subject: Battery Life Is An Important Consideration For Any Portable Electronic Device [print this page] The Si4010 transmitter, the latest member of Silicon Labs EZRadio line of wireless products, is the industrys first single-chip remote control IC, requiring only one external bypass capacitor, a printed circuit board (PCB), battery and an external casing with push buttons to form a complete remote control. The Si4010 includes a patented antenna tuning circuit that automatically fine-tunes the antenna for optimum transmit power on every button press. With standard remote control designs, variations in the RF transmitter, component and antenna manufacturing tolerances and the environment can lead to large antenna inefficiencies and wasted power.
An additional feedback loop is incorporated into the power amplifier (PA) to maintain constant output power by monitoring the voltage at the output of the PA and adjusting the PAs current drive to compensate for changes in the antenna impedance. This feedback loop works to maintain constant output power in spite of temperature variations and the hand effect, which, as stated above, changes the antenna impedance when a persons hand is covering the remote control. The net result of antenna tuning is to provide consistently reliable and optimal performance on every button press while reducing the cost and design complexity of the RF matching requirements. Remote controls designed with the Si4010s automatic antenna tuning feature can reliably and consistently operate at the government transmit limit for maximum transmit range.
Battery life is an important consideration for any portable electronic device, especially a remote control. When we consider typical remote control usage, more than 99 percent of the time, a remote control is waiting for a user to activate a button press. During this time, the Si4010 consumes less than 10 nA at room temperature, making it an ideal choice for battery-powered applications. Additionally, wake-on-touch GPIOs further minimize current consumption of the remote control and extend battery life.
During transmission, the Si4010 consumes either 14.2 mA in on-off keying (OOK) mode or 19.8 mA in frequency-shift keying (FSK) mode while transmitting at +10 dBm output power. If we assume that the transmitter transmits at a data rate of 1 kBaud, the data is Manchester encoded and each packet is 100 bits long and repeats three times for each button press, then we have the following results: At 50 button presses per day for five consecutive years, we use only 52 percent of the charge in a 220 mAhr CR2032 battery in OOK mode and 71 percent of the charge in FSK mode.
Although this example does not include the self leakage of the battery, it does illustrate the low power characteristics of the Si4010 transmitter and the importance of low standby current. The Si4010 transmitters ultra-low standby current is an order of magnitude lower than many existing solutions and is an important differentiator for extending the battery life of a remote control.
