PS for a device (need 3 different voltage)

Hi all,

I am designing a device that needs to have total 3 different voltage as Vdd:
1. chip: Vdd(min)=3.3, Vdd(max)=4.3, Vdd(norm)=3.8 with I(max)=2.6A
2. chip: Vdd(min)=3.14, Vdd(max)=3.46, Vdd(norm)=3.3 with I(max)=0.9A
3. chip (battery charger): Vdd(min)=3.75, Vdd(max)=6, Vdd(norm)=5 with I(max)=1.2A

Whole device will be powered from 8-14V, so input to all mentioned DC/DC or LDO is 12V. The device will automatically switch to Li-ion battery if external (12V) power supply is removed. To get all stated voltage levels, there are two possibilities:
1) would require one buck switcher and two LDO.
12V -> buck -> 5V and then using two LDO to get 3.8 and 3.3V. Output 5V would be just fine as input to battery charger and returning voltage from battery to LDOs would give satisfying voltage range for both chips.

2) would require one buck and two buck/boost switchers
12V as direct input to buck switcher that would give 5V as input for battery charger. two buck/boost switchers would be used to generate 3.8 and 3.3 from 12V or from Li-Ion battery.

Based on your experience, what would be better solution to achieve:
1. less energy loos
2. lower price
3. less complexity

Thanks!

Kind regards,
Gabrijel

1) Lowest energy loss=> switchers
2) Lower price=> LDO
3) Less complexity => LDO

But you also need (perhaps) to consider noise (switchers produce more noise).

Hi,

We had about the same discussion a couple of weeks ago.
Please do a forum search.

Klaus

Hi,

@KlausST: sorry, I was unable to find it so I asked... I apologize :|

@barry: by your opinion, switcher to 5V then two LDO would be a "compromise solution" (if I understand you well)...

Kind regards,
Gabrijel