ZHCSOB0A july 2021 – august 2023 LM5157
PRODUCTION DATA
- 1
- 1 特性
- 2 應用
- 3 說明
- 4 Revision History
- 5 Device Comparison Table
- 6 Pin Configuration and Functions
- 7 Specifications
-
8 Detailed Description
- 8.1 Overview
- 8.2 Functional Block Diagram
- 8.3
Feature Description
- 8.3.1 Line Undervoltage Lockout (UVLO/SYNC/EN Pin)
- 8.3.2 High Voltage VCC Regulator (BIAS, VCC Pin)
- 8.3.3 Soft Start (SS Pin)
- 8.3.4 Switching Frequency (RT Pin)
- 8.3.5 Dual Random Spread Spectrum – DRSS (MODE Pin)
- 8.3.6 Clock Synchronization (UVLO/SYNC/EN Pin)
- 8.3.7 Current Sense and Slope Compensation
- 8.3.8 Current Limit and Minimum On Time
- 8.3.9 Feedback and Error Amplifier (FB, COMP Pin)
- 8.3.10 Power-Good Indicator (PGOOD Pin)
- 8.3.11 Hiccup Mode Overload Protection (MODE Pin)
- 8.3.12 Maximum Duty Cycle Limit and Minimum Input Supply Voltage
- 8.3.13 Internal MOSFET (SW Pin)
- 8.3.14 Overvoltage Protection (OVP)
- 8.3.15 Thermal Shutdown (TSD)
- 8.4 Device Functional Modes
- 9 Application and Implementation
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information
8.3.11 Hiccup Mode Overload Protection (MODE Pin)
To further protect the converter during prolonged current limit conditions, the device provides selectable Hiccup mode overload protection. This function is enabled by a single resistor (37.4 kΩ or 62.0 kΩ) between the MODE pin and the AGND pin or by programming the MODE pin voltage (370 mV or 620 mV) during initial power up. The internal Hiccup mode fault timer of the device counts the PWM clock cycles when the cycle-by-cycle current limiting occurs after soft start is finished. When the Hiccup mode fault timer detects 64 cycles of current limiting, an internal Hiccup mode off timer forces the device to stop switching and pulls down SS. Then, the device restarts after 32?768 cycles of Hiccup mode off time. The 64-cycle Hiccup mode fault timer is reset if eight consecutive switching cycles occur without exceeding the current limit threshold. The soft-start time must be long enough not to trigger the Hiccup mode protection after the soft start is finished.
Figure 8-20 Hiccup Mode Overload Protection