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LM7800: Please recommend LDO for my customer.

Chase Jeong
Genius 4650 points
Part Number: LM7800
Other Parts Discussed in Thread: TPS7B88-Q1, TPS7B87-Q1, TL751M-Q1, TL750M-Q1, TL1963A-Q1, LM1117, LM2940C, LM2940-N

Hello TI experts,

my customer considers LDO for their new product. please recommend LDO for my customer.

- Input : 12V

- output : 5V, 100mA(normal), 450mA (peak, within 10 seconds)

(I recommended buck converter, but they are worried about switching noise.)

I looked thermal specification of some LDOs, but I could not find suitable one.

Could you recommend one regarding thermal specification and dropout voltage?

Best regards,

Chase

  • 0
    TI__Mastermind 37855 points

    Hi Chase,

    This is a tough one because 10 seconds is plenty long to reach thermal equilibrium at the elevated power dissipation. I found a device that can work, but it will depend on the expected ambient temperature. TPS7B86/7/8-Q1, TPS7B87-Q1, and TPS7B88-Q1 all come in a TO-252 package with a large thermal tab, so I think it would work if their expected ambient temperature isn't too high (would need to be less than about 40C). Or if they have room on the board to have a lot of GND copper to connect the device to, they could get the RθJA down a bit so that they could operate it at a higher ambient temperature. Otherwise, they may need to do a buck converter because more than 3W is a lot of power for any LDO to dissipate. If they aren't too restrained by size or cost, they can do a buck converter + LDO to get the voltage down more efficiently and also not have the switching noise. 

    Regards,

    Nick

  • 0 in reply to Nick Butts
    Genius 4650 points

    Dear Nick,

    Thank you for your support.

    Customer also want the LDO which has over 700mA current, because of voltage drop.

    Could you recommend more for this condition?

    (I found TL750M-Q1, TL751M-Q1 and TL1963A-Q1 but I am not sure that these are suitable or not.)

    Best regards,

    Chase

  • 0 in reply to Chase Jeong
    TI__Mastermind 37855 points

    Hi Chase,

    I think their best bets are LM2940-N, LM2940C, and LM1117 if they want to use a single LDO. I think a better approach (if they have the board space and budget) is to use a buck regulator in front of the LDO to limit power dissipation because even these best devices for high power dissipation will be regularly ran at close to the upper limit of a safe operating area, so it is getting close to entering reliability-related regions of operation. This is also all assuming a room-temperature ambient. If they will be using this device at an elevated temperature then these devices probably won't work.

    Regards,

    Nick