LT3045 Solder Problem

Hi, 

I'm using LT3045 as the LDO to suppress power noise from the power supplies.
The package I bought is LT3045EMSE#PBF and I adopt the "Low Noise CC/CV Lab Power Supply" configuration in official datasheet.


However, the datasheet states that "EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB".
PIN 13 is under the chip and is really hard to solder by hand.
1) I am not sure whether it is catastrophic not to solder the PIN 13.
2) If I don't solder PIN13, do the output noise degrade?




3) If I need multiple pairs of VDD and VSS, and there are multiple LT3045s on a single PCB with one power supply.
    Do you suggest that I separate them under the consideration of output noise?


Thank you.

Top Replies

  • Hi ,

    1.)
    As stated, you have to connect EXP to GND as stated, foremost because of thermal dissipation and often because of noise considerations.
    Yes, those ICs are not easy to hand-solder. For such…

Parents
  • Hi ,

    1.)
    As stated, you have to connect EXP to GND as stated, foremost because of thermal dissipation and often because of noise considerations.
    Yes, those ICs are not easy to hand-solder. For such cases I use two temperature regulated hot air guns.
    (For unregulated ones you have to measure the temperature carefully and adjust it.)
    One for bottom heating (350-420°C) and one for heating the top side (360°C).
    On youtube there are some videos showing how to hand solder QFN ICs. MSOP is similar.
    Unfortunately, only practical experience provides the self-confidence and skill to get it done properly in short time.
    So you must start to try it for the first time. And if it doesn't work or you've "roasted" the IC, don't be frustrated. But try it again with new IC...
    Also a good starting exercise is to desolder ICs on a already damaged PCB with this technique!
    The more practical experience you built up, the more easy it gets!

    2.) Maybe, but foremost it will overheat

    3.) That depends on your layout and the current flows, especially when high dI/dt.
    Best is to have a solid ground plane so you can connect all GND, EXP to that plane by multiple vias.

Reply
  • Hi ,

    1.)
    As stated, you have to connect EXP to GND as stated, foremost because of thermal dissipation and often because of noise considerations.
    Yes, those ICs are not easy to hand-solder. For such cases I use two temperature regulated hot air guns.
    (For unregulated ones you have to measure the temperature carefully and adjust it.)
    One for bottom heating (350-420°C) and one for heating the top side (360°C).
    On youtube there are some videos showing how to hand solder QFN ICs. MSOP is similar.
    Unfortunately, only practical experience provides the self-confidence and skill to get it done properly in short time.
    So you must start to try it for the first time. And if it doesn't work or you've "roasted" the IC, don't be frustrated. But try it again with new IC...
    Also a good starting exercise is to desolder ICs on a already damaged PCB with this technique!
    The more practical experience you built up, the more easy it gets!

    2.) Maybe, but foremost it will overheat

    3.) That depends on your layout and the current flows, especially when high dI/dt.
    Best is to have a solid ground plane so you can connect all GND, EXP to that plane by multiple vias.

Children