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# LM5110: A question about driver's input voltage level of LM5110

Part Number: LM5110

hi, I'm a FAE of TI, My customer has a question about LM5110

from the Datasheet, we can know that the maximum input voltage level of LM5110's IN_A and IN_B pin is "IN to IN_REF -0.3-15V"

so we just need to consider the voltage between IN and IN-REF? Don't need to think the voltage between IN and VCC?

For example:

if we connect IN_REF and VEE, and IN is 12V, VCC is 9V, so the device also can work normally?

• Hi Erwin,

Thanks for reaching out! Im an apps eng with this device.

The datasheet should say the input voltage level is not restricted by the supply voltage, but it doesnt. Therefore I believe this device has clamping diodes on the input to VCC. So if the input voltage is more than VCC then this diode will conduct during this time and heat up the part more. Although the device should still work there will be more power dissipation to consider. Let me confirm the LM5110 has these diodes and I will update you tomorrow.

Thanks,

• hi, Jeffrey,

• Hi Erwin,

Further looking at the DS it is not clear if the inputs are restricted by the VCC voltage or not. However I do see the inputs can go as high as VCC.

Since the DS does not state that the inputs or limited by VCC, there is a good chance they are not.

To check if there is an internal Vf clamping the inputs to VCC:

Set VDD at ~8V and inject 14 V into the inputs, measure the current into the input pin and confirm the VCC stays at 8V.

That would confirm there is no diode from input to VCC.

If there is a diode:

You can use a divider to lower the input voltage, if that is necessary.

Let me know the results of the test or if you need help testing.

Thanks,