ZHCSI27C April 2018 – October 2021 LM5036
PRODUCTION DATA
- 1 特性
- 2 應用
- 3 說明
- 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 High-Voltage Start-Up Regulator
- 7.3.2 Undervoltage Lockout (UVLO)
- 7.3.3 Reference Regulator
- 7.3.4 Oscillator, Synchronized Input
- 7.3.5 Voltage-Mode Control
- 7.3.6 Primary-Side Gate Driver Outputs (LSG and HSG)
- 7.3.7 Half-Bridge PWM Scheme
- 7.3.8 Maximum Duty Cycle Operation
- 7.3.9 Pre-Biased Start-Up Process
- 7.3.10 Zero Duty Cycle Operation
- 7.3.11 Enhanced Cycle-by-Cycle Current Limiting with Pulse Matching
- 7.3.12 Reverse Current Protection
- 7.3.13 CBC Threshold Accuracy
- 7.3.14 Hiccup Mode Protection
- 7.3.15 Hiccup Mode Blanking
- 7.3.16 Over-Temperature Protection (OTP)
- 7.3.17 Over-Voltage / Latch (ON_OFF Pin)
- 7.3.18 Auxiliary Constant On-Time Control
- 7.3.19 Auxiliary On-Time Generator
- 7.3.20 Auxiliary Supply Current Limiting
- 7.3.21 Auxiliary Primary Output Capacitor Ripple
- 7.3.22 Auxiliary Ripple Configuration and Control
- 7.3.23 Asynchronous Mode Operation of Auxiliary Supply
- 7.4 Device Functional Modes
-
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 Custom Design With WEBENCH? Tools
- 8.2.2.2 Input Transient Protection
- 8.2.2.3 Level-Shift Detection Circuit
- 8.2.2.4 Applications with VIN > 100-V
- 8.2.2.5 Applications without Pre-Biased Start-Up Requirement
- 8.2.2.6 UVLO Voltage Divider Selection
- 8.2.2.7 Over Voltage, Latch (ON_OFF Pin) Voltage Divider Selection
- 8.2.2.8 SS Capacitor
- 8.2.2.9 SSSR Capacitor
- 8.2.2.10 Half-Bridge Power Stage Design
- 8.2.2.11 Current Limit
- 8.2.2.12 Auxiliary Transformer
- 8.2.2.13 Auxiliary Feedback Resistors
- 8.2.2.14 RON Resistor
- 8.2.2.15 VIN Pin Capacitor
- 8.2.2.16 Auxiliary Primary Output Capacitor
- 8.2.2.17 Auxiliary Secondary Output Capacitor
- 8.2.2.18 Auxiliary Feedback Ripple Circuit
- 8.2.2.19 Auxiliary Secondary Diode
- 8.2.2.20 VCC Diode
- 8.2.2.21 Opto-Coupler Interface
- 8.2.2.22 Full-Bridge Converter Applications
- 8.2.3 Application Curves
- 9 Power Supply Recommendations
- 10Layout
- 11Device and Documentation Support
- 12Mechanical, Packaging, and Orderable Information
8.2.2.10 Half-Bridge Power Stage Design
For a PWM operating frequency of 400kHz applied to the output inductor the oscillator frequency of LM5036 must also be set to 400kHz. The value of resistor RT is obtained using Equation 54.
Maximum effective duty cycle that can be applied to the output inductor is Equation 55.
Maximum transformer turns ratio that will deliver the required output voltage from minimum input voltage is given by Equation 56.
For our example design we will opt for a planar transformer with 4 primary turns and 3 secondary turns. The turns are located in an un-gapped RM7/ILP ferrite core made of 3C95 material. This core has an inductance factor AL = 4.4-μH/turn2. Hence the actual turns ratio (NPS) and magnetising inductance (LMag) are given by Equation 57 and Equation 58.
Maximum inductor current ripple will occur at maximum input voltage. The output inductor value LO will be selected to limit inductor current ripple amplitude to 20-% of the maximum output current ILIM
Hence a catalog part with an inductance of 4.7-μH, capable of carrying the full output current, and with a saturation current of more that 120-% of ILIM, is selected.
