MAX31840EVKIT# Analog Devices

Evaluates: MAX31840 MAX31840 Evaluation Kit General Description Quick Start The MAX31840 evaluation kit (EV kit) demonstrates the Required Equipment MAX31840 LED driver IC used for dimmable 12V MR16 MAX31840 EV kit as well as AR111 and other 12V lighting applications. The 12V AC or DC supply, or a 12V electronic transformer EV kit is configured in a boost topology that provides an output power of up to 13W for up to 35V LED forward Trailing edge dimmer voltage. The IC is designed for the boost architecture to Current probe to measure the LED current address 35W and 50W MR16 LED replacement bulbs. The EV kits typical efficiency 90% at 12V AC and features Procedure a power-factor correction of 0.9 (typ). The EV kit is fully assembled and tested. Follow the steps The EV kit is a fully assembled and tested surface-mount below to verify board operation. Caution: Do not turn on the power supply until all connections are completed. PCB designed and optimized to accommodate an MR16 application form factor. The EV kit is dimmable with most Test with AC or DC Source electronic transformers and trailing-edge dimmer combi- 1) Connect the AC or DC source to the AC1 and AC2 nations. The EV kit includes bleeder and constant power test-point pads. circuits for enhanced electronic transformer performance. 2) Enable the power supply. Features 3) Measure the LED current using the current probe. Input Voltage Ranges Test with Electronic Transformer Plus Dimmer 9V AC to 13.2V AC from AC Source 1) Connect the output of a trailing edge dimmer to the 6.5V to 13.8V DC or Output of Electronic input of electronic transformer. Transformers 2) Connect the output of the electronic transformer to Drives Up to 35V LED Forward Voltage the AC1 and AC2 test-point pads. 36V Overvoltage Protection 3) Connect the input of the dimmer to power outlet. Up to 13W Output Power 4) Turn on the dimmer. Demonstrates IC Power-Factor Correction 5) Measure the LED current using the current probe. Proven PCB Layout 6) Adjust dimmer setting to change brightness on the Fully Assembled and Tested LED. Ordering Information appears at end of data sheet. 319-100049 Rev 0 8/17Evaluates: MAX31840 MAX31840 Evaluation Kit With 0.2 R2 and 0.5 R5, the power consumption of Detailed Description of Hardware the system is approximately 1000mA x 12V = 12W IN The MAX31840 EV kit demonstrates the MAX31840 (average current times input RMS voltage). This is equivalent MR16 LED driver. The MAX31840 is an average current- to 50W halogen bulb. For 35W equivalent application, use mode control LED driver IC for boost topology in low- 0.33 for R4 and 0.82 for R2. voltage SSL applications. The MAX31840 incorporates a proprietary circuit that enables deep dimming and an R3 and C5 are lowpass filters to eliminate the high- integrated bleeder to improve compatibility with a broad frequency components and glitches on the output signal range of electronic transformers. of the electronic transformer. The EV kit circuit is configured in boost topology that The electronic transformer constantly outputs short pulses operates at the ICs fixed 700kHz switching frequency and checks the existence of any connected devices. If the and provides up to 13W of output power for HBLEDs load is too small, the electronic transformer does not turn on. connected at the LED+ and LED- test-point holes. The EV The D1 diode provides a direct path for the electronic kit circuit operates from a 6.5V to 13.8V AC or 9V to 13.2V transformer to turn on the internal LDO of the MAX31840. DC supply or from electronic transformers. The EV kit is The bleeder FET can be turned on only after LDO is enabled. designed on a proven 2oz copper, two layer, small PCB Maximum LED+ Voltage footprint design that fits in a MR16 application form factor. The IC features an internal 36V overvoltage protection at The IC regulates the average voltage on CS to 200mV. the IN pin to protect the internal switching MOSFET from The average input current is set by the current-sense damage if the LED string is open or if the voltage on the resistor R4. The average current is: LED string is too high. 0.2 Electronic Transformer Compatibility I = AV R 4 The MR16 board was tested with 8 LEDs for electronic transformer compatibility and also with the appropriate where 0.2 is the voltage at the ICs CS pin and R4 is dimmers. See Table 1 for the results with the different in ohms. The R4 on the EV kit is 0.2 and the average transformer models tested. current is about 1000mA. The CS pin monitors the current through the sense resistor R4. When V falls below 180mV, the bleeder FET is CS turned on to maintain the minimum load requirement and keep the electronic transformer on. Current through the bleeder FET is set by R2: 0.5 I = BLEEDER R 2 where 0.5 is the voltage at the BSRC pin and R2 is in ohms. The R2 on the EV kit is 0.5, and I is BLEEDER about 1000mA. R5 and R7 are used to provide protection to the bleeder FET against high voltage at the output of the rectifier. Maxim Integrated 2 www.maximintegrated.com