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stawiski
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Last seen: 6 months 6 days ago
Joined: 2019-10-25 12:00
DC/DC converter buck/boost capacitors

Hi Dialog,

I'm confused about DC/DC input capacitors looking at your "hardware guidelines" document and referencing that to Basic Development kit (USB dongle).

In hardware guidelines for the buck configuration says to use:

C1: 10 μF effective (output capacitor)
C2: 1 μF effective (input filter capacitor)

While the schematic shows 10uF input capacitor (on the battery side), and 1uF capacitor on the output (VBAT_LOW).

My understanding is that the comment in the brackets is wrong and you meant, considering the boost configuration has those capacitors swapped (10uF is always on the input, 1uF is on the output).

Then, looking at the schematic for the kit I have (DA14531/D2632 Basic Development Kit (USB dongle)) it has 2.2uF on VBAT_HIGH, and 10uF on VBAT_LOW, which indicates boost configuration recommended capacitors. But in this kit, by default, VBAT_HIGH gets 3.3V from the LDO and we operate in buck mode to make 1.1V-1.8V on VBAT_LOW!

Is it a mistake in the schematic?

Please elaborate on this topic.

Regards

Attachment: 
Device: 
LC_Dialog
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Last seen: 6 months 1 week ago
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Joined: 2016-09-19 23:20
Hi stawiski,

Hi stawiski,

Thanks for pointing it out and sorry about the confusion that created. It seems to me like there is an error in one of them. In Buck configuration the cap on the battery should be a 10uF and an effective 1.6uF on the Vbat_LOW. I am checking on this and will follow up again. Stay tuned. 

Best regards,
LC_Dialog

stawiski
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Last seen: 6 months 6 days ago
Joined: 2019-10-25 12:00
Any updates?

Any updates?

LC_Dialog
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Last seen: 6 months 1 week ago
Staff
Joined: 2016-09-19 23:20
Hi stawiski,

Hi stawiski,

Often times, the Development kits can include different component values to make it flexible for configuration changes like changing the board config from BUCK to BOOST by simple rework etc., 

The component values in the HW Design guidelines are accurate. We have also published the schematics and board files for all 3 configurations (BUCK, BOOST &Bypass) in DA14531 flat designs. I would recommend you to review and follow these design guidelines instead of the dev kit schematics. 

https://www.dialog-semiconductor.com/sites/default/files/da14531-ed-qfn-buck-376-33-a.zip

Best,
LC_Dialog