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SN6501-Q1: Efficiency and behavior at fault

Part Number: SN6501-Q1

Hi,

I am considering the operation of SN6501-Q1 and I have some questions.

(1) When Load Current is small, efficiency of VIN = 5 V is worse than VIN = 3.3 V.
Is this the difference in operating frequency affected?
Is there a way to improve efficiency at VIN = 5V?

(2) If the LDO is series-connected, will the SN6501-Q1 break or reach the absolute maximum rating even if the secondary side current stops output due to overcurrent or the like?
(It is assumed that the LDO stops with overcurrent detection)

(3) Assume the case where VIN is fixed at 5 V and used.
What is the behavior of VOUT when VIN rises or falls with respect to 5 V due to malfunction?
Does VOUT output incomplete voltage? Or will VOUT stop completely?

(specification)
VIN: 5V or 5V to 16 V
VOUT: 5V or 3.3V
Vout accuracy: ±5%
IOUT: 1mA to 40mA

Best Regards,

  • Hi,

    Thanks for this post,
    I am discussing with internal teams (at TI) for answers to few of your questions, I will get back to you as soon as possible.

    Regards
    Tejas
  • In reply to Tejas Hommaradi:

    Thank you for your reply.
    Since this device does not feed back control and there is also no protection circuit, I am concerned about what kind of behavior will happen in case of malfunction.
    The reason for considering this device is that it is advantageous about price.
  • In reply to Kaji@PAN:

    Hi,

    Apologies for delay in response.

    Please find the summary of our internal discussion.

    1) The efficiency of SN6501 at 5V input is relatively lower compared to 3.3V input due to switching losses of the power supply. The switching losses of SN6501 solution increase with increase in input voltage swing leading to lower efficiency at higher input voltage. Hence the difference in efficiency with 5V & 3.3V inputs. Please note that this only the case for light loads (<10% of max load).
    Switching losses can be improved by lowering switching frequencies but SN6501 has a fixed switching frequency hence can't be improved any further for light loads.

    2) Since SN6501 operates with a fixed duty cycle, there wouldn't be any violation of absolute max of SN6501. Hence devices wouldn't be damaged. Under over-current condition, the output voltage might drop below it's designed value.

    3) Since SN6501 operates in open-loop configuration, VOUT rises and falls in proportion to VIN rise and fall provided VIN is within the operating range of SN6501 (3V to 5.5V).

    Regarding your question on the protection features of SN6501, the device is developed to keep customer application design very simple and hence it doesn't feature many protections capabilities. For application specific protections, you may need to add external circuitry per your application requirements.

    I hope this answers your questions, please let me know if you have further questions. Thanks.

    Regards
    Tejas
  • In reply to Tejas Hommaradi:

    Thank you for your reply.
    I appreciate the detailed answers.