I want to measure the voltage drop across a shunt resistor, amplify it to 50 times the original value, and feed that (0 - 5 V) to an ADC. I'd prefer to do the "high side" current sense method (rather than having the shunt between load and ground), but might have to change that to get it all to work.
This is driving me mildly insane. I've spent many hours on this by now, but I still can't find a single IC that meets all my requirements - just most of them.
Anyway, my requirements are:
- Less than $7 or so (I only need 2, so no "per 1k" prices!)
- Able to tolerate the common-mode voltage of ~15 V (either side of the resistor with respect to ground)
- Able to measure up to ~1.5 A (always less than 2) with good precision, preferably with precision at the low end as well (5 mA = 0.25 mV, 1.5 A = 75 mV, 2 A = 100 mV)
- Rail-to-Rail
- 50 gain, or adjustable via resistors
- DIP package/through-hole mounting. This one appears to remove about every single solution that otherwise works.
The requirements are absolute, perhaps except for the price... Still, I don't want to pay too much for this one part (current sensing) of the project; other ICs are involved in this as well, so the total for just the current sensing will turn out quite high.
All I can find based on this is the Maxim MAX472, which is obsolete and not available. Its replacements are surface-mount only, and I'd rather avoid making my first (after a small test) PCB double-sided, as long as routing will be theoretically possible with a single-sided board.