How to Use MAX3421E: Examples, Pinouts, and Specs

The MAX3421E is a USB peripheral controller manufactured by Analog Devices / Maxim Integrated. It enables microcontrollers to communicate with USB devices by providing a full-speed USB interface. The MAX3421E supports various USB protocols, including control, bulk, interrupt, and isochronous transfers, making it a versatile solution for USB connectivity in embedded systems.

• USB host controllers for embedded systems
• USB device communication in microcontroller-based designs
• USB protocol analyzers
• Industrial and consumer electronics requiring USB connectivity
• USB-to-serial converters

• Manufacturer Part IDs: MAX3421EETJ+, MAX3421EEHJ+
• USB Interface: Full-speed (12 Mbps) USB host or peripheral controller
• Operating Voltage: 3.0V to 3.6V (core), 4.0V to 5.5V (USB transceiver)
• Current Consumption: 15 mA (typical, active mode)
• Operating Temperature Range: -40°C to +85°C
• Package Options:
  • MAX3421EETJ+: 32-pin TQFP
  • MAX3421EEHJ+: 32-pin TQFN
• Communication Interface: SPI (Serial Peripheral Interface)
• Integrated Features:
  • USB transceiver
  • Internal clock oscillator
  • 3.3V regulator for USB signaling
  • Interrupt output for event signaling
• ESD Protection: ±15kV (human body model)

1. Power Supply: Connect the VCC pin to a 3.3V regulated power source and the VBUS pin to a 5V USB power source. Ensure proper decoupling capacitors are placed near the power pins.
2. SPI Communication: Connect the SPI pins (MOSI, MISO, SCK, SS) to the corresponding SPI pins of the microcontroller. Configure the SPI interface for mode 0 (CPOL=0, CPHA=0).
3. USB Connection: Connect the D+ and D- pins to the USB device or host. Use proper termination resistors as specified in the datasheet.
4. Interrupt Handling: Connect the INT pin to a GPIO pin on the microcontroller to handle USB or SPI events.
5. Reset: Use the RESET pin to initialize the MAX3421E during power-up or when required.

• Voltage Levels: Ensure the SPI signals are compatible with the MAX3421E's 3.3V logic levels.
• ESD Protection: Use external ESD protection diodes if the device is exposed to harsh environments.
• Clock Source: The MAX3421E has an internal oscillator, but an external crystal (12 MHz) can be used for better timing accuracy.
• Firmware: Use a USB stack or library compatible with the MAX3421E to simplify development.

The MAX3421E can be used with an Arduino UNO to create a USB host controller. Below is an example of initializing the MAX3421E using the popular USB Host Shield library.

#include <Usb.h> // Include USB Host Shield library
#include <usbhub.h> // Include USB hub support

USB Usb; // Create USB object
USBHub Hub(&Usb); // Create USB hub object

void setup() {
  Serial.begin(9600); // Initialize serial communication
  if (Usb.Init() == -1) {
    // If USB initialization fails, print an error message
    Serial.println("USB initialization failed. Check connections.");
    while (1); // Halt execution
  }
  Serial.println("USB initialized successfully.");
}

void loop() {
  Usb.Task(); // Handle USB tasks
  // Add your USB device handling code here
}

• Install the USB Host Shield library in the Arduino IDE before running the code.
• Ensure proper wiring between the Arduino UNO and the MAX3421E SPI pins.

1. USB Initialization Fails:

   • Cause: Incorrect SPI connections or power supply issues.
   • Solution: Verify SPI wiring and ensure the VCC and VBUS pins are powered correctly.

2. No Response from USB Device:

   • Cause: Improper USB connection or unsupported device.
   • Solution: Check the D+ and D- connections and ensure the device is compatible with the MAX3421E.

3. Interrupts Not Triggering:

   • Cause: INT pin not connected or microcontroller not configured to handle interrupts.
   • Solution: Verify the INT pin connection and configure the microcontroller to detect falling edges.

4. Overheating:

   • Cause: Excessive current draw or incorrect power supply voltage.
   • Solution: Ensure the power supply voltage is within the specified range and check for short circuits.

• Q: Can the MAX3421E act as both a USB host and device?
  A: Yes, the MAX3421E can function as either a USB host or peripheral, depending on the configuration.

• Q: What is the maximum USB speed supported?
  A: The MAX3421E supports full-speed USB (12 Mbps).

• Q: Is the MAX3421E compatible with 5V logic microcontrollers?
  A: No, the MAX3421E operates at 3.3V logic levels. Use level shifters if interfacing with 5V logic.

• Q: Does the MAX3421E require an external crystal?
  A: No, it has an internal oscillator, but an external 12 MHz crystal can be used for better accuracy.