Multichannel MOSFET chip

Other Hardware General Electronics
1

I once had a number and datasheet of a chip that fits my current needs precisely, but I cannot find it anymore.

What I'm looking for is to control 12V LED strips from my RPI Pico's I/Os. There is the TPIC6B595 which I used in the old design with the Arduino Nano, which pulls its output pins to ground, which is basically what I need, except instead of the shift register input I need something with one input per output, so I can finally use real PWM instead of emulating it over SPI.

If there is a solution that has more power than the 150mA of the TPIC, even with fewer channels, I'm fine. What I'm not looking for is "just MOSFETS on a chip" where I need to add all the chicken feed around it. What I want/need is a setup of just Controller -> Chip -> GND side of 12V LED strip.

Any ideas?

2

You can see TLC6C598-Q1. https://www.ti.com/product/TLC6C598-Q1. It's a Automotive power logic 8-bit Shift Register LED driver.

3

But it is as far from my needs as possible. I explicitely don't want a shift register based chip, and the TLC6C598 has even less mA than the TPIC I''ve used.

4

Through hole or surface mount?

TBD62003A

TBD62783A (source type)

5

How about a PCA9685 servo board, with as many TO220 logic level fets as needed.
That's up to 16 channels of 12-bit PWM at your choosen frequency.
Leo..

6

That TBD62003A looks good. And through it I found the chip I had originally been looking for, the ULN62003A, but according to what I read the TBD is a) better and b) a drop in replacement. So I'll probably use the TBD.

What makes me wonder - the data sheet says 500mA/channel, which, with eight channels would imply 4A running through the ground pin. Has anyone tried this?

And: Does the chip need cooling? Like, a pad and a metal sheet or something? I have no idea how much 1.25W thermal dissipation is in real life.

7

That is for only channel only provided you don't exceed the power dissipation.

How much current will you have for each channel and how many channels will be on at a time at max PWM?

Which package are you using?

8

Interesting thing I'll bookmark for other projects, but for this, it is way too big for this application. I've got a total height of about 7.8mm, so I'm looking for a chip, not a board with headers. I could either use an SMD variant that I solder on a small board, or take a DIL chip and bend the pins horizontal and and wire them floating.

9

Up to 200mA per channel (10x20mA LED strip). In my original design I even clamped them down to stay under the 150mA limit of the TPIC.

Six channels for this project altogether. In the original design, I had used two TPICs with three channels each.

The duty cycle varies, but it involves a few sub-second flashes of 100% for 1-2 seconds at the end.

10

Let us know if you find a high current mosfet array like that.
Maybe the ULN2803 will do if you can tolerate the 1volt saturation loss.
There are plenty of 2mm thick SMD mosfets that can carry several Amps.

Another option is addressable LED strips.
Leo..

11

I don't care, I can solder an SMD on a small prototype adapter board, or use the DIL with pins bent horizontal, and wire them "in the air". DIL+Pad+AL sheet is possible, if needed. As long as I'm staying under about 7.8mm total height.

12

If they are your two choices, then use the DIP package. It can dissipate more heat than the SMD part mounted on a small PCB.

200mA/ channel will be OK. Worst case power dissipation at room temperature would be 0.91W. It will get warm but that is OK

13

Have a nice day!