XPERT – TECHNO – PROJET

Test Report« LT3065 Voltage Regulation»

Date de création

16/02/2023

Révision

1.0

Niveau de classification

C2 – Equipe projet© XPERT 2023

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References© XPERT 2023

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Contents
References ........................................................................................................................................ 2
1.

Test Objectives .......................................................................................................................... 4

2.

Test setup and description ......................................................................................................... 5

3.

Results and analysis ................................................................................................................... 7
1.

Regulated 5V and 3.3V in function of Vin ............................................................................... 7

2.

Regulated 5V in function of R_load ........................................................................................ 93.

Regulated 3.3V in function of R_load ................................................................................... 114.

Conclusion ............................................................................................................................... 13

5.

Annexes................................................................................................................................... 14© XPERT 2022

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1. Test Objectives
These tests is realized in order to observe the performance of LT3065 in terms of:•LT3605’s limitation and applicability on our design.

•The variation of the regulated output in function of Vin injected when the current drawn isimportant.

•Stability of the regulated output when the current drawn is important.

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2. Test setup and description
Site of test : XPERT Laboratory
Materials used : A programmable power supply (ref: GW Instek PSP-405), digital multimeter (ref:Keithley DAQ6510), adjustable multimeter (ref: Time Electronics Model 1051)

Test description and setup :These tests are carried out on LT3065 following the component’s demo board (DC2072A) schematicconfiguration proposed by Analog Device.

Exceptionally in our case, we made our measurements only on regulated output of 5V and 3.3V

1. The first test carried out is to measure the variation of regulated voltage when Vin varies. We
also intentionally fixed a smaller value of charge (Rload = 10 Ohm) at the output in order todraw a significant current and observe how it affects the component performance.
2. The second test carried out is to measure the variation of the regulated voltage when Rloadvaries. To do that, an adjustable resistance box is used and connected at the output.
For Vin = [7, 10, 15, 20], we measure Vout while varying Rload = [9k, 900, 90, 70, 50, 20, 10].

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56TECHNO | Projet | LT3065 Output PowerThe images above show where the input voltage, Vin, is injected

The images above show where the regulated 5V or 3.3V is measured. We have soldered 442k Ohm
and 274k Ohm in order to produce a regulated 5V and 3.3V respectively for this test.

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3. Results and analysis
For both tests, we have decided to use several LT3065 components to verify the reliability of thetest (and to make sure the test’s results are not influenced by the imperfection of the soldering ofthe component) and all the measurements are constant.

1. Regulated 5V and 3.3V in function of Vin

From LT3065’s datasheet, we know that, at room temperature, and for small current drawn by thecharge, I_load = 1 mA, LT3065 able to provide 5V regulated at the output.
We then carried out a test with a fix charge of 10 Ohm is connected to the regulated output (thecharge is small to draw significant current in order to simulate our application that needs a current
supply of at least 400 mA). Therefore, we are able to put together few results from the test.

VReg in function of Vin
4,5Vreg measured (V)

43,5
3
2,52

1,5
10,50
1234

56789 10 11 12 13 14 15 16 17 18 19 20

Vin (V) - Vreg (V)Vreg = 5V

Vreg = 3.3V

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TECHNO | Projet | LT3065 Output PowerWe observe that, starting at the 7V of difference between Vin and regulated output, the voltage
measured starts to drop and continues in that pattern as the difference increases.

Currrent drawn in function of Vin
0,50Current (mA)

80,400,300,200,100,00
123456789 10 11 12 13 14 15 16 17 18 19 20Vin - Vreg (V)Vreg = 5V

Vreg = 3.3V

The same pattern is observed for the current drawn as the charge is fixed at 10 Ohm.

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2. Regulated 5V in function of R_load

According to LT3065’s datasheet, at room temperature, for Vin = 7V and Vin =10V, we shouldbe able to deliver 500 mA (as the current limit ~510 mA). On the other hand, when thedifference of the Vin and the regulated output is between 5V to 10V, the current limit is at 1A,
therefore it is possible for us to measure at least 500 mA current at the output.

We then decided to carried out a test with a different charge connected at the regulated output,
and we measure Vout when Vin equals to 7V, 10V, 12V, 15V and 20V.

VReg_5V in function of Rload

Vreg measured (V)65432109k900907050209R_load (Ohm)
Vin=7V

Vin=10V

Vin=12V

Vin=15V

Vin=20V

We state that for a larger charge, the regulated output is stable. However, as the charge
decreases, the regulated output dropped significantly (starting at Rload = 50 Ohm).

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Current drawn in function of Rload (mA)
600
500

Current (mA)

10400
300

200
10009k900

90705020

9R_load (Ohm)
Vin=7V

Vin=10V

Vin=12VVin=15V

Vin=20V

Theoretically

From this graph, we can see that current drawn increases as the charge decreases, which isnormal according to Ohm’s law.
However when we compare the variation of Vreg measured and the current, we notice that asthe current drawn is important, the regulated output is no longer stable (starting when at least
250 mA is measured, the regulated voltage dropped). We also remarked that the temperatureof the component increases as the current drawn increases.

In this test, we also decided to measure the voltage across the RImax = 604 Ohm (in order tolimit the current at 500 mA according to the datasheet) to observe its variation and influences
on current limit.

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V_RImax in function of Rload
600

V_RImax m(V)

500
400
300

200
100

09k

900

9070

50

20

9

R_load (Ohm)
Vin=7V

Vin=10V

Vin=12V

Vin=15V

Vin=20V

We notice that, the voltage measured can achieve more than 500 mV when the current draw
is important.

3. Regulated 3.3V in function of R_loadAdditionally, we also made measurements on regulated 3.3V output to see if the results weobtained on regulated 5V have the same pattern on regulated 3.3V.

VReg_3.3V in function of Rload
3,5Vreg easured (V)32,521,510,50
9k

900

90

9Rload (Ohm)
Vin=5.3V

Vin=8.3V

Vin=13.3V

Vin=13.3V2

Vin=23.3V

We observed the same pattern of variation on regulated 5V. The output voltage measured
dropped as the charge decreases.

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Current drawn in function of Rload
400350Current (mA)

300
250
200
150
100
5009k900

90

9Rload (Ohm)
Vin=5.3V

Vin=8.3V

Vin=13.3V

Vin=18.3V

Vin=23.3V

Theoretically

Theoretically for regulated 3.3V (the green curve), the max current drawn that we can obtainfor all the charges’ value is up to 360 mA but here but according to the we are limited at 300
mA.

V_RImax in function of Rload
400350

V_RImax (mV)

12300
250

200
150
100

5009k900

90

9Rload (Ohm)
Vin=5.3V

Vin=8.3V

Vin=13.3V

Vin=18.3V

Vin=23.3V

We also obtained the same variation on both current drawn and VRimax for regulated 3.3V.

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4. Conclusion
To conclude, we carried out these tests to verify the performance of LT3065 (in reference to thedatasheet) and to see if this component can be well applied on our design and we learned that,the results are not coherent to what we expected.
This is probably caused by our method of test, equipment’s accuracy or even the environment
during the test.

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5. Annexes

Programmable power supply used.

Digital multimeter used.

Variable resistance box.

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