ZHCSI53A May 2018 – November 2018 LM5122ZA
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 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 Undervoltage Lockout (UVLO)
- 7.3.2 High-Voltage VCC Regulator
- 7.3.3 Oscillator
- 7.3.4 Slope Compensation
- 7.3.5 Error Amplifier
- 7.3.6 PWM Comparator
- 7.3.7 Soft Start
- 7.3.8 HO and LO Drivers
- 7.3.9 Bypass Operation (VOUT = VIN)
- 7.3.10 Cycle-by-Cycle Current Limit
- 7.3.11 Clock Synchronization
- 7.3.12 Maximum Duty Cycle
- 7.3.13 Thermal Protection
- 7.4 Device Functional Modes
-
8 Application and Implementation
- 8.1
Application Information
- 8.1.1 Feedback Compensation
- 8.1.2 Sub-Harmonic Oscillation
- 8.1.3 Interleaved Boost Configuration
- 8.1.4 DCR Sensing
- 8.1.5 Output Overvoltage Protection
- 8.1.6 SEPIC Converter Simplified Schematic
- 8.1.7 Non-Isolated Synchronous Flyback Converter Simplified Schematic
- 8.1.8 Negative to Positive Conversion
- 8.2
Typical Application
- 8.2.1 Design Requirements
- 8.2.2
Detailed Design Procedure
- 8.2.2.1 Timing Resistor RT
- 8.2.2.2 UVLO Divider RUV2, RUV1
- 8.2.2.3 Input Inductor LIN
- 8.2.2.4 Current Sense Resistor RS
- 8.2.2.5 Current Sense Filter RCSFP, RCSFN, CCS
- 8.2.2.6 Slope Compensation Resistor RSLOPE
- 8.2.2.7 Output Capacitor COUT
- 8.2.2.8 Input Capacitor CIN
- 8.2.2.9 VIN Filter RVIN, CVIN
- 8.2.2.10 Bootstrap Capacitor CBST and Boost Diode DBST
- 8.2.2.11 VCC Capacitor CVCC
- 8.2.2.12 Output Voltage Divider RFB1, RFB2
- 8.2.2.13 Soft-Start Capacitor CSS
- 8.2.2.14 Restart Capacitor CRES
- 8.2.2.15 Low-Side Power Switch QL
- 8.2.2.16 High-Side Power Switch QH and Additional Parallel Schottky Diode
- 8.2.2.17 Snubber Components
- 8.2.2.18 Loop Compensation Components CCOMP, RCOMP, CHF
- 8.2.3 Application Curves
- 8.1
Application Information
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文档支持
- 12机械、封装和可订购信息
8.2.2.18 Loop Compensation Components CCOMP, RCOMP, CHF
RCOMP, CCOMP and CHF configure the error amplifier gain and phase characteristics to produce a stable voltage loop. For a quick start, follow the following 4 steps:
- Select fCROSS
- Determine required RCOMP
- Determine CCOMP to cancel load pole. Place error amplifier zero at the twice of load pole frequency. Knowing RCOMP, CCOMP is calculated as follows:
- Determine CHF to cancel ESR zero.
Select the cross over frequency (fCROSS) at one fourth of the RHP zero or one tenth of the switching frequency whichever is lower.
5.3 kHz of the crossover frequency is selected between two. RHP zero at minimum input voltage should be considered if the input voltage range is wide.
Knowing fCROSS, RCOMP is calculated as follows:
A standard value of 68.1 kΩ is selected for RCOMP
A standard value of 22 nF is selected for CCOMP
Knowing RCOMP, RESR and CCOMP, CHF is calculated as follows:
A standard value of 330 pF is selected for CHF.