My trailblazer wants to die when i come to a stop any clues my rpms go low

I would start with fuel filter.

check for a vacuum leak especially when you have the foot on the brake.. IF so it will be a faulty brake booster.

MAYBE CHECK (MAF) MASS AIR FLOW SENSOR

The low idle and wanting to stall is caused by a dirty throttle body, it needs to be cleaned thoroughly front and back sides using throttle body cleaning spray. Also while doing the cleaning, disconnect the battery to reset the computer so it will relearn to the newly cleaned throttle body.

are you reading your rpms right....5-6000 rpms should equal 70- 85 mph....that is certainly not idle speed....invest 20bucks in a Haynes manual----it is good reading

Assuming you have the correct size battery, this really shouldn't happen! I am assuming the engine is idling at fairly low RPMs, so when the AC kicks on, it kills the engine? It might be that you need to drive the car for a bit so that the engine computer can "relearn" your settings, which disappear when you change the battery. Or, when your battery died, one of your sensors might have gone with it. There is a idle sensor on most cars that raises the idle RPMs when the AC comes on.

check throttlr sensor

your idle speed too low.take it to a dealer.they have to reset idle.it should be 600-800 rpms.when you turn on air conditioner.the computer steps up idling to keep engine from stalling .your curb idle too low.

the same thing happened to me last week, turns out it was the idle valve that needed to be replaced...seems like some oil got inside and clogged it....

check the vacuum hose first and if it's been over 30,000 miles and you havn't had a transmission service it is a good idea to have that done