Electronics Logic Gates: Open Collector Output Terry Sturtevant November 13, 2012
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Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Electronics Logic Gates: Open Collector Output Terry Sturtevant Wilfrid Laurier University November 13, 2012 Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Totem pole outputs Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Totem pole outputs Vcc Vout Two transistors Only one on at one time Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Totem pole outputs Vcc Vout Two transistors Only one on at one time Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Totem pole outputs Vcc Vout Two transistors Only one on at one time Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high TTL Totem Pole Output Equivalent Circuit Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high TTL Totem Pole Output Equivalent Circuit Vcc Vout Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high TTL Totem Pole Output Equivalent Circuit Vcc Vout Transistor acts like a switch Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high TTL Totem Pole Output Equivalent Circuit Vcc Vout Transistor acts like a switch Output is a voltage divider Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Totem pole outputs; output low Vcc Vout Upper transistor OFF (open switch) Lower transistor ON (closed switch) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Totem pole outputs; output high Vcc Vout Upper transistor ON (closed switch) Lower transistor OFF (open switch) The voltage at the output will depend on the current drawn because of the resistor. Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open collector outputs Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open collector outputs Vout Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open collector outputs Vout Single transistor; ON or OFF Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open collector outputs Vout Single transistor; ON or OFF Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open collector output equivalent circuit Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open collector output equivalent circuit Vout Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open collector output equivalent circuit Vout Output is either grounded or floating Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open collector output equivalent circuit Vout Output is either grounded or floating An external pull-up resistor is required to produce a high output Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open Collector Output Equivalent Circuit (Output Low) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open Collector Output Equivalent Circuit (Output Low) Vsupply Inside chip Vout Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open Collector Output Equivalent Circuit (Output Low) Vsupply Inside chip Vout Transistor ON (closed switch) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open Collector Output Equivalent Circuit (Output Low) Vsupply Inside chip Vout Transistor ON (closed switch) Vout pulled to GROUND Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open Collector Output Equivalent Circuit (Output Low) Vsupply Inside chip Vout Transistor ON (closed switch) Vout pulled to GROUND Current into gate Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs Output circuit Output equivalent circuit Equivalent circuit;output low Equivalent circuit;output high Open Collector Output Equivalent Circuit (Output High) Vsupply Inside chip Vout Transistor OFF (open switch) Vout pulled to Vsupply Current from supply Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Why use open collector gates? Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Why use open collector gates? More current Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Why use open collector gates? More current Mixing logic families Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Why use open collector gates? More current Mixing logic families Wired ANDing of outputs Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations More current Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations More current A TTL gate can source 0.4 mA. Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations More current A TTL gate can source 0.4 mA. A TTL gate can sink 16 mA. Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations More current A TTL gate can source 0.4 mA. A TTL gate can sink 16 mA. A TTL open collector gate can source ? Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations More current A TTL gate can source 0.4 mA. A TTL gate can sink 16 mA. A TTL open collector gate can source ? A TTL open collector gate can sink 16 mA. Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations More current A TTL gate can source 0.4 mA. A TTL gate can sink 16 mA. A TTL open collector gate can source ? A TTL open collector gate can sink 16 mA. Note: IOH for open-collector gate? Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations More current A TTL gate can source 0.4 mA. A TTL gate can sink 16 mA. A TTL open collector gate can source ? A TTL open collector gate can sink 16 mA. Note: IOH for open-collector gate? Look at the sign given for IOH , and consider what that means. Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Mixing logic families Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Mixing logic families VOH for TTL is 2.4V. Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Mixing logic families VOH for TTL is 2.4V. VIH for 5V CMOS is 3.5V. Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Mixing logic families VOH for TTL is 2.4V. VIH for 5V CMOS is 3.5V. VIH for 10V CMOS is 7V. Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Mixing logic families VOH for TTL is 2.4V. VIH for 5V CMOS is 3.5V. VIH for 10V CMOS is 7V. Examples TTL open collector output can feed into 10V CMOS if the output is pulled up to 10V. (But Vcc is still 5V!) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Totem pole outputs tied together Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Totem pole outputs tied together Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Totem pole outputs tied together Which gate will win? Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Totem pole outputs tied together Which gate will win? (Think about current limits.) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Wire ANDing of outputs Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Wire ANDing of outputs Vsupply Vout Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Wire ANDing of outputs Vsupply Vout No gate is grounded, so output is pulled high. Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Wire ANDing of outputs Vsupply Vout Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Wire ANDing of outputs Vsupply Vout One gate is grounded, so output is low. Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor Calculations Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor Calculations How do you calculate the pull-up resistor value? Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor Calculations How do you calculate the pull-up resistor value? When the output is low, the gate must be able to sink the current from the pull-up resistor and anything else connected. This will produce a minimum value for the resistor. Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor Calculations How do you calculate the pull-up resistor value? When the output is low, the gate must be able to sink the current from the pull-up resistor and anything else connected. This will produce a minimum value for the resistor. When the output is high, the current through the pull-up resistor must be high enough for whatever is connected to it. This will produce a maximum value for the resistor. Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output low Calculating Rmin Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output low Calculating Rmin 1 X 0 When the output is low, Rmin = (Vcc − VOL ) / (IOL ) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output low Calculating Rmin 1 X 1 IIL When the output is low, Rmin = (Vcc − VOL ) / (IOL − IIL ) (Current through R is reduced by IIL .) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output low Calculating Rmin 2 X X 1 IIL When the output is low, Rmin = (Vcc − VOL ) / (IOL − IIL ) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output low Calculating Rmin 2 X X 2 IIL When the output is low, Rmin = (Vcc − VOL ) / (IOL − 2 × IIL ) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output low Calculating Rmin 3 X X X 2 IIL When the output is low, Rmin = (Vcc − VOL ) / (IOL − 2 × IIL ) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output low Calculating Rmin 3 X X X 3 IIL When the output is low, Rmin = (Vcc − VOL ) / (IOL − 3 × IIL ) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output low Calculating Rmin M X X X N IIL X When the output is low, Rmin = (Vcc − VOL ) / (IOL − N × IIL ) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output high Calculating Rmax Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output high Calculating Rmax 1 X 0 IIH When the output is high, Rmax = (Vcc − VOH ) / (IOH ) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output high Calculating Rmax 1 X 1 IIH When the output is high, Rmax = (Vcc − VOH ) / (IOH + IIH ) (Current through R is increased by IIH .) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output high Calculating Rmax 2 X X 1 IIH When the output is high, Rmax = (Vcc − VOH ) / (2 × IOH + IIH ) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output high Calculating Rmax 2 X X 2 IIH When the output is high, Rmax = (Vcc − VOH ) / (2 × IOH + 2 × IIH ) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output high Calculating Rmax 3 X X X 2 IIH When the output is high, Rmax = (Vcc − VOH ) / (3 × IOH + 2 × IIH ) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output high Calculating Rmax 3 X X X 3 IIH When the output is high, Rmax = (Vcc − VOH ) / (3 × IOH + 3 × IIH ) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs More current Mixing logic families Wire ANDing of outputs Pull-up Resistor Calculations Pull-up Resistor; output high Calculating Rmax M X X X N IIH X When the output is high, Rmax = (Vcc − VOH ) / (M × IOH + N × IIH ) Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs CMOS Output circuit CMOS output Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs CMOS Output circuit CMOS output VDD Vout Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs CMOS Output circuit CMOS output VDD Vout Two transistors Terry Sturtevant Electronics Logic Gates: Open Collector Output Totem pole outputs Open collector outputs Open Collector Advantages CMOS outputs CMOS Output circuit CMOS output VDD Vout Two transistors Only one on at one time Terry Sturtevant Electronics Logic Gates: Open Collector Output
