Datasheet nRF51822 - 28

link to page 28 link to page 40 link to page 41 link to page 76 link to page 40 link to page 41 link to page 41 nRF51822 Product Specification v3.1
3.6.1 16/32 MHz crystal oscillator
The crystal oscillator can be controlled either by a 16 MHz or a 32 MHz external crystal. However, the system clock is always 16 MHz, see the nRF51 Series Reference Manual for more details. The crystal oscillator is designed for use with an AT-cut quartz crystal in parallel resonant mode. To achieve correct oscillation frequency, the load capacitance must match the specification in the crystal data sheet.
Figure 7
shows how the crystal is connected to the 16/32 MHz crystal oscillator.
XC1 XC2
C1 C2 16/32 MHz crystal
Figure 7
Circuit diagram of the 16/32 MHz crystal oscillator The load capacitance (CL) is the total capacitance seen by the crystal across its terminals and is given by: C1'  C2' CL = -------------- C1' + C2' C1’ = C1 + C_pcb1 + C_pin C2’ = C2 + C_pcb2 + C_pin C1 and C2 are ceramic SMD capacitors connected between each crystal terminal and ground. C_pcb1 and C_pcb2 are stray capacitances on the PCB. C_pin is the pin input capacitance on the XC1 and XC2 pins, see
Table 22
on page 40 (16 MHz) and
Table 23
on page 41 (32 MHz). The load capacitors C1 and C2 should have the same value. See
Chapter 11 “Reference circuitry”
on page 76 for the capacitance value used for C_pcb1 and C_pcb2 in reference circuitry. For reliable operation, the crystal load capacitance, shunt capacitance, equivalent series resistance (RS,X16M/ RS,X32M), and drive level must comply with the specifications in
Table 22
on page 40 (16 MHz) and
Table 23
on page 41 (32 MHz). It is recommended to use a crystal with lower than maximum RS,X16M/RS,X32M if the load capacitance and/or shunt capacitance is high. This will give faster startup and lower current consumption. A low load capacitance will reduce both startup time and current consumption. Page 28 Document Outline 1 Introduction 1.1 Required reading 1.2 Writing conventions 2 Product overview 2.1 Block diagram 2.2 Pin assignments and functions 2.2.1 Pin assignment QFN48 2.2.2 CDAB WLCSP ball assignment and functions 2.2.3 CEAA and CFAC WLCSP ball assignment and functions 3 System blocks 3.1 CPU 3.2 Memory 3.2.1 Code organization 3.2.2 RAM organization 3.3 Memory Protection Unit (MPU) 3.4 Power management (POWER) 3.4.1 Power supply 3.4.2 Power management 3.5 Programmable Peripheral Interconnect (PPI) 3.6 Clock management (CLOCK) 3.6.1 16/32 MHz crystal oscillator 3.6.2 32.768 kHz crystal oscillator 3.6.3 32.768 kHz RC oscillator 3.6.4 Synthesized 32.768 kHz clock 3.7 GPIO 3.8 Debugger support 4 Peripheral blocks 4.1 2.4 GHz radio (RADIO) 4.2 Timer/counters (TIMER) 4.3 Real Time Counter (RTC) 4.4 AES Electronic Codebook Mode Encryption (ECB) 4.5 AES CCM Mode Encryption (CCM) 4.6 Accelerated Address Resolver (AAR) 4.7 Random Number Generator (RNG) 4.8 Watchdog Timer (WDT) 4.9 Temperature sensor (TEMP) 4.10 Serial Peripheral Interface (SPI/SPIS) 4.11 Two-wire interface (TWI) 4.12 Universal Asynchronous Receiver/Transmitter (UART) 4.13 Quadrature Decoder (QDEC) 4.14 Analog to Digital Converter (ADC) 4.15 GPIO Task Event blocks (GPIOTE) 4.16 Low Power Comparator (LPCOMP) 5 Instance table 6 Absolute maximum ratings 7 Operating conditions 7.1 WLCSP light sensitivity 8 Electrical specifications 8.1 Clock sources 8.1.1 16/32 MHz crystal startup 8.1.2 16 MHz crystal oscillator (16M XOSC) 8.1.3 32 MHz crystal oscillator (32M XOSC) 8.1.4 16 MHz RC oscillator (16M RCOSC) 8.1.5 32.768 kHz crystal oscillator (32k XOSC) 8.1.6 32.768 kHz RC oscillator (32k RCOSC) 8.1.7 32.768 kHz Synthesized oscillator (32k SYNT) 8.2 Power management 8.3 Block resource requirements 8.4 CPU 8.5 Radio transceiver 8.5.1 General radio characteristics 8.5.2 Radio current consumption with DC/DC disabled 8.5.3 Radio current consumption with DC/DC enabled 8.5.4 Transmitter specifications 8.5.5 Receiver specifications 8.5.6 Radio timing parameters 8.5.7 Antenna matching network requirements 8.6 Received Signal Strength Indicator (RSSI) specifications 8.7 Universal Asynchronous Receiver/Transmitter (UART) specifications 8.8 Serial Peripheral Interface Slave (SPIS) specifications 8.9 Serial Peripheral Interface (SPI) Master specifications 8.10 I2C compatible Two Wire Interface (TWI) specifications 8.11 GPIO Tasks and Events (GPIOTE) specifications 8.12 Analog to Digital Converter (ADC) specifications 8.13 Timer (TIMER) specifications 8.14 Real Time Counter (RTC) 8.15 Temperature sensor (TEMP) 8.16 Random Number Generator (RNG) specifications 8.17 AES Electronic Codebook Mode Encryption (ECB) specifications 8.18 AES CCM Mode Encryption (CCM) specifications 8.19 Accelerated Address Resolver (AAR) specifications 8.20 Watchdog Timer (WDT) specifications 8.21 Quadrature Decoder (QDEC) specifications 8.22 Non-Volatile Memory Controller (NVMC) specifications 8.23 General Purpose I/O (GPIO) specifications 8.24 Low Power Comparator (LPCOMP) specifications 9 Mechanical specifications 9.1 QFN48 package 9.2 CDAB WLCSP package 9.3 CEAA WLCSP package 9.4 CFAC WLCSP package 10 Ordering information 10.1 Chip marking 10.2 Inner box label 10.3 Outer box label 10.4 Order code 10.5 Abbreviations 10.6 Code ranges and values 10.7 Product options 10.7.1 nRF ICs 10.7.2 Development tools 11 Reference circuitry 11.1 PCB guidelines 11.1.1 PCB layout example 11.2 Reference design schematics 11.3 QFAA QFN48 package 11.3.1 QFAA QFN48 schematic with internal LDO setup 11.3.2 QFAA QFN48 schematic with low voltage mode setup 11.3.3 QFAA QFN48 schematic with DC/DC converter setup 11.4 QFAB QFN48 package 11.4.1 QFAB QFN48 schematic with internal LDO setup 11.4.2 QFAB QFN48 schematic with low voltage mode setup 11.4.3 QFAB QFN48 schematic with DC/DC converter setup 11.5 QFAC QFN48 package 11.5.1 QFAC QFN48 schematic with internal LDO setup 11.5.2 QFAC QFN48 schematic with low voltage mode setup 11.5.3 QFAC QFN48 schematic with DC/DC converter setup 11.6 CDAB WLCSP package 11.6.1 CDAB WLCSP schematic with internal LDO setup 11.6.2 CDAB WLCSP schematic with low voltage mode setup 11.6.3 CDAB WLCSP schematic with DC/DC converter setup 11.7 CEAA WLCSP package 11.7.1 CEAA WLCSP schematic with internal LDO setup 11.7.2 CEAA WLCSP schematic with low voltage mode setup 11.7.3 CEAA WLCSP schematic with DC/DC converter setup 11.8 CFAC WLCSP package 11.8.1 CFAC WLCSP schematic with internal LDO setup 11.8.2 CFAC WLCSP schematic with low voltage mode setup 11.8.3 CFAC WLCSP schematic with DC/DC converter setup 12 Glossary