SLUS772G March 2008 – June 2020 TPS40210 , TPS40211
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 Soft Start
- 7.3.2 BP Regulator
- 7.3.3 Shutdown (DIS/ EN Pin)
- 7.3.4 Minimum On-Time and Off-Time Considerations
- 7.3.5 Setting the Oscillator Frequency
- 7.3.6 Synchronizing the Oscillator
- 7.3.7 Current Sense and Overcurrent
- 7.3.8 Current Sense and Subharmonic Instability
- 7.3.9 Current Sense Filtering
- 7.3.10 Control Loop Considerations
- 7.3.11 Gate Drive Circuit
- 7.3.12 TPS40211
- 7.4 Device Functional Modes
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Applications
- 8.2.1
12-V to 24-V Nonsynchronous Boost Regulator
- 8.2.1.1 Design Requirements
- 8.2.1.2
Detailed Design Procedure
- 8.2.1.2.1 Custom Design with WEBENCH Tools
- 8.2.1.2.2 Duty Cycle Estimation
- 8.2.1.2.3 Inductor Selection
- 8.2.1.2.4 Rectifier Diode Selection
- 8.2.1.2.5 Output Capacitor Selection
- 8.2.1.2.6 Input Capacitor Selection
- 8.2.1.2.7 Current Sense and Current Limit
- 8.2.1.2.8 Current Sense Filter
- 8.2.1.2.9 Switching MOSFET Selection
- 8.2.1.2.10 Feedback Divider Resistors
- 8.2.1.2.11 Error Amplifier Compensation
- 8.2.1.2.12 RC Oscillator
- 8.2.1.2.13 Soft-Start Capacitor
- 8.2.1.2.14 Regulator Bypass
- 8.2.1.2.15 Bill of Materials
- 8.2.1.3 Application Curves
- 8.2.2 12-V Input, 700-mA LED Driver, Up to 35-V LED String
- 8.2.1
12-V to 24-V Nonsynchronous Boost Regulator
- 9 Power Supply Recommendations
- 10Layout
- 11Device and Documentation Support
- 12Mechanical, Packaging, and Orderable Information
7.3.9 Current Sense Filtering
In most cases, a small filter placed on the ISNS pin improves performance of the converter. These are the components RIFLT and CIFLT in Figure 7-7. The time constant of this filter should be approximately 10% of the nominal pulse width of the converter. The pulse width can be found using Equation 20.
Equation 20. 
The suggested time constant is then
Equation 21. 
The range of RIFLT should be from about 1 kΩ to 5 kΩ for best results. Higher values can be used but this raises the impedance of the ISNS pin connection more than necessary and can lead to noise pickup issues in some layouts. CIFLT should be located as close as possible to the ISNS pin as well to provide noise immunity.