From: Bob Blick <bobblick@outlook.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Sat, 29 Aug 2020 17:49:51 -0700
Subject: Re: [EE] High Side LCD Backlight Control
Thread-Topic: [EE] High Side LCD Backlight Control
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Hi Josh,
Simplest is a P-channel Mosfet, recommend something from Alpha and Omega Se=
miconductor, part number AO3-something.
Cheapest solution is probably a PNP transistor with a base resistor.
Either will be fine. Hard to say which I'd choose. Both will invert, so 0 i=
s ON.
Cheerful regards, Bob

________________________________________
From: piclist-bounces@mit.edu <piclist-bounces@mit.edu> on behalf of Josh K=
offman
Sent: Saturday, August 29, 2020 1:42 PM
To: Microcontroller discussion list - Public.
Subject: [EE] High Side LCD Backlight Control

Repost with topic tag - I am so ashamed...

Hi all,

I'm working on a small project that uses a graphic LCD. I'd like to be
able to control the backlight (possibly PWM for brightness). On this
module the backlight ground is tied to the module ground, so I can't
switch the low side.

The backlight runs at 3.3V and maxes out at about 50mA. A bit of extra
capacity might be nice just in case I ever size up a bit on the
screen.

What would be a good way to handle this? Space will be a bit limited
so fewer parts would be better, and this is a low volume thing so I'm
happy to spend a bit more on a transistor if it means fewer external
parts. 3.3V is definitely not my area of expertise when it comes to
switching, so any help would be appreciated.

Thank you!

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
        -Douglas Adams


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