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ADF-4355-3 Power Up Sequence When Controlled by STM32F030R8

Category: Software
Product Number: ADF-4355-3

When programming the ADF-4355-3 on the Analog Devices EVAL board using an STM32F030R8 microcontroller with the SPI bus connected to TP3,4,5, I found that I had to power the EVAL board before powering the STM32F030R8. If I did not, I could not initialize the ADF-4355-3 even if I  reset the microcontroller after both devices were powered. One successful solution was to add some delay before programming and initializing the GPIO.

1) I have 4 bit banged SPI busses to program 16 ADF-4355-3s

2) LE GPIO pin(s) are initialized low after making them outputs 

3) MOSI and SCLK are initialized high after making them outputs

4) I did not modify the EVAL board to include a pull-up on the LE signal. 

//************************************ Setup ****************************************
void setup() {


delay(5000); <<<<<<<<<  If I don't add some delay here, the EVAL board cannot be initialized. 5000ms is excessive, but OK for now in this application.

// Initialize the IWDG (WatchDog) with 4 seconds timeout.
// This would cause a CPU reset if the IWDG timer
// is not reloaded in approximately 4 seconds.

/* Setup Bank Select Pins - BANK A is low order bit */
pinMode(BoardSelect, INPUT_PULLUP);

// 0 = STALO, 1 = TRANSMIT
SelectedBoard = (digitalRead(BoardSelect) & 0x0001);

// Configure GPIO
digitalWrite(ACTIVITYLED, LOW);

/* Setup Load Enable and Lock Detect Pins */
for (int s = 0; s <= 16; ++s) {
pinMode(ADF4355_LE[s], OUTPUT);
digitalWrite(ADF4355_LE[s], HIGH);
pinMode(ADF4355_LD[s], INPUT_PULLUP);

/* Setup MOSI and SCLK Pins */
for (int s = 0; s <= 3; ++s) {
pinMode(ADF4355_MOSI[s], OUTPUT);
digitalWrite(ADF4355_MOSI[s], LOW);
pinMode(ADF4355_SCLK[s], OUTPUT);
digitalWrite(ADF4355_SCLK[s], LOW);



I wanted to share that for anyone who's code is "correct", but is not successful at programming the ADF-4355-3 device. I may also decide to put pull-ups on the 15 LE signals.

  • Hi,

    thank you for sharing your solution. You need to power ADF4355-3 before powering up the controller and SPI lines. Table-3 in the ADF5355-3's datasheet defines the absolute maximum of the part. when you power MCU first, digital input pins may be in an over-voltage situation because the  AVDD is 0 voltage. so powering the synthesizer first can help to protect your EVAL also.

    In some scenarios, we have observed that when you power MCU first, writing the first register twice makes the EVAL work. you can try this also to simplify your work.



  • Thank you for confirming. 

    1) We added a device to delay power up to the microcontroller

    2) We added delay before programming the GPIO on the microcontroller

    3) We added pull-ups on the LE pins

    4) I will revert the above to test your recommendation to program the "first" register twice and I will share those results. I will include this suggestion in any case.