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MLX10803
High Power LED Driver
 Download MLX10803 Datasheet (PDF)
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MLX10803 General Description
MLX10803 is a general purpose LED driver for high power LEDs
MLX10803 Features and Benefits
- Low cost
- High current and voltage
- Temperature compensation and regulation
- Temperature protection of LED
- High temperature operation
- Several regulation features
MLX10803 Environmental Information
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MLX10803 Frequently asked Questions
mlx10803
Answer
The minimum value that you can use on the ROSC is 39 kOhm to ground, a value below that gives unpredictable results on the internal oscillator. It will stop most likely. See page 10 in MLX10803 IC specification.
Coil_calc is made little bit more general so it should be possible to use for other and future types of buck regulators also, so it does not warn you for a too high switching frequency (or too low). Please control your result to the min and max value in the MXL10803 and MLX10801 IC-specification.
Here are also some warnings for high switching frequencies even if they seem to be a cheaper solution on paper due to smaller coil:
A general rule for all switch regulators is to avoid high switching frequencies due to efficiency loss and noise problems. To get an efficient regulator you should stay below 150kHz also most coils are designed for that.
The noise is always a direct function of the size of the current you switch and the frequency. The worst source of noise is the fly back diode. In a buck topology current regulator you switch quite high currents, actually the peak current. This peak current is independent on the size of the coil. The noise is in principle a direct function of the frequency! The fly back diode generates exact the same noise at every switching occasion.
MLX10803 does the most to suppress noise by randomizing switching, but still you need to pay attention!
If you still want to use high switching frequency, notice that you lose precision, due to the delay in the comparator on the RSENSE pin. Something that all buck regulators have.
In MLX10803 this is deliberately set to 300nS (200 – 400) and named debunch time in the IC-specification. This debunch time is used to filter away switching noise on this pin. The coil_calc excel sheet handles that and will show you the effect.
Answer
1. On the Melexis web-site EVB10803 and EVB10803mini are represented and these evaluation boards are targeted for the automotive applications with 6-32VDC input voltage.
2. The MLX10803 can also be used for HV applications as well.
In order to evaluate the behavior of the MLX10803 in the case described above it is suggested to download the Coil_calc software from the Melexis web-site. Then use the following values:
Supply voltage - 300V
Led threshhold - 3,4V
Number Led - 8
Rsense - 1 Ohm
Vpeak - 510 mV
Tmon - 17 us
L - 1500 uH
Coil_cal will generate the next info:
Rosc = 300 K
Riref = 51 K
You can use these values in the application.
Of course it needs to choose the HV transistor (400V) and flyback diode.
Question
Which components to use with the MLX10803 to drive high power LEDs from Luxeon (1 A, 3W or 5W, forward voltage about 3.5 V for the 3W type or 6.5 V for the 5 W) or Ostar Ligthning (1A, forward voltage about 21 V)? The supply voltage for the circuit is 24-28 V. The circuit should also allow dimming the LEDs.
Question
Which settings to program for the MLX10803 to drive a halogen lamp: 100W bulb (e.g. Osram Halostar 64460 U, 24 V, 100 W, D 12/L 44 mm, GY 6,35) with a rating of 24V.
Analog dimming is required as well. The supply voltage of the Melexis chip can be assumed to be >24V e.g. 26V.
high frequency strobe mlx10803
Question
How to design a circuit that can strobe HB LEDs at high frequencies (1000Hz to 35kHz). It will be overdriving 2-5 Luxeon III (3A, 3.8V each) or 2-5 Osram dragons (2A, 1.8V each). The input voltage will be 24-32 VDC. Is this possible using the MLX10803?
Answer
Let's take as example the configuration with 3 Dragon LEDs from ) OSRAM.
1. Use Coil_Calc software to set the MLX10803 mode. In this case with a minimum switching frequecy 270KHz at 24V.
2. From OSRAM Dragon spec.(LRW5 for example) page 9 follows that for desirable 2A pulse current the max. duty cycle's 3% ( D= 0,03).
3. The maximum strobe frequency starts as (270 * 0,03) / 3 = 2,7 KHz.
In this calculation it is assumed that the minimum strobe duration is 3 periods of 270KHz.
White LED Driver
Question
Can you provide the schematic for the MLX10803 to drive 5 LEDs in series at 700mA with LED Forward drop = 3.5V. Input is 160 to 265V AC
MLX10803 version
Question
What is differences of MLX10803 and MLX10803A?
On Digikey I found MLX10803KDC and MLX1083KDC-ND. I can not find what these number stand for.
Answer
The MLX10803A is an obsolete revision and is no longer available. It has the same features as MLX10803, but the current from the IREF pins is 20uA instead of 50uA. The reference voltage at the ref pins are 10 times higher in contrast to the specification that says 5 times.
The MLX10803KDC-ND is the same as MLX10803KDC. Digikey adds -ND to the manufacturer's part number.
Buy MLX10803
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