5v high level to operate a 2v mosfet 

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1

Hello,

i need to operate a mosfet in high logic level and trying to understand how to do that if arduino high is 5v and the mosfet high = 2v at max! (gate source th = 2v).

for example to use this model - DMN3026LVT.

do you have any idea or sketch ho to fix this issue?

thanks,

2

barg:
Hello,

i need to operate a mosfet in high logic level and trying to understand how to do that if arduino high is 5v and the mosfet high = 2v at max! (gate source th = 2v).

for example to use this model - DMN3026LVT.

do you have any idea or sketch ho to fix this issue?

thanks,

Please post a link to the datasheet that you read that specified: 2 Volts max on Gate

3

Hi,

please find the link nelow to the data sheet of DMN3026LVT which is on the middle of page 2. in addition, i added the relevant details below:

http://www.google.co.il/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CBsQFjAAahUKEwi_sOfpmpjJAhUFeQ8KHavdDSg&url=http%3A%2F%2Fwww.diodes.com%2F_files%2Fdatasheets%2FDMN3026LVT.pdf&usg=AFQjCNFEaCFQew1ubiqVMm7_v-QRP93YnA

Gate Threshold Voltage VGS(th) 1.0 1.5 2.0 V VDS = VGS, ID = 250µA
Static Drain-Source On-Resistance R
DS(ON)

i took this mosfet details as an example to the issue of getting from high 5v or 3.3v to this Gth 1.5v in the mosfet.

thanks,

4

You are misinterpreting the data sheet.

The very first line of the "product summary" states Rds(on)max = 23 milliOhms at Vgs = 10V.

5

as i fuguer, this detail is only to show rdson performance.

what about the threshold GS of 1.5v as noted?

6

Threshold is the voltage where the mosfet just starts conducting (0.00025Amp).
Twice that voltage (3.3 or 5volt) might be needed to switch your load.
And a bit more (10volt) to reach minimum Rds(on).
Look at the graphs in the datasheet.
Leo..

7

Hi Leo,

Thanks for the inlighting notification!

So, high puls starts from range of 1.5v to 20v = GS th as noted (1.5v typ) up to mAX GS VOLTAGE (which is in this case GS max = 20v)?

Barg

8

Vth is the OFF point, this tells you that once the gate is below 1V (the minimum value for Vth) then
the device is conducting negligible current - ie it is off.

A MOSFET or IGBT is on only when the gate has fully passed the plateau (which depends somewhat on the
load current). You'll see a total-gate-charge typical graph in MOSFET datasheets showing the plateau
in gate voltage as the conduction channel is formed. This is where the bulk of the switching happens.

The normal way to drive a MOSFET is down to 0V for off and upto about twice the plateau voltage
for on. This device has a typical plateau of 3V, so it just works at 5V. It will not be suitable for 3.3V.

Threshold and plateau voltages vary significantly between devices due to manufacturing tolerances,
so never rely on typical values, so treat the "Rds(on) at Vgs=?" as definitive, not the graphs.

Normally the plateau voltage is 2 to 3 times larger than the Vth, and typical Vgs would be twice that,
so a Vth of "2--4V" definitely means a device that requires a minimum of 10V drive, preferably 12V.

Most logic level devices specify a Vth of 0.5--1.0V.

9

Hi Mark,

Thank you for your explanation.

i didnot understand why it will not work with 3.3v mcu high output?

if in the data sheet noted minimum GS th=1v, thats means according to your explenation to min 2v (double for plateu assurance ) so 3.3v is not safe enough to design according this data sheet?

Meaning in practical, the minimum details cannot be trusted based on the d"s in order to be sure in the design?

10

The plateau voltage is 3V +/- device variability (ie 2--4 probably), so you cannot operate from 3.3V - you need to
exceed the plateau voltage by a healthy margin. plateau voltage and size varies with load current too.

11

Hi Mark,

Well noted, and Thanks.