Why TPS70933DBVR Doesn’t Start Up Possible Faults

Analysis of Why the TPS70933DBVR Doesn’t Start Up: Possible Faults and Solutions

The TPS70933DBVR is a low-dropout (LDO) voltage regulator used in various electronic devices. If it fails to start up, it can be due to several factors. Below is a step-by-step guide to help diagnose and fix the issue.

1. Check Power Supply Voltage

Possible Fault:

The TPS70933DBVR requires an input voltage that is higher than the output voltage by a certain margin. If the input voltage is too low, the device cannot start.

How to Check:

Use a multimeter to measure the input voltage. Ensure that the input voltage is at least 1.5V higher than the desired output voltage.

If the input voltage is below the required level, the device will not turn on.

Solution:

Ensure the power supply providing input voltage is working correctly and has the right voltage rating.

If necessary, replace or adjust the power supply to meet the required voltage specifications.

2. Verify the Enable Pin

Possible Fault:

The TPS70933DBVR includes an enable pin (EN), which must be driven high to turn on the regulator. If the enable pin is floating or low, the device will not start.

How to Check:

Check the voltage on the EN pin. It should be logic high (typically above 1.2V for the TPS70933DBVR) to enable the regulator.

If the EN pin is connected to a pull-down resistor or not driven properly, the LDO will not start up.

Solution:

Ensure that the EN pin is connected correctly and driven high by an external signal or a pull-up resistor.

If the EN pin is floating, add a pull-up resistor to ensure it gets the correct voltage level.

3. Examine Output capacitor and Load

Possible Fault:

An inappropriate or faulty output capacitor can cause startup issues. The TPS70933DBVR requires a specific output capacitance to operate correctly.

How to Check:

Ensure the output capacitor is within the recommended range (typically 10µF ceramic).

Check for any short circuits or damage to the capacitor, which can prevent the regulator from starting.

Also, check if the load connected to the output is within the specified limits.

Solution:

Replace the output capacitor with a known good one that matches the recommended specifications.

Ensure that the connected load is within the operating range of the regulator.

4. Look for Overcurrent or Overtemperature Protection

Possible Fault:

If the regulator is drawing too much current or is overheating, it may enter protection mode, which can prevent startup.

How to Check:

Measure the current drawn by the circuit to ensure it is within the maximum current output of the TPS70933DBVR (typically 300mA).

If the regulator is overheating, you may see a thermal shutdown, especially if the input voltage is high or there is insufficient heat dissipation.

Solution:

Reduce the current draw or improve heat dissipation to prevent the regulator from entering protection mode.

Check for any short circuits in the load or external circuitry that could be causing excessive current draw.

5. Inspect the PCB Design

Possible Fault:

Incorrect PCB layout or poor soldering can lead to startup issues.

How to Check:

Inspect the PCB for any potential issues like poor solder joints, especially around the enable pin, input, and output pins.

Ensure the PCB traces are wide enough to handle the required current and that there is no short circuit between traces.

Solution:

Rework any poor solder joints and ensure there are no shorts.

If necessary, redesign the PCB layout to ensure proper voltage levels and good routing of signals to the regulator.

Conclusion

If your TPS70933DBVR doesn’t start up, check these common factors:

Input voltage. Enable pin voltage. Output capacitor. Overcurrent or overheating conditions. PCB design and soldering issues.

By following this step-by-step guide, you should be able to diagnose and resolve the issue effectively.