MLX10803 Information:

The MLX10803 is optimised for the use of low cost coils and n-channel MOSFETs. For a standard application with 1 LED and an average current of 350mA, a coil of about 100μH…220μH and ≤ 1W DC resistance should be
chosen. The sense resistor should have a value between 0.27W…0.47W / 250mW.

As a general rule: for higher load current lower inductance of the coil is needed because higher currents lengthen the charging time of the coil. Thus, switching frequencies may become lower than 20kHz which is often not desired.  It is possible to set the peak current and the average current of the LED by variation of the RSENSE resistor, the coil value and the internal oscillator frequency (ROCS resistor).

The flyback diode that carries the load current during the passive state (driver OFF) should be a fast switching and low intrinsic capacitance diode like ES1D or BYG80 in order to avoid parasitic spikes on RSENSE. The diode must be able to carry the LED current flowing during the OFF time of the driver.

The n-channel MOSFET should have low intrinsic capacitances, a drain-source voltage suitable for the application and must be able to carry the current flowing through the LED(s) during the ON time. To decrease the time of transistor switching and to improve the thermal behaviour of the module, the lines between transistor and IC should be minimised.

For applications that use an NTC resistor for temperature sensing, the NTC value has to be selected according to the application requirements. For most applications, a NTC value up to 470kW will be suitable.

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