Received: from PCH.mit.edu (18.7.21.50) by mail.efplus.com (192.168.0.8) with Microsoft SMTP Server (TLS) id 8.3.485.1; Sat, 29 Aug 2020 13:51:49 -0700 Received: from PCH.MIT.EDU (localhost.localdomain [127.0.0.1]) by PCH.mit.edu (8.14.7/8.12.8) with ESMTP id 07TKjm0B018480; Sat, 29 Aug 2020 16:45:49 -0400 Received: from outgoing-exchange-7.mit.edu (OUTGOING-EXCHANGE-7.MIT.EDU [18.9.28.58]) by PCH.mit.edu (8.14.7/8.12.8) with ESMTP id 07TKjkm4018477 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Sat, 29 Aug 2020 16:45:47 -0400 Received: from oc11exedge2.exchange.mit.edu (OC11EXEDGE2.EXCHANGE.MIT.EDU [18.9.3.18]) by outgoing-exchange-7.mit.edu (8.14.7/8.12.4) with ESMTP id 07TKjkxT002343 for ; Sat, 29 Aug 2020 16:45:46 -0400 Received: from w92expo30.exchange.mit.edu (18.7.74.42) by oc11exedge2.exchange.mit.edu (18.9.3.18) with Microsoft SMTP Server (TLS) id 15.0.1293.2; Sat, 29 Aug 2020 16:45:38 -0400 Received: from oc11exhyb2.exchange.mit.edu (18.9.1.98) by w92expo30.exchange.mit.edu (18.7.74.42) with Microsoft SMTP Server (TLS) id 15.0.1365.1; Sat, 29 Aug 2020 16:45:46 -0400 Received: from NAM02-CY1-obe.outbound.protection.outlook.com (104.47.37.51) by oc11exhyb2.exchange.mit.edu (18.9.1.98) with Microsoft SMTP Server (TLS) id 15.0.1395.4 via Frontend Transport; Sat, 29 Aug 2020 16:45:46 -0400 Received: from MW3PR05CA0003.namprd05.prod.outlook.com (2603:10b6:303:2b::8) by MWHPR01MB2783.prod.exchangelabs.com (2603:10b6:300:f4::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3326.24; Sat, 29 Aug 2020 20:45:43 +0000 Received: from CO1NAM03FT003.eop-NAM03.prod.protection.outlook.com (2603:10b6:303:2b:cafe::5d) by MW3PR05CA0003.outlook.office365.com (2603:10b6:303:2b::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3348.5 via Frontend Transport; Sat, 29 Aug 2020 20:45:43 +0000 Received: from mail-io1-f46.google.com (209.85.166.46) by CO1NAM03FT003.mail.protection.outlook.com (10.152.80.100) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3326.19 via Frontend Transport; Sat, 29 Aug 2020 20:45:42 +0000 Received: by mail-io1-f46.google.com with SMTP id g128so2419893iof.11 for ; Sat, 29 Aug 2020 13:45:42 -0700 (PDT) From: Josh Koffman To: Microcontroller discussion list - Public. Sender: "piclist-bounces@mit.edu" Date: Sat, 29 Aug 2020 13:45:15 -0700 Subject: Re: [EE] High Side LCD Backlight Control Thread-Topic: [EE] High Side LCD Backlight Control Thread-Index: AdZ+RjeQ/7Ku/WR0Ttq0XeGDmLoaJg== Message-ID: References: List-Help: List-Subscribe: , List-Unsubscribe: , In-Reply-To: Reply-To: Microcontroller discussion list - Public. Accept-Language: en-US X-MS-Exchange-Organization-AuthAs: Anonymous X-MS-Exchange-Organization-AuthSource: TS500.efplus4.local X-MS-Has-Attach: X-Auto-Response-Suppress: All X-MS-Exchange-Organization-SenderIdResult: Pass X-MS-Exchange-Organization-PRD: mit.edu X-MS-TNEF-Correlator: received-spf: Pass (protection.outlook.com: domain of gmail.com designates 209.85.166.46 as permitted sender) receiver=protection.outlook.com; client-ip=209.85.166.46; helo=mail-io1-f46.google.com; dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=ZAQIMQtiJwhk7/ThBHqUNAKuAcUvo1Aa7Pccwc8i8Ug=; b=vAnrocOL+2rTnjTbmovxzjqJ6zWkIH+qXf4R8xcT+6dj3Zty5m1QZEePzHwq5tKFN3 e/rwt6ZCStJDddydqX3ATXv+L7hna8fxP+gfzfRTMu3P55qT5/VAXqrrca2Kn1Kjdv1a ctGMrMNlSHSKt6T+TwazdPud2qtW39QnYIOY1Z0OqyRyCsH3o6ayt5UHyuih6YOKb4iM M/6T82eOD/DBoIQQlVkygvGe9hVASFVq7IwROV8fjs6zmEirc8UvdJ2zcfwWuU90tuxp /ZOymLlHSkEPpiaMk4T75aLGwQ2ZafUICjA+IzRq0qa9/zIZs/xDnsePvMWT56nYuPkv t1Mw== authentication-results: spf=pass (sender IP is 209.85.166.46) smtp.mailfrom=gmail.com; mit.edu; dkim=pass (signature was verified) header.d=gmail.com; mit.edu; dmarc=pass action=none header.from=gmail.com; errors-to: piclist-bounces@mit.edu list-id: "Microcontroller discussion list - Public." list-post: x-beenthere: piclist@mit.edu x-mailman-version: 2.1.6 x-received: by 2002:a05:6602:1405:: with SMTP id t5mr3575680iov.72.1598733941694; Sat, 29 Aug 2020 13:45:41 -0700 (PDT) x-topics: [EE] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 I'll reply to John's email here so it stays with the topic tag. On Sat, Aug 29, 2020 at 4:38 PM John Lawton wrote: > > What is your supply voltage, 5V or more? > > You could use a high level linear constant current driver and switch it > via PWM, or use a buck regulator with current feedback from the > baclkight, then pwm control the regulator. I have both 5V and 3.3V on the board already, so a solution that just used the existing 3.3V supply would add the least number of parts, no? Josh -- A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .