I am designing a device that has 3.3V I/O but needs to switch powers to subsystems running on 5V and 12V (low power, say 200mA or less). Currently I use two MOSFETs to turn on a 12V load with 3.3V output but I need to switch a few 5V and 12V lines.
I'm sure there is an IC for everything so before I start replicating the "two MOSFET" feature on my circuit board design, I thought I'd ask the experts for a recommendation. Are there any arrays of transistors that are designed for this purpose or can be re-purposed to do what I'd like to do? If this sounds wrong, what would you do in your design? Thanks.
I am primarily concerned with reducing the amount of components and space usage on the board.
Thanks. If I go with mosfet array I guess I'll have to go with resistor array as well. Last time I got a 1206(inch) array of 8 resistors, they were really hard to align and not have solder bridges.
liuzengqiang:
I am designing a device that has 3.3V I/O but needs to switch powers to subsystems running on 5V and 12V (low power, say 200mA or less). Currently I use two MOSFETs to turn on a 12V load with 3.3V output but I need to switch a few 5V and 12V lines.
I'm sure there is an IC for everything so before I start replicating the "two MOSFET" feature on my circuit board design, I thought I'd ask the experts for a recommendation. Are there any arrays of transistors that are designed for this purpose or can be re-purposed to do what I'd like to do? If this sounds wrong, what would you do in your design? Thanks.
I am primarily concerned with reducing the amount of components and space usage on the board.
To be clear you want high-side switches controllable from 3.3V logic? Is surface mount OK?
Oh! High side, missed that part.
That means you need a second transistor for each switch, to drive the gate. Otherwise there's no way to switch off the MOSFET and keep the higher voltage away from the MCU.
wvmarle:
Oh! High side, missed that part.
That means you need a second transistor for each switch, to drive the gate. Otherwise there's no way to switch off the MOSFET and keep the higher voltage away from the MCU.
Yes, exactly. I am using two MOSFETs so the 3.3V IO pin can switch the device off.
Thanks larryd.
According to the spec sheet, it has 4 channels but they are all powered from the same power source. This means I can only switch four 12V lines. I want to switch the 12V line, a 5V line, and potentially a 3.3V line, to turn on/off certain devices to conserve battery. I can't turn off the 12V to the 5V regulator because I don't want to turn all 5V devices off. That will make the device miss counts from digital pulses such as flow meter or rain gauge etc.
I'll keep this part in my reference and use it when I need to switch a number of 12V lines. It's really easy to use.
