RF-BM-2652P4I

RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 RF-BM-2652P4 and RF-BM-2652P4I CC2652P7 SimpleLink™ Multiprotocol 2.4 GHz Wireless Module with Integrated Power Amplifier Version 1.0 Shenzhen RF-star Technology Co., Ltd. May 25th, 2023 All rights reserved. Those responsible for unauthorized reproduction will be prosecuted. Shenzhen RF-star Technology Co., Ltd. Page 1 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 1 Device Overview 1.1 Description RF-BM-2652P4(I) is an RF module based on TI lower-power CC2652P7 SoC, which is a multiprotocol 2.4 GHz wireless module supporting Matter, Thread, Zigbee®, Bluetooth® 5.3 Low Energy, IEEE 802.15.4, IPv6-enabled smart objects (6LoWPAN), proprietary systems, including the TI 15.4-Stack (2.4 GHz), and concurrent multiprotocol through a Dynamic Multiprotocol Manager (DMM) driver. It integrates a 48 MHz crystal and a 32.768 kHz crystal, 704 KB of in-system Programmable Flash, 256 KB ROM, 8 KB of Cache SRAM, and 144 KB of ultra-low leakage SRAM. Its ARM® Cortex®-M4F core application processor can operate at an extremely low current at flexible power modes. And the module enables long-range and low-power applications using an integrated +20 dBm high-power amplifier with best-in-class transmit current consumption at 101 mA. It features a small size, robust connection distance, and rigid reliability. Optional antenna output modes (PCB, IPEX connector, and half-hole interface) make the module more convenient for application and development. 1.2 Key Features • RF Features • Memory - Bluetooth® 5.3 Low Energy - Matter, ZigBee®, - 704 KB of in-system programmable flash Thread - 256 KB of ROM for protocols and library - Proprietary systems functions - IEEE 802.15.4 - 8 KB of cache SRAM (Alternatively available as - IPv6-enabled smart objects (6LoWPAN) - SimpleLinkTM TI 15.4-Stack (2.4 GHz) general-purpose RAM) - 144 KB of ultra-low leakage SRAM. The SRAM - Dynamic Multiprotocol Manager (DDM) driver • TX power: up to +20 dBm with temperature is protected by parity to ensure high reliability of operation. • Ultra-low power sensor controller with 4 KB of compensation • Excellent receiver sensitivity SRAM - -99 dBm for 802.15.4 (2.4 GHz) - Sample, store, and process sensor data - -104 dBm for Bluetooth 125 kbps (LE coded PHY) - Operation independent from system CPU • Wide Operation Range - Fast wake-up for low-power operation • Rich Peripherals - 1.8 V to 3.8 V single power supply - Operating temperature: -40 °C to +85 °C - Storage temperature: -40 °C to +125 °C • Microcontroller - Powerful 48 MHz - Digital peripheral pins can be routed to 23 GPIOs - 4 × 32-bit or 8 × 16-bit general-purpose timers ARM® Cortex®-M4F processor - 12-bit ADC, 200 ksamples/s, 8 channels - EEBMC CoreMark® score: 148 - 2 × comparators - 2-pin cJTAG and JTAG debugging - Programmable current source - Support OTA upgrade - 2 × UART Shenzhen RF-star Technology Co., Ltd. Page 2 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 - 2 × SSI (SPI, Microwave, TI) - ECC and RSA public key hardware accelerator - I2C - SHA2 accelerator (full suite up to SHA-512) - I2S - Real-time clock (RTC) - Integrated temperature and battery monitor • Security Enablers - True random number generator (TRNG) • External system - On-chip buck DC/DC converter • Dimension: 30.0 mm × 16.4 mm × 2.2 mm - AES 128-bit and 256- bit Crypto accelerator 1.3 Applications • 2400 to 2480 MH ISM and SRD systems with down to 4 kHz of receive bandwidth • Wireless healthcare applications • Energy harvesting applications • Home and building automation • Asset tracking and management • Building security system • Electronic Shelf Label (ESL) • HVAC system • Wired networking • Gateway • Small business router • IP network camera • Portable electronics • Fire safety system • Set-top box • Smart grid • Connected peripherals • Automatic meter reading • Keyboard and keypads • Industrial transport • Home theater & entertainment • Wireless sensor networks • Electronic and robotic toys • Wearables • Factory automation and control Shenzhen RF-star Technology Co., Ltd. Page 3 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 1.4 Functional Block Diagram 48.0 MHz 32.768 kHz 2.4 GHz Balun GPIOs Jtag CC2652P7 2.4 GHz PA Balun EMI Filter Control (GPIO) Half Hole Interface A 000 PCB Antenna B Antenna Matching Switch IPEX Connector Power Supply Reset 1.8 V ~ 3.8 V Figure 1. Functional Block Diagram of RF-BM-2652P4(I) 1.5 Part Number Conventions The part numbers are of the form of RF-BM-2652P4(I) where the fields are defined as follows: RF - BM - 2652P 4 I Antenna Type Company Name IPEX Connector Module Version Number RF-STAR The Fourth PA Version Wireless Type Bluetooth Module Chipset CC2652P7 Figure 2. Part Number Conventions of RF-BM-2652P4(I) Shenzhen RF-star Technology Co., Ltd. Page 4 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 Table of Contents 1 Device Overview ............................................................................................................................................................. 2 1.1 Description............................................................................................................................................................ 2 1.2 Key Features ....................................................................................................................................................... 2 1.3 Applications .......................................................................................................................................................... 3 1.4 Functional Block Diagram .............................................................................................................................. 4 1.5 Part Number Conventions .............................................................................................................................. 4 Table of Contents................................................................................................................................................................ 5 2 Module Configuration and Functions ...................................................................................................................... 7 2.1 Module Parameters ........................................................................................................................................... 7 2.2 Module Pin Diagram ......................................................................................................................................... 8 2.3 Pin Functions ....................................................................................................................................................... 8 3 Specifications ................................................................................................................................................................. 10 3.1 Recommended Operating Conditions ..................................................................................................... 10 3.2 Handling Ratings.............................................................................................................................................. 10 3.3 PA Output Control ............................................................................................................................................ 10 4 Application, Implementation, and Layout............................................................................................................. 11 4.1 Module Photos .................................................................................................................................................. 11 4.2 Recommended PCB Footprint.................................................................................................................... 11 4.3 Schematic Diagram......................................................................................................................................... 12 4.4 Reference Design ............................................................................................................................................ 13 4.5 Antenna................................................................................................................................................................ 13 4.5.1 Antenna Design Recommendation .............................................................................................. 13 4.5.2 Antenna Output Mode Modification .............................................................................................. 14 4.5.3 External Antenna Design Recommendation of the Half-Hole ANT Pin .......................... 15 4.5.4 IPEX Connector Specification ........................................................................................................ 16 4.6 Basic Operation of Hardware Design ...................................................................................................... 16 4.7 Trouble Shooting .............................................................................................................................................. 17 4.7.1 Unsatisfactory Transmission Distance........................................................................................ 17 4.7.2 Vulnerable Module .............................................................................................................................. 18 4.7.3 High Bit Error Rate ............................................................................................................................. 18 4.8 Electrostatics Discharge Warnings ........................................................................................................... 18 Shenzhen RF-star Technology Co., Ltd. Page 5 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 4.9 Soldering and Reflow Condition................................................................................................................. 18 5 Optional Package Specification .............................................................................................................................. 20 6 Revision History ............................................................................................................................................................ 22 7 Contact Us....................................................................................................................................................................... 23 Shenzhen RF-star Technology Co., Ltd. Page 6 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 2 Module Configuration and Functions 2.1 Module Parameters Table 1. Parameters of RF-BM-2652P4(I) Chipset CC2652P7 Supply Power Voltage 1.8 V ~ 3.8 V, 3.3 V is recommended Frequency 2402 MHz ～ 2480 MHz Maximum Transmit Power +20.0 dBm Receiving Sensitivity -99 dBm @ 802.15.4 (2.4 GHz) -104 dBm @ Bluetooth 125 kbps (LE Coded PHY) GPIO 23 Flash 704 KB ROM 256 KB SRAM 152 KB RX current: 6.4 mA TX current: 7.3 mA @ 0 dBm 9.7 mA @ 5 dBm 21 mA @ 10 dBm 101 mA @ 20 dBm Power Consumption MCU 48 MHz (CoreMark): 3.1 mA (65 μA/MHz) Sensor Controller: 29.2 μA @ Low Power-Mode, 2 MHz 799 μA @ Active-Mode, 24 MHz Standby: 0.9 µA Shutdown: 0.1 µA Support Protocol Bluetooth 5.3 Low Energy, Matter, ZigBee, Thread, IEEE 802.15.4, 6LoWPAN, SimpleLinkTM TI 15.4-stack, Proprietary systems Crystal 48 MHz, 32.768 kHz Package SMT packaging (1.27-mm half-hole pitch stamp stick) Dimension 30.0 mm × 16.4 mm × 2.2 mm Type of Antenna RF-BM-2652P4: PCB antenna RF-BM-2652P4I: IPEX connector, ANT pin Operating Temperature -40 ℃ ～ +85 ℃ Storage Temperature -40 ℃ ～ +125 ℃ Shenzhen RF-star Technology Co., Ltd. Page 7 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 2.2 Module Pin Diagram Figure 3. Pin Diagram of RF-BM-2652P4(I) 2.3 Pin Functions Table 2. Pin Diagram of RF-BM-2652P4(I) Pin Name Chip Pin Function 1 DIO5 DIO_5 Digital GPIO, high-drive capability 2 DIO6 DIO_6 Digital GPIO, high-drive capability 3 DIO7 DIO_7 Digital GPIO, high-drive capability 4 DIO8 DIO_8 Digital GPIO 5 DIO9 DIO_9 Digital GPIO 6 DIO10 DIO_10 Digital GPIO 7 DIO11 DIO_11 Digital GPIO 8 DIO12 DIO_12 Digital GPIO 9 DIO13 DIO_13 Digital GPIO 10 RES RESET_N Digital Reset, active low. Internal pullup. 11 JTAG_TMSC JTAG_TMSC Digital JTAG TMSC, high-drive capability 12 JTAG_TCKC JTAG_TCKC Digital JTAG TCKC Shenzhen RF-star Technology Co., Ltd. Description Page 8 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 13 VCC VCC - 14 GND GND Ground Ground 15 DIO14 DIO_14 Digital GPIO 16 DIO15 DIO_15 Digital GPIO 17 DIO16 DIO_16 Digital GPIO, JTAG_TDO, high-drive capability 18 DIO17 DIO_17 Digital GPIO, JTAG_TDI, high-drive capability 19 DIO18 DIO_18 Digital GPIO 20 DIO19 DIO_19 Digital GPIO 21 DIO20 DIO_20 Digital GPIO 22 DIO21 DIO_21 Digital GPIO 23 DIO22 DIO_22 Digital GPIO 24 DIO23 DIO_23 Digital or Analog GPIO, analog capability 25 DIO24 DIO_24 Digital or Analog GPIO, analog capability 26 DIO25 DIO_25 Digital or Analog GPIO, analog capability 27 DIO26 DIO_26 Digital or Analog GPIO, analog capability 28 DIO27 DIO_27 Digital or Analog GPIO, analog capability 29 GND GND Ground 30 ANT Shenzhen RF-star Technology Co., Ltd. - Power supply: 1.8 V ~ 3.8 V, recommended to 3.3 V Ground External antenna interface Page 9 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 3 Specifications 3.1 Recommended Operating Conditions Functional operation does not guarantee performance beyond the limits of the conditional parameter values in the table below. Long-term work beyond this limit will affect the reliability of the module more or less. Table 3. Recommended Operating Conditions of RF-BM-2652P4(I) Condition Items Min. Typ. Max. Unit Operating Supply Voltage / 1.8 3.3 3.8 V Operating Temperature / -40 +25 +85 ℃ Min. Typ. Max. Unit -40 +25 +125 ℃ 3.2 Handling Ratings Table 4. Handling Ratings of RF-BM-2652P4(I) Condition Items Storage Temperature Tstg Human Body Model HBM ±2000 Moisture Sensitivity Level V 3 Charged Device Model ±500 V 3.3 PA Output Control The PA of the CC2652P switches the RF switch by controlling the output of DIO28 and DIO29, and then switches the PA and non-PA RF output to realize the control of the transmission power range. Table 3. RF Control Truth Table Power DIO28 (Output) DIO29 (Output) +5 dBm ~ + 20 dBm (PA) 0 1 < 5 dBm 1 0 Shenzhen RF-star Technology Co., Ltd. Page 10 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 4 Application, Implementation, and Layout 4.1 Module Photos RF-BM-2652P4 RF-BM-2652P4I Figure 3. Photos of RF-BM-2652P4(I) 4.2 Recommended PCB Footprint Figure 4. Recommended PCB Footprint of RF-BM-2652P4(I) Shenzhen RF-star Technology Co., Ltd. Page 11 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 4.3 Schematic Diagram Figure 5. Schematic Diagram of RF-BM-2652P4(I) Shenzhen RF-star Technology Co., Ltd. Page 12 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 4.4 Reference Design Figure 5. Reference Design of RF-BM-2652P4(I) 4.5 Antenna 4.5.1 Antenna Design Recommendation 1. The antenna installation structure has a great influence on the module performance. It is necessary to ensure that the antenna is exposed and preferably vertically upward. When the module is installed inside of the case, a high-quality antenna extension wire can be used to extend the antenna to the outside of the case. 2. The antenna must not be installed inside the metal case, which will cause the transmission distance to be greatly Shenzhen RF-star Technology Co., Ltd. Page 13 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 weakened. 3. The recommendation of antenna layout. The inverted-F antenna position on PCB is free-space electromagnetic radiation. The location and layout of the antenna are key factors to increase the data rate and transmission range. Therefore, the layout of the module antenna location and routing is recommended as follows: （1） Place the antenna on the edge (corner) of the PCB. （2） Make sure that there is no signal line or copper foil in each layer below the antenna. （3） It is best to hollow out the antenna position in the following figure to ensure that the S11 of the module is minimally affected. Figure 4. Recommendation of Antenna Layout Note: The hollow-out position is based on the antenna used. 4.5.2 Antenna Output Mode Modification 1. The antenna output mode can be modified according to the following steps. One 10 pF Capacitance and one 0 R resistor are mounted on the RF-BM-2652P4 as shown in the red circles. If the user would like to change the antenna output mode to IPEX or ANT pin, the 10 pF Capacitance needs to be rotated 90 degrees clockwise as shown in the yellow circle, and the 0 R resistor is needed to be removed. If the IPEX or ANT pin needs to be changed to the PCB antenna, vice versa. Figure 5. Antenna Output Mode Modification of RF-BM-2652P4(I) Shenzhen RF-star Technology Co., Ltd. Page 14 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 4.5.3 External Antenna Design Recommendation of the Half-Hole ANT Pin 1. A Π-type matching circuit is reserved for the antenna, and 50 Ω impedance control is performed on the RF traces. The traces are as short as possible, and 135°or arc traces are used as much as possible. No vias are used to change layers. More GND vias are placed around the RF traces. Figure 6. Reference Design of the External Antenna Figure 7. Reference Design of the External Antenna Traces 2. The RF trace width and copper-clad spacing can be calculated by SI9000 software, and the impedance is controlled to 50 Ω according to the actual board thickness, number of layers, plate, dielectric thickness, dielectric constant, copper thickness, line width, line spacing, and solder mask thickness. Example: FR4 is a double-layer board with a thickness of 1.0 mm. Through calculation, the width of the trace is 0.8254 mm, and the spacing between traces and copper is 0.22 mm. Figure 8. SI9000 Impedance Calculation Diagram Shenzhen RF-star Technology Co., Ltd. Page 15 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 4.5.4 IPEX Connector Specification RF-BM-2652P4I module is integrated the IPEX version 1 antenna seat, the specification of the antenna seat is as follows: Figure 9. Specification of Antenna Seat The specification of the IPEX wire end is as follows: Figure 10. Specification of IPEX Wire 4.6 Basic Operation of Hardware Design 1. It is recommended to offer the module a DC stabilized power supply, a tiny power supply ripple coefficient, and Shenzhen RF-star Technology Co., Ltd. Page 16 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 reliable ground. Please pay attention to the correct connection between the positive and negative poles of the power supply. Otherwise, the reverse connection may cause permanent damage to the module. 2. Please ensure the supply voltage is between the recommended values. The module will be permanently damaged if the voltage exceeds the maximum value. Please ensure a stable power supply and no frequently fluctuating voltage. 3. When designing the power supply circuit for the module, it is recommended to reserve more than 30% of the margin, which is beneficial to the long-term stable operation of the whole machine. The module should be far away from the power electromagnetic, transformer, high-frequency wiring, and other parts with large electromagnetic interference. 4. The bottom of the module should avoid high-frequency digital routing, high-frequency analog routing, and power routing. If it has to route the wire on the bottom of the module, for example, it is assumed that the module is soldered to the Top Layer, the copper must be spread on the connection part of the top layer and the module, and be close to the digital part of the module and routed in the Bottom Layer (all copper is well-grounded). 5. Assuming that the module is soldered or placed in the Top Layer, it is also wrong to randomly route the Bottom Layer or other layers, which will affect the spurs and receiving sensitivity of the module to some degree. 6. Assuming that there are devices with large electromagnetic interference around the module, which will greatly affect the module performance. It is recommended to stay away from the module according to the strength of the interference. If circumstances permit, appropriate isolation and shielding can be done. 7. Assuming that there are routings of large electromagnetic interference around the module (high-frequency digital, high-frequency analog, power routings), which will also greatly affect the module performance. It is recommended to stay away from the module according to the strength of the interference. If circumstances permit, appropriate isolation and shielding can be done. 8. It is recommended to stay away from the devices whose TTL protocol is the same 2.4 GHz physical layer, for example, USB 3.0. 4.7 Trouble Shooting 4.7.1 Unsatisfactory Transmission Distance 1. When there is a linear communication obstacle, the communication distance will be correspondingly weakened. Temperature, humidity, and co-channel interference will lead to an increase in the communication packet loss rate. The performances of ground absorption and reflection of radio waves will be poor when the module is tested close to the ground. 2. Seawater has a strong ability to absorb radio waves, so the test results by the seaside are poor. 3. The signal attenuation will be very obvious if there is metal near the antenna or if the module is placed inside the metal shell. Shenzhen RF-star Technology Co., Ltd. Page 17 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 4. The incorrect power register set or the high data rate in the open air may shorten the communication distance. The higher the data rate, the closer the distance. 5. The low voltage of the power supply is lower than the recommended value at ambient temperature, and the lower the voltage, the smaller the power is. 6. The unmatchable antennas and modules or the poor quality of antenna will affect the communication distance. 4.7.2 Vulnerable Module 1. Please ensure the supply voltage is between the recommended values. The module will be permanently damaged if the voltage exceeds the maximum value. Please ensure a stable power supply and no frequently fluctuating voltage. 2. Please ensure the anti-static installation and the electrostatic sensitivity of high-frequency devices. 3. Due to some humidity-sensitive components, please ensure the suitable humidity during installation and application. If there is no special demand, it is not recommended to use at too high or too low temperature. 4.7.3 High Bit Error Rate 1. There are co-channel signal interferences nearby. It is recommended to be away from the interference sources or modify the frequency and channel to avoid interferences. 2. The unsatisfactory power supply may also cause garbled. It is necessary to ensure the power supply's reliability. 3. If the extension wire or feeder wire is of poor quality or too long, the bit error rate will be high. 4.8 Electrostatics Discharge Warnings The module will be damaged by the discharge of static. RF-star suggests that all modules should follow the 3 precautions below: 1. According to the anti-static measures, bare hands are not allowed to touch modules. 2. Modules must be placed in anti-static areas. 3. Take the anti-static circuitry (when inputting HV or VHF) into consideration in product design. Static may result in the degradation in performance of the module, even causing failure. 4.9 Soldering and Reflow Condition 1. Heating method: Conventional Convection or IR/convection. 2. Solder paste composition: Sn96.5/Ag3.0/Cu0.5 3. Allowable reflow soldering times: 2 times based on the following reflow soldering profile. 4. Temperature profile: Reflow soldering shall be done according to the following temperature profile. 5. Peak temperature: 245 ℃. Shenzhen RF-star Technology Co., Ltd. Page 18 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 Table 5. Temperature Table of Soldering and Reflow Profile Feature Sn-Pb Assembly Pb-Free Assembly Sn63 / Pb37 Sn96.5 / Ag3.0 / Cu0.5 Min. Preheating Temperature (Tmin) 100 ℃ 150 ℃ Max. Preheating Temperature (Tmax) 150 ℃ 200 ℃ Preheating Time (Tmin to Tmax) (t1) 60 s ~ 120 s 60 s ~ 120 s Average Ascend Rate (Tmax to Tp) Max. 3 ℃/s Max. 3 ℃/s Liquid Temperature (TL) 183 ℃ 217 ℃ Time above Liquidus (tL) 60 s ~ 90 s 30 s ~ 90 s 220 ℃ ~ 235 ℃ 230 ℃ ~ 250 ℃ Max. 6 ℃/s Max. 6 ℃/s Max. 6 minutes Max. 8 minutes 20±10 s 20±10 s Solder Paste Peak Temperature (Tp) Average Descend Rate (Tp to Tmax) Time from 25 ℃ to Peak Temperature (t2) Time of Soldering Zone (tP) Figure 11. Recommended Reflow for Lead-Free Solder Shenzhen RF-star Technology Co., Ltd. Page 19 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 5 Optional Package Specification The default package method is by tray. If you need the modules to be shipped by tape & reel, pls contact us in advance. Figure 12. Default Package by Tray Shenzhen RF-star Technology Co., Ltd. Page 20 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 Figure 13. Package by Tape & Reel Shenzhen RF-star Technology Co., Ltd. Page 21 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 6 Revision History Date Version No. 2022.12.12 V1.0 2023.05.25 V1.0 Description The initial version is released. Update MSL level. Update the Shenzhen office address. Note: 1. The document will be optimized and updated from time to time. Before using this document, please make sure it is the latest version. 2. To obtain the latest document, please download it from the official website: www.rfstariot.com and www.szrfstar.com. Shenzhen RF-star Technology Co., Ltd. Page 22 of 23 RF-BM-2652P4(I) www.szrfstar.com V1.0 - May, 2023 7 Contact Us SHENZHEN RF-STAR TECHNOLOGY CO., LTD. Shenzhen HQ: Add.: Room 502, Podium Building No. 12, Shenzhen Bay Science and Technology Ecological Park, Nanshan District, Shenzhen, Guangdong, China, 518063 Tel.: 86-755-8632 9829 Chengdu Branch: Add.: N2-1604, Global Center, North No. 1700, Tianfu Avenue, Hi-Tech District, Chengdu, Sichuan, China, 610095 Tel.: 86-28-8692 5399 Email: sunny@szrfstar.com, sales@szrfstar.com Web.: www.rfstariot.com, www.szrfstar.com Shenzhen RF-star Technology Co., Ltd. Page 23 of 23