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Free wheeling diode for tiny motor

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Jester

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I don't have a data sheet for this tiny vibration motor: https://www.creatroninc.com/product/vibration-motor/

I will use one of the two motor drive circuits shown below.
MD.png.

Will a 1N4148 diode be adequate (100V, 300mA) as a free wheeling diode to protect Q5?

If I use the FET circuit instead can I rely on the body diode to suppress the back EMF when the motor is turned off?
 

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To check the diode rating, you need to know the motor current. I guess 1N4148 is O.K.

The substrate diode doesn't supress back EMF. Instead the MOSFET will be driven into avalanche breakdown when the motor is turned off without a freewheeling means. You'll check the MOSFET avalanche energy rating or add a freewheeling diode.
 
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Jester

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To check the diode rating, you need to know the motor current. I guess 1N4148 is O.K.

The substrate diode doesn't supress back EMF. Instead the MOSFET will be driven into avalanche breakdown when the motor is turned off without a freewheeling means. You'll check the MOSFET avalanche energy rating or add a freewheeling diode.


The datasheet for the FET is here: https://www.fairchildsemi.com/datasheets/FD/FDN337N.pdf

I don't see a graph or specification related to avalanche?
 

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I don't see a graph or specification related to avalanche?
Me neither. So you better avoid avalanche breakdown with this device.
 
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D.A.(Tony)Stewart

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Diode in reverse only works when diode is across motor to supply , V+ for both low side switches. otherwise diode across motor to gnd. for high side switch. Then driver is protected for Vmax and diode current rating must match driver for continuous current.

Small cap across motor may reduce EMI.

Current will be limited by RdsOn or Vce(sat) + series Rs of coil on motor for intermediate starting surge, 5x~8x avg typ.
 
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Hi, the ZVN4206AV can be used for that purpose. There's an application note called: "ZVN4206AV Automotive Relay Drivers" describing how it's used for motors and needs no protection for back emf, I tried but couldn't upload the pdf as it has some error thing happening.
 
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Hi, the ZVN4206AV can be used for that purpose. There's an application note called: "ZVN4206AV Automotive Relay Drivers" describing how it's used for motors and needs no protection for back emf, I tried but couldn't upload the pdf as it has some error thing happening.

d123,

Thank you, very helpful
 

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