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
8.2.2.6 UVLO Voltage Divider Selection
As described in Section 7.3.2 , two external resistors can be used to program the minimum operating voltage for the power converter, as shown Figure 8-5. When the UVLO pin voltage falls below VUVLO (1.25-V typical), an internal current sink IUVLO (20-μA typical) is enabled to lower the voltage at the UVLO pin, thus providing threshold hysteresis. Resistance values for RUV1 and RUV2 can be determined from Equation 50 and Equation 51.
where
- VHYS(UVLO) is the UVLO hysteresis
where
- VIN(on) is the input voltage above which the main converter will start to operate.
Figure 8-6 illustrates one way to configure a latch reset operation by pulling the UVLO pin voltage below VUVLO. The diode voltage drop must be between 0.35 V and 1.25 V. The controller can be forced to enter shutdown mode by pulling UVLO pin to GND.
Figure 8-5 UVLO Configuration
Figure 8-6 Latch Reset