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Original question:

TPS92692: TPS92692 Circuit review

TPS92692: TPS92692 Question about PMOSFET and Buck-Boost Topology

Kami Huang60
Genius 3830 points
Part Number: TPS92692

Dear Sir/Ms.

I read the specification of TPS92692, I have some questions about the content. Can you consult with you?


1. We have an example of TPS92692EVM. In the Boost architecture, if Vin > Vout, will PDRV open -MOSET?
2. We have an example of EVM, can P-MOSFET be removed? If you don't need P-MOSFET, how to design? Is R2 shorted directly? How is Pin12 PDRV connected? Is it connected or connected to the ground?


 3. The third and fourth questions are the same. Can the Resistor of CSN and CSP be placed on the Low Side? I have customers who want to use Low Side Sense.
4. We have an example of EVM, what is the Voltage Margin of CSN and CSP? The customer has this problem because of the extension of Buck-Boost? They want to know the design boundary of the LED? Is it filtered by the output capacitor? So the border can catch a little less.
The customer will ask the third and fourth questions because they want to make the output voltage higher, and the LEDs can be several strings.

5. The fifth problem is that the customer wants Class 5, which requires -18dB in this band of 76Mhz~108Mhz. According to their past experience, because of the spread spectrum, in the high frequency band, the signal strength after 76Mhz is more dispersed, and the filter is not well designed. So customers want to ask if there is any experience in TI that can be shared with them.
My English is not good. If you have any interesting sentences, please tell me. I will use another sentence to explain.

Best Regards,

Kami Huang

  • 0
    TI__Mastermind 18890 points

    Hi Kami,

    Please see answer:

    1.  The current in the LED will rise depending on how her the input voltage is above the LED forward voltage.  The TPS92692 will shut down the PWM FET if the LED current is 1.5 times greater than the current set point for 36mS then the SS will begin again.

    2.  You can just short R2 on the EVM...The PDRV can be left open if you are not using it.

    3.  You can have have CSP and CSN on the low side but this will affect your slope compensation and compensation component. 

    4.  I really do not understand your question here at all.

    5.  For class 5 they will need proper shielding of the board.  The spread spectrum should help them with low frequencies around the switching frequency.  For higher frequencies they might need ferrite beads and appropriate high frequency caps (0.01uF) at the output.

    Thanks Tuan

  • 0 in reply to Tuan Tran74
    Genius 3830 points

    Hello Tuan,

    Sorry for the description is not clear enough.
    Regarding the fourth question, I will ask you for another sentence.

    For the Buck-Boost architecture, Vcc >= Vin+Vout. The maximum voltage of CSN, CSN, and Vin is 65V.  The customer's quesiton is  what is the maximum voltage for designing the LEDs in series in Buck-Boost topology? The customer is concerned that the CSN and CSP voltages must be less than the Vin+Vout in the Buck-boost topology.

    In other words, what is the maximum output voltage that can be used for the topology of Buck-boost?

    This is why customers will ask CSN and CSP if they can have Low Side Sense (Question 3).

    Best Regards,

    Kami Huang

  • 0 in reply to Kami Huang60
    TI__Mastermind 18890 points

    Hi Kami,

    The recommended operating voltage on the CSP and CSN pin is specified in datasheet in section 7.3 as 60V.  What this means is the maximum VLED you can have is 60V minus Vin.  So if max Vin is 30V then the maximum VLED can be 60V - 30V = 30V.  Note that the absolute maximum voltage that can be on CSP and CSN pin is 65V from section 7.1 of the data sheet.

    Thanks Tuan

  • 0 in reply to Tuan Tran74
    Genius 3830 points

    Hello Tuan,

    Thank you for your detailed instructions.
    The other is my own question, not the customer. If it is not convenient to elaborate, you can email me. If the customer's needs are Max. Vin 24V and the output voltage VLED needs to be 50V and the Buck-Boost extension is used, the customer can only use CSN, CSP Low Side Sense.

    Best Regards,

    Kami Huang

  • 0 in reply to Kami Huang60
    TI__Mastermind 18890 points

    Hi Kami,

    What is the output current level?

    Thanks Tuan

  • 0 in reply to Tuan Tran74
    TI__Mastermind 18890 points

    Kami,

    You have not heard back from you so we believe you have resolved your issue.  This post will close now but will reopen if you reply.

    Thanks Tuan