SBVS125D August   2010  – June 2015 TPS7A30

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Internal Current Limit
      2. 8.3.2 Programmable Soft-Start
      3. 8.3.3 Enable Pin Operation
    4. 8.4 Device Functional Modes
      1. 8.4.1 Normal Operation
      2. 8.4.2 Dropout Operation
      3. 8.4.3 Disabled
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Adjustable Operation
      2. 9.1.2 Capacitor Recommendations
        1. 9.1.2.1 Input and Output Capacitor Requirements
        2. 9.1.2.2 Noise-Reduction and Feed-Forward Capacitor Requirements
      3. 9.1.3 Maximum AC Performance
      4. 9.1.4 Output Noise
      5. 9.1.5 Power-Supply Rejection
      6. 9.1.6 Transient Response
      7. 9.1.7 Post DC-DC Converter Filtering
      8. 9.1.8 Audio Applications
      9. 9.1.9 Power for Precision Analog
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
    3. 9.3 Do's and Don’ts
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Board Layout Recommendations to Improve PSRR and Noise Performance
    2. 11.2 Layout Examples
    3. 11.3 Thermal Considerations
    4. 11.4 Power Dissipation
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
        1. 12.1.1.1 Evaluation Modules
        2. 12.1.1.2 Spice Models
      2. 12.1.2 Device Nomenclature
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

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8 Detailed Description

8.1 Overview

The TPS7A30 family of devices are wide VIN, low-noise, 150-mA linear regulators (LDOs). These devices feature an enable pin, programmable soft-start, current limiting, and thermal protection circuitry that allow the device to be used in a wide variety of applications. As bipolar-based devices, the TPS7A30 devices are ideal for high-accuracy, high-precision applications at higher voltages.

8.2 Functional Block Diagram

TPS7A30 fbd_bvs125.gif

8.3 Feature Description

8.3.1 Internal Current Limit

The fixed internal current limit of the TPS7A30 family helps protect the regulator during fault conditions. The maximum amount of current the device can source is the current limit (330 mA, typical), and is largely independent of the output voltage. For reliable operation, do not operate the device in current limit for extended periods of time.

8.3.2 Programmable Soft-Start

The NR/SS capacitor also functions as a soft-start capacitor to slow down the rise time of the output. The rise time of the output when using an NR/SS capacitor is governed by Equation 1. In Equation 1, tSS is the soft-start time in milliseconds and CNR/SS is the capacitance at the NR pin in nanofarads. Figure 29 shows the relationship between the CNR/SS size and the start-up time without a CFF.

Equation 1. TPS7A30 q_tss_cnr_bvs125.gif
TPS7A30 D001_SBVS125.gifFigure 29. Soft-Start Time vs CNR/SS

8.3.3 Enable Pin Operation

The TPS7A30 provides a dual-polarity enable pin (EN) that turns on the regulator when |VEN| > 2 V, whether the voltage is positive or negative, as shown in Figure 30.

This functionality allows for different system power management topologies:

  • Connecting the EN pin directly to a negative voltage (such as VIN).
  • Connecting the EN pin directly to a positive voltage, such as the output of digital logic circuitry.

TPS7A30 ai_threshold_bvs125.gifFigure 30. Enable Pin Positive and Negative Threshold

8.4 Device Functional Modes

8.4.1 Normal Operation

The device regulates to the nominal output voltage under the following conditions:

  • The input voltage is at least as high as the |VIN(min)|.
  • The input voltage magnitude is greater than the nominal output voltage magnitude added to the dropout voltage.
  • |VEN| > |V(HI)|.
  • The output current is less than the current limit.
  • The device junction temperature is less than the maximum specified junction temperature.

8.4.2 Dropout Operation

If the input voltage magnitude is lower than the nominal output voltage magnitude plus the specified dropout voltage magnitude, but all other conditions are met for normal operation, the device operates in dropout mode. In this mode of operation, the output voltage magnitude is the same as the input voltage magnitude minus the dropout voltage magnitude. The transient performance of the device is significantly degraded because the pass device (such as a bipolar junction transistor, or BJT) is in saturation and no longer controls the current through the LDO. Line or load transients in dropout can result in large output voltage deviations.

8.4.3 Disabled

The device is disabled under the following conditions:

  • |VEN| < |V(HI)|.
  • The device junction temperature is greater than the thermal shutdown temperature.

Table 1 shows the conditions that lead to the different modes of operation.

Table 1. Device Functional Mode Comparison

OPERATING MODE PARAMETER
VIN VEN IOUT TJ
Normal mode |VIN| > { |VOUT(nom)| + |VDO|, |VIN(min)| } |VEN| > |V(HI)| I OUT < ICL T J < 125°C
Dropout mode |VIN(min)| < |VIN| < |VOUT(nom)| + |VDO| |VEN| > |V(HI)| — TJ < 125°C
Disabled mode
(any true condition disables the device)		 — |VEN| < |V(LO)| — TJ > 170°C