ZHCSLM3B August 2020 – May 2024 LP8864-Q1
PRODUCTION DATA
- 1
- 1 特性
- 2 應用
- 3 說明
- 4 Pin Configuration and Functions
- 5 Specifications
-
6 Detailed Description
- 6.1 Overview
- 6.2 Functional Block Diagram
- 6.3
Feature Description
- 6.3.1 Control Interface
- 6.3.2 Function Setting
- 6.3.3 Device Supply (VDD)
- 6.3.4 Enable (EN)
- 6.3.5 Charge Pump
- 6.3.6 Boost Controller
- 6.3.7 LED Current Sinks
- 6.3.8 Brightness Control
- 6.3.9
Protection and Fault Detections
- 6.3.9.1 Supply Faults
- 6.3.9.2
Boost Faults
- 6.3.9.2.1 Boost Overvoltage Faults (BSTOVPL, BSTOVPH)
- 6.3.9.2.2 Boost Overcurrent Faults (BSTOCP)
- 6.3.9.2.3 LEDSET Resistor Missing Faults (LEDSET)
- 6.3.9.2.4 MODE Resistor Missing Faults (MODESEL)
- 6.3.9.2.5 FSET Resistor Missing Faults (FSET)
- 6.3.9.2.6 ISET Resistor Out of Range Faults (ISET)
- 6.3.9.2.7 Thermal Shutdown Faults (TSD)
- 6.3.9.3 LED Faults
- 6.3.9.4 Overview of the Fault and Protection Schemes
- 6.4 Device Functional Modes
- 6.5 Programming
-
7 Application and Implementation
- 7.1 Application Information
- 7.2
Typical Applications
- 7.2.1
Full Feature Application for Display Backlight
- 7.2.1.1 Design Requirements
- 7.2.1.2
Detailed Design Procedure
- 7.2.1.2.1 Inductor Selection
- 7.2.1.2.2 Output Capacitor Selection
- 7.2.1.2.3 Input Capacitor Selection
- 7.2.1.2.4 Charge Pump Output Capacitor
- 7.2.1.2.5 Charge Pump Flying Capacitor
- 7.2.1.2.6 Output Diode
- 7.2.1.2.7 Switching FET
- 7.2.1.2.8 Boost Sense Resistor
- 7.2.1.2.9 Power-Line FET
- 7.2.1.2.10 Input Current Sense Resistor
- 7.2.1.2.11 Feedback Resistor Divider
- 7.2.1.2.12 Critical Components for Design
- 7.2.1.3 Application Curves
- 7.2.2 Application with Basic/Minimal Operation
- 7.2.3
SEPIC Mode Application
- 7.2.3.1 Design Requirements
- 7.2.3.2
Detailed Design Procedure
- 7.2.3.2.1 Inductor Selection
- 7.2.3.2.2 Coupling Capacitor Selection
- 7.2.3.2.3 Output Capacitor Selection
- 7.2.3.2.4 Input Capacitor Selection
- 7.2.3.2.5 Charge Pump Output Capacitor
- 7.2.3.2.6 Charge Pump Flying Capacitor
- 7.2.3.2.7 Switching FET
- 7.2.3.2.8 Output Diode
- 7.2.3.2.9 Switching Sense Resistor
- 7.2.3.2.10 Power-Line FET
- 7.2.3.2.11 Input Current Sense Resistor
- 7.2.3.2.12 Feedback Resistor Divider
- 7.2.3.2.13 Critical Components for Design
- 7.2.3.3 Application Curves
- 7.2.1
Full Feature Application for Display Backlight
- 7.3 Power Supply Recommendations
- 7.4 Layout
- 8 Register Maps
- 9 Device and Documentation Support
- 10Revision History
- 11Mechanical, Packaging, and Orderable Information
封裝選項
機械數據 (封裝 | 引腳)
散熱焊盤機械數據 (封裝 | 引腳)
訂購信息
6.3.6.3.2 FB Divider Using Three-Resistor Method
A FB-pin circuit using a three-resistor divider circuit can be used for applications where less than 200kΩ resistors are required.
Figure 6-6 Three-Resistor FB Divider
CircuitMaximum boost voltage can be calculated with Equation 7. The maximum boost voltage can be reached during OPEN string detection or if all LED strings are left disconnected.
where
- VREF = 1.21V
- ISEL_MAX = 38.7μA
- R1 / R2 normal recommended range is 7 to 15
The minimum boost voltage must be less than the minimum LED string voltage. Minimum boost voltage is calculated in Equation 8:
When the boost OVP_LOW level is reached the boost controller stops switching the boost FET, and the BSTOVPL_STATUS bit is set. The LED drivers are still active during this condition, and the boost resumes normal switching operation once the boost output level falls. The boost OVP low voltage threshold changes dynamically with current boost voltage. It is calculated in Equation 9:
where
- VFB_OVPL= 1.423V
- VREF= 1.21V
When the boost OVP_LOW level is reached the boost controller enters fault recovery mode, and the BSTOVPH_STATUS bit is set. The boost OVP high-voltage threshold also changes dynamically with current boost voltage and is calculated in Equation 10:
where
- VFB_OVPH = 1.76V
- VREF= 1.21V
When the boost UVP level is reached the boost controller starts a 110ms OCP counter. The LP8864-Q1 device enters the fault recovery mode and sets the BSTOCP_STATUS bit if the boost voltage does not rise above the UVP threshold before the timer expires. The boost UVP voltage threshold also changes dynamically with current boost voltage and is calculated in Equation 11:
where
- VUVP = 0.886V
- VREF= 1.21V