JN516X Datasheet, PDF (27/94 Pages) NXP Semiconductors – IEEE802.15.4 Wireless Microcontroller

The JN516x radio when enabled is automatically calibrated for optimum performance. In operating environments with
a significant variation in temperature (e.g. greater than 20 deg C) due to diurnal or ambient temperature variation, it is
recommended to recalibrate the radio to maintain performance. Recalibration is only required on Routers and End
Devices that never sleep. End Devices that sleep when idle are automatically recalibrated when they wake. An
Application Note JN516x Temperature-dependent Operating Guidelines [2] describes this in detail and includes a
software API function which can be used to test the temperature using the on-chip temperature sensor and trigger a
recalibration if there has been a significant temperature change since the previous calibration.
8.1.1 Radio External Components
In order to realise the full performance of the radio it is essential that the reference PCB layout and BOM are carefully
followed. See Appendix B.4.
The radio is powered from a number of internal 1.8V regulators fed from the analogue supply VDD1, in order to
provide good noise isolation between the digital logic of the JN516x and the analogue blocks. These regulators are
also controlled by the baseband controller and protocol software to minimise power consumption. Decoupling for
internal regulators is required as described in Section 2.2.1.
For single ended antennas or connectors, a balun is not required, however a matching network is needed.
The RF matching network requires three external components and the IBIAS pin requires one external component as
shown in schematic in B.4.1. These components are critical and should be placed close to the JN516x pins and
analogue ground as defined in Table 12. Specifically, the output of the network comprising L2, C1 and L1 is
designed to present an accurate match to a 50 ohm resistive network as well as provide a DC path to the final output
stage or antenna. Users wishing to match to other active devices such as amplifiers should design their networks to
match to 50 ohms at the output of L1
IBIAS
VB_RF
To Coaxial Socket
or Integrated Antenna
L2 3.9nH
L1 5.1nH
C1 47pF
VB_RF
Figure 14: External Radio Components
8.1.2 Antenna Diversity
Support is provided for antenna diversity. Antenna diversity is a technique that maximises the performance of an
antenna system. It allows the radio to switch between two antennas that have very low correlation between their
received signals. Typically, this is achieved by spacing two antennae around 0.25 wavelengths apart or by using two
orthogonal polarisations. So, if a packet is transmitted and no acknowledgement is received, the radio system can
switch to the other antenna for the retry, with a different probability of success.
© NXP Laboratories UK 2013
JN-DS-JN516x v1.1 Production
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