digital integrated circuits - bandi.cbnu.ac.kr
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Digital Integrated Digital Integrated Digital Integrated Digital Integrated CircuitsCircuits
D i i S ti lD i i S ti lDesigning SequentialDesigning SequentialLogic CircuitsLogic Circuitsgg
© Digital Integrated Circuits2ndSequential Circuits
Sequential LogicSequential LogicSequential LogicSequential Logic
© Digital Integrated Circuits2ndSequential Circuits
Naming ConventionsNaming ConventionsNaming ConventionsNaming Conventions
In our text:a latch is level sensitivea latch is level sensitivea register is edge-triggered
There are many different namingThere are many different naming conventions
F i b k ll dFor instance, many books call edge-triggered elements flip-flopsThi l d t f i hThis leads to confusion however
© Digital Integrated Circuits2ndSequential Circuits
Latch versus RegisterLatch versus RegisterLatch versus RegisterLatch versus RegisterLatch RegisterLatchstores data when clock is low
Registerstores data when clock rises
D Q D Q
clock rises
Clk Clk
Clk Clk
DD D
Q Q
© Digital Integrated Circuits2ndSequential Circuits
Q Q
LatchesLatchesLatchesLatches
© Digital Integrated Circuits2ndSequential Circuits
LatchLatch--Based DesignBased DesignLatchLatch--Based DesignBased Design
• N latch is transparentwhen φ = 0
• P latch is transparent when φ = 1
φφ
φ
NLatch Logic P
LatchLatch Latch
Logic
© Digital Integrated Circuits2ndSequential Circuits
Timing DefinitionsTiming DefinitionsTiming DefinitionsTiming Definitions
CLK
t
CLK
tholdtsu
RegisterD Q
t
D
tc - q
DATASTABLE
CLK
t
Q DATASTABLE
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Characterizing TimingCharacterizing TimingCharacterizing TimingCharacterizing Timing
© Digital Integrated Circuits2ndSequential Circuits
Maximum Clock FrequencyMaximum Clock FrequencyMaximum Clock FrequencyMaximum Clock Frequency
s
φ
FF’
LOGIC Also:
tp,combtcdreg + tcdlogic > thold
tcd: contamination delay = minimum propagation minimum propagation delaytclk-Q + tp,comb + tsetup = T
© Digital Integrated Circuits2ndSequential Circuits
Positive Feedback: BiPositive Feedback: Bi--StabilityStabilityPositive Feedback: BiPositive Feedback: Bi--StabilityStability
Vo1
Vo1Vo
Vi25Vo
i25Vo1
Vi2
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MetaMeta--StabilityStabilityMetaMeta--StabilityStability
© Digital Integrated Circuits2ndSequential Circuits
Writing into a Static LatchWriting into a Static LatchWriting into a Static LatchWriting into a Static Latch
© Digital Integrated Circuits2ndSequential Circuits
MuxMux--Based LatchesBased LatchesMuxMux--Based LatchesBased LatchesNegative latch Positi e latchg(transparent when CLK= 0)
Positive latch(transparent when CLK= 1)
1
0D
Q 0
1D
Q
0D
CLK
1D
CLK CLK
InClkQClkQ ⋅+⋅= InClkQClkQ ⋅+⋅=
© Digital Integrated Circuits2ndSequential Circuits
MuxMux--Based LatchBased LatchMuxMux--Based LatchBased Latch
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MuxMux--Based LatchBased LatchMuxMux--Based LatchBased Latch
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MasterMaster--Slave (EdgeSlave (Edge--Triggered) Triggered) ( g( g gg )gg )RegisterRegister
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MasterMaster--Slave RegisterSlave RegisterMasterMaster--Slave RegisterSlave Register
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ClkClk--Q DelayQ DelayClkClk--Q DelayQ Delay
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Setup TimeSetup TimeSetup TimeSetup Time
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Reduced Clock Load Reduced Clock Load MasterMaster--Slave RegisterSlave Register
CLK CLK
D T I
CLK
T
CLK
ID QT1 I 1 T2
I2
I 3
I4CLK CLK
I2 I4
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Avoiding Clock OverlapAvoiding Clock OverlapAvoiding Clock OverlapAvoiding Clock OverlapCLK X CLK
AB
D
Q
CLK
(a) Schematic diagramCLK
CLK
(b) Overlapping clock pairs
CLK
© Digital Integrated Circuits2ndSequential Circuits
Avoiding Clock OverlapAvoiding Clock OverlapAvoiding Clock OverlapAvoiding Clock OverlapCLK X CLK
AB
D
Q
CLK
(a) Schematic diagramCLK
CLK
CLK
CLK
(b) Two-phase non-overlapping clock pairs
© Digital Integrated Circuits2ndSequential Circuits
Solving leakage problem using Solving leakage problem using multiplemultiple--threshold CMOSthreshold CMOS
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CrossCross--Coupled PairsCoupled PairsCrossCross--Coupled PairsCoupled Pairs
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CrossCross--Coupled NANDCoupled NANDCrossCross--Coupled NANDCoupled NAND
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Sizing IssuesSizing IssuesSizing IssuesSizing IssuesM2 vs. M5+M6 ?M2 vs. M5 M6 ?
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Storage MechanismsStorage MechanismsStorage MechanismsStorage Mechanisms
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Making a Dynamic Latch PseudoMaking a Dynamic Latch Pseudo--StaticStaticMaking a Dynamic Latch PseudoMaking a Dynamic Latch Pseudo--StaticStatic
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More Precise Setup TimeMore Precise Setup TimeMore Precise Setup TimeMore Precise Setup Time
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Setup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsCircuit before clock arrival (Setup-1 case)
Clk Q D l
Circuit before clock arrival (Setup 1 case)CN
Inv2TG1
Clk-Q Delay
DQ MD1 SM
Inv1
Inv2
TClk-Q
CP
TSetup-1 Time
ClockDataT
Time
TSetup-1
© Digital Integrated Circuits2ndSequential Circuits
t=0
Setup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsCircuit before clock arrival (Setup 1 case)
Clk Q D l
CN
Inv2TG1
Circuit before clock arrival (Setup-1 case)
Clk-Q Delay
DQ MD1 SM
Inv1
Inv2
TClk-QCP
TSetup-1 Time
ClockDataT
Time
TSetup-1
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Timet=0
Setup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsCi it b f l k i l (S t 1 )
Clk Q D l
Circuit before clock arrival (Setup-1 case)CN
Inv2TG1
Clk-Q Delay
DQ MD1 SM
Inv1
Inv2
TClk-Q
CP
TSetup-1 Time
ClockDataT
Time
TSetup-1
© Digital Integrated Circuits2ndSequential Circuits
et=0
Setup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsCircuit before clock arrival (Setup-1 case)
Clk Q Delay
CN
Inv2TG1
Circuit before clock arrival (Setup-1 case)
Clk-Q Delay
DQ MD1 SM
Inv1
Inv2
TClk-Q
CP
TSetup-1 Time
ClockData
Time
TSetup-1
© Digital Integrated Circuits2ndSequential Circuits
Timet=0
Setup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsCircuit before clock arrival (Setup-1 case)
CN
Inv2TG1
Circuit before clock arrival (Setup-1 case)
Clk Q Delay
DQ MD1 SM
Inv1
Inv2 Clk-Q DelayTClk-Q
CP
ClockDataTSetup-1 Time
Time
TSetup-1
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Timet=0
Setup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsHold-1 caseHold-1 case
CN
Inv2TG1 Clk-Q Delay
DQ MD1 SM
Inv1
Inv2
CP0
TClk-Q
DataClockTHold-1 Time
Timet 0
THold-1
© Digital Integrated Circuits2ndSequential Circuits
Timet=0
Setup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsHold-1 case
Clk-Q Delay
Hold-1 caseCN
Inv2TG1
DQ MD1 SM
Inv1
Inv2
TClk-Q
CP0
THold-1 Time
DataClock
Timet 0
THold-1
© Digital Integrated Circuits2ndSequential Circuits
Timet=0
Setup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsHold-1 case
Clk-Q Delay
CN
Inv2TG1
Hold-1 case
DQ MD1 SM
Inv1
Inv2
TClk-QCP
0
THold-1 Time
DataClock
Timet 0
THold-1
© Digital Integrated Circuits2ndSequential Circuits
Timet=0
Setup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsH ld 1
Clk-Q Delay
CN
Inv2TG1
Hold-1 case
T
DQ MD1 SM
Inv1
Inv2
TClk-Q
CP0
THold-1 Time
Clock Data
Timet 0
THold-1
© Digital Integrated Circuits2ndSequential Circuits
Timet=0
Setup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsSetup/Hold Time IllustrationsHold-1 case
Clk-Q Delay
CN
Inv2TG1
Hold-1 case
TClk-Q
DQ MD1 SM
Inv1
Inv2
CP0
THold-1 Time
Clock Data
Timet 0
THold-1⇒
© Digital Integrated Circuits2ndSequential Circuits
Timet=0
Other Latches/Registers: COther Latches/Registers: C22MOSMOSOther Latches/Registers: COther Latches/Registers: C MOSMOSClocked CMOS
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Insensitive to ClockInsensitive to Clock--OverlapOverlapInsensitive to ClockInsensitive to Clock--OverlapOverlap
M2
VDD
M6
VDD
M2
VDD
M6
VDD
M40 0X
M8X
D QX
M3
D Q
1
X
M71
M1 M5 M1 M5
(a) (0-0) overlap (b) (1-1) overlap
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PipeliningPipeliningPipeliningPipelining
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Other Latches/Registers: TSPCOther Latches/Registers: TSPCOther Latches/Registers: TSPCOther Latches/Registers: TSPC
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Including Logic in TSPCIncluding Logic in TSPCIncluding Logic in TSPCIncluding Logic in TSPC
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TSPC RegisterTSPC RegisterTSPC RegisterTSPC Register
© Digital Integrated Circuits2ndSequential Circuits
PulsePulse--Triggered LatchesTriggered LatchesA Alt ti A hA Alt ti A hAn Alternative ApproachAn Alternative ApproachWays to design an edge-triggered sequential cell:
Master-Slave Latches
Pulse-Triggered LatchLatches
D Q D QData
D QData
LatchL1 L2 L
D
Clk
Q D
Clk
Q D
Clk
Q
Clk
Clk
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Pulsed LatchesPulsed LatchesPulsed LatchesPulsed Latches
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Pulsed LatchesPulsed LatchesPulsed LatchesPulsed Latches
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Hybrid LatchHybrid Latch--FF TimingFF TimingHybrid LatchHybrid Latch--FF TimingFF Timing
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SenseSense--Amplifier Based FlipAmplifier Based Flip--FlopFlopSenseSense--Amplifier Based FlipAmplifier Based Flip--FlopFlop
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SenseSense--Amplifier Based FlipAmplifier Based Flip--FlopFlopSenseSense--Amplifier Based FlipAmplifier Based Flip--FlopFlop
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LatchLatch--Based PipelineBased PipelineLatchLatch--Based PipelineBased Pipeline
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NonNon--Bistable Sequential Circuits─Bistable Sequential Circuits─NonNon Bistable Sequential CircuitsBistable Sequential CircuitsSchmitt TriggerSchmitt Trigger
Vout VOHIn Out
VOL•VTC with hysteresis
•Restores signal slopes
VinVM– VM+
Restores signal slopes
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Noise Suppression using Schmitt Noise Suppression using Schmitt pp gpp gTriggerTrigger
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CMOS Schmitt TriggerCMOS Schmitt TriggerCMOS Schmitt TriggerCMOS Schmitt Trigger
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Schmitt Trigger Sim lated VTCSchmitt Trigger Sim lated VTCSchmitt Trigger Simulated VTCSchmitt Trigger Simulated VTC
2.5 2.5
V
2.0 2.0
VX(V) VM2
VM11.5
1.0 Vx(V) k = 1
1.5
1.0V
0.5
Vk = 2
k = 3
k = 40.5
Vin (V)
Voltage-transfer characteristics with hysteresis. The effect of varying the ratio of the
0.00.0 0.5 1.0 1.5 2.0 2.5
Vin (V)
0.00.0 0.5 1.0 1.5 2.0 2.5
© Digital Integrated Circuits2ndSequential Circuits
g y y gPMOS device M4. The width is k* 0.5 m.m
CMOS Schmitt Trigger (2)CMOS Schmitt Trigger (2)CMOS Schmitt Trigger (2)CMOS Schmitt Trigger (2)
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Multivibrator CircuitsMultivibrator CircuitsMultivibrator CircuitsMultivibrator CircuitsS
R
Bistable Multivibratorflip-flop, Schmitt Trigger
S
T
Monostable Multivibratorone-shot
Astable MultivibratorAstable Multivibratoroscillator
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TransitionTransition--Triggered MonostableTriggered MonostableTransitionTransition Triggered MonostableTriggered Monostable
DELAY
t
In
Outtd td
© Digital Integrated Circuits2ndSequential Circuits
Monostable Trigger (RCMonostable Trigger (RC--based)based)Monostable Trigger (RCMonostable Trigger (RC based)based)VDD
InOutA B
R
C (a) Trigger circuit.
In
B VM(b) Waveforms.
Out tt2t1
© Digital Integrated Circuits2ndSequential Circuits
1
Astable Multivibrators (Oscillators)Astable Multivibrators (Oscillators)Astable Multivibrators (Oscillators)Astable Multivibrators (Oscillators)
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Voltage Controller Oscillator (VCO)Voltage Controller Oscillator (VCO)Voltage Controller Oscillator (VCO)Voltage Controller Oscillator (VCO)
VDD
M4
VDD
M6
Schmitt Triggerrestores signal slopes
In
M1
M2
I I
M3M5
Vcontr Current starved inverter
Iref Iref
4
6
nsec
)
0.5 1.5 2.5Vcontr (V)
0.0
2
t pH
L (n
propagation delay as a functionof control voltage
© Digital Integrated Circuits2ndSequential Circuits
Differential Delay Element and VCODifferential Delay Element and VCO
vV V
in2v 1
v 2
v 3
v 4
Vo2 V o1
in1
two stage VCO
Vctrl
delay cell
1 5
2.0
2.5
3.0V1 V2 V 3 V4
0.0
0.5
1.0
1.5
simulated waveforms of 2-stage VCO
0.52 0.51.5
time (ns)2.5 3.5
© Digital Integrated Circuits2ndSequential Circuits
simulated waveforms of 2 stage VCO