Hi,
I need to boost a PWM signal from 3.3V to 5V to control a servo.
I use BOB-12009 ( SparkFun Logic Level Converter - Bi-Directional - SparkFun Electronics ) but it appears that the HV output low level is shifted at ~1.1V.
I can confirm that LV low level is 0V. Then the servo is not controlled and I can read in its datasheet that low level is expected to be under 0.4V.
High levels are good (+3.3V for LV, and +5V for HV).
Am I doing something wrong ?
Hi @bagelfly ,
BOB-12009 works best in applications like I2C where: a logic high is created by the pull-up resistors; and logic low is created by the controller and peripheral pulling the signal to GND. The circuit comes from an NXP Semiconductors / Nexperia Application Note AN10441.
It does not work well in applications where you need the level-shifter itself to pull / drive an output high and low.
You may need a different solution…
The SparkFun Opto-isolator Breakout would work well. The transistors on the HV side would guarantee the servo PWM signal is pulled to HV-GND (HVG) for logic low.
I hope this helps,
Paul
Hi @PaulZC ,
Thank you for quick answer !
The BOB-09118 seems better indeed. Do you know what is the reference of the transitors Q1/Q2 to deeper check the behavior ?