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490-5791-1-ND  /  LXDC2HL18A-052         

By Pat Sagsveen, Digi-Key Electronics

 

Figure 1 - LXDC2HL18A-052

https://www.digikey.com/product-detail/en/murata-electronics-north-america/LXDC2HL18A-052/490-5791-1-ND/2783646

                This article will cover the LXDC2HL18A-052 from Murata Electronics.  This device is a DC-DC converter that outputs 1.8v with up to 600mA. This device is meant to work with battery powered devices by freeing up board space and allow energy savings for the battery.  The input voltage range for this device is 2.3v – 5.5v making it a good choice for many Lithium Ion batteries.  This device is intended for applications that require low noise; there is an inductor-embedded ferrite substrate that helps to reduce noise.  There are two modes of operation for this device, PFM and PWM.  PFM stands for pulse frequency modulation.  This is done by modulating the frequency of a square wave.  The width of the pulses will remain constant, but the number of pulses will increase depending upon the demands of the load.  PWM stands for pulse width modulation.  This is done by increasing the width of the pulses when the demand on the load goes up.  Figures 2 and 3 demonstrate these modulation schemes point.

 

Figure 2 – Pulse Frequency Modulation

https://www.digikey.com/en/articles/techzone/2014/mar/the-advantages-of-pulse-frequency-modulation-for-dc-dc-switching-voltage-converters

 

Figure 3 – Pulse Width Modulation

https://learn.sparkfun.com/tutorials/pulse-width-modulation

 

The LXDC2HL18A-052 will automatically switch between PFM and PWM at around 100-200mA.  This, along with synchronous rectification, increases the efficiency of the device.  The synchronous rectifier will operate at 3MHz for the LXDC2HL18A-052.  This converter is pretty straight forward with its pin assignments.  Figure 4 shows the four pin assignments and Figure 5 shows the typical application circuit.

 

Figure 4 – Pin assignment for LXDC2HL18A-052

http://power.murata.com/data/power/LXDC2HL_Series_datasheet_E.pdf

 

 

Figure 5 – Typical Application Circuit for LXDC2HL18A-052

http://power.murata.com/data/power/LXDC2HL_Series_datasheet_E.pdf

                 

 

 

 

                        To evaluate this device it was hooked up to a DC load to monitor the current and the voltage was measured using an independent multimeter.  Using the BK Precision 150W DC electronic load (model 8540), it was possible to evaluate the voltage over an array of output currents.  This was achieved by changing the DC load resistance from 3Ω to 9 Ω and finally to 18 Ω.  This should theoretically give 600mA, 200mA, and 100mA respectively for an output.  The following tables illustrate the input and output voltages along with output current and power that was observed.

Input Voltage

Resistance

Output Voltage

Current

Power

3.3v

18Ω

1.79v

99mA

177mW

3.3v

9 Ω

1.78v

198mA

352mW

3.3v

3 Ω

1.76v

582mA

1.016W

Input Voltage

Resistance

Output Voltage

Current

Power

2.3v

18 Ω

1.79v

99mA

177mW

2.3v

9 Ω

1.78v

198mA

353mW

2.3v

4 Ω*

1.76v

439mA

768mW

*At 2.3v input using 3 ohms the test equipment would not stabilize and the power supply had to switch between constant current and constant voltage mode.  By changing to 4 ohms the system was able to stabilize.  The 3 ohm value at 2.3v is right on the edge of the maximum values for this device.

Input Voltage

Resistance

Output Voltage

Current

Power

5.5v

18 Ω

1.79v

99mA

177mW

5.5v

9 Ω

1.78v

198mA

350mW

5.5v

3 Ω

1.76v

579mA

1.006W

 

                In addition to looking through the output voltages and currents for this device, there was also a thermal examination of how this device performed.  To do this the input voltage was set at 3.3v and the load was varied to illustrate how warm the device got.  The VT04 IR thermometer from Fluke Electronics was used to capture the images.  There was only one picture taken for each different load.  Using the SmartView software from Fluke it was possible to take the image and edit it to show an actual image and an IR image.  This is because there is a camera and an IR camera on the VT04.  Figures 6, 7, and 8 show the images with the camera view on the left and the IR camera view on the right.  The higher the temperature got on the device the more the heat was concentrated on just the device.  As the device got colder the ambient temperature was picked up more by the VT04.

 

Figure 6 - 3Ω load / 1.016W / 95.7˚F

 

Figure 7 - 9Ω load / 352mW / 82.7˚F

 

Figure 8 - 18Ω load / 177mW / 76.0˚F

                Overall the device operated as advertised.  The datasheet claimed that this device would maintain a 2% tolerance over the full current range and that is what was observed.  The device was definitely working harder with the 3Ω load as evidenced by the thermal images, yet still maintained the proper output voltage within the 2% specification that was advertised.  Digi-Key carries the LXDC2HL series and there are several different output voltages available ranging from 1V-3.3V.  

Links


Video - 

Forum discussion - https://forum.digikey.com/t/murata-dc-dc-converter/503 

 

 

 

 

 

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