Voltage conversion at low energy level
Time:2022-02-26
Views:2278
Author: Frederik Dostal, ADI Field Application Engineer
This paper will introduce a new class of DC-DC converters, one of which is ltc3336. It consumes only about 65 Na of current in standby mode, which is very suitable for battery powered systems.
Conversion efficiency is a key characteristic of power converter. The conversion efficiency of common switching regulators (step-down converters) for step-down conversion is usually between 85% and 95%. The efficiency achieved depends largely on the available supply voltage, the corresponding output voltage to be generated and the required load current. However, many applications require special types of conversion efficiency, for which there are special switching regulator solutions. These deployments require converters optimized for low output power. Battery powered systems that are always on usually consume very low amounts of current in standby mode. Examples include sensors that measure bridge vibration or detect forest fires. In such cases, it is important to keep the discharge low for a long time. This feature is particularly important in systems that rely on energy collectors as energy.
Such sensors are usually also connected to other devices by radio. Usually, a single node powered by energy acquisition or battery is linked to transmit signals across multiple nodes and over long distances. These individual radio nodes must always monitor the signal in a "sleep mode". When the corresponding signal appears, it will switch to the working mode with higher energy consumption and propagate the corresponding signal.
Figure 1 A system with sensors has very low energy to continuously supply power to sensors - for example, sensors that can detect forest fires.
LTC3336 represents a new class of DC-DC converters. When the output voltage is generated and there is a low load at the output, it consumes only about 65 Na of current in standby mode. Figure 2 shows an example of a compact circuit that generates an output voltage of 2.5 V from a VIN of approximately 7 v.
Figure 2 The LTC3336 buck converter with a quiescent current of only 65na produces an output voltage of 2.5V
Usually, the output voltage of this kind of voltage converter is not set through the resistance voltage divider, otherwise too much energy will be wasted. In order to be able to set different output voltages, pins out0 to out3 are used. According to the wiring of these pins, the output voltage can be set between 1.2 V and 5 V in step mode.
In many energy collection applications, energy must be protected from excessive current loads. Some batteries or collectors can only provide limited current. If this specific current limit is exceeded, the voltage will drop, or in some cases, even damage will occur. Therefore, it is meaningful to limit the current consumption of the power converter. The input current of ltc310 can be adjusted in steps of 33ma to 33ma. This input current limit is similar to the output voltage because it can be set through the appropriate wiring of ipk0 and ipk1 pins.
Figure 3 Even if the load current is only 1 µ a, the power conversion efficiency from 7.2 V to 2.5 V is about 70%
The efficiency curve in Figure 3 shows the efficiency that can be achieved when the output current is very low (e.g. 1 µ a). This saves a lot of energy, especially in long-time work and low load applications.
This paper shows that LTC3336 consumes only 65 Na of current in standby mode, so it is an excellent choice for battery powered system. This means that circuits with a fixed battery size can work longer, or energy collectors can be designed to be smaller and therefore cheaper.
Figure 2 The LTC3336 buck converter with a quiescent current of only 65na produces an output voltage of 2.5V
Usually, the output voltage of this kind of voltage converter is not set through the resistance voltage divider, otherwise too much energy will be wasted. In order to be able to set different output voltages, pins out0 to out3 are used. According to the wiring of these pins, the output voltage can be set between 1.2 V and 5 V in step mode.
In many energy collection applications, energy must be protected from excessive current loads. Some batteries or collectors can only provide limited current. If this specific current limit is exceeded, the voltage will drop, or in some cases, even damage will occur. Therefore, it is meaningful to limit the current consumption of the power converter. The input current of ltc310 can be adjusted in steps of 33ma to 33ma. This input current limit is similar to the output voltage because it can be set through the appropriate wiring of ipk0 and ipk1 pins.
Figure 3 Even if the load current is only 1 µ a, the power conversion efficiency from 7.2 V to 2.5 V is about 70%
The efficiency curve in Figure 3 shows the efficiency that can be achieved when the output current is very low (e.g. 1 µ a). This saves a lot of energy, especially in long-time work and low load applications.
Conclusion
This paper shows that LTC3336 consumes only 65 Na of current in standby mode, so it is an excellent choice for battery powered system. This means that circuits with a fixed battery size can work longer, or energy collectors can be designed to be smaller and therefore cheaper.
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