SLUSD71A
April 2018 – May 2018
UCC28742
PRODUCTION DATA.
1
Features
2
Applications
3
Description
Device Images
Simplified Schematic
Typical Efficiency of a 10-W, 5-V AC-to-DC Converter
4
Revision History
5
Pin Configuration and Functions
Pin 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
Detailed Pin Description
7.3.1.1
VDD (Device Bias Voltage Supply)
7.3.1.2
GND (Ground)
7.3.1.3
VS (Voltage-Sense)
7.3.1.4
DRV (Gate Drive)
7.3.1.5
CS (Current Sense)
7.3.1.6
FB (Feedback)
7.3.2
Secondary-Side Optically Coupled Constant-Voltage (CV) Regulation
7.3.3
Control Law
7.3.4
Constant Current Limit and Delayed Shutdown
7.3.5
Valley-Switching and Valley-Skipping
7.3.6
Start-Up Operation
7.3.7
Fault Protection
7.4
Device Functional Modes
8
Applications 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
Custom Design With WEBENCH® Tools
8.2.2.2
VDD Capacitance, CDD
8.2.2.3
VDD Start-Up Resistance, RSTR
8.2.2.4
Input Bulk Capacitance and Minimum Bulk Voltage
8.2.2.5
Transformer Turns Ratio, Inductance, Primary-Peak Current
8.2.2.6
Transformer Parameter Verification
8.2.2.7
VS Resistor Divider and Line Compensation
8.2.2.8
Standby Power Estimate
8.2.2.9
Output Capacitance
8.2.2.10
Feedback Loop Design Consideration
8.2.3
Application Curves
8.3
Do's and Don'ts
9
Power Supply Recommendations
10
Layout
10.1
Layout Guidelines
10.2
Layout Example
11
Device and Documentation Support
11.1
Device Support
11.1.1
Development Support
11.1.1.1
Custom Design With WEBENCH® Tools
11.1.2
Device Nomenclature
11.1.2.1
Capacitance Terms in Farads
11.1.2.2
Duty Cycle Terms
11.1.2.3
Frequency Terms in Hertz
11.1.2.4
Current Terms in Amperes
11.1.2.5
Current and Voltage Scaling Terms
11.1.2.6
Transformer Terms
11.1.2.7
Power Terms in Watts
11.1.2.8
Resistance Terms in Ω
11.1.2.9
Timing Terms in Seconds
11.1.2.10
Voltage Terms in Volts
11.1.2.11
AC Voltage Terms in VRMS
11.1.2.12
Efficiency Terms
11.2
Documentation Support
11.2.1
Related Documentation
11.3
Receiving Notification of Documentation Updates
11.4
Community Resources
11.5
Trademarks
11.6
Electrostatic Discharge Caution
11.7
Glossary
12
Mechanical, Packaging, and Orderable Information
11.1.2.8
Resistance Terms in Ω
R
CS
primary current programming resistance
R
ESR
total ESR of the output capacitor(s).
R
PL
preload resistance on the output of the converter.
R
S1
high-side VS pin resistance.
R
S2
low-side VS pin resistance.
R
STR
Start-up resistor connected between bulk voltage and VDD