MCP6001 Spice Model Posted

Jim Thompson

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Jul 1, 2016, 3:58:14 PM7/1/16

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Allan Herriman

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Jul 1, 2016, 11:24:25 PM7/1/16

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On Fri, 01 Jul 2016 12:58:03 -0700, Jim Thompson wrote:

> MCP6001 Spice Model Posted...
>
> See MCP6001_JT.zip on the Device Models & Subcircuits Page of my
> website.

The MCP600x parts have an interesting (for an opamp) input protection
circuit - it has clamps to the negative rail but no clamps to the
positive rail, much like the input protection used in many digital
logic families.

Despite that, the datasheet abs max ratings say the input voltage cannot
go above the positive rail. I never established whether that was because
of some fundamental limitation of the device, or just an overly
conservative datasheet. I asked about it in s.e.d. earlier this year,
but no-one knew:
<https://groups.google.com/d/msg/sci.electronics.design/78hf-Wjbxjw/LFINvpsqHQAJ>

BTW, the input protection doesn't seem to be modelled in MCP6001_JT.zip
(Either that, or I've lost my ability to read netlists.)

Regards,
Allan

bloggs.fred...@gmail.com

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Jul 2, 2016, 4:02:55 AM7/2/16

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On Friday, July 1, 2016 at 11:24:25 PM UTC-4, Allan Herriman wrote:
> On Fri, 01 Jul 2016 12:58:03 -0700, Jim Thompson wrote:
>
> > MCP6001 Spice Model Posted...
> >
> > See MCP6001_JT.zip on the Device Models & Subcircuits Page of my
> > website.
>
>
> The MCP600x parts have an interesting (for an opamp) input protection
> circuit - it has clamps to the negative rail but no clamps to the
> positive rail, much like the input protection used in many digital
> logic families.

"They (ESD diodes to Vss) also clamp any voltages that go too far
above VDD; their breakdown voltage is high enough to
allow normal operation, and low enough to bypass
quick ESD events within the specified limits."

>
> Despite that, the datasheet abs max ratings say the input voltage cannot
> go above the positive rail. I never established whether that was because
> of some fundamental limitation of the device, or just an overly
> conservative datasheet. I asked about it in s.e.d. earlier this year,
> but no-one knew:
> <https://groups.google.com/d/msg/sci.electronics.design/78hf-Wjbxjw/LFINvpsqHQAJ>

Those input limits are to prevent phase reversal. Like most spec sheets they define an envelope inside of which maloperation is guaranteed not to occur.

>
>
> BTW, the input protection doesn't seem to be modelled in MCP6001_JT.zip
> (Either that, or I've lost my ability to read netlists.)

They do insist on input currents being limited to 2mA...

>
> Regards,
> Allan

http://ww1.microchip.com/downloads/en/DeviceDoc/21733j.pdf

Jim Thompson

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Jul 2, 2016, 11:19:38 AM7/2/16

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On 02 Jul 2016 03:24:22 GMT, Allan Herriman

No. That model was a quicky for John Woodgate (remember him from back
when SED was about electronics ?:-) So only fundamental function was
modeled.

In the wings I am modeling a universal output stage that properly
routes rail current and has current limiting.

My "commercial-grade" models include protection devices and quiescent
current ramp up versus rails... and various shutdown modes... you name
it, I model it >:-}

Wonder who was better, AG Loretta Lynch or Monica Lewinsky ?>:-}