ZHCSCK8H May 2014 – April 2025 LP8860-Q1
PRODUCTION DATA
- 1
- 1 特性
- 2 應用
- 3 說明
- Device Comparison Table
- 4 Pin Configuration and Functions
-
5 Specifications
- 5.1 Absolute Maximum Ratings
- 5.2 ESD Ratings
- 5.3 Recommended Operating Conditions
- 5.4 Thermal Information
- 5.5 Electrical Characteristics
- 5.6 Current Sinks Electrical Characteristics
- 5.7 Boost Converter Characteristics
- 5.8 Logic Interface Characteristics
- 5.9 VIN Undervoltage Protection (VIN_UVLO)
- 5.10 VDD Undervoltage Protection (VDD_UVLO)
- 5.11 VIN Overvoltage Protection (VIN_OVP)
- 5.12 VIN Overcurrent Protection (VIN_OCP)
- 5.13 Power-Line FET Control Electrical Characteristics
- 5.14 External Temp Sensor Control Electrical Characteristics
- 5.15 I2C Serial Bus Timing Parameters (SDA, SCLK)
- 5.16 SPI Timing Requirements
- 5.17 Typical Characteristics
-
6 Detailed Description
- 6.1 Overview
- 6.2 Functional Block Diagram
- 6.3 Feature Description
- 6.4 Device Functional Modes
- 6.5 Programming
- 6.6
Register Maps
- 6.6.1
Register Bit Explanations
- 6.6.1.1 Display/Cluster1 Brightness Control MSB
- 6.6.1.2 Display/Cluster1 Brightness Control LSB
- 6.6.1.3 Display/Cluster1 Output Current MSB
- 6.6.1.4 Display/Cluster1 Output Current LSB
- 6.6.1.5 Cluster2 Brightness Control MSB
- 6.6.1.6 Cluster2 Brightness Control LSB
- 6.6.1.7 Cluster2 Output Current
- 6.6.1.8 Cluster3 Brightness Control MSB
- 6.6.1.9 Cluster3 Brightness Control LSB
- 6.6.1.10 Cluster3 Output Current
- 6.6.1.11 Cluster4 Brightness Control MSB
- 6.6.1.12 Cluster4 Brightness Control LSB
- 6.6.1.13 Cluster4 Output Current
- 6.6.1.14 Configuration
- 6.6.1.15 Status
- 6.6.1.16 Fault
- 6.6.1.17 LED Fault
- 6.6.1.18 Fault Clear
- 6.6.1.19 Identification
- 6.6.1.20 Temp MSB
- 6.6.1.21 Temp LSB
- 6.6.1.22 Display LED Current MSB
- 6.6.1.23 Display LED Current LSB
- 6.6.1.24 Display LED PWM MSB
- 6.6.1.25 Display LED PWM LSB
- 6.6.1.26 EEPROM Control
- 6.6.1.27 EEPROM Unlock Code
- 6.6.2
EEPROM Bit Explanations
- 6.6.2.1 EEPROM Register 0
- 6.6.2.2 EEPROM Register 1
- 6.6.2.3 EEPROM Register 2
- 6.6.2.4 EEPROM Register 3
- 6.6.2.5 EEPROM Register 4
- 6.6.2.6 EEPROM Register 5
- 6.6.2.7 EEPROM Register 6
- 6.6.2.8 EEPROM Register 7
- 6.6.2.9 EEPROM Register 8
- 6.6.2.10 EEPROM Register 9
- 6.6.2.11 EEPROM Register 10
- 6.6.2.12 EEPROM Register 11
- 6.6.2.13 EEPROM Register 12
- 6.6.2.14 EEPROM Register 13
- 6.6.2.15 EEPROM Register 14
- 6.6.2.16 EEPROM Register 15
- 6.6.2.17 EEPROM Register 16
- 6.6.2.18 EEPROM Register 17
- 6.6.2.19 EEPROM Register 18
- 6.6.2.20 EEPROM Register 19
- 6.6.2.21 EEPROM Register 20
- 6.6.2.22 EEPROM Register 21
- 6.6.2.23 EEPROM Register 22
- 6.6.2.24 EEPROM Register 23
- 6.6.2.25 EEPROM Register 24
- 6.6.1
Register Bit Explanations
-
7 Application and Implementation
- 7.1 Application Information
- 7.2
Typical Applications
- 7.2.1
Typical 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 Diode
- 7.2.1.2.7 Boost Converter Transistor
- 7.2.1.2.8 Boost Sense Resistor
- 7.2.1.2.9 Power Line Transistor
- 7.2.1.2.10 Input Current Sense Resistor
- 7.2.1.2.11 Filter Component Values
- 7.2.1.3 Application Performance Plots
- 7.2.2 Low VDD Voltage and Combined Output Mode Application
- 7.2.3 High Output Voltage Application
- 7.2.4 High Output Current Application
- 7.2.5 Three-Channel Configuration Without Serial Interface
- 7.2.6 Solution With Minimum External Components
- 7.2.1
Typical Application for Display Backlight
- 7.3 Power Supply Recommendations
- 7.4 Layout
- 8 Device and Documentation Support
- 9 Revision History
- 10Mechanical, Packaging, and Orderable Information
6.3.2.6 LED Dimming Methods
In additional to conventional PWM dimming control the LP8860-Q1 supports Hybrid PWM and Current dimming. Hybrid dimming combines the PWM and current dimming methods. PWM dimming operates with a lower range of light, and linear current dimming is used with higher brightness values. If the <EN_PWM_I EEPROM> bit is set to 1, the system enables hybrid dimming. Principles of PWM dimming and Hybrid PWM and Current dimming are illustrated by Figure 6-7. Only 25% switch points and slope gain = 1 are shown for simplicity.
Figure 6-7 Principles of PWM Dimming and Hybrid PWM and Current DimmingLED forward voltage increases and efficiency declines when forward current is increased. Use of constant current with PWM dimming at lower brightness and current dimming at greater brightness (instead of PWM dimming at full brightness range), yields better optical efficiency and resolution especially at lower brightness values. The optimum switch point between PWM and current dimming modes and current slope depend on the LED type.
PWM control ranges from 12.5% to 50% and the current slope can be selected using <GAIN_CTRL[2:0]> and <I_SLOPE[2:0]> EEPROM bits, respectively (see Table 6-6 and Table 6-7).
Figure 6-8 Optical Efficiency Improvement With PWM and Current Dimming| GAIN_CTRL[2:0] | SWITCH POINT FROM PWM TO CURRENT DIMMING |
|---|---|
| 000 | 50.0% |
| 001 | 40.6% |
| 010 | 31.3% |
| 011 | 25.0% |
| 100 | 21.9% |
| 101 | 18.8% |
| 110 | 15.6% |
| 111 | 12.5% |
| I_SLOPE[2:0] | SLOPE GAIN |
|---|---|
| 000 | 1.000 |
| 001 | 1.023 |
| 010 | 1.047 |
| 011 | 1.070 |
| 100 | 1.094 |
| 101 | 1.117 |
| 110 | 1.141 |
| 111 | 1.164 |
The current setting for DISP_CL1_CURRENT[11:0] in Hybrid PWM and Current dimming mode can be defined by the following formula (assuming individual LED sink current correction DRV_OUTx_CORR[3:0] is 0%):
Example of calculation for Hybrid PWM and Current dimming mode, 100-mA maximum output current:
| Target maximum current 100 mA | IDISP_CL1_CURRENT = 100 – 100 × 1 × ((100 – 25) / 100) = 25 mA |
| Maximum scale 100 mA (DRV_LED_CURRENT_SCALE[2:0]=101) | |
| Slope = 1.000 (I_SLOPE[2:0]=000) | |
| Switch point = 25% (GAIN_CTRL[2:0]=011) |
Example of calculation for Hybrid PWM and Current dimming mode, 23-mA maximum output current:
| Target maximum current 23 mA | IDISP_CL1_CURRENT = 23 – 25 × 1.094 × ((100 – 25) / 100) = 2.49 mA |
| Maximum scale 25 mA (DRV_LED_CURRENT_SCALE[2:0]=000) | |
| Slope = 1.094 (I_SLOPE[2:0]=100) | |
| Switch point = 25% (GAIN_CTRL[2:0]=011) |
- Formula is only approximation for the actual value.
- DISP_CL1_CURRENT[11:0] value must be chosen to avoid current saturation before 100% brightness is achieved.