TLV62568: 2.4MHz switching

Shota Mago

Part Number: TLV62568

Hi team,

One of my customer will use TLV62568.

They measured switching frequency and TLV62568 showed 2.4MHz switching as these captured waveforms whereas its datasheet sates fsw is 1.5MHz(typ).

5Vin/3.3Vout/Iout=156mA
5Vin/1.2Vout/Iout=15mA

Although fsw doesn't specify max value, is this value possible or defect of device?

Best regards,

Shota Mago

over 3 years ago

0 Stefano Panaro over 3 years ago

TI__Expert 7585 points

Hi Shota,

Thank you for your question.

Can you please share the schematic of your application, so I can replicate the test condition?

Thanks,

Stefano

All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml).

0 Shota Mago over 3 years ago in reply to Stefano Panaro

TI__Expert 6580 points

Hi Stefano,

Please find the schematic from here which can be accessed via TI network.

The inductor which is used with TLV65268 is VLS252010HBX-1R0M.

Best regards,

Shota Mago

0 Stefano Panaro over 3 years ago in reply to Shota Mago

TI__Expert 7585 points

Hi Shota,

Thanks for the data.

Just a clarification: is the second waveform really taken for 15mA? It seems strange to me that the converter is already in CCM for such a small current (maybe the two pictures names are simply reversed).

Moreover, could you check if the device marking matches the one indicated in the datasheet: 14VF?

Thanks,

Stefano

0 Shota Mago over 3 years ago in reply to Stefano Panaro

TI__Expert 6580 points

Hi Stefano,

I'm sorry for having mistake for naming the pictures.

As you pointed out, the two pictures names were reversed. I modified them.

Also, I'll check device marking just in case.

Best regards,

Shota Mago

0 Stefano Panaro over 3 years ago in reply to Shota Mago

TI__Expert 7585 points

Hi Shota,

Thanks again.

I will send you the measurement data by tomorrow.

Thanks,

Stefano

0 Shota Mago over 3 years ago in reply to Stefano Panaro

TI__Expert 6580 points

Hi Stefano,

Thank you for your support.

The customer confirmed that the device marking is "14VF".

Best regards,

Shota Mago

+1 Stefano Panaro over 3 years ago in reply to Shota Mago

TI__Expert 7585 points

Hi Shota,

I have replicated your conditions on the EVM, and it seems that the results are quite coherent with the one reported from your customer..

VOUT = 3.3V, IOUT = 156mA

VOUT = 1.2V, IOUT = 15mA

I think that the behavior can be explained considering the peak current control scheme and the fact that the customer is using a 1uH inductor instead of a 2.2uH one, as reported in the application example of the datasheet. The device sets the peak current, that is reached earlier with a small inductance value. This reduces the time period and consequently it increases the switching frequency.

If you use a 2.2uH, you obtain a different behavior and a frequency coherent with the typical one (1.5MHz).

VOUT = 3.3V, IOUT = 156mA

Thanks,

Stefano

0 Shota Mago over 3 years ago in reply to Stefano Panaro

TI__Expert 6580 points

Hi Stefano,

Thank you so much for confirming with EVM and helpful answer!

I agree to that smaller inductance reaches peak current earlier and it would cause higher switching frequency than expected because the device doesn't have internal oscillator and switching frequency is determined by timing of reaching peak current and adaptive off time.

Best regards,

Shota Mago

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TLV62568: 2.4MHz switching