Hi
I have some questions about nRF5340 & nPM1300 decoupling cap
nRF5340
1.For pin A3/D2/H11/K1/L5/L11, ref. SCH is 1uF*1 and 0.1uF*5, could we only connect 1uF*1 and 0.1uF*2?
2.For consider all VDD pin(A3/D2/H11/K1/L5/L11/B7/B10/E11/B12), could we connect 1uF*3 and 0.1uF*2?
nPM1300
1.We don't use pin C3 VBUSOUT function, could we let C3 pin floating?
2.Pin C6 VOUT2 ref. SCH is 10uF*1，could we connect 4.7uF*1?
3.Pin A4 LSOUT1/VOUTLDO1 ref. SCH is 10uF*2，could we connect 4.7uF*3?
Thank you
Poki
Hello Poki,
1.For pin A3/D2/H11/K1/L5/L11, ref. SCH is 1uF*1 and 0.1uF*5, could we only connect 1uF*1 and 0.1uF*2?
2.For consider all VDD pin(A3/D2/H11/K1/L5/L11/B7/B10/E11/B12), could we connect 1uF*3 and 0.1uF*2?
Our Reference design has several 100nF (0.1uF) for QKAA and 1 × 1 µF and 5 × 0.1 µ F (for WCS) capacitors per group.
Reducing this to only 1 × 1 µF and 2 × 0.1 µF is not recommended. It is highly recommended to follow the reference design. Missing decoupling capacitors can lead to instability or increased noise, especially in RF applications.
For nPm1300,
1.We don't use pin C3 VBUSOUT function, could we let C3 pin floating?
No, C3 pin can not be in floating position. A 1uF capacitor should be connected to C3 pin. https://docs.nordicsemi.com/bundle/nwp_050/page/WP/nwp_050/vbusout_capacitor.html
2.Pin C6 VOUT2 ref. SCH is 10uF*1，could we connect 4.7uF*1?
It is recommended to follow the reference design. Because 4.7 µF is allowed if its effective capacitance is ≥ 4 µF under all conditions. It may drop under some conditions. So, it's better to follow the reference design for maintaining margin
3. .Pin A4 LSOUT1/VOUTLDO1 ref. SCH is 10uF*2，could we connect 4.7uF*3?
This is possible as it's mentioned in the documentation ''The effective total output capacitance for each pin must be a minimum of 6 µF for stability and operation.'' source: LDO and load switch output capacitor
So, 4.7uF*3 can ensure 14.1uF capacitance.
Hello Poki,
1.For pin A3/D2/H11/K1/L5/L11, ref. SCH is 1uF*1 and 0.1uF*5, could we only connect 1uF*1 and 0.1uF*2?
2.For consider all VDD pin(A3/D2/H11/K1/L5/L11/B7/B10/E11/B12), could we connect 1uF*3 and 0.1uF*2?
Our Reference design has several 100nF (0.1uF) for QKAA and 1 × 1 µF and 5 × 0.1 µ F (for WCS) capacitors per group.
Reducing this to only 1 × 1 µF and 2 × 0.1 µF is not recommended. It is highly recommended to follow the reference design. Missing decoupling capacitors can lead to instability or increased noise, especially in RF applications.
For nPm1300,
1.We don't use pin C3 VBUSOUT function, could we let C3 pin floating?
No, C3 pin can not be in floating position. A 1uF capacitor should be connected to C3 pin. https://docs.nordicsemi.com/bundle/nwp_050/page/WP/nwp_050/vbusout_capacitor.html
2.Pin C6 VOUT2 ref. SCH is 10uF*1，could we connect 4.7uF*1?
It is recommended to follow the reference design. Because 4.7 µF is allowed if its effective capacitance is ≥ 4 µF under all conditions. It may drop under some conditions. So, it's better to follow the reference design for maintaining margin
3. .Pin A4 LSOUT1/VOUTLDO1 ref. SCH is 10uF*2，could we connect 4.7uF*3?
This is possible as it's mentioned in the documentation ''The effective total output capacitance for each pin must be a minimum of 6 µF for stability and operation.'' source: LDO and load switch output capacitor
So, 4.7uF*3 can ensure 14.1uF capacitance.
