ZHCSI53A May 2018 – November 2018 LM5122ZA
PRODUCTION DATA.
- 1 特性
- 2 應(yīng)用
- 3 說明
- 4 修訂歷史記錄
- 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器件和文檔支持
- 12機(jī)械、封裝和可訂購信息
封裝選項(xiàng)
機(jī)械數(shù)據(jù) (封裝 | 引腳)
- PWP|24
散熱焊盤機(jī)械數(shù)據(jù) (封裝 | 引腳)
- PWP|24
訂購信息
8.2.2.16 High-Side Power Switch QH and Additional Parallel Schottky Diode
Losses in the high-side N-channel MOSFET device can be separated into conduction loss, dead-time loss, and reverse recovery loss. Switching loss is calculated for the low-side N-channel MOSFET device only. Switching loss in the high-side N-channel MOSFET device is negligible because the body diode of the high-side N-channel MOSFET device turns on before and after the high-side N-channel MOSFET device switches.
High-side conduction loss is approximately calculated as follows:
Dead-time loss is approximately calculated as follows:
where
- VD is the forward voltage drop of the high-side NMOS body diode.
Reverse recovery characteristics of the high-side N-channel MOSFET switch strongly affect efficiency, especially when the output voltage is high. Small reverse recovery charge helps to increase the efficiency while also minimizes switching noise.
Reverse recovery loss is approximately calculated as follows:
where
- QRR is the reverse recovery charge of the high-side N-channel MOSFET body diode.
An additional Schottky diode can be placed in parallel with the high-side switch to improve efficiency. Usually, the power rating of this parallel Schottky diode can be less than the high-side switch’s because the diode conducts only during dead-times. The power rating of the parallel diode should be equivalent or higher than high-side switch’s if bypass operation is required, hiccup mode operation is required or any load exists before switching.