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TLV2371-Q1 in GND fault condition

Genius 9655 points

Replies: 4

Views: 687

Hi,

I need your help to find an op amp that I think is thought to select in or Database. The spec I’m looking for I think is not present in the Datasheet.

 

I need to buffer a front-end used in automotive application (below the block diagram)

 

 

The temperature range is -40°C to 85°C, the entire systems (AFE + Op Amp) is supplied at 5V (the voltage is regulated by a LDO present in the ECU)

 

The load driven by the Op Amp is the following

 

R1= 10K or 100K or 2.8K according to the ECU

C1= 1.5nF

R2= 10K

C2= 100nF

 

The Vout max level needs to be at least:

 

98% of VDD when R1=100K,  

96% of VDD when R1=10K

 

The Vout min level is 2% of VDD at any load

 

The current capability of the op amp should be 2mA.

 

Up to now everything is fine and an op amp can be found, the though starts here.

 

In case of GND fault the AFE puts its output at high level (see previous Vout max level ) and the Op amp has to do the same even if the GND path is not present anymore. From what I remember an op amp without the GND doesn’t work anymore as an op amp and its output tries to reach the rail. But how far will be from the rail ? Can I assume that the Vout high level specified in RR-IO op amp is still valid when the GND path is not present ?

 

Moreover the Op amp which represents the output of the Sensor has to survive in the following conditions (if possible without extra protections):

 

Short between Output pin of op amp and GND  (60s), VDD=5V

Short between Output pin and Battery car voltage, 18V  (60s), VDD=5V.   This condition could violates the ABS max unless any pin of the op amp can survive up to 18V independently form the VDD.

 

Overvoltage: the op amp has to survive if supplied at 18V.

 

I’m thinking to a RR-IO op amp, based on MOSFET (the VOUT should be able to stay very close to the Rail) such as the TLV2371-Q1

 

What about the ability of the device to sustain overvoltage and to source the high level Vout without GND path ? Adding resitances on the input pins and zener between VDD and GND could help ?

Any suggestions on alternative parts is appreciated.

 

Thanks,

 

domenyko

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