Multiple NMOS in same package - Page 1
Forum section: electronics / projects

author: lmagalhaes
author_rank: Contributor
timestamp: April 03, 2020, 04:48:44 pm
content: Hi there,Does anyone have a PN for multiple (preferablyNMOS in the same SMD package? Do NPN darlington transistors do the same job ? I'm just looking for a ground connection to be turned on and off.Thanks !

author: TheHolyHorse
author_rank: Regular Contributor
timestamp: April 03, 2020, 04:58:20 pm
content: A darlington pair wont give you individual control of each BJT. But what's the reason for wanting them all in the same package?

author: TheHolyHorse
author_rank: Regular Contributor
timestamp: April 03, 2020, 05:02:33 pm
content: If you want a package with multiple fets in one, just go on mouser or whatever and in the parametric search select the number of channels you want.https://www.mouser.se/Semiconductors/Discrete-Semiconductors/Transistors/MOSFET/_/N-ax1sf?P=1z0z7ptZ1yzxao2Z1yzxao0Z1yzvta6Z1yzvta3Z1yx7p9yZ1z0y3zr

author: Alti
author_rank: Frequent Contributor
timestamp: April 03, 2020, 06:19:10 pm
content: Well, I do not know what you need.Of course any CMOS chip is full of mos transistors in one package. I can recommend you 74HC595 which has 8 ios driven high or low, through SPI. There are also parallel driven versions, with HZ, without, whatnot.If you want higher currents and n-mos then look for LED drivers. Usually come in the package of 8 or 16. From 20mA up to 90mA per channel. Serial in.Then there is ULN2003/4 which is bipolar npnp (darlington).And various BC856 type pairs.

author: lmagalhaes
author_rank: Contributor
timestamp: April 03, 2020, 09:46:20 pm
content: I'm trying to control electrochromic displays and for that I need to connect the counter-electrode to 1.5V and each electrode to ground. Right now, the board has 8 channels to control 8 displays in parallel and each display may have up to 8 electrodes. This means that if I use discrete NMOS for each electrode (IRLML6344 is what I'm using right now) I'm going to have 64 discrete MOSFETs... that's a whole lot of mosfets. But, if there were packages of 8, it would make my job easier when it gets to the part where I have to solder them all manually.

author: up8051
author_rank: Frequent Contributor
timestamp: April 03, 2020, 10:01:19 pm
content: 7channel NMOS TPL7407LAhttp://www.ti.com/product/TPL7407LA

author: Alti
author_rank: Frequent Contributor
timestamp: April 03, 2020, 10:07:43 pm
content: Quote from: lmagalhaes on April 03, 2020, 09:46:20 pmThat is a 5A NMOS. Pulse 25A.What is the highest Rds_on that is acceptable in your design?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 03, 2020, 11:02:03 pm
content: If it's low current, why not a logic device? Does it have to be open drain? (Buffers are available in either configuration, fortunately.)Tim

author: senso
author_rank: Frequent Contributor
timestamp: April 03, 2020, 11:24:38 pm
content: Maybe TPIC6B from TI?

author: lmagalhaes
author_rank: Contributor
timestamp: April 16, 2020, 01:44:29 pm
content: Thanks for the suggestions.The TPL7407LA is the closest one to what I need. I just need a switch to ground with the lowest possible Rdson since we need to measure the current consumption. The less series resistance the better.However, the TPL7407 has a diode from the output to COM and that's not good ... I need a package without it. I've been looking in Mouser, but all of them have this, since this is to use with high power loads.Shift registers will impose a limit to how much current they can sink, which might affect the readings and that's not good and it's really necessary to have a completly open circuit at the output.Are there other circuits available ?Thanks,Luís

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 16, 2020, 06:14:02 pm
content: What's wrong with the diode?Tim

author: lmagalhaes
author_rank: Contributor
timestamp: April 16, 2020, 09:33:52 pm
content: The diode is going to make the display bleach because it leaves a current path.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 17, 2020, 03:36:45 am
content: Well, all your transistors have leakage paths too, so you're screwed..?!How much leakage is tolerable? How about pullups to bias the pin to +V or whatever?Tim

author: lmagalhaes
author_rank: Contributor
timestamp: April 17, 2020, 09:10:37 am
content: The displays work like a capacitor, so they can't have a current path available. The mosfets do have leaks, but they keep the display in open circuit just fine. However a diode across the pins drains the display almost immediately.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 17, 2020, 01:38:25 pm
content: So, it's like an LCD? Wouldn't you want half bridge logic pins then?Tim

author: lmagalhaes
author_rank: Contributor
timestamp: April 17, 2020, 04:09:23 pm
content: It's not really similar to LCD. In this case, I just want to color it and then leave it floating to measure the voltage level across the electrodes to check if there's a short.

author: thinkfat
author_rank: Unknown
timestamp: April 18, 2020, 08:22:37 am
content: TBD62783 ?

author: lmagalhaes
author_rank: Contributor
timestamp: April 21, 2020, 11:53:23 am
content: The TBD62783 also has a diode on the output, so I can't use it.Thank you all for the answers but I'm just going to use 4x NTJD5121NT1G. Too bad that I couldn't find anything like this but with more MOSFETs =\