Add low volt shutdown op amp

what is low voltage? What is shut down?

Specs please?

--- View in Courier:

PNP +-----+-------+------+------+---E C---+ | | | | | B | | | | | [R] | | | | | | | | | | [R] [R] +---|-[R]--+ [R] | |+ | | | | | | |+\ [BAT] +--[R]--|--+--|+\ | | | > | | | | >----+-----+ |-/OPAMP | |+ +-----|-/COMPARATOR | | [REF] [R] | | | | | | | +-----+-------+------+------------------+

--- JF

TLC431 plus your choice of pass device.

(If you can switch in the ground lead pass device possibly not needed.) ...Jim Thompson

-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

P-fet pass device. Beware of latch-up That is you may have to test the p-fet pass device with the op amp under various real world conditions to see if it latches.

If I may rant a bit, many parts designed for battery operation have a shutdown pin. The "trouble" is users look at the shutdown current limit and think it is too high. Perhaps a few uA. The deal is no manufacturer wants to do a really low shutdown current test on an analog part because the test is expensive and messy, so the datasheet is guardbanded with a high number that really never happens in real life. The problem with measuring shutdown current on analog parts is the bypass caps can leak. The current sense on the ATE pin driver probably needs to have it's range set and that will require settling time. Anyway the board designer sees the high shutdown current spec and then decides to put the whole board through a pass fet. OK most of the time, but it is best to soft start the board to reduce the chance of latch up.

Simplest? Maybe a crowbar and a fuse?

Good Luck! Rich