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undervoltage Lockout vor Car 12V

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6 Posts
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Norman Joerns posted on 30 Apr 2009 5:01 AM

Hello,

is there a solution vom TI to cut the load from the 12V car battery when the voltage drops below a certain level? I've seen this future e.g. with camping cooling boxes.

regards

Norman Jörns

 

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8 Posts
Texas Instruments Employee

It should be easy to implement this function with a comparator which can turn off the MOSFET in series with the load when the battery voltage is below a certain threshold.

Regards!

 

Jinrong

Top 150 Contributor
46 Posts
Texas Instruments Employee

For currents less than 300mA, you can use the UC27131 smart power switch.  For higher current you would need an external transistor to handle the power.  You can also use a voltage supervisor such as the TL7700 or TL7712.  You will need to invert the /RESET signal of the TL7700 to get this to work out correctly.  Use the /RESET pin with a pull up resisotr to drive the base of a small switching transistor such as a 2N2222A or similar.  The collector of the 2N2222A drives the gate of a higher power P channel mosfet which acts as the load switch.

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Community Member

@Jinrong: It is easy but too many parts (comparator, reference, Divider, resistors for hysteresis...)

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6 Posts
Community Member

@scot: The output of the UCX7131 and UCX7132 can be used low side. That should works fine with an external Fet. I think in this case, the UCXX7132 can even measure the current in the high path to make a short circuit protection. Thx a lot. Norman Jörns

PS: is a spice-model available?

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46 Posts
Texas Instruments Employee

Norman,

There is no spice model available for UCx713x parts.

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