SBVS204F June   2012  – September 2014


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Internal Current Limit (ICL)
      2. 7.3.2 Enable (EN) And Under-Voltage Lockout (UVLO)
      3. 7.3.3 Soft-Start And Inrush Current
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
      1. 7.5.1 ANY-OUT Programmable Output Voltage
      2. 7.5.2 Adjustable Operation (TPS7A4701 Only)
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. Capacitor Recommendations
          1. Input and Output Capacitor Requirements
          2. Noise Reduction Capacitor (CNR)
        2. Dropout Voltage (VDO)
        3. Output Voltage Accuracy
        4. Startup
        5. AC Performance
          1. Power-Supply Rejection Ratio (PSRR)
          2. Load Step Transient Response
          3. Noise
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
    1. 9.1 Power Dissipation (PD)
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Protection
    4. 10.4 Estimating Junction Temperature
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Related Links
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

9 Power Supply Recommendations

The device is designed to operate from an input voltage supply range of 3 V to 35 V. If the input supply is noisy, additional input capacitors with low ESR can help improve the output noise performance.

9.1 Power Dissipation (PD)

Power dissipation must be considered in the PCB design. In order to minimize risk of device operation above 125°C, use as much copper area as available for thermal dissipation. Do not locate other power-dissipating devices near the LDO.

Power dissipation in the regulator depends on the input to output voltage difference and load conditions. PD can be calculated using Equation 7:

Equation 7. q_pd_bvs204.gif

It is important to note that power dissipation can be minimized, and thus greater efficiency achieved, by proper selection of the system voltage rails. Proper selection allows the minimum input voltage necessary for output regulation to be obtained.

The primary heat conduction path for the QFN (RGW) package is through the thermal pad to the PCB. The thermal pad must be soldered to a copper pad area under the device. Thermal vias are recommended to improve the thermal conduction to other layers of the PCB.

The maximum power dissipation determines the maximum allowable junction temperature (TJ) for the device. Power dissipation and junction temperature are most often related by the junction-to-ambient thermal resistance (θJA) of the combined PCB and device package and the temperature of the ambient air (TA), according to Equation 8.

Equation 8. q_tj_bvs204.gif

Unfortunately, this thermal resistance (θJA) depends primarily on the heat-spreading capability built into the particular PCB design, and therefore varies according to the total copper area, copper weight, and location of the spreading planes. The θJA recorded in the Thermal Information table is determined by the JEDEC standard, PCB, and copper-spreading area and is to be used only as a relative measure of package thermal performance. Note that for a well-designed thermal layout, θJA is actually the sum of the QFN package junction-to-case (bottom) thermal resistance (θJCbot) plus the thermal resistance contribution by the PCB copper. By knowing θJCbot, the minimum amount of appropriate heat sinking can be used to estimate θJA with Figure 27. θJCbot can be found in the Thermal Information table.

NOTE: θJA value at a board size of 9-in2 (that is, 3-in × 3-in) is a JEDEC standard.
Figure 27. ΘJA vs Board Size