I'm mounting my MCU on PCB. I have done the schematic referring from https://www.st.com/resource/en/datasheet/stm32l476je.pdf . Please help me verify this. My conditions are as follows.I am using 2 Digital sensors and one LoRa as communication module. All are digital devices and don't deal with analog signals. My circuit provides 3.3 V DC to MCU.I will use few digital pins are I/O to my system.I'll use the MCU counter and timer.NOTE: Please let me know does VDD USB pin can support 5V DC? If not, then how a program should be uploaded to the MCU?

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Can you help me verify the schematic of STM32L476RGT6U?

Forum|Forum|4 years ago
September 27, 2021
11 replies
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I'm mounting my MCU on PCB. I have done the schematic referring from https://www.st.com/resource/en/datasheet/stm32l476je.pdf . Please help me verify this. My conditions are as follows.

I am using 2 Digital sensors and one LoRa as communication module. All are digital devices and don't deal with analog signals.
My circuit provides 3.3 V DC to MCU.
I will use few digital pins are I/O to my system.
I'll use the MCU counter and timer.

NOTE: Please let me know does VDD USB pin can support 5V DC? If not, then how a program should be uploaded to the MCU?

STM32L4 series

This topic has been closed for replies.

Best answer by TDK

NRST should have a 0.1uF capacitor to ground.

VDDA should be connected to VDD.

BOOT0 should be tied or pulled to to ground.

VDDUSB must be between 3.0 and 3.6V, per the datasheet.

Programs can be uploaded with the SWD debug connection, or by using a supported bootloader peripheral such as USB DFU.

PrajnyajitAuthor

Associate III

TDKBest answer

NRST should have a 0.1uF capacitor to ground.

VDDA should be connected to VDD.

BOOT0 should be tied or pulled to to ground.

VDDUSB must be between 3.0 and 3.6V, per the datasheet.

Programs can be uploaded with the SWD debug connection, or by using a supported bootloader peripheral such as USB DFU.

"If you feel a post has answered your question, please click ""Accept as Solution""."

PrajnyajitAuthor

Associate III

If I connect VDDA/VREF+ to VDD, then what about VSSA/VREF-? Should it be grounded or what?

Tesla DeLorean

Guru

Yes, the analogue supply is used by the clock, PLL and reset circuitry, not just ADC/DAC functionality.

Pull-Down on BOOT0, so you have the ability to drive it high to access the ROM based loader. Tying it to ground forecloses the ability change the pin state, and perform signs-of-life testing on the board/device.

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PrajnyajitAuthor

Associate III

Thank you TDK for your relentless support.

I have complied as per your suggestions.

NRST has been connected 0.1uF capacitor to the ground.

VDDA is connected to VDD.

BOOT0 is tied to the ground.

Additionally, I have connected VSSA/VREF- to GND.

Is it all right now? If I'm understanding correctly, then VDDUSB will be supplied when USB will be connected right?

TDK

VDDUSB needs to be supplied a voltage between 3.0V and 3.6V per the datasheet. Your VDD is 3.3V. So tie VDDUSB to VDD. It will not be supplied a voltage when a USB connector is present. Your schematic doesn't have a USB connector, or USB connections at all.

How do you intend to program this board? Recommend putting a standard debug header and connecting relevant pins.

Just a general readability note. Usually in schematics it's better to have multiple GND symbols rather than a net which connects all grounds. It's just easier to trace. Same with power rails like 3.3V.

"If you feel a post has answered your question, please click ""Accept as Solution""."

PrajnyajitAuthor

Associate III

Thanks, TDK. I have followed AN2606 (Page329/417, Table. 133) and understood the I2C connection procedure. I have modified the circuit, it would be very helpful if you kindly verify and let me know whether that is correct or not. As per your advice, I'll go for PCB fabrication. Your prompt response will be helfulful.

PrajnyajitAuthor

Associate III

Thank you TDK and Tesla DeLorean. I have modified it and assumes that it will be easier to verify.

Regarding USB, we already have a discussion but can you suggest me again with the pin connection here? Like which pin of this MCU to be connected with pins of a standard USB connector? It will be more clear if you explain it here in reference to the below-modified schematic.

PrajnyajitAuthor

Associate III

Please refer to this diagram, I have mentioned the occupied pins of MCU with Sensor and LoRa as per my application. Can you advise me again with the pin connection here? Like which pin of this MCU is to be connected with pins of a standard USB connector? It will be more clear if you explain it here in reference to the below-modified schematic.

PrajnyajitAuthor

Associate III

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