Question about using USB-C Host Shield (MAX3421E) with 1.8V SPI host

Development Boards Arduino
1

I am using SparkFun USB-C Host Shield (MAX3421E), and I would like to interface it with a SoC that only supports 1.8V SPI and GPIO.

I understand that on your board:

- MAX3421E VCC and VL are both set to 3.3V

- SPI/control signals go through a 74HC4050 level shifter

Since my SoC is 1.8V only, I would like to ask:

What modifications would you recommend to make this board compatible with a 1.8V host?

Specifically:

1. Can VL be changed from 3.3V to 1.8V while keeping VCC at 3.3V?

2. Are there any components on the board tied to VL that would prevent this change?

3. Should the 74HC4050 be bypassed or removed when using 1.8V signals?

4. Are there any other required changes to ensure reliable operation with 1.8V SPI?

I’m mainly looking for the simplest and safest way to adapt this board for a 1.8V host.

Thanks for your guidance!

2

#3 & 4 have the good news

  1. No, VL and VCC are netted together
  2. The traces
  3. No, I’d just use a level shifter between the two instead though SparkFun Voltage-Level Translator Breakout - TXB0104 - SparkFun Electronics
  4. A level shifter/level translator is probably a better method for this use-case, you’d just wire the 1.8v as the low side and 3.3v shield as high
3

Thanks for the suggestion of using the TXB0104. However, I’m planning to run SPI signals at around 1MHz or higher.

Considering the TXB0104’s weak drive strength (~2mA) and its sensitivity to capacitive loads/noise due to its auto-direction sensing, is it suitable for stable SPI data transmission?

Given that our SPI signal directions are fixed (SCK/MOSI/CS out, MISO in), would you recommend a more robust alternative like the TXS0104 or a directional-controlled buffer like the 74AVC4T245 for better signal integrity?

Looking forward to your advice.

TS-Russell <notifications@sparkfun.discoursemail.com>于2026年3月20日 周五05:48写道：

4

The 1MHz changes the options a bit, for such we really just have TXS0108E as a viable option (looks like for SPI it’s Push-pull: 60 Mbps, Open-drain: 2 Mbps, which is good for you! pg 10), but it should suit you nicely!