LR7843 Mosfet Motor Driver continuous current

Hie again. I found this controller from elechouse

http://www.elechouse.com/elechouse/index.php?main_page=product_info&cPath=100_146&products_id=2179
I contacted the seller (who built this driver) and they said that the controllers are 20A continous (without heatsink), but 30+ after adding more solder to the routs at the bottom and with a proper heatsink and cooling job. I just wanted to clarify that this is the case.

From robot kits india they sell a motor controller with the same chip but it has twice as less mosfets per channel and is 20A continous with a proper heatsink. They are quite trustworthy as i have bought a lot of stuff from them

could this mean that my motor controller can got to as much as 40A?

The data sheet says that the continuous drain current is 80+A as well. so i am a bit confused. What do you think?

MOSFETs are resistive devices. That means their power loss in the On state is P=Rdson*I^2. Please observe: I is squared meaning that if you double the current you quadruple the loss. All loss power will be heat.
But different transistors will have different values for Rdson depending on the manufacturing process. This can vary between maybe 1mOhm up to almost 1Ohm. Changing the transistors to a type with half the Rdson will allow for 41% increase in current, all other parameters unchanged.

The next factor to take into account is thermal resistance. Its measured in K/W. A free air mounted component has a resistance of maybe 70K/W meaning that 1W of loss power will raise the chip temperature by 70 degrees kelvin or centigrade. Mounting the transistor on a heatsink will lower the thermal resistance. A large heatsink has maybe 1K/W.This must be added to the thermal resistance between chip and case.

Modern surface mount transistors have their tab soldered to the circuit board. With proper thermal design the circuit board acts as a heatsink, especially if its a multilayer board with thick copper and large ground and supply voltage planes which dissipate the heat.

MOSFETs are resistive devices. That means their power loss in the On state is P=Rdson*I^2. Please observe: I is squared meaning that if you double the current you quadruple the loss. All loss power will be heat.
But different transistors will have different values for Rdson depending on the manufacturing process. This can vary between maybe 1mOhm up to almost 1Ohm. Changing the transistors to a type with half the Rdson will allow for 41% increase in current, all other parameters unchanged.

The next factor to take into account is thermal resistance. Its measured in K/W. A free air mounted component has a resistance of maybe 70K/W meaning that 1W of loss power will raise the chip temperature by 70 degrees kelvin or centigrade. Mounting the transistor on a heatsink will lower the thermal resistance. A large heatsink has maybe 1K/W.This must be added to the thermal resistance between chip and case.

Modern surface mount transistors have their tab soldered to the circuit board. With proper thermal design the circuit board acts as a heatsink, especially if its a multilayer board with thick copper and large ground and supply voltage planes which dissipate the heat.

so if i add a good heatsink and put more solder on the routs i can increase current capability?

Thanks for the help its been quite useful.

20 amps is a hell of a lot of current and is going to produce a lot of heat, even with heat sinks I wouldn't run them that high.
Personally I would use relays,, unless you need the 'fast switching' and small size of a MOSFET? (I'm learning about electronics, usually work with 12v DC systems :smiley: )

This isn't the same part but has similar characteristics, the max continuous current is well below 20 amps, if you scroll almost to bottom of page you'll see test results, your looking at 30 seconds or so at max current before overheating

20 amps is a hell of a lot of current and is going to produce a lot of heat, even with heat sinks I wouldn't run them that high.
Personally I would use relays,, unless you need the 'fast switching' and small size of a MOSFET? (I'm learning about electronics, usually work with 12v DC systems smiley-grin )
Pololu Dual VNH5019 Motor Driver Shield for Arduino (ash02a)
This isn't the same part but has similar characteristics, the max continuous current is well below 20 amps, if you scroll almost to bottom of page you'll see test results, your looking at 30 seconds or so at max current before overheating

The 4 motors im using have a stall current of 35-40Amps so two per channel. i have used the same 4 motors with two cheap 30amp rc car esc's and at the worst they have gotten warm.. They have tiny heatsinks and i have pushed them to what i though was their limmits offroad, everywhere without burning them out. so i think this one will survive 30amps with a heatsink and a small fan. but i will put a fuse at 30amps to avoid damage. Here is the link to the project if you want to have a peak

crazypj:
20 amps is a hell of a lot of current and is going to produce a lot of heat, even with heat sinks I wouldn't run them that high.

The supplier of that board quotes the mosfet on-resistance as 0.003 ohms. At 20A current, that's only 0.12W dissipation, which is hardly any heat at all. What we can't quantify without further information is the additional power dissipation due to the finite switching time of the mosfets, which could be very significant if a high PWM frequency is used.

About that ElecHouse board

and also

the last one I see there is a high side supply voltage generator, to be able to use N channel on top. Just can not understand the type of MOSFET DRIVER used, since they mention 0V to 38V. (they also removed marking... that is the secret of all H's)

I need to develop something that is 3.3V suitable, both sides. Motor side can go higher as well as Control side, but goal is that both would start at 3.3V and not 5V.

I need to run some high current FA-130 motors, and be able to reverse, so H-bridge is needed...@ 3.3V

Most if not all stuff I see are 5V rated as minimum...

Edit:
actually, now got the manual of these boards and they also mention 5V motor minimum...) So again I need a high side control for my N fets...