What chips? Connecting them to what and how? A schematic or block diagram would be helpful.connecting two 12V rated chips would destroy them?
Say just a 555 to a 4017 decade counter with both rated at 12 V.What chips? Connecting them to what and how? A schematic or block diagram would be helpful.
Both devices can safely be connected to 12V without current limiting resistors because both are rated for supply voltages higher than that. Who made you think current limiting resistors were required?Say just a 555 to a 4017 decade counter with both rated at 12 V.
The spec sheet has max output current and input for the ics. I'm assuming these are the currents at the rated voltage.Both devices can safely be connected to 12V without current limiting resistors because both are rated for supply voltages higher than that. Who made you think current limiting resistors were required?
It would be helpful if you started being more specific.The spec sheet has max output current and input for the ics. I'm assuming these are the currents at the rated voltage.
What happens if the "rated voltage" is 3-18 volts as it would be for a 4000 series CMOS part like the 4017?It would be helpful if you started being more specific.
The TTL 555.What happens if the "rated voltage" is 3-18 volts as it would be for a 4000 series CMOS part like the 4017?
Also the 555 is both a bipolar part and a CMOS part. Which of those alternatives are you considering?
If you have a 555 ttl version operating at 18 volts Max it is my belief that, at that voltage,the max current would be output at pin 3.It would be helpful if you started being more specific.
TTL is a bipolar technology. If you read the datasheet carefully you will note that +18 Volts on Vcc will very likely let the magic smoke out of the part.If you have a 555 ttl version operating at 18 volts Max it is my belief that, at that voltage,the max current would be output at pin 3.
Is this what the 200 mA max on the datasheet at pin 3 means?
As I said, a 555 timer would be okay operating at 12V. At 18V, it would be at it's absolute maximum, and no designer worth beans would operate a device at it's absolute maximum parameter.If you have a 555 ttl version operating at 18 volts Max it is my belief that, at that voltage,the max current would be output at pin 3.
Is this what the 200 mA max on the datasheet at pin 3 means?
I'm really trying to understand the datasheet. What do all the multiple ISOURCEs and ISINKs mean?As I said, a 555 timer would be okay operating at 12V. At 18V, it would be at it's absolute maximum, and no designer worth beans would operate a device at it's absolute maximum parameter.
View attachment 250811
View attachment 250812
Even the manufacturer, National Semiconductor in this case, only characterizes operation at 5-15V.
If a device survived operating at it's absolute maximum, which it isn't guaranteed to do, any spike on the supply voltage that caused it to exceed the abs max by even a small amount could be enough to cause the device to act like an SCR.
They characterized the device sinking or sourcing 200mA, so that should be safe:
View attachment 250813
In the TTL world the transistors are not symmetrical. This means that they can SINK way more current in the low state then they can SOURCE in the HIGH state. IN CMOS the output stages are symmetrical and they can SOURCE as much current as they SINK. It allows the TTLL designer to avoid a situation where the driving requirements for a device are not exceeded by connection of too many inputs to an output.I'm really trying to understand the datasheet. What do all the multiple ISOURCEs and ISINKs mean?
They're illustrating the typical increase in the collector-emitter voltage drop for various load currents and supply voltages.What do all the multiple ISOURCEs and ISINKs mean?
Read the appropriate datasheet for the appropriate chip. And here:Hello. Does anyone know if directly (without current limiting resistors) connecting two 12V rated chips would destroy them? It seems to me if they are rated at the same voltage they would draw the rated current as well (one into another). Correct?
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