emitter-coupled logic (ecl) - hacettepe universityusezen/ele312/ecl_gates-2sp.pdf ·...
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1
Emitter-Coupled Logic(ECL)
Basic ECL Inverter/Non-inverter(ECL Current Switch)
2
Basic ECL Inverter/Non-inverter VTC
VOH = VCC
According to inverting output: VINV
CIE
EE)ECL(BEIHCCOL R
RVVV
VV+−
−=
VIL = VBB – 0.05 VIH = VBB + 0.05
E
CI
EE)SAT(BEE
CI)SAT(BCCC
S
RR1
)VV(RRVV
V+
−++=
Example
Calculate the critical VTC points for the ECL current switch
VCC = 5V, VEE = 0V, VBB = 2.6V, RCI = RCR = RE = 1kΩ,
VBE(ECL) = 0.75V, VBE(SAT) = 0.8V, VBC(SAT) = 0.6V
VOH = 5V
VOL = 3.10V
VIL = 2.55V
VIH = 2.65V
VS = 3.2V
VINV (VIN = VS) = 2.6V
3
Basic ECL NOR/OR Gate
4
MECL I NOR/OR Gate
)ECL(BECIDNFCI
)ECL(BEEEOH VR
R)1(βRVV
V −++
−−=
)ECL(BECIE
EE)ECL(BEIHOL VR
RVVV
V −+−
−=
Example
Find the logical swing, noise margins and noise immunities for the MECL I circuit above.
βF = 49, VBE(ECL) = 0.75V, VBE(FA) = 0.75V, VBE(SAT) = 0.8V, VBC(SAT) = 0.6V
VOH = – 0.76V
VOL = – 1.55V
VIL = – 1.225V
VIH = – 1.125V
VS = – 0.29V
VLS = 0.79VVNMH = 0.365V
VNML = 0.325V
VNIH = 0.53V
VNIL = 0.475V
5
MECL I Fanout
⎥⎦
⎥⎢⎣
⎢=
IH
OH
IIN
RDN)FA(BN,EOH III −=
DN
EEOHRDN R
VVI +=
BN,BF)FA(BN,E I)1(βI +=
CI
)ECL(BN,BEOHBN,B R
VVI
−−=
1βIIF
REIH +=
E
EEERE R
VVI +=
)ECL(BEOHE VVV −=
Fan-out Example
Find the maximum fan-out for the MECL I circuit above
βF = 49, VBE(ECL) = 0.75V, VBE(FA) = 0.75V, VBE(SAT) = 0.8V, VBC(SAT) = 0.6V
Assume load gates reduce VOH by 0.03 volts.
VOH = – 0.79V IRDN = 2.205 mA
IB,BN = 148 μA
IE,BN = 7.4 mA
IOH = 5.2 mA
VE = -1.54 V
IRE = 2.95 mA
IIH = 59 μA
87IINIH
OH =⎥⎦
⎥⎢⎣
⎢=
6
Power Dissipation Example
Find the average power dissipated in the MECL I circuit above
IRE(NOH) = 2.64 mA
IRDN(NOH) = 2.22 mA
IEE(NOH) = 6.685 mA
IRDO(NOH) = 1.825 mA
IRE(NOL) = 2.98 mA
IRDN(NOL) = 1.825 mA
IEE(NOL) = 7.035 mA
IRDO(NOL) = 2.22 mA
PEE(avg) = 35.6 mW
Other ECL Gates
7
DeMorgan’s Theorems
• NOR and OR using ANDs and NANDs
– NOR:
– OR:
• NAND and AND using ORs and NORs
– NAND:
– AND:
BABA ⋅=+
BABA ⋅=+
BABA +=⋅
BABA +=⋅
Example
Implement the following logic using only ECL gates
)DC)(BA( ++
Solution:
)DC()BA()DC)(BA( +++≡++
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Collector Dotting Wired-AND Gates
Complex Logic Gates with Collector Dotting
9
Example
Series Gating – Basic ECL NAND/AND Current Switch
10
Series Gating NAND/AND Gate
Complex Logic Gates with Series Gating
11
Example
ECL XOR/XNOR Gates
12
ECL Decoding Tree
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