TPS7A47: noise performance across Output Capacitor

Akihisa Tamazaki

Part Number: TPS7A47

Hello team,

My customer has a question about noise performance vs Output Capacitor value.
Would you please share the noise performance in case of Cout = 10uF case?

In ds, the following is described.
8.2.2.1.1 Input and Output Capacitor Requirements
The TPS7A470x is designed and characterized for operation with ceramic capacitors of 10 µF or greater at the
input and output. Optimal noise performance is characterized using a total output capacitor value of 50 µF. Note
especially that input and output capacitances must be located as near as practical to the respective input and
output pins.

When the output capacitor is 50uF, the noise performance would be better. But The customer would like to use smaller capacitor. So he would like to know the noise performance in case of Cout = 10uF case, or comparison between 10uF and 50uF. Would you please share?

Best Regards,
Akihisa Tamazaki

over 1 year ago

John Schneider over 1 year ago

TI__Genius 12511 points

Hi Akihisa Tamazaki,

Figure 22 on the datasheet has performance showing two loading conditions with COUT = 10uF

Regards,

John

Akihisa Tamazaki over 1 year ago in reply to John Schneider

TI__Genius 10805 points

John-san,

Thank you for your comment.
Sorry for my missing it in the datasheet.

Best Regards,
Akihisa Tamazaki

Akihisa Tamazaki over 1 year ago in reply to Akihisa Tamazaki

TI__Genius 10805 points

John-san,

The customer has an additional request.
He would like to compare the noise in case of 10uF and 50uF in the same Vin and Vout condition,
so he requested TI to share it.
Can you have above noise data?

Your help is appreciated.

Best Regards,
Akihisa Tamazaki

John Schneider over 1 year ago in reply to Akihisa Tamazaki

TI__Genius 12511 points

Hi Akihisa Tamazaki,

Figure 1 has VOUT condition of 5V with Vin of 6V: 4.67uA

Figure 22 has a VOUT of 4.7V with VIN of 5.7V. The performance difference of 300mV offset is very marginal and will have little effect when comparing data.

Is this sufficient for customer?

Regards,

John

Akihisa Tamazaki over 1 year ago in reply to John Schneider

TI__Genius 10805 points

John-san,

Thank you for your comment.

The customer requested because the output current is different (Figure 1 :Iout=500mA, Figure 22: Iout=20mA or 50mA).
Can I ask you again whether do you have noise data in case of 10uF and 50uF in the same Vin and Vout condition?
If you do not have it, I will tell the customer.

Best Regards,
Akihisa Tamazaki

John Schneider over 1 year ago in reply to Akihisa Tamazaki

TI__Genius 12511 points

Hi Akihisa Tamazaki,

So the customer wants VIN/VOUT/IOUT to all be constant across the COUT change?

I will see if we have validation data for the condition and get back to you tomorrow when I'm able to get access to our Val engineers files.

Regards,
John

Akihisa Tamazaki over 1 year ago in reply to John Schneider

TI__Genius 10805 points

John-san,

Thank you for your cooperation.

The following is the condition of the customer.
Vin=27V
Vout=24V
Iout=10mA

The noise data for above or similar condition is better. In addition, 10mA or 20mA data is better.

Your cooperation is appreciated.

Best Regards,
Akihisa Tamazaki

John Schneider over 1 year ago in reply to Akihisa Tamazaki

TI__Genius 12511 points

Hi Akihisa Tamazaki,

There were no validation files for this device for the given conditions, I will be out of office over the next few days I will see if another engineer will have the bandwidth to take the noise measurements for you.

Regards,

John

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TPS7A47: noise performance across Output Capacitor