poor op-amp settling time

It is a chopper stabilized opamp - I've been bitten by the long settling time of those types when recovering from overdrive.

kw

That often happens when the vendor does some funny stuff with the compensation. You wind up with a pole/zero pair that's closely spaced but not coincident. The ancient trick for speeding up an LM101 by capacitively coupling to the offset null pins to bypass the lateral PNP level shifters is a classic example.

It gives you a little whoopdedoo in the transfer function that dominates the settling behaviour at late times when other contributions have died out. The LM318 was famous for that as well. (Come to think of it, National never did get over the idea that 400 ns was a fast settling time. Or that 1 mV was a low offset voltage.)

Cheers

Phil Hobbs

low-frequency

Never Buy Maxim!

The overload recovery time is milliseconds, so there's probably some node inside that winds up when it rails or slews. It's an autozero, and they can get messy. Intersil made one autozero opamp that took

The overload recovery graph is suggestive. Look at that time constant!

I use the DS1077 i2c clock oscillator sometimes it's cheap and does the business. But that's a Dallas Semi part to be fair.

Yikes, they measure frequency errors in per cent, not parts per million. You can get a programmable crystal oscillator for less than that.

Maxim deliberately uses nonstandard pinouts. And then they discontinue parts without notice.

It has a very long divider chain, I don't know what programmable xtal oscillator for less money would be a good substitute with that granularity that can be adjusted on the fly.

I don't know for sure about packages with the crystal in them, but they hav e PLL type devices that will give you pretty much whatever frequency you wa nt with a pretty fine granularity. I know there are programmable oscillato rs with dividers, so I assume they come with the PLL as well. Seems silly not to.

It works great for clocking a bucket-brigade delay!

I looked at AD8628 and LTC1052 and did not find any specification for settling time neither....

Exactly. I solved the problem by adding a range switch, which relaxed the Vos requirement by 10x. Then I selected an LMP7711 opamp. 17MHz GBW, 150uV Vos, and an enable pin. TI doesn't provide a settling-time spec for that part, but it has a well-behaved GBW plot; I'm sure it'll be just fine.

A heap of companies make them, PPB programmable over a huge range. Check Digikey.

Looks like a STM32G0 will be cheaper and have simelar specs wrt jitter and accuracy

You the get the rest of the micro for free

Cheers

Klaus

and i2c bus? Not SPI or some bespoke serial interface?

I like my library code for quick turn-arounds. I2C, button-debouncing, LED display driver, even rotary encoders have their own libs

I have an idea: check Digikey!

Is the Microchip MCP6V91 any use to you - the specs don't compare very directly but the Microchip part looks a lot better on recovery time.

And Microchip are much nicer to buy from :-)

MK

Hey, nice part, I hadn't found that one! Oops, no Enable pin. :-( Also, while the 65us settling/step-recovery is much better than the Maxim part, it's still rather long. Anyway, I solved the problem by adding a range switch, allowing a higher Vos spec, and avoiding a chopper amp.

I agree, I'm a huge Microchip fan.