Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

ElectronicsLogic Gates: Open Collector Output

Terry Sturtevant

Wilfrid Laurier University

October 3, 2018

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Totem pole outputs

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Totem pole outputs

Vcc

Vout

Two transistorsOnly one on at one time

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Totem pole outputs

Vcc

Vout

Two transistorsOnly one on at one time

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Totem pole outputs

Vcc

Vout

Two transistorsOnly one on at one time

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

TTL Totem Pole Output Equivalent Circuit

Vcc

Vout

Transistor acts like a switchOutput is a voltage divider

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

TTL Totem Pole Output Equivalent Circuit

Vcc

Vout

Transistor acts like a switchOutput is a voltage divider

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent 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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

TTL Totem Pole Output Equivalent Circuit

Vcc

Vout

Transistor acts like a switchOutput is a voltage divider

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent 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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent 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 drawnbecause of the resistor.

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open collector outputs

Vout

Single transistor; ON or OFF

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open collector outputs

Vout

Single transistor; ON or OFF

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open collector outputs

Vout

Single transistor; ON or OFF

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open collector outputs

Vout

Single transistor; ON or OFF

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open collector output equivalent circuit

Vout

Output is either grounded or floatingAn external pull-up resistor is required to produce a highoutput

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open collector output equivalent circuit

Vout

Output is either grounded or floatingAn external pull-up resistor is required to produce a highoutput

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent 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 highoutput

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open collector output equivalent circuit

Vout

Output is either grounded or floatingAn external pull-up resistor is required to produce a highoutput

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open Collector Output Equivalent Circuit (Output Low)

Vsupply

Vout

Inside chip

Transistor ON (closed switch)Vout pulled to GROUNDCurrent into gate

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open Collector Output Equivalent Circuit (Output Low)Vsupply

Vout

Inside chip

Transistor ON (closed switch)Vout pulled to GROUNDCurrent into gate

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open Collector Output Equivalent Circuit (Output Low)Vsupply

Vout

Inside chip

Transistor ON (closed switch)

Vout pulled to GROUNDCurrent into gate

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open Collector Output Equivalent Circuit (Output Low)Vsupply

Vout

Inside chip

Transistor ON (closed switch)Vout pulled to GROUND

Current into gate

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open Collector Output Equivalent Circuit (Output Low)Vsupply

Vout

Inside chip

Transistor ON (closed switch)Vout pulled to GROUNDCurrent into gate

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

Output circuitOutput equivalent circuitEquivalent circuit;output lowEquivalent circuit;output high

Open Collector Output Equivalent Circuit (Output High)Vsupply

Vout

Inside chip

Transistor OFF (open switch)Vout pulled to Vsupply

Current from supply

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Why use open collector gates?

More currentMixing logic familiesWired ANDing of outputsBidirectional communication

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Why use open collector gates?

More current

Mixing logic familiesWired ANDing of outputsBidirectional communication

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Why use open collector gates?

More currentMixing logic families

Wired ANDing of outputsBidirectional communication

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Why use open collector gates?

More currentMixing logic familiesWired ANDing of outputs

Bidirectional communication

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Why use open collector gates?

More currentMixing logic familiesWired ANDing of outputsBidirectional communication

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Mixing logic families

VOH for TTL is 2.4V.VIH for 4.5V HC(MOS) is 3.15V.VIH for 6V HC(CMOS) is 4.20V.

ExamplesTTL open collector output can feed into 5V HC(CMOS) if theoutput is pulled up to 5V. (But Vcc is still 5V!)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Mixing logic families

VOH for TTL is 2.4V.

VIH for 4.5V HC(MOS) is 3.15V.VIH for 6V HC(CMOS) is 4.20V.

ExamplesTTL open collector output can feed into 5V HC(CMOS) if theoutput is pulled up to 5V. (But Vcc is still 5V!)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Mixing logic families

VOH for TTL is 2.4V.VIH for 4.5V HC(MOS) is 3.15V.

VIH for 6V HC(CMOS) is 4.20V.

ExamplesTTL open collector output can feed into 5V HC(CMOS) if theoutput is pulled up to 5V. (But Vcc is still 5V!)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Mixing logic families

VOH for TTL is 2.4V.VIH for 4.5V HC(MOS) is 3.15V.VIH for 6V HC(CMOS) is 4.20V.

ExamplesTTL open collector output can feed into 5V HC(CMOS) if theoutput is pulled up to 5V. (But Vcc is still 5V!)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Mixing logic families

VOH for TTL is 2.4V.VIH for 4.5V HC(MOS) is 3.15V.VIH for 6V HC(CMOS) is 4.20V.

ExamplesTTL open collector output can feed into 5V HC(CMOS) if theoutput is pulled up to 5V. (But Vcc is still 5V!)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Bidirectional communication

If two (or more) devices are connected to the same open collectorsignal, then the signal can be an input or an output for both.

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Bidirectional communication

If two (or more) devices are connected to the same open collectorsignal, then the signal can be an input or an output for both.

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 thecurrent 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-upresistor 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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 thecurrent 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-upresistor 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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 thecurrent 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-upresistor 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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-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 thecurrent 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-upresistor 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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output lowCalculating Rmin

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output lowCalculating Rmin

1 0X

When the output is low, Rmin = (Vcc − VOL) / (IOL)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output lowCalculating Rmin

1 0X

When the output is low, Rmin = (Vcc − VOL) / (IOL)(If R were smaller, the output couldn’t be kept low.)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output lowCalculating Rmin

1 1

IILX

If another gate follows, then the output has to sink from boththe resistor and the gate input, so the current through R mustbe REDUCED.

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output lowCalculating Rmin

1 1

IILX

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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output lowCalculating Rmin

2 1

IILXX

When the output is low, Rmin = (Vcc − VOL) / (IOL − IIL)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output lowCalculating Rmin

2 1

IILXX

When the output is low, Rmin = (Vcc − VOL) / (IOL − IIL)Another gate with a wired-OR output won’t change thecurrent through R, since its output is floating.

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output lowCalculating Rmin

2 1

IILXX

When the output is low, Rmin = (Vcc − VOL) / (IOL − 2 × IIL)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output lowCalculating Rmin

3 2

IILXXX

When the output is low, Rmin = (Vcc − VOL) / (IOL − 2 × IIL)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output lowCalculating Rmin

3 3

IILXXX

When the output is low, Rmin = (Vcc − VOL) / (IOL − 3 × IIL)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output lowCalculating Rmin

M N

IILX

X

XX

When the output is low, Rmin = (Vcc − VOL) / (IOL − N × IIL)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output highCalculating Rmax

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output highCalculating Rmax

1 0

IIHX

When the output is high, Rmax = (Vcc − VOH) / (IOH)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output highCalculating Rmax

1 0

IIHX

When the output is high, Rmax = (Vcc − VOH) / (IOH)(If R were bigger, VOH wouldn’t be guaranteed.)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output highCalculating Rmax

1 1

IIHX

If another gate follows, then the current has to pull both theresistor and the gate input HIGH, so the current through Rmust be INCREASED.

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output highCalculating Rmax

1 1

IIHX

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 outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output highCalculating Rmax

2 1

IIHXX

Another gate with a wired-OR output will also need to bepulled HIGH, so the current must be INCREASED.

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output highCalculating Rmax

2 1

IIHXX

When the output is high,Rmax = (Vcc − VOH) / (2 × IOH + IIH)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output highCalculating Rmax

2 2

IIHXX

When the output is high,Rmax = (Vcc − VOH) / (2 × IOH + 2 × IIH)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output highCalculating Rmax

3 2

IIHXXX

When the output is high,Rmax = (Vcc − VOH) / (3 × IOH + 2 × IIH)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output highCalculating Rmax

3 3

IIHXXX

When the output is high,Rmax = (Vcc − VOH) / (3 × IOH + 3 × IIH)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

Pull-up Resistor; output highCalculating Rmax

M N

IIHXXX

X

When the output is high,Rmax = (Vcc − VOH) / (M × IOH + N × IIH)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

So, to summarize:

Rmin = (Vcc − VOL) / (IOL − N × IIL)Rmax = (Vcc − VOH) / (M × IOH + N × IIH)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

So, to summarize:Rmin = (Vcc − VOL) / (IOL − N × IIL)

Rmax = (Vcc − VOH) / (M × IOH + N × IIH)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

More currentMixing logic familiesWire ANDing of outputsBidirectional communicationPull-up Resistor Calculations

So, to summarize:Rmin = (Vcc − VOL) / (IOL − N × IIL)Rmax = (Vcc − VOH) / (M × IOH + N × IIH)

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

CMOS Output circuit

CMOS output

VDD

Vout

Two transistorsOnly one on at one time

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

CMOS Output circuit

CMOS output

VDD

Vout

Two transistorsOnly one on at one time

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

CMOS Output circuit

CMOS output

VDD

Vout

Two transistors

Only one on at one time

Terry Sturtevant Electronics Logic Gates: Open Collector Output

Totem pole outputsOpen collector outputs

Open Collector AdvantagesCMOS outputs

CMOS Output circuit

CMOS output

VDD

Vout

Two transistorsOnly one on at one time

Terry Sturtevant Electronics Logic Gates: Open Collector Output