Hello,
We have a regulator designed with "LM2651MTC-3.3/NOPB" part number and our characterization shows that the sleep mode current for this design is 250mA instead of 100mA.
Input:5V, output: 3.3V
Output capacitance: 150uF
Inductance: 39uH
This sleep mode load value of 250mA doesn't match the datasheet typical value of 100mA and is problematic for us.
To understand what the problem might be, we purchased the evaluation board for this regulator (LM2651-3.3EVAL/NOPB), and tested it. Even for the evaluation board, the sleep mode limit was 200mA and not 100mA.
On the evaluation board, we used a 5V input, the output was at almost 3.3V and it was regulating at 300kHz with <10mVpp of ripple for loads above 200mA, not 100mA.
The image below shows the output ripple of about 60mVpp at 8KHz, at 110mA of load for the evaluation board:
The next image shows the output ripple of about 60mVpp at 2.8KHz, at 180mA of load for the evaluation board:
The next image shows the output ripple at 200mA of load, with 300kHz of ripple frequency at about 11mVpp:
Could you please explain where the discrepancy between the 100mA of the datasheet and the 200mA of the evaluation board, (or the 250mA of our design) is coming from and how to lower down the limit to the datasheet typical value of 100mA?
Thanks,
Parisa