Datasheet
Table Of Contents
- Features
- Typical Applications
- 1. Introduction
- 2. Ordering Information
- 3. Application Circuit
- 4. Absolute Maximum Ratings
- 5. Electrical Characteristics
- 6. Block Diagram
- 7. Pinout and Pin Description
- 8. Typical Application Circuit
- 9. Detailed Description
- 10. Fault Conditions
- 11. Applications Information
- 12. Control Registers
- 13. Detailed Register Descriptions
- 13.1 RAM (0x00 through 0x1F)
- 13.2 Main String Reference Voltage register (MREF, 0x20)
- 13.3 Color-Adjust String Reference Voltage register (CAREF, 0x21)
- 13.4 Fault Disable register (FAULT, 0x22)
- 13.5 Fault Status register (FAULTSTAT, 0x23), Read Only
- 13.6 Sleep register (SLEEP, 0x24)
- 13.7 Main String Duty Cycle register, High Byte (MDUTYHIGH, 0x34)
- 13.8 Main String Duty Cycle register, Low Byte (MDUTYLOW, 0x35)
- 13.9 Color Adjust String Duty Cycle register, High Byte (CADUTYHIGH, 0x36)
- 13.10 Color Adjust String Duty Cycle register, Low Byte (CADUTYLOW, 0x37)
- 13.11 Efficiency Optimizer Control Register (EOCTRL, 0x40)
- 13.12 Registers 0x60 and 0x61, EEPROM Access
- 14. I²C Serial Interface
- 15. Packaging Information
- 16. Datasheet Revision History
- Table of Contents
18
MSL2023/2024 [DATASHEET]
42063A–LED–02/2013
9. Detailed Description
Table 9-1. Device selection guide, LED brightness control by part number.
Note: 1. Access registers through I
2
C serial interface.
The MSL2023/24 drive two LED strings, the main string and the color-adjust string. The main string LEDs are typically
white and used to provide an accurate light intensity control. The color-adjust string LEDs are used to control the color
temperature. The combined light output is a blend, with intent to offer a warmer high CRI light for example, than what
white LEDs can alone produce. The main string is directly controlled by a Pulse Width Modulated (PWM) constant
current controller (current sink to ground). An Efficiency Optimizer (EO) output controls the main string voltage, via feed-
back to the LED string power supply, to minimize the voltage across the LED current controller, minimizing power loss.
The color-adjust string is regulated by a floating buck controller. The buck controller converts the voltage of the main
string’s supply to a voltage appropriate for the color-adjust LEDs. Additionally, the MSL2023/24 have programmable 8-bit
registers that allows adjustment of the current by changing the source feedback reference voltages (see“Block Diagram”
on page 12).
10. Fault Conditions
The MSL2023/24 detect fault conditions, and take corrective action when faults are verified.
String open circuit and LED short circuit conditions of the Color-Adjust string are monitored. When one of these faults
occurs, FLTB pulls low to indicate a fault condition and the Color-Adjust LEDs turn off. Read Fault Status register 0x23 to
determine the fault type and to clear the faults, or clear faults by toggling EN low then high. Faults that persist re-
establish the fault response. Mask string faults using Fault Disable register 0x22. Clear string faults by toggling EN low
then high, or with “Fault Disable register (FAULT, 0x22)” on page 27. For the main LED string when an LED open occurs
the V
LED
voltage will reach the maximum allowed.
Over Temperature Protection puts the device to sleep when the die temperature is above 147
C. The device turns back
on when the die temperature falls below 127
C, and normal operation resumes. While asleep, the I
2
C interface remains
active (see “Fault Disable register (FAULT, 0x22)” and “Fault Status register (FAULTSTAT, 0x23), Read Only” on page
28 for more information about thermal shutdown).
Part
LED brightness control
PWM dimming frequencyMain string Color adjust string
MSL2023 Main PWM register
(1)
Color adjust PWM register
(1)
400Hz
MSL2024 Duty cycle at the PWM1 input Duty cycle at the PWM2 input
Input frequency main:
60Hz to 22kHz
(minimum t
ON
= 2µs)
CA: 100Hz to 500Hz