ADuM5402, Viso specification on datasheet

Hi,

Please let me ask to confirm the description on datasheet of ADuM5402, in case 3.3V primary (VDD1) / 3.3V secondary (Viso)

such as below.

Here, recommended operation range for VDD1 is, 3.0 V ≤ VDD1 ≤ 3.6 V.

Question is, at Setpoint in 1st row, shows Viso is  3.0 V ≤ Viso ≤ 3.6 V.  Does it mean,

a) Viso is determined by actual value of Vdd1 with in the above range ? In other words, if Vdd1 is 3.5V for example, Viso will be around 3.5V uniquely ?

or

b) Despite what voltage of VDD1 is, Viso will be in the range of 3.0 V ≤ Viso ≤ 3.6 V ? In other words, even if Vdd is quite stable around 3.5V, Viso can be 3.0 V ≤ Viso ≤ 3.6 V ?

Your confirmation would be very much appreciated.

Best Regards,

  • Hello Usagsi

    This is a fully regulated power supply, but there is a limit on how much you can step up voltage at a given load before it goes out of regulation.

    What the two specs mean is that the output regulation set point will be between 3V and 3.6V.  Typically when set for low voltage operation with the Vsel pin tied low, the output will be a bit above 3.3V, but it can shift based on temperature.  It seems like a wide range, but we have to cover a very wide range of temperature.  At a given temperature, it will hold the set point independent of the voltage on the input side.

    The input range could actually be 3.0V to 5.5V for a 3.3V setpoint and the regulation circuit would maintain the set point properly.  So the output does not track the input voltage.  There is a limit to how much the system can step up a voltage, over the full load range, it is enough to maintain the output if the input is at the lower end of its voltage range.

    So for your specific examples above,

    A) if you have a 3.5V input, the output will be 3.3V.

    B) again, if VDD1 is anywhere in the 3.0V-5.5V range the output will be 3.3V

    If you set the output for 5V, and you give it 3.5V at the input, it will likely run its PWM to 100% and the part will produce something less than 5V and be proportional to the input voltage and output load.  That is simply because the part is out of regulation under that condition.

    I hope this clarifies the operation of the part.  It is a true regulated DC-DC converter.

    Best regards,

    MSCantrell

  • Dear MSCantrell,

    Thank you very much for your answer and clear descriptions.

    One thing in addition, if you have any data or chart, which shows Viso ( between 3.0V and 3.6V ) correlated by temperature, it would be very much appreciated. I believe it is not shown in datasheet on web.

    Best Regards,

    Usaghi

  • Hello Usaghi,

    Here is some bench data on a very similar part.  It is an average of only four devices so it wanders a bit.  You can see that there is a very small dependace on Vdd1 and a larger dependace on temperature.

    Best regards,

    MSCantrell

  • 0
    •  Analog Employees 
    on Aug 2, 2018 4:46 PM over 2 years ago
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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