TPS63070RNMR Diagnosing Undervoltage Lockout (UVLO) Issues
When dealing with the TPS63070RNMR, a Step-Up/Step-Down Converter, experiencing Undervoltage Lockout (UVLO) issues, it's essential to understand the root cause of the problem and know the steps to resolve it. Let's break down the problem systematically.
1. Understanding Undervoltage Lockout (UVLO)
Undervoltage Lockout is a feature implemented in Power supply circuits to protect the system when the input voltage drops below a certain threshold. It prevents the converter from operating inefficiently or malfunctioning, as the converter requires a minimum voltage to function properly.
In the TPS63070RNMR, the UVLO threshold is a critical factor in ensuring reliable operation. If the input voltage dips below the required level, the chip will stop functioning and enter a shutdown state, which is what we call UVLO.
2. Possible Causes of UVLO Issues
Several factors can contribute to UVLO issues in the TPS63070RNMR. Here’s a breakdown of the most common causes:
a. Input Voltage Below Minimum Operating Voltage Problem: If the input voltage to the converter is consistently lower than the UVLO threshold, the device will shut down. Solution: Check the input power supply to ensure it's within the recommended voltage range. For the TPS63070RNMR, the input voltage should be at least 2.3V to ensure proper operation. If the input voltage is fluctuating, you may need a more stable power source. b. Poor Input capacitor Selection Problem: Insufficient or poor-quality input Capacitors can cause the input voltage to sag momentarily during high load or transient conditions. Solution: Use high-quality, low ESR (Equivalent Series Resistance ) capacitors as recommended in the datasheet. Ensure that the capacitance is adequate for the current requirements. c. High Output Load Demand Problem: If the output load is too high, it could cause a voltage drop at the input that brings it below the UVLO threshold. Solution: Check the output load to ensure it doesn't exceed the specifications of the converter. Consider reducing the load or using a larger power source. d. Faulty or Incorrect Voltage Reference Problem: An incorrect or faulty voltage reference could lead to improper UVLO threshold detection. Solution: Verify that the reference voltage (typically 1.2V) is stable and within the correct limits. If there is any issue with the reference voltage, it could trigger UVLO.3. How to Diagnose UVLO Issues
a. Check Input Voltage with a Multimeter Measure the input voltage while the system is powered on. Ensure the voltage is above the UVLO threshold for the TPS63070RNMR, which is around 2.3V. If the voltage is too low, the device will trigger UVLO. b. Inspect the Power Source Look for any instability in the power source. Check if there are any power dips or fluctuations that could be causing the voltage to drop below the UVLO threshold. c. Monitor the Capacitors Inspect the input and output capacitors for proper values and health. Look for signs of damage, leakage, or high ESR. Replace capacitors that don't meet the requirements. d. Measure Load Current Use a current probe to check the output load current. If the current is too high, it could be stressing the converter and causing an undervoltage at the input.4. Step-by-Step Solution to Resolve UVLO Issues
Step 1: Verify the Input Voltage Measure the input voltage using a multimeter. Ensure it is above the UVLO threshold of 2.3V. If the voltage is too low, replace or stabilize the power supply. Step 2: Check for Voltage Drops If the input voltage is steady but you still see UVLO, check for transient voltage drops. These can happen when there is a sudden change in load or power spikes. Use a scope to capture the voltage during load changes. Step 3: Inspect Capacitors Check the input capacitors (typically 10µF or higher) to ensure they are within the specifications in terms of value, ESR, and quality. If the capacitors are failing or incorrect, replace them with the recommended type and value. Step 4: Reduce Output Load If you notice high load currents, reduce the load or ensure that the converter is not being stressed beyond its maximum rated output. The TPS63070RNMR can handle up to 3A, but exceeding this limit will cause voltage sag. Step 5: Test the Voltage Reference If the issue persists, test the voltage reference for stability. A faulty reference voltage can cause improper triggering of the UVLO. If you find a problem, replace or troubleshoot the voltage reference circuit. Step 6: Re-test the System After addressing the potential issues, re-test the system. Ensure that the input voltage stays above the UVLO threshold, and monitor the converter’s operation to confirm that it runs without entering UVLO.5. Final Thoughts
When troubleshooting UVLO issues on the TPS63070RNMR, the most common causes are an insufficient input voltage, poor capacitor selection, and excessive load demand. By systematically checking the input voltage, capacitors, load conditions, and reference voltages, you can identify the source of the problem and resolve it effectively.
Ensure that all components meet the manufacturer’s specifications, and if needed, replace any faulty or undersized components. Once the system is stable, your converter should function as expected without triggering UVLO.