Cheap 10V shunt voltage reference?  - Page 1
Forum section: electronics / beginners

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: February 21, 2023, 06:59:18 pm
content: Trying to find a cheap 10v shunt voltage reference. I need it to be the shunt variety because I need it to support an input voltage of greater than 60v, which most (all?) series voltage references do not support (unless they have external circuitry, which I want to avoid). Output current support does not matter much to me, as the voltage reference will be for an op-amp.I've come across the LM4040/LM4041/LM4050 which all support 10v, but I'd love something cheaper. I've come across the NCP781/LM317HV/LR8/LR12/RT9068 linear regulators/LDO's however I don't really like them as they require a few supporting components, which again, I'm trying to avoid. The LR645 is a nice linear regulator but is more expensive than the aforementioned shunt linear regulators.

author: bdunham7
author_rank: Super Contributor
timestamp: February 21, 2023, 07:13:36 pm
content: How cheap? The REF5010 can be had for under $2 in some configurations and can work as an 'ideal zener', so all you have to to do is regulate/limit the current through it.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 21, 2023, 08:41:30 pm
content: 4x TL431 could be an option. So 4 x 2.5 V shunt reference in series. A single Tl431 and 2 resistors would be a bit cheaper.

author: Benta
author_rank: Super Contributor
timestamp: February 21, 2023, 08:43:07 pm
content: How precise? The first that comes to mind is TL431 with a couple of setting resistors.

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: February 22, 2023, 01:04:01 am
content: Quote from: bdunham7 on February 21, 2023, 07:13:36 pmMax input voltage of 18vRegarding the TL431 suggestion I'm aware that it works and is incredibly cheap, but I'm trying to minimize part count while still being cheap. The TL431 with a few resistors would definitely be the cheapest, but I'm a big fan of the LM4040 as it only requires a single resistor and can do 10v (or the LR645 with two capacitors).If nothing is cheaper + simpler than what is suggested so far, oh well.

author: jonpaul
author_rank: Super Contributor
timestamp: February 22, 2023, 02:14:54 am
content: Any HV transistor. 4:1 ..divider, série régulateur >> 15 V..TL431>>10Vj

author: bdunham7
author_rank: Super Contributor
timestamp: February 22, 2023, 05:21:51 am
content: Quote from: LooseJunkHater on February 22, 2023, 01:04:01 amThat's if you use it in its normal mode. Read this application note on making HV references by stacking these. You'll note that there is no technical reason you can't use a stack of one with appropriate current limiting. You just need to make sure the current is 3-8mA.https://www.ti.com/lit/an/sbaa203/sbaa203.pdf?ts=1677006743282&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FREF5010

author: SeanB
author_rank: Super Contributor
timestamp: February 22, 2023, 05:46:36 am
content: I had a similar issue, so instead used a zener diode as pre regulation, which means you add on 3 extra components, a resistor, a zener diode of around 15V, and a low value (100n to 1uF) ceramic capacitor across the zener as noise filter. Then you have a large choice of 10v reference devices, that you can use.

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: February 22, 2023, 06:06:44 am
content: Quote from: bdunham7 on February 22, 2023, 05:21:51 amThis is brilliant. Never thought of setting them up in series.Quote from: SeanB on February 22, 2023, 05:46:36 amAnd this is also so damn brilliant. With this idea, considering how cheap TL431's are, I may even consider using one with a zener. So many ways to go about my project...I absolutely love this forum and the members. It's been teaching me so much about EE. Thank you so much.

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: April 01, 2023, 10:37:33 pm
content: To build onto this original post that I made, I have limited knowledge and experience with zener diodes. Do I need a capacitor on the input and output of the zener diode for stability? Attached is a picture illustration. The ~50v is from a boost converter in this example image.Edit:Realized I have two capacitors on the output of the zener diode; I ended up deleting one. Still wondering though if I should have a capacitor on both the input and output?

author: pqass
author_rank: Super Contributor
timestamp: April 02, 2023, 12:30:31 am
content: That's not how you program the TL431.And choice of the 470R is too small a value resulting in a hot zener.See attached for the correct circuit and [what I think is] a more reasonable component selection.The 6.8k||220k upper resistors works out to 6.6k. Combined with the in-series 2.2k lower resistor will program the TL431 for 10V output.Online TL431 calculator:https://www.circuiteasy.com/tl431-calculator-toolThe reference designs show a 0.1uF capacitor on the output (not shown below).I don't think the capacitor after the 18V zener will hurt (not shown below).Play with it here:http://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWcMBMcUHYMGZIA4UA2ATmIxAUgoqoQFMBaMMAKGwBYQAvOgOzoBOTPOHDQMYdtgQo8YYrLDwUjclRSx4W7fk5gRrLiGkoQ7diJPG0IUz35D9LAcZm2MplO3Ueo4PHBsGFRgGITunt4RolSQLABK4GHRzJ6+sWa0GbHQCCwA7q5ppuYimKZx2MFmFtEIYMUxUM4UDdGE+NEh8CzsSiAeVFaDZoR6IAB+ACoAMlIQkAA6AM5RKCtgjA0rMDhg2MSEwQe4HSQ7tisqTOvLDBi5kCgI2Civh7pvF0vLYCv3j2er3eHTw7C+y122H2h2OxFOkHOv28KwmABcADbzOgAEwYAEdeAB9XFQFavAJk5ZeOBUwaxcnYaDYFmstls8K3MDQa7bSHiFBKQgIdjEdgYBBkcy3dRXaDsLa3BgwLTYYVYFBvSAiwgNcHfDb-FXwNUIDVanV6mUCoUisUSqX65E-dFY6G4gnEj0AQW5FQ2eGg+mDclDIcu1J5OmjkGwip20COBDw2DwYUIeDIzGIF1u7HlMe0mxuCcgoTkfQCurLlfYBt+pfLkn0iKUzbBCaTslT6czEnkGxRy1d2LxhJJeO9Gn9ywCDNWst+8f5wUgGAIGHYhA48iUGFzV2XAIsTa3DVjJGw9b+dweJ-Xkl1aDV8ITq-XmC3O+Ie8HLsxo6ehOVLeLSPxrBsy67LGRDPKEZzrhmB7UkeMBKGQhBjEQ4oHGCYCENeRpBpAGFYWMODEHhBErjBhBwWEiKIXgf6ogB7pjl6OJUpStz0EwV4rmgupHDg2qinyi7FnyyriAoBDPJq0JPCQdaQlSN4yRgcmajIbxKEQYpvkJ+FYLgdp8pI-5upsHETgw3owEgPw8ZBJZ3NBbx4PUupmpqHQ5mptxxm5xpwAQxBwGKiLeJqCiqfOTClvA4WRd4YxPCgcVEcEnneWAvlECRKwdKx1keviAAOwHOZJqHiIgEUSt4kheB2gXksuDw4HR4kcFpkhtQlN5dWqXg-n1P4WKpmkNWuIo1q1qklcObE2QSVWkjV85ziBtUheI+F4JhASpq8+D1MhvJKoGFgpkc+XbtCW4yup-w3Xgd0SAgj2PtaEgZsdsYpmgXk3pZpWAeOm0bJQ3ERnxEniB+RxPJKZb7LqyFSRpxA8m8lDA4c9QyNR8443j0j4CCxNEG+yM5WjzBqmDQ4juxQE+k5GxaLtEZSUqMCUQgXkEMKH0pocN6LldcpyCy2qSOYcCPhgWwCWTsv7GZiugSratEULItEMLH0HJjzoQ+zUNcbcbNrTi1Xc7SturR6DuklyWw3u9KZqoiZZphYL23LyGloSRm4BKKa7lHBOwtKC1hUInqacMnc4J50qcgInpR+JqgSFLntQSiUtRxAA5kUNSWG4FjZAUOe+NnKdgs0Re+OUOedF3cSFKX0TA10jcD3nQ953EFUgEPXfj7UCzNFPedd3necL33Neb8XIgb1Yq+1BPQRDG4XdWGdTQb0cjQD73jdX8YbcjNncQuPf59v236hoPAmgxtgR-dzKL4FONh153yzjYN+NhKjVBvr4Ae58wFAA

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: April 02, 2023, 09:12:08 pm
content: Quote from: pqass on April 02, 2023, 12:30:31 amHow so? I used the same calculator and it shows the resistors in the same locations? Should I be using higher resistances? Messing with the calculator, when I remove the resistor between the zener diode and TL431, the circuit produces the same voltage before and after the zener, but when adding a 1k or greater resistor, it seems to work fine? I assume I'm wrong and not falstad.com? LolQuote from: pqass on April 02, 2023, 12:30:31 amI'm using a 2W zener diode so I assumed the part will run pretty fine? Is there any way to design the circuit so that I can get at least 50mah at the output of the TL431?

author: Kleinstein
author_rank: Super Contributor
timestamp: April 02, 2023, 09:31:51 pm
content: The TL431 needs the resistors as a kind of feedback divider, not in series.For 50 mA out one would not use a simple shunt regulation like zener diode or TL431.50 mA are more like a job for a voltage regulator. To limit the input voltage one could use a zener diode for a low power reference of some 15-20 V and than a transistor for the buk of the current.

author: pqass
author_rank: Super Contributor
timestamp: April 02, 2023, 11:43:09 pm
content: Quote from: LooseJunkHater on April 02, 2023, 09:12:08 pmTwo mistakes:(a) your schematic didn't connect the REF pin to the node between the 10K and 3.3K resistors and the lower lead of the 3.3K resistor wasn't grounded. The 10K/3.3K combination works too as will other combinations. I chose 6.6k/2.2k because it came closer to 10.000V at the expense of burning a bit more microamps. There is a 4uA current into the REF pin so higher divider resistances will be more affected by this current. But you'll likely need to a trim resistor/pot anyway.(b) Also, you didn't have a resistor between the 18V zener and the TL431 (a programable zener); which would be like running two zeners in parallel. Since the lower Vz zener would do the work, the 18V zener would be superfluous. However, you're shunting from 50V so the TL431 would be vaporized since it has a 36V max. working voltage. The point of the 18V zener pre-regulator is so that we keep the max voltage seen by the TL431 to anything under its max working voltage.QuoteThe component selection I chose is really only good for a few mA for an ADC REF or opamp input while minimizing power consumption. If you need more, you should buffer the output.See below for a different component selection which meets your 50mA output need using the same circuit. A viable circuit needs to be able to work at both 50mA and 0mA drawn all the while keeping a minimum current through the zeners when 50mA is drawn and not too much when 0mA is drawn (TL431 has a max 100mA). Hover over the resistors and zeners for the power dissipated. Running the TL431 at high current (>20mA) is a bit sketchy to me.Play with the circuit (with the new component selection) here:http://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWcMBMcUHYMGZIA4UA2ATmIxAUgoqoQFMBaMMAKGwBYQAvOgOzoBOTPOHDQMYdtgQo8YYrLDwUjclRSx4W7fk5gRrLiHZhCIaSmOmQKFJ0s9+Q-SwFWzYDGdx6vUc8SQbBjq7FSe3pC+Hv5BAEo2YeB+EclmVFRJlLFQ0AgsAO7uaRRglqlB2CGl5X4IKSmxrhQNZoQYtengaCwmVBh49ghmA5zYhAYgAH4AKgAyUhCQADoAzkkoa2CMZWswOJKmhPVeHXiQxHs2aypMm6sMGHmQMsTyi-XsCHhXK6tga0ez1e72wYE+3z24jBJkIxyw7VkFy2YTWUwALgAbRZ0AAmDAAjrwAPp4qBrbBI8mrOxwakdOl-bDYaDMtnsjlme5gaC3XarfYoJR4YjM4iEdgYYhfbBXe4adg7e4MGBacaEJTEBCBOHsPAIKq-LaA1XwdWa7WQXX6w0C8RC-Ci7DiyXSg0ov4Y7FgvGEkm+gCCPMsf300H0EbkUcj1xpvJ0Ccg2CVUPaBAUeA4CElGHYsjla3Y0DCia02zuUMgEQ4+qrVds2BFPwF1IBdqrXhrlCUZRQjeIzZgaZQGazObzzcknqxOPxRNJ+IDGhDa3OGUL6i2KbtIQug2OMgZUYLNO3QL1zvaCANLszbfX-0BTwv4ow18vF-v4jgA-YB8waDHv8qKrF6s5+gu1Ilg+GxbhWO5Jn+15SpKLzDJcLbymeMDCkQlLjGAYLSl4hBGo+Dw4fgeF9hqRGSnCUIhBwB4oSE14kB6aIzj6c7+ri1LnLG9BMLKO5oBKkBCp47DinICAnuW-IqtAmZ6kKsiZhwUqmGRbbKapBBlHgmmujpYlWmEUm5rJ4KcaB3HbLxC4MAGMBIH8gncth34oN8XjirRxx4KRmEUtuppwJm15ECYA44P29wPkwlbwFFMgSvIeDxSKyr7JJfkkHChFBSFhDTt6jmEgADpBHmbv83m7lKHRSB0VSJbGybwU8JAHOCpB6nI4zyS2fzJasPVkGC-XSsZxUjcpTVkHY7XtWsZVcRVvoEjVZJ1Q+a5QfVimJfaZzsBO7S5iO7Annyyp4MWlBJucI4NldumAo9XxwI2kkKDRWCMQBgyXVgebSnZYE8RBe1bNkHlCeFKmIPIHTalGMmicdOx6cQ8ZY5SgwyC8IqfQ8+NoITshfGg3wYTAa4IGjvkDvoWNQw5218S57lbFoR2xidJrQNKkrZpISHnHCGB3duGghLYBCDPIVSED6InkwrkmyDTqudoponKWLb4mBdQVWu0nNbU5ZL3NDlW4rV-N0vbXP4k7dtwcwq7FjJpDgkoJhSscctMHplEEBdEiNoM5zMLLArNIiNh2CAKcaf4ExwMnHQ2MZ6d5xY-i2DnRQp8XcjeDIUAsAA5sUxewuYgxNEUDL5yIGcF0E7fjCUKcVIUIBV+YNcitXIYsFVIDiuEfhz2P5RNDPzOdDUS+iBkw9r5v2qWMXveNzXu+H8EmTWKkze2HobcgDgHh+KPQ9uB3N-32gncl2g8CaIm2Dn0LuvDOacli13Lnnd+b806VGqM-J+1h35gNgf0T+mdRhf2QTvBQm8K41yCKvHBmd96bywUUEhmdu4iCCG4CeJQ6EARLjnKoVB4FmDoakMhI9xQlEXkPIodDi6LzPqsbhXI86CPwf4AAZgAQ0xKsOgLAgA

author: pqass
author_rank: Super Contributor
timestamp: April 03, 2023, 02:07:50 am
content: Here is a buffered version of the previous circuit. Drawing 100mA will generate 4W of heat on the darlington.Opamp power should be taken from the 18V zener node (and ground) since most op amps have a absolute max. source voltage of 36V. The op amp shouldn't draw too many mAs (though may need to adjust the the 1K resistor) while still allowing a few mAs through the 18V zener (for it to regulate). The 1M resistor is needed to draw a minimal load to keep the output at 10V.http://www.falstad.com/circuit/circuitjs.html?ctz=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-PB-g2WgxD2asVzjFK3b6Q6yIAA70eZAECZhd7rPenznJsC6Ns5a4nP4mxELc+pyJIr5EgFxLTtVZHYT6DV5XABWcjZJWlklem0RlWXjKODH-rsuWqewcaEDYmBgBRfyBnBXrvHckG3HcuH6nxq2PMeDAbaWXE7ch+23gS82LRIK1dtRH4GXRmJHZQI67ExU51jGi1nfWCj8bMx3EAy+DnHmuBgqF0kMGDaCQbhUiQDDNS3guf3CXcgMTlRNGfq9g5mdMWi-jlVnQAunwLTOCgcEDq38oyzPiPZNi0+2UaQbMLFEseGiLJI2GJFztzfSx8HU0QhKkFs7CM49BMvf2mL8srDoImNTzwLsGtIlravTCD42CmdUgkKCBLsTBjLHTAbKibcZALQQ7DvE5zggE01giD7URlGRvguP7zB2KHFjuI+viZBHZj1OY2QsAA5lkidp4jYSxwtAfezUucNLH7RUP7+TpSAxZ2O0ldp8MUAsOXuTuE3VZmHXhclEU6dVK39eZFY3dd73DRrOobhj775R997xcUFKYQhznNjeznYdR8G6rptgBR57U-vL+3GS7zPK+cMvI-+HP8QJwfYSj6fucyAY0SH5kPeR3H9eNzIufv23WclB-mvUO0QGguBFm0KgEDh7IAvlAnEJQq4IPaK-NoOdq7RGLkfCBA8a4DwaGMNBehI44PHu4AAZgAQxhGMOgjQ4CQO8GYLcdh87DFVOuXC0AyL6nWE0fwsR2yGiLCJGqFpSSkEbD4cYCI6BUIAK4wihB6Y62AEZyDBEoS47FCLiAajiLAspPioxMKTR4siFFKPADvNeDBl6ZzsQYABtiD6gOng45eLCQCOOnl4nxXj8ip1IcwnOmAyhwJADgNuzCGFsLCOXWm7hEm91QckyOCdh5ey8e0Lx+DYFaGwQggewTfHIKgeg-IlCQCiWiZEiU4AzDEHAEgJgSAfBkyUJoKQuBmBcRwOxZAXT3Y4lMMwAE9T2kxyvnULo+RMhFkDpMOZ1S3AIJqZA6e6ycllM2UslZtQGjlyiQ0upbdI6oOOb3NJScgA

author: mawyatt
author_rank: Super Contributor
timestamp: April 03, 2023, 02:12:44 pm
content: Quote from: pqass on April 03, 2023, 02:07:50 amWhy not put the Darlington Transistor inside the feedback loop of the TL431 and eliminate the op-amp?Best,

author: pqass
author_rank: Super Contributor
timestamp: April 03, 2023, 03:05:46 pm
content: Quote from: mawyatt on April 03, 2023, 02:12:44 pmDuh! You're right. This is simpler and lower power (2.2K is <1/2W).http://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWcMBMcUHYMGZIA4UA2ATmIxAUgoqoQFMBaMMAKGwBYQAvOgOzoBOTPOHDQMYdtgQo8YYrLDwUjclRSx4W7fk5gRrLuAyEQ7AyZANiplNz6DhLAcdNN2e2Vcmd1aSGwYVNh27p4iYaJUAQBKICHeHlCJvsnstNHJMAgsAO6uKSAoKJyRAdhBRSWFmKE+UVDORRh1SdjYbvVUSnAs7ErxkKXmg3qmSihIAH4AKgAyUhCQADoAzulFa2CMYChrMDiQxHgkYBhS7AhK2PubqypMe6sMeNByeJDFhC0laGC3K1W-2er3enyIP3Yf324lwx1O5w4V0gNyB6TWUwALgAbRZ0AAmDAAjrwAPoEqBrEIfSn3dLRNYtOC09rQdrsjmc2xbaAPXYwlpKKGTYjpXYhQi3J4adg7J4MGBaDoIDwVYjYM5SD4dAFbNYKzRwZWqjDqzXYbWS1YHFBC4oIUWQcVELbo1ZY3EagnEsnegCCYF5tP00H0Yfe4f0dw0-h0Omwcph3wIGCulwU3wQWCla3Y0Hpca020eMKdprwFco8kIxQ8LutwdLZ2OladNlrUKtMGTmDTDohWYwrsBHrxhJJ5MJfpjtI+DPW6i2iet4jg1bwQQQ0iIWZz92XL3EZH6hG+tYweHYxF1QP1r1N5zAp8hF6vArXNg3kC3MkIu7RI44mOPqTrSBZgYuQLLgcKKQIQ7A-M2eDEE+e58vKMDME+QzYKQUghA+wLzsCBpYYQOF4e0mBkERq64PBiHlihVqSIBnrbOOvr4rOkH0EwqI2t+6rqiEcCVkODZPMW-LPAcxDfiQ34XuR8gXjeJFyQp8lZicbZqSuTIOrhVFiXg-6sRiQFepxk4MH62Q8Xc0kYautqipecFKIQeAVHuCYliuWgECgZqPuYG64AgN5MKW8DBaF-ThYcUWya58jmOkhBeT5EnkZZ7HekSAAOoGAjSUkHjBTpgA6JgkDIlx4H5y7ELAW6yDIZAXshXa0jFqytd+1KdVgFY2PqVXMLVp7EA1CBNaseXulZHHEiVFJlcym3zhsFUBQc2FZh4c49dIaEHq1HwZRFChXN5TzEfql1DJeN2TE+BACod5zmGJNhnQB+XAROG1bJQs53HxMkHFgShYLIj6UPWkHSSRSjQFuFY4CcHBBCFEmPc86OYxFOMIZ8ZACrDkDwxu-RIyxbqjtZIH+kggI9FtuYo5V0DwpeNhwbNuhEdGy4aHIpCnuYkwIchJg7AJjb3G88g2PBBAqheZCEIrE18ycAvkfVIvDkDLMg9xTzM6t+KlVs8B3Db3p2xSe3MGsz3mPoKk1TTkjnUwGmhlNJxPmgIS1ha+xNFebg0nH3imN0WixzYSdmOnIzBLgAQAOYFCMZymDS0R5BQSRMKYidV40+QnmYIjtNXIgBEVICpnUXid43DRt1UpT1LWvdLHXA+983vcBPkxe98P2eBN0liRLP1jjFkTQqqUNJbxnKfaIvmedF4Nc0qP09H1YO+V6Xh+T5E99nxvFRUA3tcdBET59+XDcjInC-tzfl-X+BgN71y-rXGuX8AguCCIPbuQwrAJH3ofKBXg-zH1AWXfIcDvDdxkHg1u5dcEjB7gvVYHdEEMASCQ1uyQABmABDbEqw6B9GZOweChQoFJCWHqZ4FpoDeTFB5Uan0VwOl-CUE4d0zhgFRD0NY+I6BMIAK7YkxMrahrVqKyHwKKXAUgCbiEkIQEI80abFDDOwB2gJlFqI0eAO+dQFDgC8EwVx59y4JA8XYHxXRy67E-q4qBriL6hLsFA8ijQC60MoZwLhZcX7xA6NwrhK8N4uAwYQkA2Ts7IAPvkPJIg4kX2yY8EpVCgmNCAA

author: Kleinstein
author_rank: Super Contributor
timestamp: April 03, 2023, 04:25:20 pm
content: When just driving a transistor the TL431 does not need that much current, some 1 mA would be plenty. Similar the zener diode does not need that much current - this is mainly to make sure to also work under relatively low voltage conditions.With an extra transistor in the loop one may have to make sure the output does not get that much capacitive loading and get unstable. One may want at least the option to have am additional capacitor from the base to the FB divider of the TL431.