Datasheet UC1846, UC1847, UC2846 UC2847, UC3846, UC3847 (Texas Instruments) - 9
| Manufacturer | Texas Instruments |
| Description | UCx846/7 Current Mode PWM Controller |
| Pages / Page | 24 / 9 — UC1846,. UC1847. , UC2846. UC2847,. UC3846. , UC3847. www.ti.com. Feature … |
| File Format / Size | PDF / 1.3 Mb |
| Document Language | English |
UC1846,. UC1847. , UC2846. UC2847,. UC3846. , UC3847. www.ti.com. Feature Description (continued)
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Text Version of Document
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UC1846, UC1847 , UC2846 UC2847, UC3846 , UC3847 www.ti.com
SLUS352C – JANUARY 1997 – REVISED DECEMBER 2015
Feature Description (continued)
A small RC filter may be required in some applications to reduce switch transients. Differential input allows remote, noise free sensing.
Figure 3. Current Sense Amplifier Connection 7.3.2 Oscillator
By implementing the oscillator using all NPN transistors, the UCx846/7 achieves excellent temperature stability and waveform clarity at frequencies in excess of 1 MHz. Referring to Figure 4, an external resistor RT is used to generate a constant current into a capacitor CT to produce a linear sawtooth waveform. Oscillator frequency may be approximated by selecting RT and CT such that: 2.2 OS f C RTCT (1)
Figure 4. Oscillator Circuit
Copyright © 1997–2015, Texas Instruments Incorporated Submit Documentation Feedback 9 Product Folder Links: UC1846 UC1847 UC2846 UC2847 UC3846 UC3847 Document Outline 1 Features 2 Applications 3 Description Table of Contents 4 Revision History 5 Pin Configuration and Functions 6 Specifications 6.1 Absolute Maximum Ratings 6.2 ESD Ratings 6.3 Recommended Operating Conditions 6.4 Thermal Information 6.5 Electrical Characteristics 6.6 Typical Characteristics 7 Detailed Description 7.1 Overview 7.2 Functional Block Diagram 7.3 Feature Description 7.3.1 Current Sense Amplifier 7.3.2 Oscillator 7.4 Device Functional Modes 7.4.1 Current Limit 7.4.2 Shutdown 8 Application and Implementation 8.1 Application Information 8.2 Typical Application 8.2.1 Design Requirements 8.2.2 Detailed Design Procedure 8.2.2.1 Design Switching Frequency 8.2.2.2 Error Amplifier Output Configuration 8.2.2.3 Parallel Operation Configuration 8.2.2.4 Design Pulse by Pulse Current Limit Threshold 8.2.2.5 Soft-Start and Shutdown, Restart Function Design 8.2.3 Application Curves 9 Power Supply Recommendations 10 Layout 10.1 Layout Guidelines 10.2 Layout Example 11 Device and Documentation Support 11.1 Related Links 11.2 Community Resources 11.3 Trademarks 11.4 Electrostatic Discharge Caution 11.5 Glossary 12 Mechanical, Packaging, and Orderable Information
UC1846, UC1847 , UC2846 UC2847, UC3846 , UC3847 www.ti.com
SLUS352C – JANUARY 1997 – REVISED DECEMBER 2015
Feature Description (continued)
A small RC filter may be required in some applications to reduce switch transients. Differential input allows remote, noise free sensing.
Figure 3. Current Sense Amplifier Connection 7.3.2 Oscillator
By implementing the oscillator using all NPN transistors, the UCx846/7 achieves excellent temperature stability and waveform clarity at frequencies in excess of 1 MHz. Referring to Figure 4, an external resistor RT is used to generate a constant current into a capacitor CT to produce a linear sawtooth waveform. Oscillator frequency may be approximated by selecting RT and CT such that: 2.2 OS f C RTCT (1)
Figure 4. Oscillator Circuit
Copyright © 1997–2015, Texas Instruments Incorporated Submit Documentation Feedback 9 Product Folder Links: UC1846 UC1847 UC2846 UC2847 UC3846 UC3847 Document Outline 1 Features 2 Applications 3 Description Table of Contents 4 Revision History 5 Pin Configuration and Functions 6 Specifications 6.1 Absolute Maximum Ratings 6.2 ESD Ratings 6.3 Recommended Operating Conditions 6.4 Thermal Information 6.5 Electrical Characteristics 6.6 Typical Characteristics 7 Detailed Description 7.1 Overview 7.2 Functional Block Diagram 7.3 Feature Description 7.3.1 Current Sense Amplifier 7.3.2 Oscillator 7.4 Device Functional Modes 7.4.1 Current Limit 7.4.2 Shutdown 8 Application and Implementation 8.1 Application Information 8.2 Typical Application 8.2.1 Design Requirements 8.2.2 Detailed Design Procedure 8.2.2.1 Design Switching Frequency 8.2.2.2 Error Amplifier Output Configuration 8.2.2.3 Parallel Operation Configuration 8.2.2.4 Design Pulse by Pulse Current Limit Threshold 8.2.2.5 Soft-Start and Shutdown, Restart Function Design 8.2.3 Application Curves 9 Power Supply Recommendations 10 Layout 10.1 Layout Guidelines 10.2 Layout Example 11 Device and Documentation Support 11.1 Related Links 11.2 Community Resources 11.3 Trademarks 11.4 Electrostatic Discharge Caution 11.5 Glossary 12 Mechanical, Packaging, and Orderable Information
