When SN65HVD233DR Doesn't Go Into Standby Mode Causes and Fixes

Troubleshooting: When SN65HVD233D R Doesn't Go Into Standby Mode – Causes and Fixes

The SN65HVD233DR is a popular CAN transceiver used in embedded systems for Communication over the Controller Area Network (CAN). If the transceiver doesn't go into standby mode as expected, it can lead to Power issues or improper functioning of your system. Here is a detailed guide to help you understand the causes and solutions for this problem.

Common Causes of SN65HVD233DR Not Entering Standby Mode

Incorrect Voltage Levels on Pins: The SN65HVD233DR has specific voltage requirements for its mode control pins (e.g., STB pin for standby). If these pins are not correctly configured, the device might not enter standby mode.

Faulty STB Pin: The STB (standby) pin controls the transceiver's mode. If this pin is not driven properly (either floating or in the wrong state), it can prevent the device from entering standby mode.

Improper Logic Levels: If the logic levels on the control pins (such as EN or STB) are not within the specified voltage ranges, the transceiver may stay in normal mode instead of entering standby.

Communication Activity: The device might not enter standby mode if CAN communication is active. This is because the SN65HVD233DR typically stays in normal mode when it's transmitting or receiving data on the CAN bus.

Power Supply Issues: In some cases, if the power supply to the transceiver is unstable or incorrect, the standby functionality might not work as expected.

Internal Circuit Malfunction: A fault in the internal circuitry of the transceiver, such as damaged components or improper connections, could prevent the standby mode from being activated.

Step-by-Step Troubleshooting Process

Step 1: Check Voltage on Control Pins (STB and EN Pins) Use a multimeter or oscilloscope to measure the voltage levels on the STB and EN pins. Ensure that the STB pin is pulled low (to ground) to enter standby mode. According to the datasheet, the voltage on the STB pin should be below 0.5V to trigger standby mode. If the voltage on the STB pin is floating or outside the expected range, try pulling it low using an external pull-down resistor (typically 10kΩ) or adjust the logic controlling this pin. Also, check the EN (Enable) pin to make sure it is in the correct state for standby mode. Step 2: Ensure CAN Bus Is Inactive Ensure that there is no active communication on the CAN bus. If the device is receiving or transmitting data, it will not go into standby mode. Disconnect any active communication from the CAN bus if possible, and check whether the device enters standby mode. You may use an oscilloscope or a CAN bus analyzer to monitor the traffic on the bus. Step 3: Verify Power Supply Stability Check the power supply voltage (typically 5V for this transceiver). Ensure that it is within the specified operating range (4.5V to 5.5V). Use a multimeter to verify that the transceiver’s power pins (VCC and GND) are stable and not fluctuating. If the power supply is unstable, consider using a more stable power source or adding decoupling capacitor s (e.g., 100nF near the VCC pin). Step 4: Inspect for Short Circuits or Faulty Components Visually inspect the board for any visible signs of damage such as burnt components or broken solder joints, especially around the STB and EN pins. If possible, try replacing the SN65HVD233DR transceiver with a known working unit to see if the issue persists. If the issue is resolved, the original transceiver may be faulty. Step 5: Test with Alternative Control Logic If you're using a microcontroller or other logic circuit to control the STB and EN pins, verify that the control signals are generated correctly. Try controlling the standby mode manually by connecting the STB pin directly to ground, bypassing any microcontroller or logic circuit to rule out software or logic issues. Step 6: Check for External Interference External noise or electromagnetic interference ( EMI ) can affect the performance of the transceiver. Check for sources of EMI near the device, such as high-frequency switching power supplies or large motors. Use shielding or proper grounding techniques to reduce interference and ensure stable operation of the transceiver.

Fixes

Adjust STB Pin Voltage: If the STB pin is not being driven low, ensure it is correctly pulled to ground (below 0.5V) to trigger standby mode.

Remove Active CAN Bus Traffic: Stop any ongoing communication on the CAN bus to allow the transceiver to enter standby.

Replace Faulty Transceiver: If the SN65HVD233DR is damaged or malfunctioning, replacing the transceiver might be necessary.

Improve Power Supply: Ensure that the power supply is stable and within specifications. Add decoupling capacitors if necessary.

Implement Proper Control Logic: Ensure that your microcontroller or external logic is properly controlling the STB and EN pins according to the datasheet's requirements.

Conclusion

By following these steps, you should be able to identify the cause of why the SN65HVD233DR is not entering standby mode and apply the necessary fix. The key factors to check include voltage levels on the control pins, CAN bus activity, and power supply stability. Troubleshooting these areas systematically will help ensure the proper functionality of the transceiver.