JN517X Datasheet, PDF (20/100 Pages) NXP Semiconductors – Supports multiple network stacks

NXP Semiconductors
JN517x
IEEE802.15.4 Wireless Microcontroller
XTAL_IN
JN517x
R1
XTAL_OUT
C1
Fig 10. 32 MHz crystal oscillator connections
C2
aaa-021454
For operation over the extended temperature range, 85 C to 125 C, special care is
required; this is because the temperature characteristics of crystal resonators are
generally in excess of 40 ppm frequency tolerance defined by the IEEE802.15.4
standard. The oscillator cell contains additional circuitry to compensate for the poor
performance of the crystal resonators above 100 C. Full details, including the software
API function, can be found in the Temperature Dependent Operating Guidelines
JN-AN-1186 on the Wireless Connectivity area of the NXP web site Ref. 2.
9.4.1.2 High-speed RC oscillator
An on-chip high-speed RC oscillator is provided in addition to the 32 MHz crystal oscillator
for 2 purposes, to allow a fast start-up from reset or sleep and to provide a lower current
alternative to the crystal oscillator for non-timing critical applications. By default the
oscillator will run at 27 MHz typically with a wide tolerance. It can be calibrated, using a
software API function, which will result in a nominal frequency of 32 MHz with a 1.6 %
tolerance at 3 V and 25 C. However, it should be noted that over the full operating range
of voltage and temperature this will increase to 5%. The calibration information is
retained through speed cycles and when the oscillator is disabled, so typically the
calibration function only needs to be called once. No external components are required for
this oscillator. The electrical specification of the oscillator can be found in Section 14.3.9.
9.4.2 Low-speed (32 kHz) system clock
The 32 kHz system clock is used for timing the length of a sleep period (see Section 10.
The clock can be selected from one of 2 sources through the application software:
• 32 kHz RC oscillator
• 32 kHz external clock
• 32 kHz crystal oscillator
Upon a chip reset or power-up, the JN517x defaults to using the internal 32 kHz RC
oscillator. If another clock source is selected, then, it will remain in use for all 32 kHz
timing until a chip reset is performed.
9.4.2.1 32 kHz RC oscillator
The internal 32 kHz RC oscillator requires no external components. The internal timing
components of the oscillator have a wide tolerance due to manufacturing process
variation and so the oscillator runs nominally at 32 kHz 20.7 %/+52.6 %. To make this
useful as a timing source for accurate wake-up from sleep, a frequency calibration factor
derived from the more accurate 16 MHz peripheral system clock may be applied. The
JN517X
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2.0 — 8 November 2016
© NXP Semiconductors N.V. 2016. All rights reserved.
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