Design Overview
The TIDA-01096 TI Design is a tested DC-DC LED driver subsystem for tunable, white LED luminaires. The design has been built on a wireless system-on-chip (SoC) platform, which can enable intensity adjustment (dimming) and correlated color temperature (CCT) control using any Bluetooth low energy (BLE) device.
Key Innovation: Tunable white luminaires simulate daylight conditions. With separate warm-white and cold-white LED strings, the design allows CCT tuning, which helps achieve proper circadian stimulation for human wellness applications.
Key Performance Specifications
Key Features & Benefits
High-Efficiency Operation
98% efficiency over 100% to 50% brightness with analog dimming, reducing energy consumption and heat generation in LED lighting systems.
Advanced Dimming Capabilities
1:25 contrast ratio with analog dimming and 1:50 with PWM dimming, providing precise brightness control for various lighting scenarios.
Wireless Bluetooth Control
Bluetooth Smart connectivity enables wireless control of intensity and color temperature using smartphones or other BLE devices.
Ambient Light Sensing
OPT3001-based light measurement enabling daylight harvesting and constant lumen implementations in software for energy efficiency.
Comprehensive Protection
Overcurrent and overtemperature protection for driver and LED module ensures reliable operation and extended lifespan.
Circadian Lighting Support
Tunable white capability supports human wellness applications by simulating natural daylight conditions throughout the day.
Detailed Content Overview
Document Contents
System Overview
Light-emitting diodes (LEDs) are increasingly being used as a light source. At the time of this writing, the focus of lighting is currently shifting from simply illuminating areas with constant light output to providing quality and controlled light output. High quality lighting with adjustable intensity and adjustable color temperature plays a key role in enhancing architecture and human wellness.
To change the color temperature of white light, the designer can implement a combination of warm LEDs (color temperature of around 2500 K) and cold LEDs (color temperature of around 5700 K). Tunable, white chip-on-board (COB) LEDs are available with two separate strings. By changing the current through the strings, the designer can create color temperatures ranging from 2500 K to 5700 K.
The tunable white-LED engine with the drivers can be used as a platform for circadian lighting, which targets human wellness. Lighting has a profound effect on sleep, alertness, work efficiency, and health. A tunable, white-LED lighting system can be used for proper maintenance of the circadian rhythm, allowing the necessary amount of white light and warm light, which improves wellness in indoor conditions.
Key System Specifications
| PARAMETERS | MIN | TYP | MAX | UNIT |
|---|---|---|---|---|
| Input voltage | 35 | - | 42 | V |
| Output (LED) current | 0 | - | 700 | mA |
| Switching frequency | - | 600 | - | kHz |
| PWM dimming frequency | 200 | - | 5000 | Hz |
| Warm LED forward voltage | 34 | 37 | 40 | V |
| Cold LED forward voltage | 35 | 38 | 41 | V |
| Operating temperature | -30 | - | 100 | °C |
System Block Diagram
The system architecture is built around the SimpleLink CC2650 Wireless MCU LaunchPad Kit, which controls two TPS92513HV buck LED drivers for the warm and cold LED strings. The design includes:
- CC2650 Wireless MCU: Generates PWM signals for dimming control and manages Bluetooth connectivity
- TPS92513HV Buck LED Drivers: Two independent drivers for warm and cold LED strings with integrated analog current adjust
- OPA376 Op-Amps: Buffer filtered PWM signals for analog dimming control
- OPT3001 Ambient Light Sensor: Enables daylight harvesting and constant lumen output
- LMT84 Temperature Sensor: Monitors heatsink temperature for thermal protection
- RC Low-Pass Filters: Convert PWM signals to analog voltages for current reference setting
Design Note: The system accepts 35-42V DC input and drives a 35W tunable white LED COB with separate warm and cool LED strings, enabling color temperature tuning from 2500K to 5700K.
Highlighted Components
TPS92513HV
1.5-A step-down (buck) current regulator with integrated MOSFET for driving high-current LEDs.
- 4.5-60V input voltage range
- ±5% LED current accuracy
- 100kHz to 2MHz switching frequency
- Dedicated PWM dimming input
- Integrated 220-mΩ high-side MOSFET
CC2650
Wireless MCU targeting Bluetooth Smart, ZigBee, and 6LoWPAN applications.
- 32-bit ARM Cortex-M3 processor at 48MHz
- Ultra-low-power sensor controller
- BLE controller embedded in ROM
- 128KB Flash, 20KB SRAM
- Rich peripheral set including I²C, UART, SPI
OPT3001
Ambient light sensor with precision optical filtering to match human eye response.
- Rejects >99% of IR
- 0.01 lux to 83k lux measurement range
- 23-bit effective dynamic range
- Low operating current: 1.8µA
- I²C compatible digital output
OPA376
Low-noise operational amplifier with e-trim, offering outstanding DC precision and AC performance.
- Low noise: 7.5 nV/√Hz at 1 kHz
- Low offset voltage: 5µV typical
- 5.5 MHz gain bandwidth product
- Rail-to-rail input and output
- 2.2V to 5.5V supply voltage
LMT84
Precision CMOS temperature sensor with analog output voltage inversely proportional to temperature.
- ±0.4°C typical accuracy
- -50°C to 150°C temperature range
- Low 5.4-µA quiescent current
- -5.5 mV/°C average sensor gain
- Low 1.5-V operation
System Design Theory
LEDs require constant current drive and tunable white light requires current in two separate LED strings to be varied and controlled. A tunable white LED luminaire requires an AC-DC constant-voltage power supply combined with two DC-DC buck current controllers to vary the current through the LED strings.
The TIDA-01096 platform uses two TPS92513HV buck LED drivers with integrated analog current adjust for controlling the current through warm and cold LED strings. The TPS92513/HV LED drivers feature separate inputs for analog and pulse width modulation (PWM) dimming for no-compromise brightness control to achieve contrast ratios greater than 100:1.
The buck LED drivers are controlled by the SimpleLink CC2650 Wireless MCU LaunchPad kit, which generates two PWMs for PWM dimming of both strings. Achieving analog dimming requires two variable analog inputs to set the IADJ of the buck LED drivers. Variable IADJ is derived using the PWM from the CC2650 device as a digital-to-analog converter (DAC). For this process, the PWM generated from the CC2650 device is filtered by a four-stage low-pass RC filter and the filtered output is buffered using op amp OPA376.
Design Equations
The design includes comprehensive calculations for:
- Undervoltage Lockout Setting: R1=120kΩ and R6=5kΩ set UVLO at 30.5V
- Switching Frequency: RRT=190.63kΩ sets fSW=600kHz
- LED Current Setting: RISENSE=0.05Ω for maximum 700mA LED current
- Analog Dimming Filter: Four-stage RC filter with cutoff frequency of 391Hz
- Inductor Selection: Calculated for 275mA ripple current at full load
- Output Capacitor: 4.7μF selected to achieve 5mA LED ripple current
Dimming Techniques
The design implements three distinct dimming methods to provide flexibility and optimize performance for different operating conditions:
Analog Dimming
Using IADJ pin to dynamically set LED current. More efficient with less EMI but may cause color temperature variation at very low currents.
- Uses PWM filtered through 4-stage RC filter
- Provides 12-bit resolution
- Higher efficiency: up to 98%
- 1:25 contrast ratio
PWM Dimming
Using PDIM pin to enable/disable gate driver. Avoids color temperature issues at low currents and provides higher resolution.
- 200Hz to 5kHz frequency range
- Direct control of gate driver
- Better dimming linearity at low currents
- 1:50 contrast ratio
Hybrid Dimming
Combines both methods - analog for efficiency and PWM for fine tuning and better resolution at low currents.
- Optimizes efficiency and resolution
- Analog for main dimming range
- PWM for fine adjustment at low currents
- Best of both techniques
Flicker-Free Operation: The design can achieve flicker-free operation down to 6mA output current by modifying the current-sensing resistor from 50mΩ to 250mΩ, enabling high-quality lighting even at very low brightness levels.
Test Data & Performance
Comprehensive testing demonstrates the excellent performance of the design across various operating conditions:
Efficiency Performance
- Analog Dimming: 98.15% peak efficiency at full load, maintaining >95% efficiency down to 20% load
- PWM Dimming (1kHz): 97.39% efficiency at 100% duty cycle, gradually decreasing to 84.88% at 3% duty cycle
- PWM Dimming (5kHz): 97.82% efficiency at 100% duty cycle, maintaining >90% efficiency down to 5% duty cycle
- Input Voltage Variation: Efficiency remains above 97% across 35V to 48V input range
Tunable White Performance
The system efficiently maintains color temperature tuning across different brightness levels:
- 100% Brightness: System efficiency ranges from 97.27% (cool white) to 98.15% (warm white)
- 75% Brightness: Efficiency ranges from 97.24% to 98.01% across color temperatures
- 50% Brightness: Efficiency ranges from 97.18% to 98.31% across the tuning range
Sensor Performance
- OPT3001 Ambient Light Sensor: Provides accurate lux measurements from 2.57 lux to 12,902 lux
- LMT84 Temperature Sensor: Monitors heatsink temperature from 36.21°C to 61.60°C under various load conditions
Design Files & Resources
The complete design package includes all necessary files for implementation:
- Schematics: Complete circuit diagrams for the LED driver system
- Bill of Materials: Comprehensive parts list with manufacturer references
- PCB Layout: Gerber files and layout recommendations
- Altium Project: Complete design project files
- Assembly Drawings: Detailed assembly instructions
- Software Files: Firmware for CC2650 MCU with BLE connectivity
Application Areas: This reference design is ideal for indoor LED lighting (residential, retail, hospitality, accent lighting), wireless connected lighting systems, and low-voltage DC LED lighting applications requiring precise color temperature control and wireless connectivity.
Note: The above is a comprehensive summary of the reference design. The complete PDF document contains detailed schematics, layout guidelines, firmware implementation details, and extensive test data. We recommend downloading the full PDF for complete implementation details.