Fixing TPS22918DBVR : What to Do When Your IC Doesn’t Reset
If you’re working with the TPS22918DBVR IC and facing an issue where it doesn’t reset properly, it’s important to troubleshoot the situation step by step. Let’s break down the potential causes of this issue, why it happens, and how to resolve it.
1. Understanding the Problem:
The TPS22918DBVR is a Power distribution switch with built-in overcurrent protection and thermal shutdown. It’s designed to control power to a device by switching the connection between Vin and Vout based on an enable signal. When you press the reset button or trigger a reset event, the IC should return to its default state, but if it doesn’t reset, that can lead to unexpected behavior in your circuit.
2. Common Causes of Reset Failures:
a. Faulty Enable Pin (EN): The EN pin controls the output state. If this pin is not being correctly pulled high or low, the IC will fail to reset as expected. This could happen if the voltage on the EN pin is unstable or if there’s poor connection to the pin.
b. Missing or Incorrect Input Voltage: If Vin is not within the recommended operating range (1.8V to 5.5V), the IC may fail to reset or perform improperly. A low or unstable Vin can prevent the IC from initializing correctly.
c. Power Supply Issues: Any noise or fluctuations in the power supply (e.g., from power rails or other nearby components) can interfere with the reset process. Make sure that the power supply is clean and within the recommended limits.
d. Thermal Shutdown or Overcurrent Protection: The IC has built-in thermal and overcurrent protection. If the IC is overheating or detects excessive current, it might enter a shutdown state. This can prevent a proper reset if the conditions don’t return to normal.
e. Grounding Issues: Poor grounding can result in erratic behavior, preventing the IC from properly resetting. Ground loops or high impedance on the ground plane can lead to unstable performance.
3. How to Troubleshoot and Fix the Issue:
Step 1: Check the Enable Pin (EN):
Verify that the EN pin is being driven correctly. It should be either pulled high (to enable the IC) or low (to disable the IC). If this pin is floating, you may need to add a pull-up or pull-down resistor to set its state.
Use an oscilloscope or multimeter to measure the voltage on the EN pin. If the signal is unstable, investigate the components driving this pin.
Step 2: Inspect the Input Voltage (V_in):
Measure the input voltage (V_in) with a multimeter to make sure it’s within the recommended range of 1.8V to 5.5V.
If V_in is fluctuating or outside this range, stabilize the input voltage by fixing the power supply or using filtering capacitor s.
Step 3: Confirm Proper Power Supply:
Make sure the power supply is providing clean, stable voltage. If there’s noise on the power rails, consider using decoupling capacitors or other filtering solutions to smooth the power supply.
Check for voltage drops or spikes that could trigger the thermal shutdown or overcurrent protection.
Step 4: Investigate Thermal Shutdown:
Check if the IC is overheating by measuring the temperature with an infrared thermometer or thermal camera.
If the IC is too hot, improve heat dissipation by adding a heat sink or improving airflow around the IC.
Review the circuit design for components that might be drawing excessive current or causing high temperatures.
Step 5: Check Grounding:
Ensure that the ground plane is solid and has low impedance. Look for any broken or high-resistance connections that could cause grounding issues.
If you suspect grounding problems, check the routing of the ground traces and make sure there are no noise sources or loose connections.
4. Additional Solutions:
a. Capacitor Placement:
Place decoupling capacitors close to the Vin and Vout pins to reduce noise and improve stability.
A good starting point is a 10nF ceramic capacitor in parallel with a 100nF capacitor.
b. Add a Reset Circuit:
Consider adding an external reset circuit (such as a push-button reset with an external supervisor IC) to ensure the IC is reliably reset during power-up or manual reset events.
c. Review Circuit Design:
If the issue persists after checking the above points, revisit the circuit design to ensure all components are within the recommended specifications and that no design flaws are causing the reset problem.
5. Conclusion:
Fixing a TPS22918DBVR that doesn’t reset requires a systematic approach to identify the root cause, whether it’s related to the enable pin, input voltage, power supply, thermal issues, or grounding. By following the steps outlined above, you can ensure the IC behaves as expected and resolves the reset issue, ultimately restoring your circuit to full functionality.