SBOS724A September   2015  – June 2022 OPA1688

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 EMI Rejection
      2. 8.3.2 Phase-Reversal Protection
      3. 8.3.3 Capacitive Load and Stability
    4. 8.4 Device Functional Modes
      1. 8.4.1 Common-Mode Voltage Range
      2. 8.4.2 Electrical Overstress
      3. 8.4.3 Overload Recovery
  9. 9 Applications and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Headphone Amplifier Circuit Configuration
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
        1. 12.1.1.1 PSpice® for TI
        2. 12.1.1.2 TINA-TI™ Simulation Software (Free Download)
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Support Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9.2.1.3 Application Curves

The headphone amplifier circuit in Figure 9-1 is tested with three common headphone impedances: 16 Ω, 32 Ω, and 600 Ω. The total harmonic distortion and noise (THD+N) for increasing output voltages is given in Figure 9-3. This measurement is performed with a 1-kHz input signal and a measurement bandwidth of 22.4 kHz. The maximum output power and THD+N before clipping are given in Table 9-1. The maximum output power into low-impedance headphones is limited by the output current capabilities of the amplifier. For high-impedance headphones (600 Ω), the output voltage capabilities of the amplifier are the limiting factor. The circuit in Figure 9-1 is tested using ±5-V supplies that are common in many portable systems. However, using higher supply voltages increases the output power into 600-Ω headphones.

GUID-F5582664-0A4A-4F34-9910-BD97FFDDA7B0-low.png
Input signal = 1 kHz, measurement bandwidth = 22.4 kHz
Figure 9-3 THD+N for Increasing Output Voltages Into Three Load Impedances
Table 9-1 Maximum Output Power and THD+N Before Clipping for Different Load Impedances
LOAD IMPEDANCE (Ω)MAXIMUM OUTPUT POWER BEFORE CLIPPING (mW)THD+N AT MAXIMUM OUTPUT POWER (dB)
1632–104.1
3250–109.5
60016–117.8

Figure 9-4, Figure 9-5, and Figure 9-6 further illustrate the exceptional performance of the OPA1688 as a headphone amplifier.

Figure 9-4 shows the THD+N over frequency for a 500-mVRMS output signal into the same three load impedances previously tested.

GUID-C1A9D1B6-A0E6-4466-86F1-E0D6AB31EDCE-low.png
90-kHz measurement bandwidth
Figure 9-4 THD+N Measured over Frequency for a 500-mVRMS Output Level

Figure 9-5 and Figure 9-6 show the output spectrum of the OPA1688 at low (1 mW) and high (50 mW) output power levels into a 32-Ω load. The distortion harmonics in both cases are approximately 120 dB below the fundamental.

GUID-74BF5EBC-4478-4C9A-83BA-A2B6E11581C1-low.png
Third harmonic is dominant at a level of –117.6 dB relative to the fundamental
Figure 9-5 Output Spectrum of a 1-mW, 1-kHz Tone into a 32-Ω Load
GUID-2EC742E7-31EF-47D0-9882-D3C37A9B5435-low.png
Highest harmonic is the second harmonic at –119 dB below the fundamental
Figure 9-6 Output Spectrum of a 50‑mW, 1‑kHz Tone Into a 32‑Ω Load, Immediately Below the Onset of Clipping