Friday, April 24, 2015

Level Shifter: Power Reduction Techniques and its Applications

Level shifters are one of the important components in electronic devices and there common work is to convert the digital signal from one voltage level to other .The major parameters for performance analysis of a level shifter include its power consumption and delay.  These are commonly used circuit component in any multi-voltage electronic system. This approach leads to a design in which different blocks of circuit operate at distinct voltage levels. This factor can be used for enhancement of the circuit operation for minimum energy consumption. A variety of level shifter designs have been designed with single and dual output voltages. Usual shifters have disadvantage of higher power consumption, delay discrepancy and faulty operation at lower supply voltage VddL.

Power Reduction Techniques:

  Capacitive Coupling   -  The basic concept for using this approach is to reduce short circuit current and thus reducing the power consumption. The fast switching characteristic of capacitive coupling reduces the short circuit current during the transition time of input signal. The power can be reduced to about half by implementing this technique.

  Body Biasing Approach – The main feature is using selected body bias where minimum leakage current flows. It is better than bootstrap technique which resulted in delay increment in circuit. This approach limits the power consumption with minimum complexity in design and with slight negotiation in delay parameter.

  Bootstrapping Technique - In this technique, the output node is boosted Up as well as Down by Cboost  capacitor. A bootstrapping switch is used to improve the drivability of pull-up transistors in the level shifter. Furthermore, a pull-down driver is used to have elevated driving capability. Utilizing this approach, it has become possible to reduce the power dissipation keeping along a great performance in low voltage applications.

Power consumption in range of Nano-Watts and Pico-Watts can be achieved in circuit using these techniques.


There are frequent cases in digital electronics where different sections of the system operate from different power supply voltages. A very straightforward example that can illustrates the operation of level shifter is its utility in a circuit that alters the logic levels from the level supplied by one domain to second domain,  like a +5 Volt power supply to a +9 Volt power supply or a +/- 5 Volt dual supply.

1.  One of the very significant applications includes control of Analog Switches where the bipolar signals are necessary and require dual +/- 5 Volt supplies.

2.  A level shifter can be used for shifting the Bus Signals so that different devices operating at different voltages can communicate over the bus.

3.  These are most important block in any Inter-Integrated-Circuit. 

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