TPS7A4101 EN pin

Anthony Berwin

Other Parts Discussed in Thread: LP2951

Is there a reason that the EN pin to the IN pin has an absolute maximum voltage rating of 0.3V?

For example, if there is a logic high on the EN pin and the IN pin is connected to ground. Based on the datasheet, this part is now operating in a region outside of its absolute maximum rating.

Is this correct? Please explain and advise on a practical solution.

Thanks, Anthony

over 13 years ago

0 Darwin Fernandez over 13 years ago

TI__Mastermind 41790 points

Hi Anthony,

Unfortunately, this is not a typo and this IC must not EN HIGH before VIN or ramping down VIN while EN is HIGH. What is your application? What are your power requirements VIN, VOUT, IOUT? Perhaps we can find a solution with a different IC.

Regards,

Darwin

0 Anthony Berwin over 13 years ago in reply to Darwin Fernandez

Prodigy 250 points

Hi Darwin,

Vin=12-30V, Vout=10V

Lets assume Iout=20mA. (This is an estimate.)

Thanks, Anthony

0 Darwin Fernandez over 13 years ago in reply to Anthony Berwin

TI__Mastermind 41790 points

Hi Anthony,

Looking at TI's parametric search yields several LDOs that meet your requirements such as the LP2951. The datasheet does not have a restriction on EN/VIN voltage differential.

http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&familyId=659&uiTemplateId=NODE_STRY_PGE_T

0 Anthony Berwin over 13 years ago in reply to Darwin Fernandez

Prodigy 250 points

Hi Darwin,

The operating voltage is up to 30V. Voltage spikes or oscillations may be higher than that. A 35V rating would be sufficient. A 30V rating is not sufficient.

(1a) Internally, why must VIN be HIGH before EN is HIGH? Can I merely current limit to the EN pin?

(1b) At what voltage will this condition damage the chip. Is it 0.3V? Unfortunately, the 0.3V leaves little room for even a diode (placed from EN to IN) to protect the chip.

(2) Will the TPS79801 work? I assume this chip operates the same as the TPS7A4101.

Thanks, Anthony

0 Anthony Berwin over 13 years ago in reply to Anthony Berwin

Prodigy 250 points

Bump

0 Darwin Fernandez over 13 years ago in reply to Anthony Berwin

TI__Mastermind 41790 points

Hi Anthony,

According to the designers, for the topology used in these devices, there is no work around (including your suggestions above) that will allow an EN voltage larger than VIN without effecting the reliability of the device. They may be damaged and not work according to spec when the abs max is violated. However, there should be no need for EN to be HIGH when there is no input power. Nonetheless, if this is a more controlled application, you may need to use a logic/transistor circuit to drive the EN.

For the TPS798, you may want to inquire this in the automotive forums where they support automotive ICs

Regards,

Darwin

0 Anthony Berwin over 13 years ago in reply to Darwin Fernandez

Prodigy 250 points

Hi Darwin,

I wouldn't be asking if there was not a need.

Thanks for the help.

Regards, Anthony

0 Darwin Fernandez over 13 years ago in reply to Anthony Berwin

TI__Mastermind 41790 points

Hi Anthony,

Making a similar IC as the TPS7A41 that meet your abs max specs can be done in a business by busniess case. Please talk to your local TI FAE to discuss this opportunity.

Regards,

Darwin

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TPS7A4101 EN pin