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AFE5809: Demodulator's DVDD_LDO1/2 sepcification questions

Genius 3235 points

Replies: 14

Views: 709

Part Number: AFE5809

Hi there,

For AFE5809, DVDD_LDO 1/2, it is digital power for modulator. It can be internally generated. also , external higher performance 1.4-V supply can be applied to N4 and N6 for minimizing digital noise emission.

What is the requirement for this power supply if we use external spply? Such as, current it consumes, noise requirement, and so on?

Thanks! 

  • Hi Yi,
    Thank you for using AFE5890 device.
    We will look into your question and will reply to you soon.
    Thank you very much.
    Best regards,
    Chen
  • In reply to Chen Kung:

    Hi Yi,
    How are you?
    Looks like AFE5809 data sheet only mentions DVDD_LDO1 and DVDD_LDO2
    could be enabled to be external power and tie 1.4V externally but it does not
    mention about power consumption (current or noise) at all.
    I will try to ask our system engineer and let you know later.

    Thank you very much!
    Have a nice day!

    Best regards,
    Chen
  • In reply to Chen Kung:

    Thanks for helping. We must to know this in order to choose proper power IC to supply for DVDD_LDO1/2. Thanks.
  • In reply to Chen Kung:

    Hi Chen, is there any reply from your SE colleagues? Thanks.
  • In reply to yi xiao:

    Hi Yi,

    How are you?

    For AFE5809, DVDD_LDO 1/2, it is digital power for modulator.

    According to the AFE5809 data sheet:

    Please take a look at the following:


    Thank you and best regards,

    Chen

  • In reply to Chen Kung:

    Hi Chen,

    Thanks for reply.

    I read Section 7.6 on datasheet, and found it is ADDITIONAL power consumption, 90mW/CH means 8*90/1.8 = 400mA [additional ] for one AFE5809. with 30% margin, it is max. 520mA.

    And in Section7.5(Page15), DVDD_1.8V current is max. 110mA.   

    Here is question about power supply designing:  When we enable the demodulator : 

    1. If we use Internal 1.4V for DVDD_LDO1/2, we should provide 520mA +110mA = 630mA for DVDD_1.8V per chip. Is this perception correct?

    2. If we use External 1.4V for DVDD_LDO1/2, the external 1.4V power should provide 520mA per chip, and DVDD_1.8V is still 110mA. Is this perception correct?

    Thanks again.

  • In reply to yi xiao:

    Hi Yi,

    How are you?\

    Both are right!

    Thanks!

    and best regards,

    Chen

  • In reply to Chen Kung:

    Thanks very much, Chen!
  • In reply to Chen Kung:

    Hi Chen,

    We have another question For DVDD_LDO1/2: we use External power supply for them.  

    In Pin Description Page9 of Datasheet, it writes: "These two pins should be separated on the PCB and decoupled respectively with 0.1-µF capacitors". 

    How to understand this requirement?  My understanding is, although these two pins are connected together INSIDE the IC,  BUT still require Independent Traces on PCB, and Independent 0.1uf decouple-caps. Is it so?

    Should we use TWO external LDO to supply for DVDD_LDO1/2? 

    Thanks!

    XY

  • In reply to yi xiao:

    Hi Yi,
    How are you?
    For your question for DVDD_LDO1 and DVDD_LDO2:
    from the description from the AFE5809 data sheet
    inside the AFE5809 device, these two pins (DVDD_LDO1 and DVDD_LDO2)
    are using 1.4V supplies, but inside they may not be connected together because their pin names
    are not the same (one is called as LDO1 and the other is called as LDO2).
    So looks like they are used for the different circuitries (inside one IC)
    but using the same voltage value.
    That means (when you are using external mode)
    LDO1=1.4V but may consume 300mA for circuitry #a
    but LDO2=1.4V but may consume 220mA for circuitry #b.
    Therefore please follow exactly as the same as the data sheet mentions.
    It must have its own purposes.
    Also each LDO pin needs its own (external) 0.1uF cap.
    That is very important too.

    Thank you!
    Best regards,
    Chen

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