i/o pads in, out, inout, gnd, vdd, source follower
TRANSCRIPT
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I/O PADSI/O PADS
In, Out , InOut , In, Out , InOut , Gnd , Vdd,Gnd , Vdd,
Source followerSource follower
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Bidirectional Pad -Bidirectional Pad -Digital Component.Digital Component.
•Operates as Pad_in or Pad_out:
•EO high => pad out.
•EO low => pad in.
pad
dataInUnBuff
dataOut
EO
DataIn
DataInB PadBidirHE_SCMOS
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Pad LayoutPad Layout
DataIn OE DataOu
tDataInUnBufDataInBu
f
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Pad In DC AnalysisPad In DC Analysis
DataInB, after one inverter, has less gain than dataIn
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
vpad (V)
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Vol
tage
(V
)
v(dataInB)v(dataIn)v(pad)
simIn
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Max frequency 100MhzMax frequency 100Mhz
•Dx = 4.11nsec (>80%*5=4nsec)
•Cursers mark position where output exceed 80% of max input value
0 1 2 3 4 5 6 7 8 9 10 11
Time (ns)
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Vol
tage
(V
)
v(dataInB)
3.98
v(dataIn)
122.11m
v(Pad)
0.00
x1= x2= dx=6.05n 10.16n 4.11nsimIn
•VinBar
•Vin
•Vpad
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Pad out Dc AnalysisPad out Dc Analysis
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
vdataout (V)
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Vol
tage
(V
)
v(pad)v(dataout)
simOut
DataOut
Pad
Data
InB DataIn
Data
InUn
Buf
OE
OE
OEB
OEB
R=10
0
T0L=2u
W=22uT0L=2u
W=22uT0L=2u
W=22uT0L=2u
W=22u
T0L=2u
W=22u
T0L=2u
W=22u
BONDING
PAD
T0L=2u
W=22uT0L=2u
W=22uT0L=2u
W=22uT0L=2u
W=22u
T0L=2u
W=22u
T0L=2u
W=22u
•Response similar to dataIn.
•Explanation: It has two levels of amplifying, as the dataIn node.
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
vpad (V)
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Vol
tage
(V
)
v(dataInB)v(dataIn)v(pad)
simIn
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0 5 10 15 20 25 30 35 40
Time (ns)
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Vol
tage
(V
)
v(Pad)4.10
v(dataout)0.00
x1= x2= dx=4.81n 18.87n 14.06nsimOut
Max frequency 30Mhz Max frequency 30Mhz with 10pF capacitor as with 10pF capacitor as
loadload•Vpad
•DataOut
Dx = 14.06nsec (> 80%*17=13.6nsec)Cursors mark position where output exceed 80% of max input value
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SfSf with no ideal current with no ideal current sourcesource
•Function: Pad follows Signal, with DC offset.
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SFSF LayoutLayout
Signal
Vdd
Vss
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SF behavior (with the pmos SF behavior (with the pmos as current source) as current source)
•Current source values -190 to -150 uA
•0<Vin<4 volt, the SF follow the input with 0.85 V offset.
3.5V
4 V
0 .0 0 .5 1 .0 1 .5 2 .0 2 .5 3 .0 3 .5 4 .0 4 .5 5 .0
vs (V)
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
3 .5
4 .0
4 .5
5 .0
Volta
ge (V
)
v (sig n al)
v (Pad )
simSF_no_ideal_current
0 .0 0 .5 1 .0 1 .5 2 .0 2 .5 3 .0 3 .5 4 .0 4 .5 5 .0
vs (V)
-1 5 0
-1 0 0
-5 0
-0
Curre
nt (u
A)
i1 (M1 )
i1 (M2 )
i1 (M0 )
simSF_no_ideal_current
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Let’s have a closer look
Vpad – Vsignal = 0.85 constant when 0 < Vsignal <= 4
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
vs (V)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Vol
tage
(V
)
v(signal)
v(Pad)
c-b
simSF_no_ideal_current
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Slew Rate of the SFSlew Rate of the SF
0.0 0.5 1.0 1.5 2.0
Time (us)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Vol
tage
(V
)
v(Signal)
3.92
v(pad)
4.72
c-b
802.11m
x1= x2= dx=670.33n 1.22u 546.41nsimSF_no_ideal_current_slewRate_good
•Vsignal
•Vpad
•Vpad-Vsignal
Vsignal = ramp from 0 to 5v in 1usec
The SF still follow the step in the range of 0<VSignal<4volt
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Pad I/O With ESDPad I/O With ESD
•Two diodes are placed to protect the chip, and are normally at reverse charge.
•When signal exceeds 5+Vb volts, then D2 is forward biased and discharges the excess voltage.
•When signal is below –Vb, then a similar discharging process occurs through D1.
D2
D1
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PadIOEsd LayoutPadIOEsd Layout
Diode 1 D1 in schematic
Diode 2 D2 in scehematicsignal
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Modeling the PadModeling the Pad
The modeling was The modeling was done by attaching a done by attaching a capacitor, and a capacitor, and a resistor, to the pad. resistor, to the pad. They reperesent They reperesent the capacitance the capacitance and resistance of and resistance of three main models: three main models: Human, machine, Human, machine, and package.and package.
SIGNALSIGNAL
vinit
Gnd
V=5.0
R=1.5K
BONDING
PAD
Dpdiff
Dndiff
C=100pF
To run simulation, an initial voltage was To run simulation, an initial voltage was initialized on the model.initialized on the model.
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Human model.Human model.
R=1.5kΩ, C=100pF,Initial Voltage = 2kV
0 50 100 150 200 250 300 350 400 450 500
Time (ns)
0.5
1.0
1.5
2.0 V
olta
ge (
kV)
v (v in it)
simPadWithESD_human_modelnew
0 50 100 150 200 250 300 350 400 450 500
Time (ns)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Cur
rent
(A
)
i1 (R4 )
simPadWithESD_human_modelnew
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Machine Model.Machine Model.
R=25Ω, C=200pF,Initial Voltage = 200V
0 5 10 15 20 25 30 35 40 45 50
Time (ns)
0
50
100
150
200
Vol
tage
(V
)
v (v in it)
simPadWithESD_human_modelnew
0 5 10 15 20 25 30 35 40 45 50
Time (ns)
0
1
2
3
4
5
6
7
8
Cur
rent
(A
)
i1 (R4 )
simPadWithESD_human_modelnew
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Package ModelPackage Model
R=1Ω, C=1.5pF,Initial Voltage = 2kV
0 10 20 30 40 50 60 70 80 90 100
Time (ps)
0.0
0.5
1.0
1.5
2.0
Vol
tage
(kV
)v (v in it)
simPadWithESD_human_modelnew
0 10 20 30 40 50 60 70 80 90 100
Time (ps)
0.0
0.5
1.0
1.5
2.0
Cur
rent
(kA
)
i1 (R4 )
simPadWithESD_human_modelnew