TLV62085: Switching frequency and Over current protection

Hi Nagata-san,

There is a particular load conditions where the device operates in double pulses (ex. Load = 0.6A) and this is inherent to the device but this not be a cause of concern.

With regards to the hiccup behavior during OCP, I will get back to you asap.

Best regards,

Excel

Hi, Excel -san,

In your comment of

> This is inherent to the device but this not be a cause of concern.

Could you please give me advice which aspect you said it is not cause of concern? (Why you can say this is not issue?)

Regards,
Nagata.

Hi Nagata-san,

The double pulses at Iout = 0.6A are inherent to the device.  And this is the loop response to reach the feedback regulation, which was not achieved in the initial pulse.

Best regards,

Excel

Hello Nagata-san,

I tested the TLV62085 EVM at Vout = 0.85V and measured the inductor current during OCP (as describe in section 7.3.4 of the datasheet) instead of the output current. The result show that the device shutdown once the ILIM is reached for 32 times. Refer to the figure below for reference.

Please ask the customer to measure the inductor current during OCP to determine the exact number of cycles before it shutdown to be precise.

Best regards,

Excel

Hi, Excel -san,

Thank you very much for your supports.

For SW frequency phenomenon, could you please break - down your comment "The double pulses at Iout = 0.6A are inherent to the device.  And this is the loop response to reach the feedback regulation, which was not achieved in the initial pulse"?

SW frequency of DCS is fsw = Vout / Vin * 1 / Ton. And Vout = fsw * Vin * Ton.
With customer test result, Ton( ON time) is about 150ns in Iout = 0.4A and Iout = 0.6A. ( I guess the minimum ON time may be 150ns. The 0.85V is low Vout, It may be min on time.)

The first pulse doesn't achieve target voltage. Then, the 2nd pulse support following Vout = fsw * Vin *Ton. (Vin is 4.5V and Ton is 150ns) to achieve target Vout.

Is my understanding correct? 

Regards,
Nagata.

Hi Nagata-san,

To calculate for Ton and Fsw at PFM mode, refer to the equations indicated in the datasheet.

On the other hand, you are correct. The initial pulse does not fulfill the required pulse to reach the feedback regulation (this is internal signal and not accessible to user) hence loop initiates another pulse to attain the target. Hence, there is some sort of double pulse. Refer to the figure below for reference.

Best regards,

Excel