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LMG5200: LMG5200

Yehoram har even
Prodigy 80 points
Part Number: LMG5200
Other Parts Discussed in Thread: , LMG2100R044

TI support good morning

i plan to work with the LMG5200MOFT and have some questions.

1.  VCC maximum current is 5mA,  why  evaluation board  LMG5200EVM-02 has 1A LDO?  can i use 50mA LDO?

2.  do you have similar part in  H bridge configuration?

3. can you recommend a driver ( half bridge and full bride) for the input signals instead of the logic with 2 invertor and diode?  

  (need to include dead time control and enable).

4. notice that VCC (5v) has 5 capacitors, not according to part data sheet .

  do I need so many capacitors? 

also notice that LDO input has 4 capacitors (again not according to LDO data sheet)

total capacitors 9,   is it require?  or just good practice?    

5. can i drive the LDO voltage from the bridge source?  or noise from the bridge might affect LDO output?

6. if 2 half bridge generating H bridge, can i drive both (5v) with single LDO ( 2-3 capacitor near each LMG5200MOFT pin and LDO between  parts)?

Yehoram

   

  • 0
    TI__Expert 6935 points

    Hi Yehoram,

    1. 1A LDO is much higher current rating than necessary. Supply current for the Vdd pin is dependent on switching frequency, Figure 1 in the data sheet has a graph that shows the VDD current across frequencies.

    2. We don't have parts that come in a full bridge module. Similar to this part (LMG5200), we also have LMG2100R044. This is also a half bridge with integrated gate driver at 4.4mohm.

    3.For this device the gate driver is integrated into the package so an external gate driver is not necessary. To add deadtime control we typically use an RC circuit and set the rise time in relation to the threshold voltage of the HI and LI pins in the datasheet. To add enable, I've emailed you a schematic we've seen commonly used for adding enable feature as well as deadtime.

    4. For the LMG5200 we suggest placing the 1uF and 2.2uF capacitors. We suggest placing the 1uF cap as close to the Vcc - Agnd pins as possible. The 2.2uF cap should also be placed near the Vcc - Agnd pins but priority is not as high on how close. The other 7 caps in the EVM schematic are for the LDO, they may not be necessary for this LDO. We suggest following the LDO datasheet that you choose.

    5. I may be reading this question wrong, but from my understanding bridge source would be the Vin voltage. From this understanding, since Vin would be a DC voltage you can connect the LDO to this net to create Vcc voltage. I would suggest connecting this on the net where it is least noisy, possibly before the Vin caps.

    6. You can drive both half bridges with the same LDO.

    Best,

    Kyle

  • 0
    Prodigy 80 points

    Good morning Kyle

    Thank you for your fast replay.

    at the moment I can see on old version board

    1. 430mA consumption from 5v.

    2. when switching start I can see current oscillation in 5v supply for 200usec. after that current stable at 450mA.

    3. 5V linear drop until FET stop working.

    4. when FET stop working linear drop stop.

    5. when  switching stop, 5v return to original value.

    my initial thoughts are influence from 5v driver to the LDO feedback.

    the LDO is fix voltage but maybe implemented with internal feedback resistors and capacitor in parallel to one of the feedback resistor.

    when I look at the LMG2100R044 evaluation board I notice that there is serial 6 ohm resistor between LDO and 5v driver

    if serial resistor in serial place at my design with 450mA consumption, there will be no 5v.

    you can place that resistor only if low current value.

    that resister is part of RC filter and direction is to filter noise from  LMG5200 to LDO (if I understand correctly the purpose)

    so high current consumption indicate that the  LMG5200 doesn't work properly.

    from your experience - is the add resistor that present in  LMG2100R044 is the answer for that problem?

    or maybe there is anther reason?

    Yehoram   

  • 0 in reply to Yehoram har even
    Prodigy 80 points

    can you explain how can i load pictures?

    Yehoram

  • 0 in reply to Yehoram har even
    TI__Expert 6935 points

    Hi Yehoram,

    We've reached out to continue this thread via email. It should be easier to include pictures there without the quality degrading.

    Best,

    Kyle Wolf