How to Fix TPS61252DSGR Undervoltage Lockout Problems

How to Fix TPS61252DSGR Undervoltage Lockout Problems

How to Fix TPS61252DSGR Undervoltage Lockout Problems

The TPS61252DSGR is a highly efficient boost converter typically used for Power ing devices like IoT gadgets, wearables, and other low-power applications. If you are experiencing undervoltage lockout (UVLO) issues with this device, it means the converter is preventing operation because the input voltage has dropped below a specific threshold. This is an important safety feature designed to protect the circuit and ensure proper operation. Here’s a detailed, step-by-step guide to understanding and fixing undervoltage lockout problems with the TPS61252DSGR.

1. Understanding the Undervoltage Lockout (UVLO) Function

The UVLO function ensures that the converter only operates when the input voltage is sufficient to provide stable and reliable operation. If the input voltage drops below a certain level, the TPS61252DSGR automatically disables its output to prevent damage to the system.

UVLO Thresholds: The TPS61252DSGR has specific voltage thresholds, typically between 1.8V to 2.4V depending on the configuration. When the input voltage falls below this range, the converter enters lockout mode and stops functioning until the voltage rises again. 2. Common Causes of Undervoltage Lockout Issues

Several factors could lead to undervoltage lockout problems with the TPS61252DSGR:

Inadequate Input Voltage: If your input voltage is not high enough to meet the converter's minimum requirements, it will trigger UVLO. This could be due to a weak power source or an insufficient battery voltage. Power Supply Instability: Fluctuations in the power supply or noise in the system could cause the input voltage to dip below the required threshold. Incorrect PCB Layout: Poor PCB design, such as long traces or insufficient decoupling capacitor s, could introduce voltage drops, leading to the undervoltage lockout condition. Excessive Load Current: If the load current exceeds the capabilities of the power supply, it can cause voltage sagging, triggering UVLO. 3. Steps to Fix TPS61252DSGR Undervoltage Lockout Problems Step 1: Measure the Input Voltage

Start by checking the input voltage with a multimeter. Compare the actual input voltage to the datasheet’s minimum threshold for UVLO (typically around 1.8V to 2.4V). If the input voltage is too low:

For Battery-Powered Systems: Ensure that the battery is not discharged. Replace or recharge the battery as needed. For Power Supply Issues: Verify that the external power source is capable of supplying a stable voltage within the required range. Step 2: Check for Voltage Drops Due to Excessive Load

Excessive current draw can cause voltage sagging, leading to undervoltage lockout. To check:

Measure the output current from the TPS61252DSGR and compare it to the maximum rated output current. If the current draw exceeds the rated limits, reduce the load or upgrade to a higher-capacity power supply. Step 3: Inspect the PCB Layout

Ensure that your PCB layout is optimized for low-voltage operation:

Minimize Trace Lengths: Long traces between the power source and the TPS61252DSGR can cause voltage drops. Use shorter, wider traces to reduce resistance. Proper Decoupling Capacitors : Ensure the recommended input and output capacitors are installed near the converter’s pins. These capacitors help maintain stable voltage and filter out noise. Step 4: Add an Input Capacitor (If Needed)

If you’re experiencing noise or instability in the power supply, you can add an additional input capacitor close to the input pin of the TPS61252DSGR. This will help stabilize the input voltage and prevent sudden drops.

Step 5: Adjust the UVLO Threshold (If Applicable)

If you’re using the adjustable UVLO threshold version of the TPS61252DSGR, you can change the UVLO threshold by modifying the resistor divider that sets the threshold voltage. However, this should only be done if you are sure the system can operate reliably at a lower input voltage. Check the datasheet for guidance on this adjustment.

Step 6: Use a Power-On Reset Circuit (Optional)

If power-up sequencing is causing undervoltage lockout due to slow rise time or delayed input voltage, you might want to add a power-on reset circuit. This ensures that the converter starts operating only when the input voltage has stabilized above the minimum threshold.

4. When to Seek Professional Help

If you’ve checked all the above steps and the problem persists, it might be necessary to:

Inspect for potential damage to the TPS61252DSGR chip, which could cause it to malfunction. Check for issues in other parts of your circuit, such as a damaged power supply or faulty components.

At this point, consulting the manufacturer’s technical support or working with an experienced electrical engineer can help identify more complex issues.

5. Conclusion

Undervoltage lockout issues with the TPS61252DSGR are typically caused by low input voltage, excessive load, poor PCB design, or power supply instability. By carefully diagnosing the issue and following the steps above, you can resolve the problem and ensure stable operation of your boost converter. Always ensure the input voltage is within the specified range and that the PCB is properly designed to avoid future undervoltage lockout events.