TPS61390: question related to current mirror monitoring

Kazuhiko Hirano

Part Number: TPS61390
Other Parts Discussed in Thread: TPS61391

Hello,

My customer plans to use TPS61390.

But he does not use VSP pin, instead he would like to translate MON1/MON2 pin current to voltage using a trans impedance amp and monitor the output voltages by ADC.

Is this usage OK?

If this is OK, VSP can be left unconnected? Or some terminations are required?

Best regards,

K.Hirano

over 4 years ago

0 Helen chen over 4 years ago

TI__Mastermind 40080 points

Hi Hirano,

Let's discuss by email.

Yes, the VSP can left open.

Please check below application note for the detailed application:

0 Helen chen over 4 years ago in reply to Helen chen

TI__Mastermind 40080 points

www.ti.com/.../slvaeh5.pdf

0 Kazuhiko Hirano over 4 years ago in reply to Helen chen

TI__Genius 11613 points

Helen,

Thank you for the app note.

After reading the app note, my customer has further questions as follows.

Q1:

When VSP is left unconnected, no trigger is required. SAMPLE pin should be just connected to GND?

Q2:

Rsvcc for AVCC is mandatory? If yes, please let me know the maximum current could flow or power rating of Rsvcc.

Q3:

Rprotect for MONIN is mandatory, though WeBench does not show the Rprotect.

(Customer app is an optical module and they would like to remove as many component as possible to make the module small.)

Q4:

How much is the max voltage at ISHORT pin? (need to decide power rating of Rshort.)

Q5:

How much is the max voltage at CAP pin? (need to decide voltage rating of Ccap.)

Best regard,

K.Hirano

0 Helen chen over 4 years ago in reply to Kazuhiko Hirano

TI__Mastermind 40080 points

Dear Sir,

If the customer just want to use it as a pure boost, then they can use TPS61391.

They can check the TPS61391 UG. It is much simple than TPS61390.

0 Kazuhiko Hirano over 4 years ago in reply to Helen chen

TI__Genius 11613 points

Hello,

Thank you for your suggestion.

My customer plans to use TPS61391 now.

Since TPS61391EVM does not have Rprotect, my customer understood it is not mandatory.

However, they still would like to use smaller components than EVM if possible.

So, please respond to Q2, Q4 and Q5.

And one more question.

Q6:

At APD, maximum voltage is 30V and maximum load current is 1mA.

Can they use the following diode as D1 in the EVM schematics?

rb520cm_60t2r_e.pdf

Or any better recommended diode?

Best regards,

K.Hirano

0 Helen chen over 4 years ago in reply to Kazuhiko Hirano

TI__Mastermind 40080 points

Hi Hirano,

The diode should be OK for the application.

Please check my reply below:

Q2:

Rsvcc for AVCC is mandatory? If yes, please let me know the maximum current could flow or power rating of Rsvcc. --> <10mA current, a 0402 resistor is OK!

Q3:

Rprotect for MONIN is mandatory, though WeBench does not show the Rprotect. --> Webench just for boost stage, it is for power stage component selection.

(Customer app is an optical module and they would like to remove as many component as possible to make the module small.) --> for optical application, APD voltage ripple is a big concern, this RC filter helps reduce ripple.

Q4:

How much is the max voltage at ISHORT pin? (need to decide power rating of Rshort.) --> Lower than Maximum Vin. If Vin=3.6V, it is lower than 3.6V.

Q5:

How much is the max voltage at CAP pin? (need to decide voltage rating of Ccap.) --> Boost output voltage. If it is 30V, then a 35-50V rating cap need to be used.