SNVSCH7 February 2024 LMR38025
PRODUCTION DATA
- 1
- 1 Features
- 2 Applications
- 3 Description
- 4 Device Comparison Table
- 5 Pin Configuration and Functions
- 6 Specifications
-
7 Detailed Description
- 7.1 Overview
- 7.2 Functional Block Diagram
- 7.3
Feature Description
- 7.3.1 Fixed Frequency Peak Current Mode Control
- 7.3.2 Adjustable Output Voltage
- 7.3.3 Enable
- 7.3.4 Switching Frequency and Synchronization (RT/SYNC)
- 7.3.5 Power-Good Flag Output
- 7.3.6 Minimum On Time, Minimum Off Time, and Frequency Foldback
- 7.3.7 Bootstrap Voltage
- 7.3.8 Overcurrent and Short-Circuit Protection
- 7.3.9 Soft Start
- 7.3.10 Thermal Shutdown
- 7.4 Device Functional Modes
- 8 Application and Implementation
- 9 Device and Documentation Support
- 10Revision History
- 11Mechanical, Packaging, and Orderable Information
7.3.2 Adjustable Output Voltage
A precision 1.0V reference voltage (VREF) is used to maintain a tightly regulated output voltage over the entire operating temperature range. The output voltage is set by a resistor divider from the output voltage to the FB pin. TI recommends to use 1% tolerance resistors with a low temperature coefficient for the FB divider. Select the bottom-side resistor RFBB for the desired divider current and use Equation 1 to calculate the top-side resistor RFBT. TI recommends RFBT in the range from 10kΩ to 100kΩ for most applications. A lower RFBT value can be used if static loading is desired to reduce VOUT offset in PFM operation. Lower RFBT reduces efficiency at very light load. Less static current goes through a larger RFBT and can be more desirable when light-load efficiency is critical. TI does not recommend RFBT larger than 1MΩ because RFBT larger than 1MΩ makes the feedback path more susceptible to noise. Larger RFBT values require more carefully designed feedback path on the PCB. The tolerance and temperature variation of the resistor dividers affect the output voltage regulation.
Figure 7-1 Output Voltage Setting