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LP87524J-Q1: LP87524B-Q1: About the VANA pin(SDA/SCL)

mingyu OH
Prodigy 40 points
Part Number: LP87524J-Q1
Other Parts Discussed in Thread: AWR1843AOP

Tool/software:

HI, TI

I am using the LP87524J-Q1 and have a few questions.

1.Currently, I am supplying 5V to BIN_BX and VANA of the LP87524J-Q1. In the datasheet, the maximum voltage for SCL and SDA is listed as "VANA with 3.6 maximum." Does this mean that VANA can handle up to 3.6V, and SDA/SCL pin should not exceed 3.6V ? I am having trouble understanding this, so please explain.

2.When using VVANA = VVIN_BX = 5V and the PMIC output is 3.3V,

how can I determine the minimum value? The datasheet is based on VVANA = VVIN_BX = 3.7V, so I have this question.

I look forward to your response. Thank you.

  • 0
    TI__Genius 13750 points

    Hi,

    mingyu OH said:
    1.Currently, I am supplying 5V to BIN_BX and VANA of the LP87524J-Q1. In the datasheet, the maximum voltage for SCL and SDA is listed as "VANA with 3.6 maximum." Does this mean that VANA can handle up to 3.6V, and SDA/SCL pin should not exceed 3.6V ? I am having trouble understanding this, so please explain

    Yes that's correct, the voltage on SCL and SDA should not be greater than 3.6V . This is in the case when VIN = 3.3 V if it is 5V then, you need to provide from externally. 

    For example, in the  LP8752xQ1EVM (User guide), the SCL and SDA have been pulled up to 1.8V which has been taken out of MCU and the standard I2C mode is selected. 

    mingyu OH said:

    2.When using VVANA = VVIN_BX = 5V and the PMIC output is 3.3V,

    how can I determine the minimum value? The datasheet is based on VVANA = VVIN_BX = 3.7V, so I have this question.

    Did you mean the minimum voltage between input VIN and output Vout voltage? Please correct me if that's not what you mean. 

    So in that case, it has to be 0.5V minimum voltage difference between Vin and Vout that needs to be there no matter whether VIN is 3.3 V or 5V. 

    so you are good here in the case that 5V is input and 3.3 V is the vout and the difference is 1.7 V, so quite okay in that respect. 

    What radar SoC are you powering up with this PMIC ?

    Regards,

    Ishtiaque 

  • +1 in reply to Ishtiaque Panhwar
    Prodigy 40 points

    HI,

    Thank you for your response.

    1.Regarding the voltage of SCL and SDA: If it should not exceed 3.6V, it seems sufficient to just state the MAX value as 3.6V. However, I still don't understand the meaning of "VANA with." If VANA is also not supposed to exceed 3.6V, is it incorrect to use Vin_bx = Vana = 5V in the AWR1843AOP EVM that I am using? Naturally, I don't think the circuit provided by the EVM is incorrect, but I still don't understand the meaning of "VANA with," so I'm asking.

    2. I am using the AWR1843AOP: In the datasheet, the condition for DC OUTPUT Voltage accuracy is set to a minimum of -2% when Vana = Vin_bx = 3.7V. What minimum value would it have when Vana = Vin_bx = 5V?

    Regards,

    mingyu

  • 0 in reply to mingyu OH
    TI__Genius 13750 points

    Hi,

    mingyu OH said:
    1.Regarding the voltage of SCL and SDA: If it should not exceed 3.6V, it seems sufficient to just state the MAX value as 3.6V. However, I still don't understand the meaning of "VANA with." If VANA is also not supposed to exceed 3.6V, is it incorrect to use Vin_bx = Vana = 5V in the AWR1843AOP EVM that I am using? Naturally, I don't think the circuit provided by the EVM is incorrect, but I still don't understand the meaning of "VANA with," so I'm asking

    You are correct. It could be misunderstood in that sense but VANA is not necessarily 5V always it can be below that voltage level as well. For example if the VIN is 3.3V then in that case VANA can be used. The 3.6V in the spec defines the limit for SCL/SDA so VANA can be used for those up to 3.6V and if the VANA is greater then SCL/SDA voltages need to be supplied separately.

    mingyu OH said:
    2. I am using the AWR1843AOP: In the datasheet, the condition for DC OUTPUT Voltage accuracy is set to a minimum of -2% when Vana = Vin_bx = 3.7V. What minimum value would it have when Vana = Vin_bx = 5V?

    I need to check but to my understanding this should be the same. 

    Regards,

    Ishtiaque 

  • 0 in reply to Ishtiaque Panhwar
    Prodigy 40 points

    Hi,

    1. Thanks to your explanation, I now understand that the maximum voltage for SDA and SCL depends on the VANA value and should not exceed 3.6V.
    Then, if VANA is set to 5V as shown in the AWR1843AOP EVM schematic, wouldn’t the voltage on the SDA/SCL pins exceed the "VANA with 3.6V maximum" condition and cause an issue?
    To use SDA/SCL without any issues, shouldn’t the voltage on the VANA pin not exceed 3.6V?

    2. Please confirm this.

    Regards,

  • +1 in reply to mingyu OH
    TI__Genius 13750 points

    Hi,

    mingyu OH said:
    1. Thanks to your explanation, I now understand that the maximum voltage for SDA and SCL depends on the VANA value and should not exceed 3.6V.
    Then, if VANA is set to 5V as shown in the AWR1843AOP EVM schematic, wouldn’t the voltage on the SDA/SCL pins exceed the "VANA with 3.6V maximum" condition and cause an issue?

    Let correct your understanding here Maximum voltage on SDA and SCL doesn't not depend on VANA, it is just that if the VANA is 3.3V then you can use the VANA voltage for I2C interface and if the VANA is 5V like in your case then you cannot use the VANA voltage for I2C interface. You need to provide it separately. I hope this is now clear. 

    mingyu OH said:
    2. Please confirm this.

    Yes it applies to 5V Vin as well.

    Regards,

    Ishtiaque