SBVS415A april   2023  – july 2023 TPS7A96

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Output Voltage Setting and Regulation
      2. 7.3.2 Ultra-Low Noise and Ultra-High Power-Supply Rejection Ratio (PSRR)
      3. 7.3.3 Programmable Current Limit and Power-Good Threshold
      4. 7.3.4 Programmable Soft-Start (NR/SS Pin)
      5. 7.3.5 Precision Enable and UVLOs
      6. 7.3.6 Active Discharge
      7. 7.3.7 Thermal Shutdown Protection (TSD)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Normal Operation
      2. 7.4.2 Dropout Operation
      3. 7.4.3 Disabled
      4. 7.4.4 Current-Limit Operation
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1  Output Voltage Restart (Overshoot Prevention Circuit)
      2. 8.1.2  Precision Enable (External UVLO)
      3. 8.1.3  Undervoltage Lockout (UVLO) Operation
      4. 8.1.4  Dropout Voltage (VDO)
      5. 8.1.5  Power-Good Feedback (FB_PG Pin) and Power-Good Threshold (PG Pin)
      6. 8.1.6  Adjusting the Factory-Programmed Current Limit
      7. 8.1.7  Programmable Soft-Start and Noise-Reduction (NR/SS Pin)
      8. 8.1.8  Inrush Current
      9. 8.1.9  Optimizing Noise and PSRR
      10. 8.1.10 Adjustable Operation
      11. 8.1.11 Paralleling for Higher Output Current and Lower Noise
      12. 8.1.12 Recommended Capacitor Types
      13. 8.1.13 Load Transient Response
      14. 8.1.14 Power Dissipation (PD)
      15. 8.1.15 Estimating Junction Temperature
      16. 8.1.16 TPS7A96EVM-106 Thermal Analysis
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Development Support
        1. 9.1.1.1 Evaluation Modules
        2. 9.1.1.2 Spice Models
      2. 9.1.2 Device Nomenclature
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

8.1.9 Optimizing Noise and PSRR

Noise can be generally defined as any unwanted signal combining with the desired signal (such as the regulated LDO output). Noise can easily be noticed in audio as a hissing or popping sound. Noise produced from an external circuit or the 50- to 60-hertz power-line noise (spikes), along with the harmonics, is an excellent representative of extrinsic noise. Intrinsic noise is produced by components within the device circuitry, such as resistors and transistors. The two dominating sources of intrinsic noise are the error amplifier and the internal reference voltage (VNR/SS). Extrinsic noise, including the switching mode power-supply ac ripple voltage, coupled onto the input supply of the LDO is attenuated by the LDO power-supply rejection ratio, or PSRR. PSRR is a measurement of the noise attenuation from the input to the output of the LDO.

Optimize the intrinsic noise and PSRR by carefully selecting:

  • CNR/SS for the low-frequency range up to the device bandwidth
  • COUT for the high-frequency range close to and higher than the device bandwidth
  • Operating headroom, VIN – VOUT (VDO), mainly for the low-frequency range up to the device bandwidth, but also for higher frequencies to a lesser effect

These behaviors are described in the Typical Characteristics curves.

Figure 8-14 shows the measured PSRR for a 1.2-V device output voltage with a 0.7-V headroom for 1-A, 1.5-A, and 2-A load currents. Table 8-3 lists the typical output noise for these capacitors.

GUID-20230629-SS0I-H5CG-XX3N-Q3LRKNF6ZFDS-low.svg Figure 8-14 PSRR vs Frequency and IOUT for VOUT = 1.2 V, COUT = 10 μF
Table 8-3 Typical Output Noise for 1.2-VOUT vs CNR/SS, COUT, and Typical Start-Up Time
Vn (μVRMS), 10-Hz to 100-kHz BW CNR/SS (µF) COUT (µF) START-UP TIME (ms)
0.98 1 10 3.73
0.62 2.2 10 6.21
0.489 4.7 10 13.97
0.42 10 10 28.21

PSRR can be viewed as being simply the ratio of the output capacitor impedance by the LDO output impedance. At low frequency, the output impedance is very low whereas the output impedance of the capacitor is high, resulting in high PSRR. As the frequency increases, the output capacitor impedance reduces and reaches a minima set by the ESR.

As given in Figure 8-14, to achieve high PSRR at high frequencies, make sure that the output capacitor equivalent series resistance (ESR) and equivalent series inductance (ESL) are minimal. This figure shows how to use a single 10-μF output capacitor implementation. However, minimizing the ESR- and ESL-generated resonance point in the output capacitance allows for a smoother transition between the LDO active PSRR component to the passive PSRR of the capacitors, therefore using output capacitors in parallel helps above 200 kHz, improving the PSRR by 5 dB to 7 dB.

Note:

The TPS7A96 is optimized for the 1-A to 2-A output current range. For current below this range, consider the TPS7A94 device.