Texas Instruments | Getting Started With CC2652RB for Crystal-less BAW Operation | Application notes | Texas Instruments Getting Started With CC2652RB for Crystal-less BAW Operation Application notes

Texas Instruments Getting Started With CC2652RB for Crystal-less BAW Operation Application notes
Application Report
SWRA649 – February 2019
Getting started with CC2652RB for Crystal-less BAW
operation
ABSTRACT
The SimpleLink™ CC2652RB device has a high frequency internal oscillator allowing you to design any
2.4 GHz wireless-stack based product for Zigbee®, Thread, Bluetooth® Low Energy or 802.15.4 without
the need for external crystals. This simplifies design, testing and integration as wells as reducing the total
required footprint.
This document helps you get started using the SimpleLink crystal-less BAW CC2652RB multiprotocol 2.4GHz wireless MCU. If you are currently using a SimpleLink product such as the CC2642R or CC2652R in
your design, leveraging the CC2652RB device and porting your application code to this device is
explained in the application report.
1
2
3
4
5
Contents
Differences Between CC26x2R and CC2652RB ........................................................................
Hardware Design ............................................................................................................
Low Frequency Clock Source ..............................................................................................
Software Changes ...........................................................................................................
References ...................................................................................................................
2
2
2
3
4
Trademarks
SimpleLink is a trademark of Texas Instruments.
Cortex is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.
Bluetooth is a registered trademark of Bluetooth SIG, Inc.
Zigbee is a registered trademark of ZigBee Alliance.
SWRA649 – February 2019
Submit Documentation Feedback
Getting started with CC2652RB for Crystal-less BAW operation
Copyright © 2019, Texas Instruments Incorporated
1
Differences Between CC26x2R and CC2652RB
1
www.ti.com
Differences Between CC26x2R and CC2652RB
SimpleLink CC2652RB is a multi-standard ultra-low power wireless MCU for 2.4 GHz operations that
comes with the same features as CC2652R, but additionally includes an internal high precision (HP) bulk
acoustic wave (BAW) resonator that enables wireless communication and operation without the need for
any external crystals. The internal BAW resonator is the source for the high frequency (HF) clock and
eliminates the need for a 48 MHz crystal, which is required for the other CC13x2/CC26x2 device family
members. For applications that require a low frequency (LF) clock source, a total crystal-less design can
be obtained by using either the internal LF RC oscillator, or deriving the LF clock from the HF clock.
CC2652RB shares the same pin-out and package (RGZ) as CC2652R and can replace CC2652R in
existing designs without any required changes to the PCB or the bill of materials (BOM). The pinout is also
compatible with CC2642R and the previous generation of CC26xx wireless MCUs; CC2640, CC2650 and
CC2640R2F.
The integrated high precision resonator is being compensated in the Cortex®-M0 radio core for
temperature and voltage variations to ensure ±40 ppm accuracy. Using the high precision resonator as a
clock source marginally increases the current consumption compared to using an external crystal.
2
Hardware Design
When designing a new PCB for CC2652RB, it is highly recommended to follow the reference design: LPCC2652RB. For more detailed information about PCB design considerations, see CC13x2, CC26x2
SimpleLink™ wireless MCU technical reference manual.
2.1
Hardware Migration From the CC26xx Device Family
To enable crystal-less operation of an existing design based on CC26x2R, no changes are required, but it
is recommended to remove the 48 MHz crystal from the BOM, or mark it as “DNP” as this component is
no longer needed. This can also be done for the 32.768 kHz crystal. If a new PCB spin is planned one can
also leverage any potential footprint savings.
For designs based on the CC26x0 family of products, see Hardware Migration From CC26x0 to CC26x2R.
While the CC2652RB is very similar to CC26xx from an RF perspective, there are several updates to the
device (for example clock frequencies), which typically triggers the need for new regulatory compliance
certification.
3
Low Frequency Clock Source
Most low power applications need a LF clock to keep track of time when entering Standby mode to save
power. For synchronous RF stacks such as BLE, an LF clock is required to synchronize RF transmission
and there are also requirements for the clock accuracy to be compliant with specific stacks. For example,
BLE requires a real time clock (RTC) accuracy of ±500 ppm. CC2652RB has multiple options for the LF
clock with different benefits and drawbacks as listed in Table 1.
Table 1. LF Clock Sources
LF Clock Source
Cost
Power
Accuracy
Internal LF RC oscillator
Low
Low
±500 ppm
Derived from the HF clock
Low
High
±40 ppm
External LF crystal
Med
Low
Crystal dependent
(1)
(1) Only when running the supported BLE roles and using the recommended calibration as described in Running Bluetooth® Low
Energy on CC2640 without 32 kHz crystal.
3.1
Internal LF RC oscillator
The internal LF RC oscillator enables a crystal-less design with no added cost. This alternative is only
available for certain Bluetooth Low Energy roles. For more information, see Running Bluetooth® low
energy on CC2640 Without 32 kHz Crystal.
2
Getting started with CC2652RB for Crystal-less BAW operation
Copyright © 2019, Texas Instruments Incorporated
SWRA649 – February 2019
Submit Documentation Feedback
Low Frequency Clock Source
www.ti.com
3.2
Derive LF Clock From the HF Clock
Another option for a crystal-less design is to use the BAW resonator with a divider as LF clock source.
This will give a clock with ±40 ppm accuracy. The only downside to this solution is that the high precision
resonator must be active at all time, which will increase the average current consumption.
3.3
External LF Crystal
To achieve low power consumption as well as high RTC accuracy, an external crystal should be used. On
the reference design, LP-CC2652RB, a footprint for a LF crystal is available and a 32.768 kHz crystal can
be mounted to evaluate this type of configuration.
3.4
External LF Clock Source
A fourth option is to connect an external LF clock source to one of CC2652RB pins and use this signal to
increment the RTC.
4
Software Changes
The CC2652RB device is supported by SimpleLink CC2652RB BLE SDK 3.10 and SimpleLink CC13x2
and CC26x2 SDK 3.20 or newer. If you already have a CC26x2R project, you can follow the SDK
migration guide in the SDK documentation. In the CC2652RB project files, the BAW resonator is enabled
and selected as HF clock source. By default, the BAW resonator will also be the source for the LF clock.
This can be changed by using the RCOSC build configuration that uses the LF RC oscillator as LF clock
source. If you want to use an external LF crystal oscillator, or an external LF clock you have to do the
following changes:
1. Make sure to use the non RCOSC build configuration where USE_RCOSC is not defined.
2. Make sure that the HF oscillator is disabled when entering standby mode. This requires a change in
the RF Driver settings in CC2652RB_LAUNCHXL.c which is linked to from the board.c-file:
const RFCC26XX_HWAttrsV2 RFCC26XX_hwAttrs = {
.hwiPriority
= ~0,
/* Lowest HWI priority */
.swiPriority
= 0,
/* Lowest SWI priority */
#ifdef USE_RCOSC
.xoscHfAlwaysNeeded = false,
/* Keep XOSC dependency while in standby */
#else
.xoscHfAlwaysNeeded = false,
/* <-- Set to false */
#endif
.globalCallback
= NULL,
/* No board specific callback */
.globalEventMask
= 0
/* No events subscribed to */
};
3. Add this line to the project’s CCFG-file to use the LF crystal oscillator:
(1)
#define SET_CCFG_MODE_CONF_SCLK_LF_OPTION 0x2 // LF XOSC
4. Or to use an external LF clock source, add the following lines:
#define SET_CCFG_MODE_CONF_SCLK_LF_OPTION 0x1 // External LF clock
#define SET_CCFG_EXT_LF_CLK_DIO 0x01 // DIO number if useing external LF clock
(1)
Note that you’ll have to solder on an external 32.768 kHz crystal oscillator and load capacitors to use this option.
SWRA649 – February 2019
Submit Documentation Feedback
Getting started with CC2652RB for Crystal-less BAW operation
Copyright © 2019, Texas Instruments Incorporated
3
References
5
References
•
•
•
•
•
•
•
4
www.ti.com
CC2652RB Data Sheet
CC2652RB LaunchPad
Texas Instruments: CC13x2, CC26x2 SimpleLink™ wireless MCU technical reference manual
Texas Instruments: Running Bluetooth® low energy on CC2640 Without 32 kHz Crystal
Texas Instruments: Hardware migration from CC26x0 to CC26x2R
Texas Instruments: CC13xx/CC26xx hardware configuration and PCB design considerations
Texas Instruments: SimpleLink crystal-less BAW CC2652RB multiprotocol 2.4GHz wireless MCU
devopment kit
Getting started with CC2652RB for Crystal-less BAW operation
Copyright © 2019, Texas Instruments Incorporated
SWRA649 – February 2019
Submit Documentation Feedback
IMPORTANT NOTICE AND DISCLAIMER
TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATASHEETS), DESIGN RESOURCES (INCLUDING REFERENCE
DESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS”
AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANY
IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD
PARTY INTELLECTUAL PROPERTY RIGHTS.
These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate
TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicable
standards, and any other safety, security, or other requirements. These resources are subject to change without notice. TI grants you
permission to use these resources only for development of an application that uses the TI products described in the resource. Other
reproduction and display of these resources is prohibited. No license is granted to any other TI intellectual property right or to any third
party intellectual property right. TI disclaims responsibility for, and you will fully indemnify TI and its representatives against, any claims,
damages, costs, losses, and liabilities arising out of your use of these resources.
TI’s products are provided subject to TI’s Terms of Sale (www.ti.com/legal/termsofsale.html) or other applicable terms available either on
ti.com or provided in conjunction with such TI products. TI’s provision of these resources does not expand or otherwise alter TI’s applicable
warranties or warranty disclaimers for TI products.
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2019, Texas Instruments Incorporated
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Related manuals

Download PDF

advertising