Serial In-Parallel Out IC with current sink or source of 500mA per output

Thread Starter

fieldeng

Joined Nov 1, 2019
15
Hello,

I want to drive in parallel 8 coils with a current of 500 mA each, simultaneously. For the moment the ICs that I found have very low current sourcing capabilities compared to 500 mA. Then for current sinking the maximum I have found is 350 mA per output, all outputs simultaneously on (https://www.ti.com/lit/ds/symlink/tpic6a595.pdf).

Do you have any other suggestions of ICs that reach such a high current sink? Or other ways of implementation?
 

ericgibbs

Joined Jan 29, 2010
10,446
hi f,
Is using a MOSFET Sink for each of the 8 coils an acceptable option.
Why do you need to source 500mA when one side of the coil is at VDD.?
E
 

Thread Starter

fieldeng

Joined Nov 1, 2019
15
hi f,
Is using a MOSFET Sink for each of the 8 coils an acceptable option.
Why do you need to source 500mA when one side of the coil is at VDD.?
E
In fact I would like to sink 500mA, that's why I am connecting to VDD. And this because sinking ICs provide higher currents. If it is possible to source 500mA then I can connect the one side of the coil to GND.
 

jpanhalt

Joined Jan 18, 2008
10,065
So, you suggest that I use one logic-level mosfet implementation for each output in order to achieve 500 mA?
I am assuming each coil will be controlled separately, e.g., by information in the SPI byte(s), and as I assumed from the device in your first post.
 

crutschow

Joined Mar 14, 2008
25,247
So, you suggest that I use one logic-level mosfet implementation for each output in order to achieve 500 mA?
If all coils are always on or off simultaneously then you only need one high-current N-MOSFET.
I suggest one with less than 0.06Ω on-resistance so the device won't need a heat-sink.

Note that you will need a diode (e.g. 1N4004) across the coils (cathode to Vdd) to suppress the inductive transient when the coils are turned off.
 

Thread Starter

fieldeng

Joined Nov 1, 2019
15
You are right. I am not planning to turn on and off all of them at the same time. According to the byte sent through SPI some coils will be on and some will be off at the same moment.
So in the end I am going to use as many MOSFETs as the number of coils.
 

Reloadron

Joined Jan 15, 2015
5,601
Consider N Channel MOSFETs like the FQP30N06L or the IRL540N while their max current and voltage is overkill they should work. Remember to place flyback diodes across your solenoid coils like maybe a 1N4002 diode with Cathode to + supply. Keep a common ground (MCU supply and Solenoid supply). Also, good idea to place a 10K resistor between each MOSFET Gate and Ground. That will make sure when you turn your MOSFETs off they do turn off.

Ron
 

ElectricSpidey

Joined Dec 2, 2017
1,191
You might want to look into 8 channel load drivers, they can handle 500mA per channel, but not all at once, usually the package is limited to about 1.1 watt.

Their outputs can usually be paralleled, might make the board layout simpler.

I know the Darlington type can be paralleled, not sure about the MOSFET type.

And, they include the flyback diode right in the package. (the pulldowns as well, makes life easier)
 

Reloadron

Joined Jan 15, 2015
5,601
You might want to look into 8 channel load drivers, they can handle 500mA per channel, but not all at once, usually the package is limited to about 1.1 watt.

Their outputs can usually be paralleled, might make the board layout simpler.

I know the Darlington type can be paralleled, not sure about the MOSFET type.

And, they include the flyback diode right in the package. (the pulldowns as well, makes life easier)
Good point you may want to also look at ULN2803A Darlington Transistor Arrays or similar. You can parallel two channels so each chip would handle 4 Solenoids. Someone may be offering them on a ready to go break out board.

Ron
 
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