SLUSDW9A June 2020 – June 2020 TPS51215A
PRODUCTION DATA.
- 1 Features
- 2 Applications
- 3 Description
- 4 Revision History
- 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 Switch Mode Power Supply Control
- 7.3.2 VREF, V0, V1, V2, V3 and Output Voltage
- 7.3.3 Soft-Start and Power Good
- 7.3.4 SLEW and VID Function
- 7.3.5 MODE Pin Configuration
- 7.3.6 Light-Load Operation
- 7.3.7 Out-of-Bound Operation
- 7.3.8 Current Sensing and Overcurrent Protection
- 7.3.9 Overvoltage and Undervoltage Protection
- 7.3.10 V5IN Undervoltage Lockout Protection
- 7.3.11 Thermal Shutdown
- 7.4 D-CAP2 Control Mode
- 8 Application and Implementation
-
9 Typical Applications
- 9.1 Design Requirements
- 9.2
Detailed Design Procedure
- 9.2.1 Step One: Determine the Specifications
- 9.2.2 Step Two: Determine System Parameters
- 9.2.3 Step Three: Determine Inductor Value and Choose Inductor
- 9.2.4 Step Four: Set the Output Voltages
- 9.2.5 Step Five: Calculate SLEW Capacitance
- 9.2.6 Step Six
- 9.2.7 Step Seven: Determine the Output Capacitance
- 9.2.8 Step Eight: Select Decoupling and Peripheral Components
- 9.3 Application Examples
- 9.4 Application Curves of Design 1
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information
9.2.5 Step Five: Calculate SLEW Capacitance
SLEW can be used to program the soft-start time and voltage transition timing. During soft-start operation, the current source used to program the SLEW rate is 4.5 µA (nominal). During VID transition, the current source is switched to a higher current of 45 µA.
In this design example, the requirement is to complete VID_00 to VID_11 transition within 120 µs, calculate the SLEW capacitance based on Equation 8.
Equation 8. 
For VOUT = 1.8 V, the soft start timing based on CSLEW is 1.2 ms.
The slower slew rate is desired to minimize large inductor current perturbation during startup and voltage transition, thus reducing the possibility of acoustic noise.