Datasheet ILD8150, ILD8150E (Infineon) - 6

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ILD8150/ILD8150E LED driver IC for high power LEDs with hybrid dimming down to 0.5% Functional description 3 Functional description
This chapter provides a summary of the integrated functions and features, and describes the relationships between them. The parameters and equations are based on typical values at TA = 25 °C.
3.1 Buck controller features 3.1.1 Output current regulation
The hysteretic control allows fast and always stable output current and guarantees an intrinsic cycle-by-cycle over-current protection. The pin CS feeds back the voltage level on the current sense resistor RCS to the hysteretic controller. The hysteretic controller implements two voltage thresholds VCSH and VCSL. When the CS voltage crosses above the VCSH threshold the internal switch turns-off. When the CS voltage crosses below the VCSL the internal switch turns-on. The thresholds VCSH and VCSL determine the output current peak-to-peak ripple IOUT,RIPPLE = VCSH − VCSL /RCS . The target LEDs current is the undimmed average current determined by the formula ILED, AVG = VCS, AVG/RCS with VCS, AVG = VCSH + VCSL /2 . The continuous-conduction-mode (CCM) timings are tON = IOUT,RIPPLE ∙ L / VVIN − VOUT and tOFF = IOUT,RIPPLE ∙ L /VOUT .
Figure 4
show the CCM output current waveform. IOUT [A] ILED,AVG time [s] 1/fSW tON tOFF
Figure 4 Output current waveform 3.1.2 Dimming
In analog dimming the output current is proportional to the internal CS reference voltage and the output current varies analogically between 100% and 12.5% of the target output current. Hybrid dimming applies below 12.5% of the target output current so that the output current is stable at 12.5% and amplitude modulated. The modulation signal has a frequency of typically 3.4 kHz to satisfy the IEEE1789-2015 recommendation for no observable flicker in light.
Figure 5
shows the mapping between the input PWM duty cycle and the output current as a ratio of the target output current.
Figure 8
shows the detail of dim-to-off. Datasheet 6 V1.0 2019-01-31 Document Outline Features Potential applications Description Table of contents 1 Functional block diagram 2 Pin configuration 3 Functional description 3.1 Buck controller features 3.1.1 Output current regulation 3.1.2 Dimming 3.1.3 Digital soft-start 3.1.4 Low power mode 3.2 Protection features 3.2.1 Over-temperature protection 3.2.2 Under-voltage protection 4 Thermal and electrical characteristics 4.1 Package characteristics 4.2 Absolute maximum ratings 4.3 Operating conditions 4.4 Electrical characteristics 5 Package dimensions Disclaimer