Texas Instruments 3138 155 232931 manual Crystal Oscillator

Page 53

The battery monitor is controlled through the BATTMON control register. The battery monitor is enabled and disabled using the BATTMON.BATTMON_EN control bit. The voltage regulator must also be enabled when using the battery monitor.

The battery monitor status bit is available in the BATTMON.BATTMON_OK status bit. This bit is high when the VREG_IN input voltage is higher than the toggle voltage

Vtoggle.

The battery monitor toggle voltage is set in the 5-bit BATTMON.BATTMON_VOLTAGE control bits. BATTMON_VOLTAGE is an unsigned, positive number from 0 to 31. The toggle voltage is given by:

Vtoggle = 1.25 V⋅

72 − BATTMON_VOLTAGE

27

31 Crystal Oscillator

An external clock signal or the internal crystal oscillator can be used as main frequency reference. The reference frequency must be 16 MHz. Because the crystal frequency is used as reference for the data rate as well as other internal signal processing functions, other frequencies cannot be used.

If an external clock signal is used this should be connected to XOSC16_Q1, while XOSC16_Q2 should be left open. The MAIN.XOSC16M_BYPASS bit must be set when an external clock signal is used.

Using the internal crystal oscillator, the crystal must be connected between the XOSC16_Q1 and XOSC16_Q2 pins. The oscillator is designed for parallel mode operation of the crystal. In addition, loading capacitors (C381 and C391) for the crystal are required. The loading capacitor values depend on the total load capacitance, CL, specified for the crystal. The total load capacitance seen between the crystal terminals should equal CL for the crystal to oscillate at the specified frequency.

CC2420

Alternatively, for a desired toggle voltage, BATTMON_VOLTAGE should be set according to:

BATTMON_VOLTAGE = 72 − 27 ⋅ Vtoggle

1.25 V

The voltage regulator must be enabled for at least 100 µs before the first measurement. After being enabled, the BATTMON_OK status bit needs 2 µs to settle for each new toggle voltage programmed.

The main performance characteristics of the battery monitor is shown in the Electrical Specifications section on page 9.

CL = 1 1 1 + Cparasitic

C381 + C391

The parasitic capacitance is constituted by pin input capacitance and PCB stray capacitance. The total parasitic capacitance is typically 2 pF - 5 pF.

The crystal oscillator circuit is shown in Figure 30. Typical component values for different values of CL are given in Table 10.

The crystal oscillator is amplitude regulated. This means that a high current is used to start up the oscillations. When the amplitude builds up, the current is reduced to what is necessary to maintain a stable oscillation. This ensures a fast start-up and keeps the drive level to a minimum. The ESR of the crystal must be within the specification in order to ensure

areliable start-up (see the Electrical Specifications section).

SWRS041B

Page 53 of 89

Page 52 Page 54
Image 53
Page 52 Page 54
Contents Product Description Key FeaturesApplications Table of contents RF Data Buffering Ordering Information General Information ITU-T AbbreviationsReferences Features Operating Conditions Absolute Maximum RatingsParameter Min Max Units Condition Parameter Min Typ Max Units ConditionOverall Electrical SpecificationsTransmit Section Parameter Min Typ Max Unit Condition / NoteReceive Section Frequency Synthesizer Section Rssi / Carrier SenseIf Section VDD Digital Inputs/OutputsVoltage Regulator Battery MonitorPower Supply CC2420 Pin Pin Name Pin type Pin Description Pin AssignmentAvddadc Circuit Description CC2420 simplified block diagramCC2420 Application Circuit Power supply decoupling and filteringInput / output matching Bias resistorDescription Overview of external componentsTransceiver Transceiver Bill of materials for the application circuits Ieee 802.15.4 Modulation Format Symbol Chip sequence C0, C1, C2, … , C31Phase Configuration OverviewSmartRF Studio user interface Evaluation SoftwareRegister access 13 4-wire Serial Configuration and Data InterfacePin configuration Parameter Symbol Min Max Units Conditions SPI timing specification Status byteRAM access Configuration registers write and read operations via SPI Address Byte Ordering Name Description CC2420 RAM Memory Space Fifo accessMultiple SPI access Microcontroller Interface and Pin Description Configuration interfaceRxfifo overflow Receive modePin activity examples during receive Demodulator, Symbol Synchroniser and Data Decision Frame Format Demodulator Simplified Block DiagramMAC protocol data unit Transmitted Synchronisation Header Length fieldFormat of the Frame Control Field FCF Frame check sequence RF Data Buffering Buffered transmit modeBuffered receive mode Fifop Unbuffered, serial modeAcknowledge Frames Address RecognitionAcknowledge frame format Radio control state machine Radio control states Keys MAC Security Operations Encryption and AuthenticationNonce / counter Ieee 802.15.4 NonceIn-line security operations CC2420 Security Flag Byte Stand-alone encryption21.7 CCM CTR mode encryption / decryptionCBC-MAC Mode LMIC Time Linear if and AGC SettingsRssi / Energy Detection TimingRF Level dBm Link Quality IndicationValue Frequency and Channel Programming Clear Channel AssessmentVCO and PLL Self-Calibration Output Power ProgrammingVoltage Regulator 27.1 VCOVoltage regulator, simplified schematic Battery MonitorCrystal Oscillator Transmitter Test Modes Input / Output MatchingCrystal oscillator component values Unmodulated carrierCC2420 Modulated spectrum plot System Considerations and Guidelines BER / PER measurements Battery operated systemsLow-cost systems Antenna Considerations PCB Layout RecommendationsCC2420 Address Register Register type Description Configuration RegistersSaes Configuration registers overviewXOSC16MBYPASS Bit Field Name ResetMain 0x10 Main Control Register CCAHYST20 CCAMODE10 Autocrc Autoack Preamblelength MDMCTRL0 0x11 Modem Control RegisterReservedframemode Pancoordinator Adrdecode Rssi 0x13 Rssi and CCA Status and Control Register MDMCTRL1 0x12- Modem Control RegisterCORRTHR40 Demodavgmode Modulationmode RSSIVAL70Txctrl 0x15 Transmit Control Register Syncword 0x14 Sync WordRXMIXBUFCUR10 RXCTRL0 0x16 Receive control registerRXCTRL1 0x17 Receive control register Caldone Calrunning Locklength Lockstatus Fsctrl 0x18 Frequency Synthesizer Control and StatusSECMODE10 SECCTRL0 0x19 Security Control RegisterSECCTRL1 0x1A Security Control Register Battmon 0x1B Battery Monitor Control registerSectxl Secrxl Battmonok Battmonen BattmonvoltageIOCFG1 0x1D I/O Configuration Register IOCFG0 0x1C I/O Configuration RegisterManfidl 0x1E Manufacturer ID, Lower 16 Bit HSSDSRC20 SFDMUX40 CCAMUX40Fsmtc 0x20 Finite state machine time constants Manfidh 0x1F Manufacturer ID, Upper 16 BitIsused = is * Isandmask + Isormask Manand 0x21 Manual signal and override register1Agcctrl 0x23 AGC Control Manor 0x22 Manual signal or override registerVgagainoe LnamixgainmodeoAGCTST2 0x26 AGC Test Register AGCTST0 0x24 AGC Test RegisterAGCTST1 0x25 AGC Test Register FSTST2 0x29 Frequency Synthesizer Test Register FSTST0 0x27 Frequency Synthesizer Test RegisterFSTST1 0x28 Frequency Synthesizer Test Register Fsmstate 0x2C Finite state machine information FSTST3 0x2A Frequency Synthesizer Test RegisterRxbpftst 0x2B Receiver Bandpass Filters Test Register Dactst 0x2E DAC Test Register AdcclockdisableAdctst 0x2D ADC Test Register Toptst 0x2F Top Level Test Register Oscillator must be running for accessing the RxfifoTxfifo 0x3E Transmit Fifo Byte register Rxfifo 0x3F Receive Fifo Byte registerSignal output on CCA pin Description Test Output SignalsCCA test signal select table Signal output on SFD pin Description SFD test signal select tableQuad Leadless Package QLP Package Description QLPPackage thermal properties Recommended layout for package QLPSoldering information Thermal resistance40.4 Carrier tape and reel specification 40.3 Plastic tube specificationTube Specification Tape and Reel SpecificationRevision Date Description/Changes General Information42.1 Document History Product Status Definitions Data Sheet Identification Product Status DefinitionProduct Information Centers Address InformationTI Worldwide Technical Support Internet 2007, Texas Instruments. All rights reserved Important Notice
Top Page Image Contents