Reference circuitry

To ensure good RF performance when designing PCBs, it is highly recommended to use the PCB layouts and component values provided by Nordic Semiconductor.

Documentation for the different package reference circuits, including Altium Designer files, PCB layout files, and PCB production files can be downloaded from the product page for the nRF52840 on www.nordicsemi.com.

In this section there are reference circuits for QIAA aQFN™73 and CKAA WLCSP, showing the components and component values to support on-chip features in a design.

Note: This is not a complete list of configurations, but all required circuitry is shown for further configurations.
Some general guidance is summarized here:
  • External supply from VDD is only available when power is supplied to VDDH. External supply is annotated with the VEXT net name.
  • When supplying power from a USB source only, VBUS must be connected to VDDH if USB is to be used.
  • Components required for DC/DC function are only needed if DC/DC mode is enabled for that regulator.
  • NFC can be used in any configuration.
  • USB can be used in any configuration as long as VBUS is supplied by the USB host.
  • The schematics include an optional series resistor on the USB supply for improved immunity to transient overvoltage during VBUS connection. Using the series resistor is recommended for new designs.
  • Two component values for the RF-Match network for the QIAA aQFN™73 package are given and referred to as v1.0 and v1.1 in the following tables. The reference schematics use v1.1 component values, which are recommended for new designs to improve the margin for spurious emissions during regulatory approval tests. However, both v1.0 and v1.1 are valid and can be used. All other RF parameters are unchanged.

Circuit configurations for QIAA aQFN™73

Table 1. Circuit configurations
Config no. Supply configuration Features that can be enabled for each configuration example
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 1 USB (VDDH = VBUS) N/A Yes No No Yes No
Config. 2 Battery/Ext. regulator N/A Yes No No Yes No
Config. 3 N/A Battery/Ext. regulator No No No Yes No
Config. 4 Battery/Ext. regulator N/A Yes Yes Yes Yes No
Config. 5 N/A Battery/Ext. regulator No No Yes Yes Yes
Config. 6 N/A Battery/Ext. regulator No No No No No

Circuit configurations for CKAA WLCSP

Table 2. Circuit configurations
Config no. Supply configuration Features that can be enabled for each configuration example
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 1 USB (VDDH = VBUS) N/A Yes No No Yes No
Config. 2 Battery/Ext. regulator N/A Yes No No Yes No
Config. 3 N/A Battery/Ext. regulator No No No Yes No
Config. 4 Battery/Ext. regulator N/A Yes Yes Yes Yes No
Config. 5 N/A Battery/Ext. regulator No No Yes Yes Yes
Config. 6 N/A Battery/Ext. regulator No No No No No

Circuit configuration no. 1

Circuit configuration number 1 for QIAA aQFN™73, showing the schematic and the bill of materials table.

Table 3. Configuration summary for circuit configuration no. 1
Config no. Supply configuration Enabled features
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 1 USB (VDDH = VBUS) N/A Yes No No Yes No
Figure 1. Circuit configuration no. 1 schematic

Note: For PCB reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.
Table 4. Bill of material for circuit configuration no. 1
Designator Value v1.0 Value v1.1 Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2 % 0402
C3 1 pF 0.8 pF Capacitor, NP0, ±10 % 0402
C4 1 pF 0.5 pF Capacitor, NP0, ±10 % 0402
C5, C7, C8, C12 100 nF Capacitor, X7R, ±10 % 0402
C6, C20 4.7 µF Capacitor, X7R, ±10 % 0603
C9 820 pF Capacitor, NP0, ±5 % 0402
C10, C13, C22 N.C. Not mounted 0402
C11 100 pF Capacitor, NP0, ±5 % 0402
C14, C15 1.0 µF Capacitor, X7R, ±10 % 0603
C19 4.7 µF Capacitor, X7S, ± 10 % 0603
L1 3.9 nH 4.7 nH High frequency chip inductor ±5 % 0402
R1 4R7 Resistor ±1 %, 0.063W 0402
U1 nRF52840-QIAA Multi-protocol Bluetooth low energy, IEEE 802.15.4, ANT, and 2.4 GHz proprietary system-on-chip AQFN-73
X1 32 MHz XTAL SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz XTAL SMD 3215, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_3215

Circuit configuration no. 2

Circuit configuration number 2 for QIAA aQFN™73, showing the schematic and the bill of materials table.

Table 5. Configuration summary for circuit configuration no. 2
Config no. Supply configuration Enabled features
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 2 Battery/Ext. regulator N/A Yes No No Yes No
Figure 2. Circuit configuration no. 2 schematic

Note: For PCB reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.
Table 6. Bill of material for circuit configuration no. 2
Designator Value v1.0 Value v1.1 Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2 % 0402
C3 1 pF 0.8 pF Capacitor, NP0, ±10 % 0402
C4 1 pF 0.5 pF Capacitor, NP0, ±10 % 0402
C5, C7, C8, C12 100 nF Capacitor, X7R, ±10 % 0402
C6, C20 4.7 µF Capacitor, X7R, ±10 % 0603
C9 820 pF Capacitor, NP0, ±5 % 0402
C10, C13, C22 N.C. Not mounted 0402
C11 100 pF Capacitor, NP0, ±5 % 0402
C14, C15 1.0 µF Capacitor, X7R, ±10 % 0603
C19, C21 4.7 µF Capacitor, X7S, ±10 % 0603
L1 3.9 nH 4.7 nH High frequency chip inductor ±5 % 0402
U1 nRF52840-QIAA Multi-protocol Bluetooth low energy, IEEE 802.15.4, ANT, and 2.4 GHz proprietary system-on-chip AQFN-73
X1 32 MHz XTAL SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz XTAL SMD 3215, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_3215

Circuit configuration no. 3

Circuit configuration number 3 for QIAA aQFN™73, showing the schematic and the bill of materials table.

Table 7. Configuration summary for circuit configuration no. 3
Config no. Supply configuration Enabled features
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 3 N/A Battery/Ext. regulator No No No Yes No
Figure 3. Circuit configuration no. 3 schematic

Note: For PCB reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.
Table 8. Bill of material for circuit configuration no. 3
Designator Value v1.0 Value v1.1 Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2 % 0402
C3 1 pF 0.8 pF Capacitor, NP0, ±10 % 0402
C4 1 pF 0.5 pF Capacitor, NP0, ±10 % 0402
C5, C7, C8, C12 100 nF Capacitor, X7R, ±10 % 0402
C6, C20 4.7 µF Capacitor, X7R, ±10 % 0603
C9 820 pF Capacitor, NP0, ±5 % 0402
C10, C13, C22 N.C. Not mounted 0402
C11 100 pF Capacitor, NP0, ±5 % 0402
C14, C15 1.0 µF Capacitor, X7R, ±10 % 0603
C21 4.7 µF Capacitor, X7S, ±10 % 0603
L1 3.9 nH 4.7 nH High frequency chip inductor ±5 % 0402
U1 nRF52840-QIAA Multi-protocol Bluetooth low energy, IEEE 802.15.4, ANT, and 2.4 GHz proprietary system-on-chip AQFN-73
X1 32 MHz XTAL SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz XTAL SMD 3215, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_3215

Circuit configuration no. 4

Circuit configuration number 4 for QIAA aQFN™73, showing the schematic and the bill of materials table.

Table 9. Configuration summary for circuit configuration no. 4
Config no. Supply configuration Enabled features
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 4 Battery/Ext. regulator N/A Yes Yes Yes Yes No
Figure 4. Circuit configuration no. 4 schematic for QIAA aQFN™73
Schematic: Circuit configuration no. 4 for QIAA aQFN73

Note: For PCB reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.
Table 10. Bill of material for circuit configuration no. 4
Designator Value v1.0 Value v1.1 Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2 % 0402
C3 1 pF 0.8 pF Capacitor, NP0, ±10 % 0402
C4 1 pF 0.5 pF Capacitor, NP0, ±10 % 0402
C5, C7, C8, C12 100 nF Capacitor, X7R, ±10 % 0402
C6, C20 4.7 µF Capacitor, X7R, ±10 % 0603
C9 820 pF Capacitor, NP0, ±5 % 0402
C10, C13, C22 N.C. Not mounted 0402
C11 100 pF Capacitor, NP0, ±5 % 0402
C14, C15 1.0 µF Capacitor, X7R, ±10 % 0603
C16 47 nF Capacitor, X7R, ±10 % 0402
C19, C21 4.7 µF Capacitor, X7S, ±10 % 0603
L1 3.9 nH 4.7 nH High frequency chip inductor ±5 % 0402
L2 10 µH Chip inductor, IDC,min = 50 mA, ±20 % 0603
L3 15 nH High frequency chip inductor ±10 % 0402
L4 10 µH Chip inductor, IDC,min = 80 mA, ±20 % 0603
U1 nRF52840-QIAA Multi-protocol Bluetooth low energy, IEEE 802.15.4, ANT, and 2.4 GHz proprietary system-on-chip AQFN-73
X1 32 MHz XTAL SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz XTAL SMD 3215, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_3215

Circuit configuration no. 5

Circuit configuration number 5 for QIAA aQFN™73, showing the schematic and the bill of materials table.

Table 11. Configuration summary for circuit configuration no. 5
Config no. Supply configuration Enabled features
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 5 N/A Battery/Ext. regulator No No Yes Yes Yes
Figure 5. Circuit configuration no. 5 schematic

Note: For PCB reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.
Table 12. Bill of material for circuit configuration no. 5
Designator Value v1.0 Value v1.1 Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2 % 0402
C3 1 pF 0.8 pF Capacitor, NP0, ±10 % 0402
C4 1 pF 0.5 pF Capacitor, NP0, ±10 % 0402
C5, C7, C8, C12 100 nF Capacitor, X7R, ±10 % 0402
C6, C20 4.7 µF Capacitor, X7R, ±10 % 0603
C9 820 pF Capacitor, NP0, ±5 % 0402
C10, C13, C22 N.C. Not mounted 0402
C11 100 pF Capacitor, NP0, ±5 % 0402
C14, C15 1.0 µF Capacitor, X7R, ±10 % 0603
C16 47 nF Capacitor, X7R, ±10 % 0402
C21 4.7 µF Capacitor, X7S, ±10 % 0603
CT1, CT2, CT3, CT4 Antenna dependent Capacitor, NP0, ±5 % 0402
L1 3.9 nH 4.7 nH High frequency chip inductor ±5 % 0402
L2 10 µH Chip inductor, IDC,min = 50 mA, ±20 % 0603
L3 15 nH High frequency chip inductor ±10 % 0402
U1 nRF52840-QIAA Multi-protocol Bluetooth low energy, IEEE 802.15.4, ANT, and 2.4 GHz proprietary system-on-chip AQFN-73
X1 32 MHz XTAL SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz XTAL 3215, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_3215

Circuit configuration no. 6

Circuit configuration number 6 for QIAA aQFN™73, showing the schematic and the bill of materials table.

Table 13. Configuration summary for circuit configuration no. 6
Config no. Supply configuration Enabled features
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 6 N/A Battery/Ext. regulator No No No No No
Figure 6. Circuit configuration no. 6 schematic

Note: For PCB reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.
Table 14. Bill of material for circuit configuration no. 6
Designator Value v1.0 Value v1.1 Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2% 0402
C3 1 pF 0.8 pF Capacitor, NP0, ±10 % 0402
C4 1 pF 0.5 pF Capacitor, NP0, ±10 % 0402
C5, C7, C8, C12 100 nF Capacitor, X7R, ±10 % 0402
C6 4.7 µF Capacitor, X7R, ±10 % 0603
C9 820 pF Capacitor, NP0, ±5 % 0402
C10, C13, C22 N.C. Not mounted 0402
C11 100 pF Capacitor, NP0, ±5 % 0402
C14, C15 1.0 µF Capacitor, X7R, ±10 % 0603
L1 3.9 nH 4.7 nH High frequency chip inductor ±5 % 0402
U1 nRF52840-QIAA Multi-protocol Bluetooth low energy, IEEE 802.15.4, ANT, and 2.4 GHz proprietary system-on-chip AQFN-73
X1 32 MHz XTAL SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz XTAL SMD 3215, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_3215

Circuit configuration no. 1 for CKAA WLCSP

Circuit configuration number 1 for CKAA WLCSP, showing the schematic and the bill of materials table.

Table 15. Configuration summary for circuit configuration no. 1
Config no. Supply configuration Enabled features
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 1 Battery/Ext. regulator N/A Yes Yes Yes Yes No
Figure 7. Circuit configuration no. 1 schematic for CKAA WLCSP
Schematic: Circuit configuration no. 1 for CKAA WLCSP
Note: For PCB reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.
Table 16. Bill of material for circuit configuration no. 1
Designator Value Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2 % 0201
C3 1.0 pF Capacitor, NP0, ±5 % 0201
C5, C7, C8, C12 100 nF Capacitor, X7R, ±10 % 0201
C6, C20 4.7 µF Capacitor, X7R, ±10 % 0603
C9 820 pF Capacitor, X7R, ±10 % 0201
C14, C15 1.0 µF Capacitor, X7R, ±10 % 0603
C19 4.7 µF Capacitor, X7S, ± 10 % 0603
L1 3.9 nH High frequency chip inductor ±5 % 0201
L5 4.7 nH High frequency chip inductor ±5 % 0201
R1 4R7 Resistor, ±1 %, 0.05W 0201
U1 nRF52840-CKAA Multi-protocol Bluetooth low energy, IEEE 802.15.4, ANT, and 2.4 GHz proprietary system-on-chip WLCSP-94
X1 32 MHz XTAL SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz XTAL SMD 2012, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_2012

Circuit configuration no. 2 for CKAA WLCSP

Circuit configuration number 2 for CKAA WLCSP, showing the schematic and the bill of materials table.

Table 17. Configuration summary for circuit configuration no. 2
Config no. Supply configuration Enabled features
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 2 Battery/Ext. regulator N/A Yes Yes Yes Yes No
Figure 8. Circuit configuration no. 2 schematic for CKAA WLCSP
Schematic: Circuit configuration no. 2 for CKAA WLCSP
Note: For PCB reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.
Table 18. Bill of material for circuit configuration no. 2
Designator Value Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2 % 0201
C3 1.0 pF Capacitor, NP0, ±5 % 0201
C5, C7, C8, C12 100 nF Capacitor, X7R, ±10 % 0201
C6, C20 4.7 µF Capacitor, X7R, ±10 % 0603
C9 820 pF Capacitor, X7R, ±10 % 0201
C14, C15 1.0 µF Capacitor, X7R, ±10 % 0603
C19, C21 4.7 µF Capacitor, X7S, ± 10 % 0603
L1 3.9 nH High frequency chip inductor ±5 % 0201
L5 4.7 nH High frequency chip inductor ±5 % 0201
U1 nRF52840-CKAA Multi-protocol Bluetooth low energy, IEEE 802.15.4, ANT, and 2.4 GHz proprietary system-on-chip WLCSP-94
X1 32 MHz XTAL SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz XTAL SMD 2012, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_2012

Circuit configuration no. 3 for CKAA WLCSP

Circuit configuration number 3 for CKAA WLCSP, showing the schematic and the bill of materials table.

Table 19. Configuration summary for circuit configuration no. 3
Config no. Supply configuration Enabled features
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 3 Battery/Ext. regulator N/A Yes Yes Yes Yes No
Figure 9. Circuit configuration no. 3 schematic for CKAA WLCSP
Schematic: Circuit configuration no. 3 for CKAA WLCSP
Note: For PCB reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.
Table 20. Bill of material for circuit configuration no. 3
Designator Value Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2 % 0201
C3 1.0 pF Capacitor, NP0, ±5 % 0201
C5, C7, C8, C12 100 nF Capacitor, X7R, ±10 % 0201
C6, C20 4.7 µF Capacitor, X7R, ±10 % 0603
C9 820 pF Capacitor, X7R, ±10 % 0201
C14, C15 1.0 µF Capacitor, X7R, ±10 % 0603
C21 4.7 µF Capacitor, X7S, ± 10 % 0603
L1 3.9 nH High frequency chip inductor ±5 % 0201
L5 4.7 nH High frequency chip inductor ±5 % 0201
U1 nRF52840-CKAA Multi-protocol Bluetooth low energy, IEEE 802.15.4, ANT, and 2.4 GHz proprietary system-on-chip WLCSP-94
X1 32 MHz XTAL SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz XTAL SMD 2012, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_2012

Circuit configuration no. 4 for CKAA WLCSP

Circuit configuration number 4 for CKAA WLCSP, showing the schematic and the bill of materials table.

Table 21. Configuration summary for circuit configuration no. 4
Config no. Supply configuration Enabled features
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 4 Battery/Ext. regulator N/A Yes Yes Yes Yes No
Figure 10. Circuit configuration no. 4 schematic for CKAA WLCSP
Schematic: Circuit configuration no. 4 for CKAA WLCSP
Note: For PCB reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.
Table 22. Bill of material for circuit configuration no. 4
Designator Value Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2 % 0201
C3 1.0 pF Capacitor, NP0, ±5 % 0201
C5, C7, C8, C12 100 nF Capacitor, X7R, ±10 % 0201
C6, C20 4.7 µF Capacitor, X7R, ±10 % 0603
C9 820 pF Capacitor, X7R, ±10 % 0201
C14, C15 1.0 µF Capacitor, X7R, ±10 % 0603
C16 47 nF Capacitor, X7R, ± 10 % 0201
C19, C21 4.7 µF Capacitor, X7S, ± 10 % 0603
L1 3.9 nH High frequency chip inductor ±5 % 0201
L2 10 µH Chip inductor, IDC,min = 50 mA, ±20 % 0603
L3 15 nH High frequency chip inductor ±10 % 0402
L4 10 µH Chip inductor, IDC,min = 80 mA, ±10 % 0603
L5 4.7 nH High frequency chip inductor ±5 % 0201
U1 nRF52840-CKAA Multi-protocol Bluetooth low energy, IEEE 802.15.4, ANT, and 2.4 GHz proprietary system-on-chip WLCSP-94
X1 32 MHz XTAL SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz XTAL SMD 2012, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_2012

Circuit configuration no. 5 for CKAA WLCSP

Circuit configuration number 5 for CKAA WLCSP, showing the schematic and the bill of materials table.

Table 23. Configuration summary for circuit configuration no. 5
Config no. Supply configuration Enabled features
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 5 Battery/Ext. regulator N/A Yes Yes Yes Yes No
Figure 11. Circuit configuration no. 5 schematic for CKAA WLCSP
Schematic: Circuit configuration no. 5 for CKAA WLCSP
Note: For PCB reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.
Table 24. Bill of material for circuit configuration no. 5
Designator Value Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2 % 0201
C3 1.0 pF Capacitor, NP0, ±5 % 0201
C5, C7, C8, C12 100 nF Capacitor, X7R, ±10 % 0201
C6, C20 4.7 µF Capacitor, X7R, ±10 % 0603
C9 820 pF Capacitor, X7R, ±10 % 0201
C14, C15 1.0 µF Capacitor, X7R, ±10 % 0603
C16 47 nF Capacitor, X7R, ± 10 % 0201
C21 4.7 µF Capacitor, X7S, ± 10 % 0603
CT1, CT2, CT3, CT4 Antenna dependent Capacitor, X7R, ± 10 % 0201
L1 3.9 nH High frequency chip inductor ±5 % 0201
L2 10 µH Chip inductor, IDC,min = 50 mA, ±20 % 0603
L3 15 nH High frequency chip inductor ±10 % 0402
L5 4.7 nH High frequency chip inductor ±5 % 0201
U1 nRF52840-CKAA Multi-protocol Bluetooth low energy, IEEE 802.15.4, ANT, and 2.4 GHz proprietary system-on-chip WLCSP-94
X1 32 MHz XTAL SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz XTAL SMD 2012, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_2012

Circuit configuration no. 6 for CKAA WLCSP

Circuit configuration number 6 for CKAA WLCSP, showing the schematic and the bill of materials table.

Table 25. Configuration summary for circuit configuration no. 6
Config no. Supply configuration Enabled features
VDDH VDD EXTSUPPLY DCDCEN0 DCDCEN1 USB NFC
Config. 6 Battery/Ext. regulator N/A Yes Yes Yes Yes No
Figure 12. Circuit configuration no. 6 schematic for CKAA WLCSP
Schematic: Circuit configuration no. 6 for CKAA WLCSP
Note: For PCB reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.
Table 26. Bill of material for circuit configuration no. 6
Designator Value Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2 % 0201
C3 1.0 pF Capacitor, NP0, ±5 % 0201
C5, C7, C8, C12 100 nF Capacitor, X7R, ±10 % 0201
C6 4.7 µF Capacitor, X7R, ±10 % 0603
C9 820 pF Capacitor, X7R, ±10 % 0201
C14, C15 1.0 µF Capacitor, X7R, ±10 % 0603
L1 3.9 nH High frequency chip inductor ±5 % 0201
L5 4.7 nH High frequency chip inductor ±5 % 0201
U1 nRF52840-CKAA Multi-protocol Bluetooth low energy, IEEE 802.15.4, ANT, and 2.4 GHz proprietary system-on-chip WLCSP-94
X1 32 MHz XTAL SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz XTAL SMD 2012, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_2012

PCB guidelines

A well designed PCB is necessary to achieve good RF performance. A poor layout can lead to loss in performance or functionality.

A qualified RF layout for the IC and its surrounding components, including matching networks, can be downloaded from www.nordicsemi.com.

To ensure optimal performance it is essential that you follow the schematics- and layout references closely. Especially in the case of the antenna matching circuitry (components between device pin ANT and the antenna), any changes to the layout can change the behavior, resulting in degradation of RF performance or a need to change component values. All the reference circuits are designed for use with a 50 Ω single-ended antenna.

A PCB with a minimum of two layers, including a ground plane, is recommended for optimal RF performance. On PCBs with more than two layers, put a keep-out area on the inner layers directly below the antenna matching circuitry (components between device pin ANT and the antenna) to reduce the stray capacitances that influence RF performance.

A matching network is needed between the RF pin ANT and the antenna, to match the antenna impedance (normally 50 Ω) to the optimum RF load impedance for the chip. For optimum performance, the impedance for the matching network should be set as described in the recommended aQFN™73 package reference circuitry from Circuit configuration no. 1 or the recommended WLCSP reference circuitry from Circuit configuration no. 1 for CKAA WLCSP depending on the package variant used in your design.

The DC supply voltage should be decoupled as close as possible to the VDD pins with high performance RF capacitors. See the schematics for recommended decoupling capacitor values. The supply voltage for the chip should be filtered and routed separately from the supply voltages of any digital circuitry.

Long power supply lines on the PCB should be avoided. All device grounds, VDD connections, and VDD bypass capacitors must be connected as close as possible to the IC. For a PCB with a topside RF ground plane, the VSS pins should be connected directly to the ground plane. For a PCB with a bottom ground plane, the best technique is to have via holes as close as possible to the VSS pads. A minimum of one via hole should be used for each VSS pin.

Fast switching digital signals should not be routed close to the crystal or the power supply lines. Capacitive loading of fast switching digital output lines should be minimized in order to avoid radio interference.

PCB layout example

The PCB layout shown below is a reference layout for the aQFN™ package with internal LDO setup and VBUS supply.

Note: Pay attention to how the capacitor C3 is grounded. It is not directly connected to the ground plane, but grounded via VSS_PA pin F23. This is done to create additional filtering of harmonic components.

For all available reference layouts, see the product page for the nRF52840 on www.nordicsemi.com.

Figure 13. Top silk layer

Figure 14. Top layer

Figure 15. Mid layer 1

Figure 16. Mid layer 2

Figure 17. Bottom layer

Note: No components in bottom layer.