That paragraph does not exist in the datasheet i have.
** Wonderful; a chip cap is so much more convenient..so one might cheat by putting a SMD resistor in series? What about caps on the input? Same ugly story?
Sounds like Obama..
Hah! You like to cheat..i just proposed it sort-of like a joke. But you Kellogs Serious..
I'm looking at the 26 page data sheet? Mind you 20 pages are package info. The graph claims stability over the full operating temp range with a load greater then about 5mA with the recommended cap in the recommended esr range.
Don't you have TI's data sheet?
Here is a direct link.
The product folder link I posted earlier has an application note on PMOS LDO's.
Winning by moving the goal posts is a way of life in both analogue and electrooptics.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
What i was looking at was a TI book, Data Book #3 in a series of 3; Linear Circuits: Voltage Regulators and Supervisors. Now i have that data sheet courtesy of you and see the crap i found - the same large current draw peak before regulation.
I think i will go back to the 78L05..
The data sheet doesn't say whether it is a MOS or BJT LDO but it must be a BJT PNP since it has high Quiescent current particularly near the dropout. Try a PMOS LDO I've been testing the MCP1791T-5002EDC it has about 70 to 90uA Quiescent current no matter the load current. The regulator shuts down at 4V in and wont restart until about 5.6V.
I just measured the Quiescent current for the 78L05 (ST part) for the same line and load conditions that I used on the MCP1791T-5002EDC 8VDC in 12.86mA load current the Quiescent current for the 78l05 was 3.2mA compared to the 86uA of the MCP1791T.The Quiescent current for the MCP1791T will be consistent over load range and only varies widely over temp and line voltage but still they spec a max of 130uA. Whereas the 78L05 will vary over all those parameters and particularly over load range (Ic = B*Ib) and Vce(sat) depends on Ib.
Like Joerg already mentioned you really want to test the LDO over your line, load and operating temp though. They can be finicky particularly PMOS ones.
Alternatively Semtech makes some inexpensive Buck controllers with integrated switches with low Vce sat and 2 to 5mA Quiescent current (SC4521) about a buck in low quantities.
Sorry got my PNP NPN screwed up for an NPN the base current contributes to the load current for a PNP regulator the base current is wasted through the ground.There wouldnt be a large variation in Quiescent current for an NPN pass regulator for variation in load current. Sorry for the error.
Seems that neither Mouser nor DigiKey carries the SC4521. Who does?
Digikey stocks the SC4524A.
Thanks.
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