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SN75477 reference schematic

Lucifer
Expert 2600 points
Other Parts Discussed in Thread: SN75477, ULN2003V12

Dear Sir,

I want to use SN75477 2ch driver for Fan control with 5V /80mA and 12V /310mA

Do you have any reference schematic of SN75477 for reference, thanks.

  • 0
    TI__Guru*** 140136 points

    Passer,

    310mA is just slightly above the recommended maximum of 300mA.  I have no schematic, but usage is very simple. The negative fan terminal goes to the SN75477 and the positive fan terminal goes to the 5V or 12V supply.  The clamp pin goes to the higher supply, 12V. A side effect is that the 5V fan will run via the clamp diode if the 5V supply is powered and the 12V supply hasn't powered up yet.

    I attached typical and maximum power dissipation calculations for SN75477 and alternative ULN2003V12

    Cost and power can be reduced with ULN2003V12. Use 3 channel to drive 12V 310mA load and 1 channel for 5V 80mA load.

    This leaves 3 channel free for other inverting open drain functions. It has the same side effect because clamp diode on COM pin.

    5148.SN75477.xlsx