We would like to use a LTM4620A in our design powered from a nominal 5V Vin. This device has minimum Vin of 4.5V but is this still valid when using INTVcc? Or will device internal power need to be provided on EXTVcc pin?
The minimum of 4.5V Vin is valid when using INTVcc. The use of EXTVcc is mainly for improving the efficiency. Please do not exceed 6V on INTVcc and EXTVcc pins. In addition, please keep in mind that the maximum duty cycle for this device is 95%, and you cannot output voltage equal to or higher than Vin.
Please let me know if you have any further questions.