Improved capacitance multiplier

Started by Phil Hobbs in sci.electronics.design12 years ago 29 replies

So, I had this application requiring really absurd amounts of ripple rejection--it's a piezo driver in a laser wavelength locker that (for...

So, I had this application requiring really absurd amounts of ripple rejection--it's a piezo driver in a laser wavelength locker that (for historical reasons) has to run off a fairly crappy dual isolated 48V DC-DC converter. The 48V has almost a half volt of ripple at 47 kHz, and the output noise needed to be in the nanovolts. As we've discussed here before, ordinary cap multipliers ar...


Why does it work so well?

Started by Piotr Wyderski in sci.electronics.design6 years ago 8 replies

I have the following simple converter: CD4093 drives the power logic shift register's NPIC6C596A OE pin with 500kHz square wave signal...

I have the following simple converter: CD4093 drives the power logic shift register's NPIC6C596A OE pin with 500kHz square wave signal with duty cycle 40%. Both chips are powered from 5V, the shift register is set to all ones. Hence I have 8 modulated open drain channels, everything works as expected. Now I connect a 1:1 transformer wound on a PC40 6mm toroid (AL=2300), 16 turns each. The p...


charge pump/boost converter

Started by bitrex in sci.electronics.design7 years ago 57 replies

For a hobby project, I'd like to be able to generate +48 volts or so from +5 volt USB. Current requirements are small, maybe 15 mA or so?...

For a hobby project, I'd like to be able to generate +48 volts or so from +5 volt USB. Current requirements are small, maybe 15 mA or so? I'd like uh, low noise (I don't have an exact spec so this is just kind of existential at this point), so maybe a charge pump would be in order rather than a boost switcher? Does anyone make a charge pump IC that I could feed an external clock to...


UC3825 help with Pspice

Started by Waldes in sci.electronics.design14 years ago 1 reply

Hi all! I need simulation file for this IC. If someone has it, please share with me. I found here some files for UC3843, UC3842, but they...

Hi all! I need simulation file for this IC. If someone has it, please share with me. I found here some files for UC3843, UC3842, but they are current mode, and I want something with voltage mode for flyback converter, which has voltage regulated from 30V to 300V. So I will be gratefull for model UC3825 or information how to simulate in Pspice PWM modulator with Soft Start and limit max cur...


complementary cmos levels

Started by Anonymous in sci.electronics.design3 years ago 11 replies

I have a fast 3.3 volt logic level that I'd like to split into inverted and non-inverted copies with minimum time skew. I think that TI...

I have a fast 3.3 volt logic level that I'd like to split into inverted and non-inverted copies with minimum time skew. I think that TI once had a buffer with one input and complementary outputs, but I can't find a reference to that. It's probably slow and obsolete. A TTL to RS485 converter sort of works but would be slow. I could use two separate XOR gates, one as a buffer and the...


AD7793 error?

Started by jmariano in sci.electronics.design6 years ago 25 replies

Dear All, I'm currently evaluating the AD7793 \Sigma-\Delta converter. I'm using an A= duino Due (SAM3X8E) connected to the ADC through SPI...

Dear All, I'm currently evaluating the AD7793 \Sigma-\Delta converter. I'm using an A= duino Due (SAM3X8E) connected to the ADC through SPI with CS permanently ti= ed low. I use the Arduino's SPI library to control the SPI UART and AD's li= brary (available on-line) to access the ADC. After correcting a couple of bugs in both libraries, I'm able to read the A= D7793 on-chip registers but...


CV/CC synchronous buck -- do they exist?!

Started by Piotr Wyderski in sci.electronics.design2 years ago 14 replies

Hi, I need a simple synchronous buck converter capable of seamless CV/CC transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had...

Hi, I need a simple synchronous buck converter capable of seamless CV/CC transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled a lot but was unable to find a nice part for the job. All the candidates either have too low I_OUT, self-protect themselves like Jackie Chan with various hiccup/latch off algorithms or require so many external components that it is hard to di...


RGB to XYZ

Started by bitrex in sci.electronics.design1 year ago 12 replies

A simplistic VGA to XYZ-scope converter like this: just uses a passive resistor network to linearly scale the RGB components and sum...

A simplistic VGA to XYZ-scope converter like this: just uses a passive resistor network to linearly scale the RGB components and sum them to monochrome. However I don't think this really works for a "modern" SVGA output because the gamma will be wrong; you have to apply a nonlinear gamma-expanding transform prior to i


Driving 74LS from 3.3V uP

Started by bitrex in sci.electronics.design6 years ago 48 replies

Prototyping a little toy for the kiddos out of junk box parts... I have a IV-9 Numitron connected up on a PCB to a 74LS47 BCD to 7 segment...

Prototyping a little toy for the kiddos out of junk box parts... I have a IV-9 Numitron connected up on a PCB to a 74LS47 BCD to 7 segment driver. uP is a 3.3 volt ATTiny (Adafruit "Trinket" devboard) powered via an on-board LDO directly off a 3.7 V 150mAh lipo. 3.7 volts is boosted to around 5 to power the 74LS and Numitron segments via an eBay special micro boost converter with shutdo...


delta-sigma again

Started by Anonymous in sci.electronics.design3 years ago 41 replies

I'm still playing with delta-sigma A/D conversion in LT Spice. I'll be using the ADUM7703 isolated 2nd order converter, clocked at 20...

I'm still playing with delta-sigma A/D conversion in LT Spice. I'll be using the ADUM7703 isolated 2nd order converter, clocked at 20 MHz, and we're thinking now about decimation filters in an FPGA. Win was considering using a d-s encoder and an analog recovery filter. My filter will be digital, and it will be inside a high-power control loop. The FPGA will drive a bunch of DACs at 50...


Quadratic DC-DC converters?

Started by piglet in sci.electronics.design1 year ago 13 replies

I need to make an isolated DC-DC switching converter with a 9:1 output range and 5:1 input range. Power is about ten watt. Resulting 45:1 duty...

I need to make an isolated DC-DC switching converter with a 9:1 output range and 5:1 input range. Power is about ten watt. Resulting 45:1 duty cycle range looks tricky to make work well. So far I am most tempted to boost to an intermediate rail (which takes up the 5:1 range) and then convert from that over the 9:1 range. The intermediate rail could be useful for other purposes too. H...


MOSFET selection for boost converter problem

Started by John Nagle in sci.electronics.design6 years ago 30 replies

I've been working on a power supply for antique Teletype selector magnets. These need 120VDC 60mA for the first 2ms or so of each bit time,...

I've been working on a power supply for antique Teletype selector magnets. These need 120VDC 60mA for the first 2ms or so of each bit time, but the sustain voltage needed is only 3-4V. So I've built an isolated boost supply and interface board, all powered from a USB port. The whole project is on Github: https://github.com/John-Nagle/ttyloopdriver where there's an explanation of how...


48v isolated dc/dc converter

Started by Anonymous in sci.electronics.design1 year ago 1 reply

This will have to work at up to 200 watts maybe; 48 in and out. Those surface-mount Coilcraft planar transformers are wonderful....

This will have to work at up to 200 watts maybe; 48 in and out. Those surface-mount Coilcraft planar transformers are wonderful. https://www.coilcraft.com/en-us/products/transformers/planar-transformers/planar/pl300/ I suspect some air flow can sneak in between the flat kapton windings. I guess I should include the leakage inductances, but they are tiny. The LTC gate drivers are ...


Picking a transistor for low output impedance circuit

Started by amdx in sci.electronics.design2 months ago 17 replies

Hi all,   I'm following a group discussing building a Q meter. HP has a two transistor Impedance Converter Ass'y. >...

Hi all,   I'm following a group discussing building a Q meter. HP has a two transistor Impedance Converter Ass'y. > https://www.dropbox.com/s/n5gj8powzph6611/HP4342A%20impedance%20converter%20and%20injection%20tr ansformer..jpg?dl=0 One builder got down to 0.86? output impedance at 50kHz, 1.05? at 1MHz, on up to 7.70? at 30MHz after trying several common transistors for the first trans


Sound localization with Raspberry pi

Started by Anonymous in sci.electronics.design8 years ago 10 replies

I want to use the RPI to process the incoming data from five crystal microphones in order to obtain the direction of arrival of sound so that i...

I want to use the RPI to process the incoming data from five crystal microphones in order to obtain the direction of arrival of sound so that i can steer a camera mounted on two servos to that direction. Since there is no audio inputs to the RPI i think of using a two-channel analog to digital converter, one channel is connected to a refrence mic and the other channel is connected to the out...


dual neg switcher

Started by Anonymous in sci.electronics.design2 years ago

I'm on my 3rd day of BOM minimization of my big timing board, trying to consolidate enough parts so we can load the pick-and-place, which has...

I'm on my 3rd day of BOM minimization of my big timing board, trying to consolidate enough parts so we can load the pick-and-place, which has 200 feeder slots. The board has about 750 parts, over 200 bypass caps! We have +24 volts and need -7 and -5. The current design uses a Cuk converter to make -7, then an LM2991 linear to make -5. Lots of parts. Looks like I can switch 24 to (about...


Low level AC measuremets with HP 34401

Started by Reinhard Zwirner in sci.electronics.design11 months ago 11 replies

Hello, Due to the used RMS converter low level AC measurememts with this DMM are less precise to incorrect. There is a lab note as to this...

Hello, Due to the used RMS converter low level AC measurememts with this DMM are less precise to incorrect. There is a lab note as to this problem by Gellerlabs containing three pictures. I have this note which, unfortunately, lacks the mentioned pictures. And, unfortunately too, the link to this note doesn't work any more. Has anyone


The 12V level shifter saga

Started by Piotr Wyderski in sci.electronics.design3 years ago 42 replies

Hi, I am working on a high-current 4-switch buck-boost converter. The switches are psmnr70-40sshj, which -- with their 202nC gate charge --...

Hi, I am working on a high-current 4-switch buck-boost converter. The switches are psmnr70-40sshj, which -- with their 202nC gate charge -- makes the 12A gate driver MCP14A1202 a perfect spouse. The problem is with passing the control signals to the upper switches. I want to have true 100% duty cycle operation capability, which excludes AC coupling techniques such as a signal transform...


Flybuck converter funnies

Started by Phil Hobbs in sci.electronics.design7 years ago 24 replies

So I built this board for my fire prevention equipment customer. (An excellent outfit BTW: Argus Fire Control.) It needed two isolated...

So I built this board for my fire prevention equipment customer. (An excellent outfit BTW: Argus Fire Control.) It needed two isolated 5-V supplies, one for the analogue stuff and one for RS-485. A few months ago we were discussing those supplies in this very boutique, in the "Coupled Inductors--how coupled is coupled?" thread. I wound up with a flybuck design using an LM3103 sync buck c...


A quiet SEPIC negative supply

Started by Winfield Hill in sci.electronics.design3 years ago 8 replies

I needed to add a -3.3V to -6V supply to my RIS-796A 250A pulser, analog version. The PCB didn't have much space, so I implemented a simple...

I needed to add a -3.3V to -6V supply to my RIS-796A 250A pulser, analog version. The PCB didn't have much space, so I implemented a simple inverting switcher with an LM2840 buck converter. See circuit and layout on file U7=LM2840_sch+pcb.jpg in the DropBox folder: https://www.dropbox.com/sh/rfqohfvubj9pddh/AAC9dSrWbeJmY9iq_rODYonIa?dl=1 There's also a sub-folder with relevant...