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 www.nordicsemi.com.

In this section there are 6 reference circuits to show the components and component values to support on-chip features in a design.

Important: 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.
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 configuration no. 1

Table 2. 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

Important: For PCB reference layouts, see the Reference Layout section on the Downloads tab for the nRF52840 on www.nordicsemi.com.
Table 3. Bill of material for circuit configuration no. 1
Designator Value Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2% 0402
C3 0.8 pF Capacitor, NP0, ±5% 0402
C4 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, C10, C13 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 3.3 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 Crystal SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz Crystal SMD 3215, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_3215

Circuit configuration no. 2

Table 4. 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

Important: For PCB reference layouts, see the Reference Layout section on the Downloads tab for the nRF52840 on www.nordicsemi.com.
Table 5. Bill of material for circuit configuration no. 2
Designator Value Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2% 0402
C3 0.8 pF Capacitor, NP0, ±5% 0402
C4 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, C10, C13 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 3.3 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 Crystal SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz Crystal SMD 3215, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_3215

Circuit configuration no. 3

Table 6. 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

Important: For PCB reference layouts, see the Reference Layout section on the Downloads tab for the nRF52840 on www.nordicsemi.com.
Table 7. Bill of material for circuit configuration no. 3
Designator Value Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2% 0402
C3 0.8 pF Capacitor, NP0, ±5% 0402
C4 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, C10, C13 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 3.3 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 Crystal SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz Crystal SMD 3215, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_3215

Circuit configuration no. 4

Table 8. 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

Important: For PCB reference layouts, see the Reference Layout section on the Downloads tab for the nRF52840 on www.nordicsemi.com.
Table 9. Bill of material for circuit configuration no. 4
Designator Value Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2% 0402
C3 0.8 pF Capacitor, NP0, ±5% 0402
C4 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, C10, C13 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 3.3 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, ±10% 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 Crystal SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz Crystal SMD 3215, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_3215

Circuit configuration no. 5

Table 10. 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

Important: For PCB reference layouts, see the Reference Layout section on the Downloads tab for the nRF52840 on www.nordicsemi.com.
Table 11. Bill of material for circuit configuration no. 5
Designator Value Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2% 0402
C3 0.8 pF Capacitor, NP0, ±5% 0402
C4 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, C10, C13 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, X7S, ±10% 0402
C21 4.7 µF Capacitor, X7S, ±10% 0603
Ctune1, Ctune2 TBD Capacitor, NP0, ±5% 0402
L1 3.3 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 Crystal SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz Crystal SMD 3215, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_3215

Circuit configuration no. 6

Table 12. 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

Important: For PCB reference layouts, see the Reference Layout section on the Downloads tab for the nRF52840 on www.nordicsemi.com.
Table 13. Bill of material for circuit configuration no. 6
Designator Value Description Footprint
C1, C2, C17, C18 12 pF Capacitor, NP0, ±2% 0402
C3 0.8 pF Capacitor, NP0, ±5% 0402
C4 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, C10, C13 N.C. Not mounted 0402
C11 100 pF Capacitor, NP0, ±5% 0402
C14, C15 1.0 µF Capacitor, X7R, ±10% 0603
L1 3.3 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 Crystal SMD 2016, 32 MHz, Cl=8 pF, Total Tol: ±40 ppm XTAL_2016
X2 32.768 kHz Crystal SMD 3215, 32.768 kHz, Cl=9 pF, Total Tol: ±50 ppm XTAL_3215

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 ohm 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 ohm) 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 AQFN73 package reference circuitry from Circuit configuration no. 1.

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.

Important: 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 Reference Layout section on the Downloads tab for nRF52840 on www.nordicsemi.com.

Figure 7. Top silk layer

Figure 8. Top layer

Figure 9. Mid layer 1

Figure 10. Mid layer 2

Figure 11. Bottom layer

Important: No components in bottom layer.

Documentation feedback | Developer Zone | Updated 2017-07-06