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L6491 Dev Board Control

Question asked by prast.eric on Jun 15, 2016
Hello again,

As an update I got my Development Board working blinking a light. I noticed that increasing the pulse frequency in HIN/LIN causes the Gate pulse width to change. The input is symmetrical to the output until about 10 kHz. Further increasing the drive frequency causes the top transistor (Q1) duty cycle to increase while the bottom transistor (Q2) duty cycle decreases. After about 20 kHz the gate shuts off. 

My dead-time pot is set to 150 kHz (2 uS) and comparator pot is set to 430 Ohms. 

Attached screenshots show CH1 the microprocessor PWM signal and CH2 is the gate drive oscillating. The first image is the Gate drive of Q2 and the second image is looking at the Gate drive of Q1,  both running at 10 kHz. See here: Screenshot

Any help would be appreciated. This is a simple part and I would think the output on the gate should mirror the input from my microprocessor up to 800 kHz which is the max frequency of the chip.

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