[DA14531] Selection of Capacitor at Buck mode

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Eric Kim
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[DA14531] Selection of Capacitor at Buck mode

Hello~ Dialog Support Team,

I am designing with two documents for the DA14531. One is DATASHEET(Revision 2.1 / 17-Oct-2019) and the other is User Manual(UM-B-114 / Revision 1.1 / 25-Oct-2019). However, I found a difference information between two documents.

     [Datasheet 30page/352page] Figure 6. Lithium Coil Cell Powered System Diagram (BUCK configuration)

          C1 : 10uF, C2 : 1uF

     [User manual 13page/80page] Figure 6. DA14531 PRO-DB Power Selection

          C1 :  input capacitor for buck mode and output capacitor for boost mode. As input capacitor this must be equal to 2.2 µF. As an output capacitor, the effective capacitance must be at least 1 μF.

          C2 : for the PRO-daughterboard, this capacitor is set to 10 μF

 

I wonder which information is correct.

 

Thanks~

Device: 
PM_Dialog
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Last seen: 1 week 6 days ago
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Joined: 2018-02-08 11:03
Hi Eric Kim,

Hi Eric Kim,

According to DA14531 Datasheet and the AN-B-075: DA14531 Hardware Guidelines application mote, in buck mode configuration, the suggested value of the capacitors for the DCDC converter setup should be :

C1 = 10 µF effective capacitance (output capacitor – VBAT_HIGH)

C2 = 1 µF effective capacitance (input filter capacitor – VBAT_LOW)

For the buck mode configuration, an effective capacitance of 1uF should be applied at VBAT_LOW. The capacitor at the battery side (VBAT_HIGH) is depending on the batterie's internal resistance. Usually a 10uF capacitor is enough. The DA14531 DK is designed to have configurable selection for buck, boost and bypass mode. My recommendation would be to follow the HW design guidelines document.

Thanks, PM_Dialog