Why am i getting a 5 pin comparator when downloading an 8 pin?

Thread Starter

tienk

Joined Apr 8, 2024
76
beginner here, i imported a spice file into ltspice but in the datasheet it says its 8 pins but in ltspice its 5 pin, did i do something wrong or am i missing something
 

Alec_t

Joined Sep 17, 2013
14,384
Some real-world ICs have more than one pin devoted to the same function. Spice would need only one.
Logic gates in Spice don't usually have supply pins.
 

ronsimpson

Joined Oct 7, 2019
3,150
beginner here, i imported a spice file into ltspice but in the datasheet it says its 8 pins but in ltspice its 5 pin
Beginner; thanks for "LTSPICE", but we need more information. What part number? It is a good idea to include the spice file of your project.
Not knowing what part, it is most likely that the part has 5 pins what are connected. "+", "-", out, +supply, and -supply, then two no-connects.
 

Papabravo

Joined Feb 24, 2006
21,264
There
beginner here, i imported a spice file into ltspice but in the datasheet it says its 8 pins but in ltspice its 5 pin, did i do something wrong or am i missing something
Simulation does not really have any concept of pin numbers. Only the signals that are relevant are implemented. As has been mentioned power pins are often omitted as well as multiple instances of a basic element like an AND gate. A simulation model for an LM393 dual comparator only has a single instance of a comparator and is not tied to a physical package,
 

Thread Starter

tienk

Joined Apr 8, 2024
76

Thread Starter

tienk

Joined Apr 8, 2024
76
There

Simulation does not really have any concept of pin numbers. Only the signals that are relevant are implemented. As has been mentioned power pins are often omitted as well as multiple instances of a basic element like an AND gate. A simulation model for an LM393 dual comparator only has a single instance of a comparator and is not tied to a physical package,
so in simple terms ground and Vcc will not be there?
 

Alec_t

Joined Sep 17, 2013
14,384
so in simple terms ground and Vcc will not be there?
They are for some chips but not for others. When simulating ICs in a standard logic family, for example, it is assumed that inputs are within the logic range (e.g 0V-3.3V) associated with that family.
 

eetech00

Joined Jun 8, 2013
4,013
so in simple terms ground and Vcc will not be there?
There is no modeling standard for devices, so the modeled behavior and pins for any model may vary.
Regarding the LTspice LM393 model, TI has modeled this as a single comparator instance with VCC and GND pins.
Therefore, VCC and GND must be applied to the pins for each comparator instance used. However, LTspice symbols can be configured to accommodate internal or external pins if needed.
 

ronsimpson

Joined Oct 7, 2019
3,150
, i imported a spice file into ltspice but in the datasheet it says its 8 pins but in ltspice its 5 pin,
Thank you for the datasheet. There are two comparators in the IC. SPICE and most CAD programs will only give you pins 1,2,3,4,8.
1712666927789.png
Here is the inside workings of the comparator. Note there are only 5 pins.
1712667155943.png

When drawing a schematic, the two comparators might be on two different pages. Here are two different ways to draw that part on a schematic. Almost never will it be drawn as one symbol.
1712667636475.png
 

crutschow

Joined Mar 14, 2008
34,706
Another example is the LM324 quad op amp which have four op amps in one 14-pin package, but all that is shown in the LTspice model symbol are 5 pins for one op amp.
 
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