MPQ7231GLE Buck-Boost and EN Pin

Lighting Solutions
1

Hi,

I want to implement MPQ7231 LED driver reference design and noticed something i cant explain: In both the schematic (Figure 11) and PCB layout, the LED+ output (L2 output) appears to be connected to GND.

image
image782×303 65.7 KB

image

Could you please explain how the buck-boost topology achieves proper LED driving with this configuration? Specifically, I’m interested in understanding:

  • How the current regulation works when LED+ is at GND potential
  • If LED- operates at a negative potential relative to GND

Other question regarding EN Pin Voltage:

The datasheet specifies EN pin maximum voltage as 5.5V, however, the typical application shows EN connected with a resistor to VIN with Abs. max of 50V. The internal zener diode is specified to regulate at 7V. This seems to create a window where the EN pin could be damaged.
How is the EN pin protected in applications where VIN > 5.5V?
image

Thank you for your clarification.

Best regards,
Timo

2

Hello timob,

I will look into this and get back to you.

3

Hello,
LED+ is connected to ground as you stated. This changes the topology from the buck to inverting buck-boost. The output ends up occurring at the AGND and PGND. I believe setting the mode properly will impact the operation.

I will follow up with the enable pin recommendations.