NXP Semiconductors PN7462 series User Manual page 56

NXP Semiconductors
7.1.1 27.12 MHz Crystal oscillator (XTAL)
The 27.12 MHz crystal oscillator is used as a reference for all operations requiring high
stability of the clock frequency. This includes: contactless interface, contact interface, SPI
and I2C master interfaces, HSUART and USB PLL for the USB interface.
To ensure the stability of the clock frequency, it is recommended to adopt the circuit with
the external quartz and the trimming capacitors shown in
the requirements for the crystals.
Table 49. Crystal requirements
Symbol Parameter
f CLK frequency
CLK
f CLK frequency accuracy
CLK_ACC
ESR Equivalent series resistance
C Load capacitance
LOAD
P Drive level
CLK
[1] This requirement is according FCC regulations requirements. To meet only ISO/IEC 14443 and ISO/IEC 18092 then +/-
14 kHz apply.
7.1.1.1 XTAL activation sequence
The XTAL is automatically activated by the digital control unit as soon as the system
reset is released. The LFO needs to be activated to start the XTAL Oscillator.
XTAL activation sequence description:
UM10858
User manual
COMPANY PUBLIC
Fig 19. 27.12 MHz crystal oscillator connection
Conditions
ISO/ IEC and FCC compliancy
[1]
All information provided in this document is subject to legal disclaimers.
Rev. 1.4 — 14 May 2018
PN7462AU
Min
-50
314514
UM10858
PN7462 family HW user manual
Fig 19. Table 49 summarizes
Typ Max Unit
27.12 MHz
+50 Ppm
50 100 Ohm
10 pF
100 µW
© NXP B.V. 2018. All rights reserved.
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