hello friends,
I have a digital circuit consisting of square wave oscillator ,counters,flip flops etc....Now the thing is i want a 5 v supply for the whole logic block.Input voltage is 8-12 V.5V regulator is what i need.
I thought of designing a buck converter.So calculated the average current of the whole cmos circuit and found it to be around 3 mA.
Two questions:
1)Somebody help me out in designing a buck regulator for this much low current or is it wise to use a LDO.
2) My next question is only the average current is 3 mA.But the distribution of the current isn't going to be uniform.Only during switching the current will be there in the circuit that too for a very low time.Also that current will be much greater than 3 mA (Hope i am correct).Now how do i design a buck converter.
Thanks,
Datta
Hi ,
But the average current is only 3 mA.During switching ,the current will be much more than 3 mA right?That too for some short time say in nS.Won't that be a problem
Hi ,
But the average current is only 3 mA.During switching ,the current will be much more than 3 mA right?That too for some short time say in nS.Won't that be a problem
Hi,
But if you see the lm7805 datasheet, the output voltage will be given for test condition i out >5mA.So , one cannot say there will be regulation at low currents.
And as i said only the average current of the CMOS logic circuit is 3 mA. Switching current will be much higher.Hence i think i have to design a buck converter for a higher load.
And i preferred buck cos i thought power consumption will be low
Hi,
But if you see the lm7805 datasheet, the output voltage will be given for test condition i out >5mA.So , one cannot say there will be regulation at low currents.
And as i said only the average current of the CMOS logic circuit is 3 mA. Switching current will be much higher.Hence i think i have to design a buck converter for a higher load.
And i preferred buck cos i thought power consumption will be low
78L05 works with a load as low as 1mA. With (almost?) all DC power supplies, transient load currents are handled by a capacitor in parallel with the regulator output. In your case, 100nF will probably handle it. If you want to be safe, add a 100uF electrolytic cap in parallel with the 100nF.