LM74681: Max Switching Frequency?

johny radio

Expert 1220 points

Part Number: LM74681
Other Parts Discussed in Thread: LM74680,

Tool/software:

Max Switching Frequency of this part? I don't see it in the datasheet.

thx

1 month ago

0 Shiven Dhir 1 month ago

TI__Guru 53115 points

Hi Johny,

Max switching frequency is not defined as the controller is not meant for switching applications.

You can consider LM74680 which can switch for upto max 1KHz frequency.

Regards,

Shiven Dhir

0 johny radio 1 month ago in reply to Shiven Dhir

Expert 1220 points

Unclear. The name of the part is "100V Ideal diode bridge controller for PoE powered applications". The datasheet schematic shows the device switching an H bridge. How can you have an H bridge without switching?

It appears that the input signal is switching the mosfets, rather than a clock, like a bridge rectifier. What's the max allow input frequency?

0 Shiven Dhir 1 month ago in reply to johny radio

TI__Guru 53115 points

Hi Johny,

POE powered applications do not have switching.

It seems to be an HBRIDGE but LM74680 and LM74681 share the same schematic.

680 uses HBRIDGE for switching and 681 uses HBRIDGE to polarity agnostic application.

Regards,

Shiven Dhir

0 johny radio 1 month ago in reply to Shiven Dhir

Expert 1220 points

The expected input for both devices is AC, correct? 680 datasheet says "The LM74680 supports voltage rectification from DC to 1kHz."

0 Shiven Dhir 1 month ago in reply to johny radio

TI__Guru 53115 points

Hi Johny,

Expected Input for LM74681 is DC

Regards,

Shiven Dhir

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LM74681: Max Switching Frequency?