description
- 9 Application and Implementation
- 10Power-Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information
9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
9.1 Application Information
The OPAx192-Q1 family offers outstanding dc precision and ac performance. These devices operate up to 36-V supply rails and offer true rail-to-rail input and output, ultra-low offset voltage and offset voltage drift, as well as
10-MHz bandwidth and high capacitive load drive. These features make the OPAx192-Q1 a robust, high-performance operational amplifier for high-voltage industrial applications.
9.2 Typical Applications
9.2.1 16-Bit Precision Multiplexed Data-Acquisition System
Figure 61 shows a 16-bit, differential, 4-channel, multiplexed data-acquisition system. This example is typical in industrial applications that require low distortion and a high-voltage differential input. The circuit uses the ADS8864, a 16-bit, 400-kSPS successive-approximation-resistor (SAR) analog-to-digital converter (ADC), along with a precision, high-voltage, signal-conditioning front end, and a 4-channel differential multiplexer (mux). This TI Precision Design details the process for optimizing the precision, high-voltage, front-end drive circuit using the OPAx192-Q1 and OPA140 to achieve excellent dynamic performance and linearity with the ADS8864.
Figure 61. OPAx192-Q1 in 16-Bit, 400-kSPS, 4-Channel, Multiplexed Data Acquisition System for High-Voltage Inputs With Lowest Distortion
9.2.1.1 Design Requirements
The primary objective is to design a ±20 V, differential 4-channel multiplexed data acquisition system with lowest distortion using the 16-bit ADS8864 at a throughput of 400 kSPS for a 10 kHz full-scale pure sine-wave input. The design requirements for this block design are:
- System Supply Voltage: ±15 V
- ADC Supply Voltage: 3.3 V
- ADC Sampling Rate: 400 kSPS
- ADC Reference Voltage (REFP): 4.096 V
- System Input Signal: A high-voltage differential input signal with a peak amplitude of 10 V and frequency (fIN) of 10 kHz are applied to each differential input of the mux.
9.2.1.2 Detailed Design Procedure
The purpose of this precision design is to design an optimal high voltage multiplexed data acquisition system for highest system linearity and fast settling. The overall system block diagram is illustrated in Figure 61. The circuit is a multichannel data acquisition signal chain consisting of an input low-pass filter, multiplexer (mux), mux output buffer, attenuating SAR ADC driver, digital counter for mux and the reference driver. The architecture allows fast sampling of multiple channels using a single ADC, providing a low-cost solution. The two primary design considerations to maximize the performance of a precision multiplexed data acquisition system are the mux input analog front-end and the high-voltage level translation SAR ADC driver design. However, carefully design each analog circuit block based on the ADC performance specifications in order to achieve the fastest settling at 16-bit resolution and lowest distortion system. The diagram includes the most important specifications for each individual analog block.
This design systematically approaches each analog circuit block to achieve a 16-bit settling for a full-scale input stage voltage and linearity for a 10-kHz sinusoidal input signal at each input channel. The first step in the design is to understand the requirement for extremely low impedance input-filter design for the mux. This understanding helps in the decision of an appropriate input filter and selection of a mux to meet the system settling requirements. The next important step is the design of the attenuating analog front-end (AFE) used to level translate the high-voltage input signal to a low-voltage ADC input when maintaining amplifier stability. The next step is to design a digital interface to switch the mux input channels with minimum delay. The final design challenge is to design a high-precision, reference-driver circuit that provides the required REFP reference voltage with low offset, drift, and noise contributions.
9.2.1.3 Application Curve
Figure 62. ADC 16-Bit Linearity Error for the Multiplexed Data Acquisition Block
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For step-by-step design procedure, circuit schematics, bill of materials, PCB files, simulation results, and test results, refer to TI Precision Design TIDU181, 16-bit, 400-kSPS, 4-Channel, Multiplexed Data Acquisition System for High Voltage Inputs with Lowest Distortion. |
9.2.2 Slew Rate Limit for Input Protection
In control systems for valves or motors, abrupt changes in voltages or currents can cause mechanical damages. By controlling the slew rate of the command voltages into the drive circuits, the load voltages ramps up and down at a safe rate. For symmetrical slew-rate applications (positive slew rate equals negative slew rate), one additional op amp provides slew-rate control for a given analog gain stage. The unique input protection and high output current and slew rate of the OPAx192-Q1 make the device an optimal amplifier to achieve slew rate control for both dual- and single-supply systems.Figure 63 shows the OPAx192-Q1 in a slew-rate limit design.
Figure 63. Slew Rate Limiter Uses One Op Amp
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For step-by-step design procedure, circuit schematics, bill of materials, PCB files, simulation results, and test results, see TI Precision Design TIDU026, Slew Rate Limiter Uses One Op Amp. |
9.2.3 Precision Reference Buffer
The OPAx192-Q1 features high output current drive capability and low input offset voltage, making the device an excellent reference buffer to provide an accurate buffered output with ample drive current for transients. For the 10-µF ceramic capacitor shown in Figure 64, RISO, a 37.4-Ω isolation resistor, provides separation of two feedback paths for optimal stability. Feedback path number one is through RF and is directly at the output (VOUT). Feedback path number two is through RFx and CF and is connected at the output of the op amp. The optimized stability components shown for the 10-µF load give a closed-loop signal bandwidth at VOUT of 4 kHz and still provides a loop gain phase margin of 89°. Any other load capacitances require recalculation of the stability components: RF, RFx , CF , and RISO.
Figure 64. Precision Reference Buffer