LM3488 Shutdown

Mike H Meyer

Other Parts Discussed in Thread: LM3488, TL431

I'm looking at the LM3488 for a SEPIC application. The FA/SYNC/SD pin voltage has a max value of 7V and note 5 recommends connecting the pin to Vin through a resistor to turn the regulator off. Can it be assumed that if Vin is larger than 7V and the circuit from Figure 8 is used that the VSD and Isd specs will not be violated? If not, is there a configuration that would be more preferable?

over 13 years ago

0 Denislav Petkov over 13 years ago

TI__Mastermind 19891 points

Hello Mike,

It cannot be assumed that if VIN is greater than 7V the circuit in figure 8 will not violate the abs max spec on the SD pin. The voltage you apply on the right of the 10k resistor in figure 8 must be less than 7V to ensure no abs max rating violation.

What is the minimum and maximum VIN that you are planning to use? May be we can suggest another configuration for your case.

Regards,
Denislav

0 Mike H Meyer over 13 years ago in reply to Denislav Petkov

Expert 1560 points

Vin 11-20V
Iout 500mA

I'm looking at using a TL431 to provide an intermediate voltage rail for the shutdown pin pull-up.

0 Denislav Petkov over 13 years ago in reply to Mike H Meyer

TI__Mastermind 19891 points

Hello Mike,

The TL431 you are considering will work and will be accurate.

You can also consider deriving the shutdown pull-up voltage with a resistor and a zener from VIN.

Regards,

Denislav

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LM3488 Shutdown