LP5569 datasheet(15/93 Pages) TI2

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PWM Frequency

Sample Frequency = 10MHz

0.1

0.2 0.3

0.5 0.7 1

3 4 5 6 7 8 10

D003

LP5569

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SNVSAP8A – JULY 2017 – REVISED SEPTEMBER 2017

Product Folder Links: LP5569

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Feature Description (continued)

Figure 15. Simplified Data Flow of Master Fader

8.3.1.2.3.1

PWM Master Fader on EN/PWM Pin

The EN/PWM pin provides a dual-function input. On power up, the pin functions as the device enable (EN)

function, where the first rising edge enables the LP5569 device. After the chip_en bit is set high in the CONFIG

(addresses 07h–0Fh) MF_MAPPINGx bits = 5h configures LEDx for PWM control.

The PWM input is a sampled input which converts the input duty-cycle information into an 11-bit code. The use

of a sampled input eliminates any noise and current ripple that is typical of traditional PWM-controlled LED

drivers. The PWM input uses logic-level thresholds with VIH_MIN = 1.25 V and VIL_MAX = 0.4 V. Because this is a

sampled input, there are limits on the maximum PWM input frequency as well as the resolution that can be

achieved.

8.3.1.2.3.2

PWM Master Fader Resolution and Input Frequency Range

The PWM input frequency range is 100 Hz to 20 kHz. To achieve the full 11-bit maximum resolution of PWM

duty cycle to the code, the input PWM duty cycle must be

≥ 11 bits, and the PWM sample period (1 / fSAMPLE)

must be smaller than the minimum PWM input pulse duration. Figure 16 shows the possible brightness code

resolutions based on the input PWM frequency.

Figure 16. PWM Resolution vs PWM Input Frequency

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