ADI’s high-voltage boost and inverting converters for communications

The field of Electronic communication is rapidly expanding to all aspects of daily life. Detecting, transmitting and receiving data require the use of a large number of devices, such as fiber optic sensors, RF MEMS, PIN diodes, APDs, laser diodes, high-voltage DACs, and so on. In many cases, these devices require hundreds of volts to operate, so DC-DC converters are required to meet stringent efficiency, space, and cost requirements.

The field of electronic communication is rapidly expanding to all aspects of daily life. Detecting, transmitting and receiving data require the use of a large number of devices, such as fiber optic sensors, RF MEMS, PIN diodes, APDs, laser diodes, high-voltage DACs, and so on. In many cases, these devices require hundreds of volts to operate, so DC-DC converters are required to meet stringent efficiency, space, and cost requirements.

ADI’s LT8365 is a multi-purpose single-chip boost converter that integrates a 150 V, 1.5 A switch, so it is particularly suitable for high-voltage applications including portable devices in the communications field. High voltage output can be easily generated from inputs as low as 2.8 V and as high as 60 V. The chip has an optional spread spectrum function, which can help eliminate EMI, and there are many other commonly used features. For details, please refer to the data sheet. The converters shown in Figures 1 and 2 are used to provide positive and negative piezoelectric rails for high-voltage DACs, MEMS, RF switches, and high-voltage operational amplifiers from a 12 V input source. These converters operate in discontinuous conduction mode (DCM), provide up to 10 mA of current, and +250 V and C250 V output voltages, with a conversion efficiency of approximately 80%.

Boost ratio “1:40

One advantage of implementing DCM operation in a boost converter is that a high boost ratio can be achieved no matter how high the duty cycle is. In addition, the value and physical size of the Inductor and output capacitor can be reduced, thereby reducing the overall size of the solution used on the PCB. The circuit shown in Figure 3 can be easily deployed in a space less than 1 cm2.
  

ADI’s high-voltage boost and inverting converters for communications

ADI’s high-voltage boost and inverting converters for communications

 

ADI’s high-voltage boost and inverting converters for communications

ADI’s high-voltage boost and inverting converter for communication-LT8365 Figure 3. Boost converter from 3 V input to 125 V output

In some cases, the voltage of the available input source may be very low, but a high output voltage is required. At this time, the converter shown in Figure 3 can be used to drive multiple avalanche photodiodes, PIN diodes, and other devices that require high bias voltages. These boost converters can generate 125 V output from a 3 V input with a load current of up to 3 mA.
 

ADI’s high-voltage boost and inverting converters for communications

The converter shown in Figure 4 uses a 3 V input to boost a 125 V output to a 250 V output and supports approximately 1.5 mA of current. In the communications field, there are many devices that require such a high bias voltage from a low input voltage source.

How high or how low can it be?

In situations where extremely high voltages are required, whether it is a positive voltage or a negative voltage, the boost converter can use multiple stages to increase the output by 2 times, 3 times, or even more. The converter shown in Figure 1 and Figure 2 shows how to double the switching voltage in two directions (positive voltage and negative voltage). The 3-stage boost converter shown in Figure 5 can generate 8 mA, 375 V output from a 12 V input.

ADI’s high-voltage boost and inverting converter for communication-LT8365 Figure 5.12 V input to 375 V output 3-stage boost converter

Note: The available output current must decrease as the output voltage rises, because the switch current capability does not change. For example, a single-stage converter used to provide 20 mA of current will provide approximately 10 mA of current when the second stage is added. When adding more stages, always ensure that the peak switch current is always within the guaranteed switch current limit.

The Links:   LQ64D342 IRKT56-08A

Author: Yoyokuo