Addressing Battery Voltage Fluctuations
Powering a circuit with batteries often leads to a common issue: the voltage supplied by the batteries tends to drop during operation. To counter this problem, a solution is offered by the National Semiconductor type LM3354 IC. This integrated circuit, accessible at (www.national.com/0ds/LM/LM3354.pdf), presents a viable remedy. It incorporates a dc/dc converter designed to operate as a buck converter in the step-down mode when the input voltage is excessively high. Additionally, it can adapt to input voltages that are too low by functioning as a boost converter in step-up mode. Remarkably, this functionality is achieved without the need for coils, thanks to the implementation of switched-capacitor technology.
Innovative Capacitor Charging Mechanism
To address voltage fluctuations in a circuit powered by batteries, a clever solution employs several capacitors charged to the input voltage. These capacitors are then interconnected using an internal matrix switch, either in series for step-up or in parallel for step-down operations. The regulation of the output voltage is achieved by adjusting the duration of the switch-on phase. The LM3354, available in multiple versions tailored for diverse voltages, is at the core of this system.
Notably, this IC operates at a clock frequency of 1 MHz and functions within a voltage range of +2.5 V to +5.5 V. At maximum output current, the minimum input voltage stands at 2.9 V (3.4 V for the 5-V version). Additionally, a Low signal level applied to the Shutdown input can disable the converter, and the IC features efficiency ranging from 75% to 85%. Moreover, thermal overload protection safeguards the IC from damage caused by overloads.
Versatile CMOS-Switched Capacitor DC/DC Converter
The LM3354 stands out as a versatile CMOS-switched capacitor DC/DC converter, meticulously designed to produce a regulated output voltage by intelligently adjusting the input voltage, either stepping up (boost) or stepping down (buck) as needed. This IC is compatible with input voltages ranging from 2.5V to 5.5V. It is available in standard output voltages such as 1.8V, 3.3V, 4.1V (particularly suited for white LED applications), and 5.0V. For tailored output voltage options falling between 1.8V and 5.0V, individuals are encouraged to liaise with their National Semiconductor representative for further assistance.
- Regulated VOUT with ±3% (5.0V, 4.1V, and 3.3V options) or ±4% (1.8V option) accuracy
Standard output voltages of 1.8V, 3.3V, 4.1V, and 5.0V
- Custom output voltages available from 1.8V to 5.0V in 100 mV increments with volume order
- 2.5V to 5.5V input voltage range
- Up to 90mA (5.0V, 4.1V, and 1.8V options) or 70mA (3.3V option) output current
- >75% average efficiency
- Uses a few, low-cost external components
- Very small solution size
- 375 µA typical operating current
- 2.3 µA typical shutdown current
- 1 MHz typical switching frequency
- Architecture and control methods provide high load current and good efficiency
- MSOP-10 package
- Over-temperature protection