How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters

Remotes come in many different sizes and shapes, and the choice of wireless technology varies. As a product accessory, it is widely used in consumer electronics such as televisions, video game consoles, audio systems, lighting controls, and home automation (including garage door/door starters, air conditioners, fans, and automotive RKE systems). The most common remote controls use infrared (IR) technology, mainly due to the relatively low cost of IR components, but these IR-based controllers have many drawbacks, including the need to be within the viewing angle range, limited operating angles, short transmission distances, and IR LED-related reflections and high current consumption, etc., these defects greatly shorten the battery life. RF remote control solves these problems, and because it can bring a better user experience to the user, the products are becoming more and more abundant. In addition, technological improvements are making the price difference between RF-IR components smaller.

The RF remote control has its common characteristics, as shown in the schematic diagram of Figure 1. The basic components of an RF remote control include: keys that provide the user with input commands; an MCU that converts user commands into digital information; an RF transmitter that modulates and transmits messages; an antenna; and a battery that powers the remote control. A common challenge faced by manufacturers when designing RF remote controls is how to provide a stable maximum transmission distance, ensure longer battery life and maintain low system costs.

How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters

Maximizing transmission distance involves using as much power as possible (within meeting government regulatory constraints) while providing a highly sensitive receiver, since the total transmit distance is a combination of transmitter output power and receiver sensitivity. From the remote control side, the design goal is to build a maximum output power that complies with government regulations, which also means that all remote controls should have the same output performance because they all meet the same regulatory limits. In the ideal world this is possible, but in the real world it is nearly impossible to have the best transmit output power for every remote made on the production line due to component and manufacturing tolerances. In addition, interference from the user holding the remote control, or even touching the keys (also known as the “hand effect”) can change the impedance of the antenna, which in turn changes the transmit output power. The real-world impact can reduce the effective radiated power (ERP) of the remote control, which can easily lead to the output power being 6dB lower than the government regulation limit, and the transmission distance will be correspondingly shortened by a factor of 2 according to the Friis free space path loss formula.

The Si4010 transmitter is the newest member of Silicon Labs’ EZRadio wireless product line and the industry’s first single-chip remote control IC that requires only an external bypass capacitor, a PCB, a battery, and a keyed enclosure to form a complete remote control. The Si4010 includes a patented antenna tuning circuit that automatically fine-tunes the antenna to optimal transmit power for each keystroke. In traditional remote control designs, RF transmitter differences, component and antenna manufacturing tolerances, and the surrounding environment result in low antenna efficiency and significant wasted output energy. Figure 2 is a schematic diagram of the structure of the Si4010 power amplifier and antenna tuning circuit.

How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters

The Si4010 maximizes transmit antenna efficiency by tuning an on-chip variable capacitor that resonates with the antenna’s self-inductance. These automatic capacitor adjustments maximize the transmit power of the remote control by compensating for the detuning of the antenna matching circuit, and reduce design cost by allowing relaxation of PCB antenna manufacturing tolerances.

A power amplifier (PA) contains a feedback loop that maintains a stable output power by monitoring the PA output voltage and adjusting the PA current drive (to compensate for changes in antenna impedance). The feedback loop effectively maintains a stable output power despite the effects of temperature changes and the “hand effect,” which, as described above, will change the antenna impedance when a person holds the remote control. The end result of antenna tuning is to provide reliable and optimal performance for each keystroke, while reducing design cost and complexity to meet RF matching requirements. Remote controls using the Si4010’s automatic antenna tuning feature operate reliably and stably, providing maximum transmission distance while meeting government emission restrictions.

Battery life is an important consideration for any portable Electronic device, especially remote controls. When we consider how a typical remote control is used, it is found that more than 99% of the time, the remote control is in a state of waiting for the user to press a button. During this period, Si4010 consumes less than 10nA (at room temperature), which makes it ideal for battery-powered applications. In addition, the GPIO feature with wake-on-touch function further reduces the current consumption of the remote control and prolongs the battery life.

Figure 3 is an example of the power consumption of the Si4010 in a typical remote control application. Using CR2032 battery, the maximum transmit power is +10dBm.

How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters

Figure 3: Si4010 battery life calculation example

During transmission, the Si4010 consumes 14.2mA in OOK modulation mode or 19.8mA in FSK modulation mode at +10dBm output power. If we assume the following situation: 1kBaud data rate, Manchester encoding, 100bit per packet, 3 repetitions per key press, we get the following conclusion: 50 key presses per day, 5 years of continuous operation, OOK modulation mode Only consumes 52% of the 220mAH CR2032 battery power; consumes 71% of the battery power in FSK modulation mode.

Although this example does not include battery leakage, it does illustrate the importance of the Si4010’s low transmit power consumption and low standby current. The ultra-low standby current of the Si4010 transmitter is an order of magnitude lower than many existing solutions, a distinction that is important for extending remote control battery life.

One of the most important considerations in any remote control design is minimizing system design cost, which is influenced by many factors in addition to component cost, including labor costs, inventory, testing, and manufacturing yield. So far, the dominant low-cost RF remote control solution on the market is the use of an MCU and a surface acoustic wave (SAW) based RF transmitter, as shown in Figure 4.

How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters
Figure 4: Simplified schematic of a SAW-based remote control transmitter

This designed topology is widely accepted, mainly because of its low cost and simplicity. The SAW device resonates with transistor Q1 in the Colpitts oscillator structure to form the carrier frequency, and transistor Q2 provides the isolation required for output power amplification and stable operation. The data from the MCU is directly applied to the SAW resonator to form the OOK modulated signal, and GPIO6 from the MCU provides the voltage (VCC) to the SAW based transmitter. The entire solution uses 24 external components, including the MCU, a bypass capacitor, a quartz crystal that clocks the MCU, a PCB board with an on-board antenna, and capacitors. RF component cost (excluding PCB, MCU, and bypass capacitors) is $0.77 (on the order of 100,000). Traditionally, this has been the lowest component cost reliable RF transmission solution. From a system cost perspective, a higher BOM count increases other costs, such as labor costs, inventory and testing, and reduces yield.

While SAW-based transmitters are widely used in remote controls (due to their lower component cost), the older technology suffers from a number of drawbacks. In addition to the higher system cost caused by a large number of RF components, SAW-based transmitters have the following disadvantages: low carrier frequency accuracy, single-frequency operation, only supports OOK modulation, poor performance stability, sensitivity to device tolerances, low yield .

In contrast, the Si4010 transmitter is a complete SoC remote control IC. Based on the patented Si500 silicon oscillator, its patented crystal-less architecture achieves a carrier frequency accuracy of ±150ppm in the commercial temperature range and ±250ppm in the industrial temperature range, which is a traditional SAW-based low-cost transmitter (No external crystal) 2 times the frequency accuracy. The Si4010 operates over a continuous frequency range of 27-960MHz and includes a programmable PA with maximum output power up to +10dBm, automatic antenna tuning and PA edge rate control to meet FCC, ETSI and ARIB radio frequency regulations. The embedded 8051 MCU is instruction optimized for fast processing with 512B internal RAM, 4kB RAM, 8kB OTP NVM, 128b EEPROM, 12kB library ROM and hardware accelerated 128b AES encryption logic. The 1.8-3.6V supply range, less standby current than ultra-low power consumption (10nA), and wake-on-touch operation make the Si4010 ideal for coin cell battery applications. Figure 5 is Si4010 SoC Transmitter block diagram.

How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters

Figure 6 is a schematic diagram of a remote control using the Si4010, with an optional LED light for key operation indication. The total BOM of the remote control (excluding the optional LED lights) includes a Si4010 IC, a bypass capacitor, and a PCB with on-board antenna and capacitors. Not only does the Si4010 have less total BOM count than SAW-based transmitters (3 vs. 24), but the Si4010 also does not require any RF components because all components are integrated inside the chip. In addition, the automatic antenna tuning function of the Si4010 device guarantees stable and reliable output power and reduces system cost by relaxing the tolerance range in the manufacturing process (since highly accurate antenna matching is no longer required).

How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters
Figure 6: Schematic diagram of remote control using Si4010

A remote control designed using the Si4010 overcomes many of the problems faced by traditional RF transmitters. The Si4010 utilizes the antenna tuning feature to eliminate difficult and cumbersome RF matching issues, while also reducing costly RF design overhead and time-to-market. The task of hardware design is reduced to: selecting the best PCB antenna for a given remote control geometry, proper placement and routing for the Si4010, PCB on-board antenna, bypass capacitors, buttons, and batteries.

Remote control software development is very easy using the Si4010 transmitter library integrated in the 12kB ROM. The library includes key service, AES encryption, encoding modules, battery voltage detection and other useful remote control functions to reduce code size and speed time-to-market.


Fig. 8 is the Si4010 control flow chart in the remote control application. After installing the battery or waking up from standby mode by pressing a key, the Si4010 automatically starts the boot process, it copies the user code from non-volatile memory to RAM, and then runs the user code. After booting, the digital part of the device is initialized first (MCU, interrupts, timers, peripherals, etc.), and then the analog part is initialized using functions in the ROM library. For example, modulation type (OOK or FSK), data rate, PA emission level, carrier frequency, etc. are all set at this stage.

When the initialization is completed, the program enters the main loop and monitors the key operation for event processing. Depending on which key was pressed, the program decides what to do and builds the appropriate packet based on the key. Then, the Si4010 fine-tunes the frequency and transmits the packet. Once the information is transmitted, the Si4010 shuts down completely and goes into an ultra-low power standby state. In standby mode, the chip consumes less than 10nA (at a temperature of 25°C) and can wake up from any GPIO key press to restart processing.

Remotes come in many different sizes and shapes, and the choice of wireless technology varies. As a product accessory, it is widely used in consumer electronics such as televisions, video game consoles, audio systems, lighting controls, and home automation (including garage door/door starters, air conditioners, fans, and automotive RKE systems). The most common remote controls use infrared (IR) technology, mainly due to the relatively low cost of IR components, but these IR-based controllers have many drawbacks, including the need to be within the viewing angle range, limited operating angles, short transmission distances, and IR LED-related reflections and high current consumption, etc., these defects greatly shorten the battery life. RF remote control solves these problems, and because it can bring a better user experience to the user, the products are becoming more and more abundant. In addition, technological improvements are making the price difference between RF-IR components smaller.

The RF remote control has its common characteristics, as shown in the schematic diagram of Figure 1. The basic components of an RF remote control include: keys that provide the user with input commands; an MCU that converts user commands into digital information; an RF transmitter that modulates and transmits messages; an antenna; and a battery that powers the remote control. A common challenge faced by manufacturers when designing RF remote controls is how to provide a stable maximum transmission distance, ensure longer battery life and maintain low system costs.

How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters

Maximizing transmission distance involves using as much power as possible (within meeting government regulatory constraints) while providing a highly sensitive receiver, since the total transmit distance is a combination of transmitter output power and receiver sensitivity. From the remote control side, the design goal is to build a maximum output power that complies with government regulations, which also means that all remote controls should have the same output performance because they all meet the same regulatory limits. In the ideal world this is possible, but in the real world it is nearly impossible to have the best transmit output power for every remote made on the production line due to component and manufacturing tolerances. In addition, interference from the user holding the remote control, or even touching the keys (also known as the “hand effect”) can change the impedance of the antenna, which in turn changes the transmit output power. The real-world impact can reduce the effective radiated power (ERP) of the remote control, which can easily lead to the output power being 6dB lower than the government regulation limit, and the transmission distance will be correspondingly shortened by a factor of 2 according to the Friis free space path loss formula.

The Si4010 transmitter is the newest member of Silicon Labs’ EZRadio wireless product line and the industry’s first single-chip remote control IC that requires only an external bypass capacitor, a PCB, a battery, and a keyed enclosure to form a complete remote control. The Si4010 includes a patented antenna tuning circuit that automatically fine-tunes the antenna to optimal transmit power for each keystroke. In traditional remote control designs, RF transmitter differences, component and antenna manufacturing tolerances, and the surrounding environment result in low antenna efficiency and significant wasted output energy. Figure 2 is a schematic diagram of the structure of the Si4010 power amplifier and antenna tuning circuit.

How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters

The Si4010 maximizes transmit antenna efficiency by tuning an on-chip variable capacitor that resonates with the antenna’s self-inductance. These automatic capacitor adjustments maximize the transmit power of the remote control by compensating for the detuning of the antenna matching circuit, and reduce design cost by allowing relaxation of PCB antenna manufacturing tolerances.

A power amplifier (PA) contains a feedback loop that maintains a stable output power by monitoring the PA output voltage and adjusting the PA current drive (to compensate for changes in antenna impedance). The feedback loop effectively maintains a stable output power despite the effects of temperature changes and the “hand effect,” which, as described above, will change the antenna impedance when a person holds the remote control. The end result of antenna tuning is to provide reliable and optimal performance for each keystroke, while reducing design cost and complexity to meet RF matching requirements. Remote controls using the Si4010’s automatic antenna tuning feature operate reliably and stably, providing maximum transmission distance while meeting government emission restrictions.

Battery life is an important consideration for any portable Electronic device, especially remote controls. When we consider how a typical remote control is used, it is found that more than 99% of the time, the remote control is in a state of waiting for the user to press a button. During this period, Si4010 consumes less than 10nA (at room temperature), which makes it ideal for battery-powered applications. In addition, the GPIO feature with wake-on-touch function further reduces the current consumption of the remote control and prolongs the battery life.

Figure 3 is an example of the power consumption of the Si4010 in a typical remote control application. Using CR2032 battery, the maximum transmit power is +10dBm.

How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters

Figure 3: Si4010 battery life calculation example

During transmission, the Si4010 consumes 14.2mA in OOK modulation mode or 19.8mA in FSK modulation mode at +10dBm output power. If we assume the following situation: 1kBaud data rate, Manchester encoding, 100bit per packet, 3 repetitions per key press, we get the following conclusion: 50 key presses per day, 5 years of continuous operation, OOK modulation mode Only consumes 52% of the 220mAH CR2032 battery power; consumes 71% of the battery power in FSK modulation mode.

Although this example does not include battery leakage, it does illustrate the importance of the Si4010’s low transmit power consumption and low standby current. The ultra-low standby current of the Si4010 transmitter is an order of magnitude lower than many existing solutions, a distinction that is important for extending remote control battery life.

One of the most important considerations in any remote control design is minimizing system design cost, which is influenced by many factors in addition to component cost, including labor costs, inventory, testing, and manufacturing yield. So far, the dominant low-cost RF remote control solution on the market is the use of an MCU and a surface acoustic wave (SAW) based RF transmitter, as shown in Figure 4.

How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters
Figure 4: Simplified schematic of a SAW-based remote control transmitter

This designed topology is widely accepted, mainly because of its low cost and simplicity. The SAW device resonates with transistor Q1 in the Colpitts oscillator structure to form the carrier frequency, and transistor Q2 provides the isolation required for output power amplification and stable operation. The data from the MCU is directly applied to the SAW resonator to form the OOK modulated signal, and GPIO6 from the MCU provides the voltage (VCC) to the SAW based transmitter. The entire solution uses 24 external components, including the MCU, a bypass capacitor, a quartz crystal that clocks the MCU, a PCB board with an on-board antenna, and capacitors. RF component cost (excluding PCB, MCU, and bypass capacitors) is $0.77 (on the order of 100,000). Traditionally, this has been the lowest component cost reliable RF transmission solution. From a system cost perspective, a higher BOM count increases other costs, such as labor costs, inventory and testing, and reduces yield.

While SAW-based transmitters are widely used in remote controls (due to their lower component cost), the older technology suffers from a number of drawbacks. In addition to the higher system cost caused by a large number of RF components, SAW-based transmitters have the following disadvantages: low carrier frequency accuracy, single-frequency operation, only supports OOK modulation, poor performance stability, sensitivity to device tolerances, low yield .

In contrast, the Si4010 transmitter is a complete SoC remote control IC. Based on the patented Si500 silicon oscillator, its patented crystal-less architecture achieves a carrier frequency accuracy of ±150ppm in the commercial temperature range and ±250ppm in the industrial temperature range, which is a traditional SAW-based low-cost transmitter (No external crystal) 2 times the frequency accuracy. The Si4010 operates over a continuous frequency range of 27-960MHz and includes a programmable PA with maximum output power up to +10dBm, automatic antenna tuning and PA edge rate control to meet FCC, ETSI and ARIB radio frequency regulations. The embedded 8051 MCU is instruction optimized for fast processing with 512B internal RAM, 4kB RAM, 8kB OTP NVM, 128b EEPROM, 12kB library ROM and hardware accelerated 128b AES encryption logic. The 1.8-3.6V supply range, less standby current than ultra-low power consumption (10nA), and wake-on-touch operation make the Si4010 ideal for coin cell battery applications. Figure 5 is Si4010 SoC Transmitter block diagram.

How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters

Figure 6 is a schematic diagram of a remote control using the Si4010, with an optional LED light for key operation indication. The total BOM of the remote control (excluding the optional LED lights) includes a Si4010 IC, a bypass capacitor, and a PCB with on-board antenna and capacitors. Not only does the Si4010 have less total BOM count than SAW-based transmitters (3 vs. 24), but the Si4010 also does not require any RF components because all components are integrated inside the chip. In addition, the automatic antenna tuning function of the Si4010 device guarantees stable and reliable output power and reduces system cost by relaxing the tolerance range in the manufacturing process (since highly accurate antenna matching is no longer required).

How to Simplify RF Remote Control Design with Highly Integrated SoC Transmitters
Figure 6: Schematic diagram of remote control using Si4010

A remote control designed using the Si4010 overcomes many of the problems faced by traditional RF transmitters. The Si4010 utilizes the antenna tuning feature to eliminate difficult and cumbersome RF matching issues, while also reducing costly RF design overhead and time-to-market. The task of hardware design is reduced to: selecting the best PCB antenna for a given remote control geometry, proper placement and routing for the Si4010, PCB on-board antenna, bypass capacitors, buttons, and batteries.

Remote control software development is very easy using the Si4010 transmitter library integrated in the 12kB ROM. The library includes key service, AES encryption, encoding modules, battery voltage detection and other useful remote control functions to reduce code size and speed time-to-market.


Fig. 8 is the Si4010 control flow chart in the remote control application. After installing the battery or waking up from standby mode by pressing a key, the Si4010 automatically starts the boot process, it copies the user code from non-volatile memory to RAM, and then runs the user code. After booting, the digital part of the device is initialized first (MCU, interrupts, timers, peripherals, etc.), and then the analog part is initialized using functions in the ROM library. For example, modulation type (OOK or FSK), data rate, PA emission level, carrier frequency, etc. are all set at this stage.

When the initialization is completed, the program enters the main loop and monitors the key operation for event processing. Depending on which key was pressed, the program decides what to do and builds the appropriate packet based on the key. Then, the Si4010 fine-tunes the frequency and transmits the packet. Once the information is transmitted, the Si4010 shuts down completely and goes into an ultra-low power standby state. In standby mode, the chip consumes less than 10nA (at a temperature of 25°C) and can wake up from any GPIO key press to restart processing.

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