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TL1963A: VIN Max of 27V?

Darren (FAE)
Expert 5483 points
Part Number: TL1963A
Other Parts Discussed in Thread: LM317-N, LM317, LM1086

The DS for the TL1963A lists the ABS MAX VIN and VOUT as ±20V.
Then it lists the MAX Input-Output Voltage differential as 20V.
A lot of LDO's just list the MAX Input-Output Voltage in the DS.

I have a customer considering another vendor's device, and I really like the package-size / output power / thermal characteristics of the DCQ package for the TL1963A. 

The problem is, the device would need to support an Input-Output voltage differential of 1.4V, with VIN = 26.4V and VOUT = 25V, with a max 1.1A load current.
This is a really unique case...but yes, these are the input/output requirements.
There is also some inrush current needs based on the output bus capacitance.

I know the DS lists the ABS MAX VIN and VOUT as ±20V, but is there some internal device structure reason why going up to say 27V or 30V for VIN could damage or destroy the device? Or is this VIN/VOUT just based on the max voltage drop across the internal pass element the device can support?

Can we run a characterization/simulation to see if the device might be able to support a higher input voltage - up to 26.4V and output voltage - 25V?

If this needs to be taken offline, I am in the directory.

PS: I did find the LM317-N, which looks perfect...but there was some reason I didn't like it...but I can't remember what it is now...fa
The LM317 doesn't have the DCQ package, so ℃/W is almost 10℃/W higher for LM317 DCY package than for TL1963A DCQ package.

third party device lists, for a package "similar" to the DCY, a thermal Tja of around 22℃/W, and list both JESD specs for single layer / four layer measurements...this is just crazy thermal performance...and it is the one thing we really need, besides a small package....I am having trouble finding a good fit.

Darren

  • 0
    TI__Mastermind 23361 points

    Hi Darren, 

    I have reviewed your request carefully, and I understand the differential voltage between Vin and Vout is only 1.4V. But having a 26V input is exceeding the absolute max and may reduce the reliability of the device and result in damage. 

    When releasing an LDO, we always tried to give the best input range possible, which means if the datasheet has listed 20V as the maximum, the device has been designed and tested only up to 20V. There are multiple things that could prevent a 20V device to run with higher than 20V. In design, the transistors used all have rated voltage and those are the characteristics of the components used. In qualification, the device has normally been tested for 1000 hours with power and likely to be on the maximum input voltage to confirm the reliability of the device. 

    Are you open to any other packages if the thermal performance is similar to DCY? 

    Regards, 
    Jason Song

  • 0 in reply to Jason Song
    TI__Expert 5483 points

    Hi Jason,

    Another package is fine, as long as it is smaller than 10x11, and has really good thermals.
    I realized the competitor device has the TO-263(5pin) package, and lists Tja (4-layer JESDEC test) as 20.3℃/W, and our similar package, TO-263(3pin) lists 41℃/W. I find it hard to believe the same package with similar dimensions (thermal pad) can have >20℃/W variation...so I might stick with the LM317 series.

    For the record, I have seen occasions where devices were characterized only up to previous-gen version specs for certain criteria, and upon further inspection, the device actually supported wider operating ranges. This was the background for this post. Just to see if characterization was really done to the device's true max specs. It looks like it was, and 20V is the true ABS MAX. Thanks.

    Regards,

    Darren

  • 0 in reply to Darren (FAE)
    TI__Mastermind 23361 points

    Hi Darren, 

    The closest LDO we have which might meet their requirements is the LM1086, but VDO comes pretty close to their max spec of 1.4-V @ 1.1-A. Here’s a spec comparison between the BDxxFD0 (device the customer is considering) and the LM1086.

    Regards, 
    Jason Song