I've got a circuit that has a Hex Buffer (specifically, a TI SN74LVC07A). I'm trying to determine what this chip does - what its function is. I reviewed the datasheet, but it doesn't tell me anything - at least not in a way I can understand. (yes, I'm a newbie at this stuff.) -- --------------------------------------------------------------------- DataGet� & PocketLog� www.dataget.com Data Collectors www.baxcode.com --------------------------------------------------------------------
What is a Hex buffer?
Started by ●June 22, 2006
Reply by ●June 22, 20062006-06-22
"Baxter" <lbax02.spamguard@baxcode.com> wrote in message news:129mdrmtivdop5a@corp.supernews.com...> I've got a circuit that has a Hex Buffer (specifically, a TI SN74LVC07A). > > I'm trying to determine what this chip does - what its function is. I > reviewed the datasheet, but it doesn't tell me anything - at least not in > a > way I can understand. > > (yes, I'm a newbie at this stuff.)"Hex" in this case just means there's 6 of 'em. (Not hexadecimal, which would be 16, just hex - no decimal.) Ok - the 7407 generic part is a 6-way open-drain buffer.(Available in various logic families since the 70s.) This means that there are 6 buffers, each with a logic family-compatible input, and each with an output which is capable of sinking some (depending on family) current, and no inversion (i.e. a HIGH input means high output, i.e. no sink, and a LOW input means a low output, i.e. the output is sinking current). Does that help? Steve http://www.fivetrees.com
Reply by ●June 22, 20062006-06-22
"Steve at fivetrees" <steve@NOSPAMTAfivetrees.com> wrote in message news:7u6dnYXK1bVD3AbZnZ2dnUVZ8s-dnZ2d@pipex.net...> "Baxter" <lbax02.spamguard@baxcode.com> wrote in message > news:129mdrmtivdop5a@corp.supernews.com... > > I've got a circuit that has a Hex Buffer (specifically, a TISN74LVC07A).> > > > I'm trying to determine what this chip does - what its function is. I > > reviewed the datasheet, but it doesn't tell me anything - at least notin> > a > > way I can understand. > > > > (yes, I'm a newbie at this stuff.) > > "Hex" in this case just means there's 6 of 'em. (Not hexadecimal, which > would be 16, just hex - no decimal.)Interesting. I came across some sites where they were comparing Hex buffers agains Octal buffers. So resolving one issue raises another - but seems tangental to what I'm after.> > Ok - the 7407 generic part is a 6-way open-drain buffer.(Available in > various logic families since the 70s.) This means that there are 6buffers, good.> each with a logic family-compatible input, and each with an output whichis> capable of sinking some (depending on family) current, and no inversion > (i.e. a HIGH input means high output, i.e. no sink, and a LOW input meansa> low output, i.e. the output is sinking current). >Here you lose me - I don't know what 'sinking some current' means (in practical terms). I understand it does NOT invert the signal (make high voltage low, and low voltage high). Do you mean that it keeps the current constant as the voltage fluctuates?
Reply by ●June 23, 20062006-06-23
Baxter wrote:> Interesting. I came across some sites where they were comparing Hex > buffers agains Octal buffers. So resolving one issue raises another > - but seems tangental to what I'm after.Octal buffers have 8 in one package.>> each with a logic family-compatible input, and each with an output >> which is capable of sinking some (depending on family) current, and >> no inversion (i.e. a HIGH input means high output, i.e. no sink, and >> a LOW input means a low output, i.e. the output is sinking current). >> > Here you lose me - I don't know what 'sinking some current' means (in > practical terms).It means able to pull a high level signal low. The standard terms are "source current" which means it outputs a high level and "sink current" which means it outputs a low level. In the case of the ICs under discussion, they have an open drain (or collector) which means to see a high level on the pin it needs to be pulled high by a resistor. -Mike
Reply by ●June 23, 20062006-06-23
Baxter wrote:> "Steve at fivetrees" <steve@NOSPAMTAfivetrees.com> wrote in message >... snip ...> >> each with a logic family-compatible input, and each with an output >> which is capable of sinking some (depending on family) current, and >> no inversion (i.e. a HIGH input means high output, i.e. no sink, and >> a LOW input means a low output, i.e. the output is sinking current). > > Here you lose me - I don't know what 'sinking some current' means (in > practical terms). > > I understand it does NOT invert the signal (make high voltage low, and > low voltage high). Do you mean that it keeps the current constant as > the voltage fluctuates?No, think of it as a switch between the output pin and the ground pin. When the input is low that switch is closed, so the output is at ground potential (with a restriction on the maximum current drawn). When the input is high the switch is open, and the output circuit goes wherever the external circuitry takes it. The usual external circuitry is simply a resistor to Vcc. That means various open collector buffers can be connected to that node, and any one of them can drive the point low. This is known as a wired or (for negative logic). The difference between open-collector and the more usual output circuit is that the normal circuit will actively drive the output node high. It can't be used in the wired or configuration, but the logic swings take place faster for rising output edges. Outputs can't be directly connected together because they could fight, with often fatal results. -- Chuck F (cbfalconer@yahoo.com) (cbfalconer@maineline.net) Available for consulting/temporary embedded and systems. <http://cbfalconer.home.att.net> USE maineline address!
Reply by ●June 23, 20062006-06-23
On 2006-06-23, Baxter <lbax02.spamguard@baxcode.com> wrote:>> "Hex" in this case just means there's 6 of 'em. (Not hexadecimal, which >> would be 16, just hex - no decimal.) > > Interesting. I came across some sites where they were comparing Hex buffers > agains Octal buffers. So resolving one issue raises anotherRaises what issue? You do know that the prefix "oct" means eight, right? -- Grant Edwards grante Yow! Now I'm telling MISS at PIGGY about MONEY MARKET visi.com FUNDS!
Reply by ●June 23, 20062006-06-23
Reply by ●June 23, 20062006-06-23
"Grant Edwards" <grante@visi.com> wrote in message news:129mnrf11vik1bd@corp.supernews.com...> On 2006-06-23, Baxter <lbax02.spamguard@baxcode.com> wrote: > > >> "Hex" in this case just means there's 6 of 'em. (Not hexadecimal, which > >> would be 16, just hex - no decimal.) > > > > Interesting. I came across some sites where they were comparing Hexbuffers> > agains Octal buffers. So resolving one issue raises another > > Raises what issue? You do know that the prefix "oct" means > eight, right? >I'm primarily a software guy - Octal means base 8 number - Hex is 16-bit number.
Reply by ●June 23, 20062006-06-23
"Mike Warren" <miwa-not-this-bit@or-this-csas.net.au> wrote in message news:449b5c6e$0$490$61c65585@uq-127creek-reader-03.brisbane.pipenetworks.com.au...> Baxter wrote:> >> each with a logic family-compatible input, and each with an output > >> which is capable of sinking some (depending on family) current, and > >> no inversion (i.e. a HIGH input means high output, i.e. no sink, and > >> a LOW input means a low output, i.e. the output is sinking current). > >> > > Here you lose me - I don't know what 'sinking some current' means (in > > practical terms). > > It means able to pull a high level signal low. The standard terms are > "source current" which means it outputs a high level and "sink current" > which means it outputs a low level. In the case of the ICs under > discussion, they have an open drain (or collector) which means to > see a high level on the pin it needs to be pulled high by a resistor. >Still pretty murky to me. The Hex Buffer connects to various pins on a MSP430. Inside the MSP430, I'm setting the pin (voltage) high or low - I just can't quite picture how the Hex Buffer affects that. As far as that goes, I'm still wrestling a bit with the semantics of a "pull-up" resistor.
Reply by ●June 23, 20062006-06-23
On Thu, 22 Jun 2006 22:50:51 -0700, "Baxter" <lbax02.spamguard@baxcode.com> wrote:>"Mike Warren" <miwa-not-this-bit@or-this-csas.net.au> wrote in message >news:449b5c6e$0$490$61c65585@uq-127creek-reader-03.brisbane.pipenetworks.com.au... >> Baxter wrote: > >> >> each with a logic family-compatible input, and each with an output >> >> which is capable of sinking some (depending on family) current, and >> >> no inversion (i.e. a HIGH input means high output, i.e. no sink, and >> >> a LOW input means a low output, i.e. the output is sinking current). >> >> >> > Here you lose me - I don't know what 'sinking some current' means (in >> > practical terms). >> >> It means able to pull a high level signal low. The standard terms are >> "source current" which means it outputs a high level and "sink current" >> which means it outputs a low level. In the case of the ICs under >> discussion, they have an open drain (or collector) which means to >> see a high level on the pin it needs to be pulled high by a resistor. >> >Still pretty murky to me. The Hex Buffer connects to various pins on a >MSP430. Inside the MSP430, I'm setting the pin (voltage) high or low - I >just can't quite picture how the Hex Buffer affects that. As far as that >goes, I'm still wrestling a bit with the semantics of a "pull-up" resistor. >A buffer is a device used to increase the drive capability of another chip. The output of an IC can drive a certain number of inputs on other chips (depends on IC family, etc.). If you don't have enough drive output to drive all the inputs you need then buffers are used to increase the output drive (think of them as amplifiers). Buffers can either be non-inverting or inverting depending on what you need to do. Obviously non-inverting buffers give you a high output for a high input and a low output for a low input. Inverting buffers operate the opposite way around (low out for high in ,etc.). Buffers also come in different package configurations the common ones being hex (=6) or octal (=8). Buffers can also be open collector/drain outputs or active driven outputs. Open collector outputs normally need external pull-up resistors or circuitry (so called because the resistor pulls up the un-driven open collector output of the buffer towards the positive supply voltage). HTH Alan -- Sell your surplus electronic components at http://ozcomponents.com Search or browse for that IC, capacitor, crystal or other component you need.
