I have a question about LM5050-1.
For details, please see the attached document.
Thank you.
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Hello Ishii-San,
What was the voltage applied on VIN when Vext was 7.15V or more?
If VIN < 5V, separate Vext(>5V) is required for powering LM5050-1 device through Vs pin.
If VIN > 5V, separate Vext(>5V) is not required for powering LM5050-1 device through Vs pin.
Hello.
thank you for your answer.
Measured under the following conditions.
Vext = 7.5 V, VIN = 3.3 V
Details are in the attached document.
When DC Vin side is OFF,
Q1 is ON.
Thank you.
Hello Ishii-San,
Please find reply below for the observations that you shared in previous post. LM5050-1 will turn-off the MOSFET when OFF pin is made high or when voltage drop across IN and OUT (IN<OUT) pins goes below VSD(REV) . You can refer to section 7.4.1section 7.3.1, Figure 1 and Figure 2 in datasheet of LM5050-1.
conditions
|
|
Gate – GND |
Drain – GND |
Source – GND |
Current (IN to OUT) |
Comment
|
Vext=6.5V |
①DC power supply=3.3V ON |
6.87
|
3.32 |
3.34 |
5 |
Q1 of 1 and 2 are ON since [VSOURCE - VDRAIN ] > 0 and MOSFETs are in forward conduction |
|
②DC power supply=3.3V ON
|
6.88 |
3.31 |
3.33 |
5 |
|
Vext=6.5V
|
①DC power supply=3.3V ON
|
10.7 |
3.27 |
3.29 |
10 |
Q1 of 1 is ON since [VSOURCE - VDRAIN ] > 0 and MOSFET is in forward conduction |
|
②DC power supply=3.3V OFF
|
0 |
3.13 |
0 |
0 |
Q1 of 2 is OFF since [VSOURCE - VDRAIN ] < VSD(REV) and LM505-1 turns-off the MOSFET |
Vext=7.5V
|
①DC power supply=3.3V ON
|
13.4 |
3.27 |
3.29 |
10 |
Q1 of 1 is ON since [VSOURCE - VDRAIN ] > 0 and MOSFET is in forward conduction |
|
②DC power supply=3.3V ON
|
13.4 |
3.13 |
3.13 |
0 |
Q1 of 2 is ON since [VSOURCE - VDRAIN ] = 0 and MOSFET does not go in reverse conduction. |
Hello Ishii-San,
LM5050-1 also regulates the voltage drop across MOSFET in forward conduction to 22mV (typical). If the voltage across MOSFET (VSD) goes more than 22mV, the gate voltage is increased (up-to max VGS of 12V) and the voltage across MOSFET (VSD) goes less than 22mV, the gate voltage is decreased . This is described in section 7.3.1 on Page 12 in the datasheet of LM5050-1
Why is the supply of Vin turned off, does Source (IN) - GND = 3.13 V come out?
This can be due to leakage in to IN and OUT pins when Vs pin is powered. Please refer to NOTE on Page 11 in the datasheet of LM5050-1
Hello Ishii-San,
there is a way to reduce this leakage in OUT/IN pins. This can be done by turning off Vs supply with a PNP transistor and MOSFET. This is shown in attached design report.
In the attached design(PMP20096), 1581.PMP20096_LIQ_REVA_TEST_BJT.pdf Vs is turned off by transistor Q2 and MOSFET Q4 by an external signal at TP7.