Shutting down the NCP3063B Buck SMPS controller - Page 1
Forum section: electronics / beginners

author: ocset
author_rank: Super Contributor
timestamp: September 19, 2018, 06:21:12 pm
content: We would like to be able to shut down the NCP3063B...or at least, put it into a mode whereby it draws less bias current. –Less than the 4mA or so that the datasheet says the NCP3063B draws.The NCP3063B has no “official” shutdown pin.As such , we were thinking of adding a 1uF capacitor to the Timing pin and putting a small NFET in series with it. Switching this relatively large capacitor in would mean a vastly reduced switching frequency, and hence less bias current draw of the NCP3063B...would you agree?NCP3063B datasheethttps://www.onsemi.com/pub/Collateral/NCP3063-D.PDF

author: mariush
author_rank: Super Contributor
timestamp: September 19, 2018, 07:05:02 pm
content: the *3063 is such an ancient and just plain average series of regulator these days, you can do so much better with maybe just a few more cents when it costs to the cost of the chip.Why don't you find something with an ENABLE pin and potentially running at higher frequencies, allowing you to use smaller inductors and ceramic capacitors instead of tantalum/electrlytic/polymer for example (less space wasted on pcb)

author: capt bullshot
author_rank: Super Contributor
timestamp: September 19, 2018, 07:24:52 pm
content: I don't think reducing the switching frequency will reduce the quiescent current.What about disconnecting the GND pin using a small N-Fet?

author: ocset
author_rank: Super Contributor
timestamp: September 20, 2018, 05:24:18 am
content: ThanksWe are using NCP3063B for 24V->6V at 20mA, and also for 24V->16V at 50mAFor this purpose, we cant find anything else anywhere near as cheap as the NCP3063B.The next up seems to be the LM5019, but this costs a lot more.The NCP3063B has the great advantage of allowing us to set the peak current with the sense resistor, this means we can use a smaller inductor. Some of the othe rmonolithic ones have a high peak current threshold, and no ability to adjust it.Why do you say NCP3063B is low quality?. We dont mind the bias current, and the switch voltage of around 1V is perfectly OK for us.

author: bd139
author_rank: Super Contributor
timestamp: September 20, 2018, 06:09:11 am
content: TI do a whole document on thishttp://www.ti.com/lit/an/slla339/slla339.pdfI still like these regulatiors. They’re pretty much unconditionally stable.

author: mariush
author_rank: Super Contributor
timestamp: September 20, 2018, 06:44:22 am
content: Quote from: treez on September 20, 2018, 05:24:18 amHere's a suggestion AOZ1282 ... 35 cents if you buy 1000 (60 cents for 100):https://www.digikey.com/product-detail/en/alpha-omega-semiconductor-inc/AOZ1282CI-1/785-1750-1-ND/5451916... maybe 10-15 cents extra compared to ncp3063 but you'd save money on the inductor (since this runs at 1 mhz, you can use smaller cheaper inductors, ceramic capacitors on output etc etc basically you save pennies on the other parts) and this ones also more efficient, getting up to 95% eff (though not at <100mA).and has enable pin ... though you'd have to be careful with the layout, follow the advice in datasheet.i wonder ... for 6v 20mA does it really make sense to use a switching regulator? you could just use a LDO ... the ncp3063 will probably be less than 50% efficient at such low output current. A LDO will use 0.48w to produce 0.12w (6v @ 20mA) ... basically 25% efficiency. You could almost argue you can save so much pcb space that you'd be able to use a bigger battery and offset the losses by using a linear regulator, and if it's a device powered from an adapter, do you really care about the power loss?

author: capt bullshot
author_rank: Super Contributor
timestamp: September 20, 2018, 06:59:07 am
content: Quote from: treez on September 20, 2018, 05:24:18 amI absolutely second that. There's some second sources available for this chip and it's dead simple and dead cheap. Manufactureres don't advertise these good ol' chips, since there's little profit in them, so they prefer to sell the shiny new chips with all the bells and whistles for four times the price.

author: ocset
author_rank: Super Contributor
timestamp: September 20, 2018, 07:33:15 pm
content: Thanks Mariush, that AOZ1282 looks great!The only worry would be if it went obselete, as it doesnt seem to be too well known about.I cant think why as it looks brilliant.Thankyou.But wow, the RT6208 looks even better...as it allows setting of peak current.https://www.richtek.com/assets/product_file/RT6208/DS6208-02.pdfI cant understand why these chips arent better known......i bet it goes obselete soon because nobody knows about it.Typical in the Western world, that our products can't compete because sales people "hide" the perfectly good el-cheapo parts because it doesnt make them money...............kind of how the West chokes on our own greed.