ISM band keyless entry solution based on SX1230

This article introduces the main features of SX1230, simplified block diagram, single application circuit diagram and multiple output power matching circuit diagrams, keyless entry system (RKS) turnkey reference design main features, detailed circuit diagram and bill of materials.

The SX1230 is a narrowband/wideband 315 MHz, 434 MHz 868 MHz and 915 MHz ISM band transmitter from Semtech, with programmable output power from +17 dBm to -18 dBm, bit rate up to 600kbps, FSK, GFSK, MSK, GMSK and OOK modulation, no host MCU required when used alone, constant RF performance at 1.8V-3.7V, low phase noise (-95 dBc/Hz at 50kHz), mainly used in keyless entry (RKE) systems, remote control and security systems, voice and data communication links, production process and building/home control, active RFID, AMR/AMI platforms.

SX1230 Key Features:

+17 dBm to -18 dBm Programmable output power.

Bit rates up to 600 kbits / sec.

FSK, GFSK, MSK, GMSK and OOK modulation.

Stand-alone mode: No need for a host MCU.

Consistent RF performance over a 1.8 to 3.7 V range.

Low phase noise (-95 dBc/Hz at 50 kHz) with automated

PLL calibration and fully integrated VCO and loop filter.

On chip RC timer for timer / wake-up applications.

Low battery detection.

SX1230 Applications:

Remote Keyless Entry (RKE) Keyless Entry Solutions

Remote Control / Security Systems

Voice and Data RF Communication Links

Process and building / home control

Active RFID

AMR/AMI Platforms

Figure 1. SX1230 Simplified Block Diagram

Figure 2. SX1230 Application Block Diagram


Figure 3. SX1230 Standalone Application Circuit Diagram

Figure 4. SX1230 MCU mode application circuit diagram

Figure 5. SX1230 and MCU interface circuit diagram

Figure 6. SX1230 RKE demo board receiver circuit diagram

Figure 7. 434MHz band 17dBm output power matching circuit diagram

Figure 8. 315MHz band 17dBm output power matching circuit diagram

Figure 9. 915MHz band 13dBm output power matching circuit diagram

Figure 10. 868MHz band 13dBm output power matching circuit diagram

Figure 11. 315/434MHz band 13dBm output power matching circuit diagram

Figure 12. SX1230 Reference Design Circuit

Keyless Entry System (RKS) Turnkey Reference Design

Turnkey Reference Design for Remote Keyless Entry System

A remote keyless system (RKS) is a system designed to remotely permit or deny access to premises or automobiles.

In the case of automobiles an RKS performs the functions of a standard car key without physical contact; power door systems can be locked or unlocked from several feet away or even from inside a building.

A remote keyless system can include both a remote keyless entry system (RKE) and a remote key less ignition system (RKI).

Remote keyless systems first began appearing as an option on several American Motors vehicles in 1983. Most RKE systems operate at 315MHz in North America and Japan, and 433.92 MHz in Europe. Modern systems implement encryption to prevent car thieves from intercepting and spoofing the signal.

The functions of a remote keyless entry system are contained on a key fob or built into the ignition key handle itself. Buttons are dedicated to locking or unlocking the doors and opening the trunk (or, on sport utility vehicles and station wagons, unlock/open the rear tailgate). Some cars will also close any open windows and roof when remotely locking the car. Some remote keyless fobs also feature a red panic button which activates the car alarm as a standard feature.

Some car engines with remote keyless ignition systems can be started by the push of a button on the key fob. For offices or residences, the system can also be coupled with the security system, garage door opener or remotely activated lighting devices.

The SX1230-13RKEA433 reference design kit provides a turnkey platform for highly secure, low-power, multi-band wireless remote keyless entry (RKE) systems. This RKE kit integrates Semtech’s high-performance transmitter, tranceiver and switching regulator ICs with Microchip’s KEELOQ® code-hopping technology running on PIC® microcontrollers (MCUs). The kit helps simplify and accelerate the development of secure, high-performance and cost-effective RKE systems for vehicles, office buildings and homes, and provides a single platform that works across virtually all major frequency regulations.

The RKE reference-design hardware includes transmitter (Tx) and receiver (Rx) boards, multi-band PCB antenna and Microchip MCUs, and runs Microchip’s KEELOQ code-hopping encryption software. Confidential information is stored inside the Flash memory of the PIC microcontroller, while the KEELOQ security algorithm encrypts the information in the RF transmission packets prior to any RF transmission, unlike some existing RKE systems in the market.

The Tx board pairs Semtech’s SX1230 industrial, scientific and medical (ISM) band transmitter with Microchip’s PIC16F631 or PIC16F677 8-bit MCUs. The Rx board employs Semtech’s SX1211 or SX1212 ISM transceivers with Microchip’s PIC16F631 or PIC16F677 MCUs. The RKE reference design also uses Semtech’s SC120 switching regulator -- the world’s smallest low VIN boost converter in a 1.5x2x0.6mm package.

参考设计主要特性:

Turnkey hardware and software RKE reference design, including:


- Hardware: integrated RF ICs, multi-band PCB antenna, MCU


- Software: KEELOQ code-hopping technology software

Highly secure:


- Encrypts all RF packets before sending, no plain text sent over air


- Code-hopping encryption produces unique RF transmission each time.

Saves design cost and time


- Same design supports multi-band (315, 434, 868, 915MHz) and multiple modulation formats (FSK, OOK, ASK)

No tuning for lower production costs

Long range: programmable POUT up to +17dBm

图13。参考设计Rx和Tx板外形图

图14。无钥匙进入系统（RKS）框图

图15。无钥匙进入系统（RKS）Tx方框图

图15。无钥匙进入系统（RKS）Rx方框图

图16。无钥匙进入系统（RKS）加密系统方框图

图17。无钥匙进入系统（RKS）解密系统方框图

图18。无钥匙进入系统（RKS）Tx板电路图

图19。无钥匙进入系统（RKS）Rx板电路图
Tx 板材料清单（BOM）：

Rx 板材料清单（BOM）：