Hi all, laying out a pcb and I realized I've got an instrument amp monitoring a voltage drop from the positive supply rail. Any recommendations?? (the one penciled in won't go there.) (AoE3 is at work, I'm heading to DK.) George H.
High side Instr. amp. 30V
Mar 13, 2016
8 Replies
Voltage on positive rail?
Range of voltages sensed down from positive rail?
Current consumption allowed from positive rail for instrumentation? ...Jim Thompson
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
24V, but looking at it I'm thinking the positive rail should have some sort of filter. A voltage regulator or cap. multiplier??
oh, might as well go to zero.. it can have a negative supply below ground.
Oww... gee, say ~0.1% of the min, 1-10uA. Jim, I don't want you to design anything... Linear or someone must make something that fits... Or an opamp.
George H.
If you're going instrumentation amp quality, why not just subtract the drop node from the rail node? ...Jim Thompson
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Floating power supply, run the inst. amp lust below the supply rail?
Or, use resistive dividers (with compensation caps, if needed) to divide the two measured points down to where they are within range of the inst. amp. I did this on a servo amp with tons of 100 KHz noise, it worked like a champ.
Jon
TI has a lot of suitable items; INA192 sucks one mA, CM goes from -16 to +80V. Power, bandwidth, cost are all tradeoffs, of course.
Oops: typo. I meant INA193...
TI's LMP8640 comes in a 6-pin SOT.
Group response, Thanks all, There are a number of the high side current sense amps, but none of those are going to work. There are some RRIO int-amp's in AoE3* but all low voltage. I'll either divide the voltage down with R's as Jon suggested or drop a few volts up stream... probably the later.
George H.
*The LT1789 input goes to the negative rail.Join the Discussion
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