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EE 435
Lecture 37
• String DAC
• Current Steering DACs
A
B
W
L
22
R
N
CC
TOPC
A
A
Top Plate
Bottom Plate
2
2
N
N
R
R
A
WL
G
D
S
W
L
ID
2 2 2 2
03
1 4
D
DN
I VT COX
EBI
A A AWL V
Matching Properties of Circuit Components
• If edge roughness effects are neglected, standard deviation of components
proportional to
• INL and DNL of most data converters (at low f) depends upon matching
characteristics of basic circuit components
• Often INL and DNL proportional to standard deviation
• Each additional bit of ENOB generally requires a factor of 2 reduction in σ
Each additional bit of ENOB generally requires a factor of 4 increase in area
in matching critical circuits !!
N
X
X
Review from Last Lecture
R-String DAC
VOUT
n
2
n
2
MS
B R
ow
De
co
de
r
n1
n2LSB Analog MUX
VREF
Review from Last Lecture
R-String DAC
RC
RF RF RF RF
RFRFRF RF
VREF
RC
RF RF RF RF
RFRFRF RF
RC
RF RF RF RF
RFRFRF RF
RC
RF RF RF RF
RFRFRF RF
n1
XIN
n2
n
1 2n = n :n
Co
lum
n D
eco
de
r
Ro
w D
eco
de
r
VOUT
Note Dual Ladder is used !
Review from Last Lecture
Cited by 51 (4/5/10)
Cited by 94 (4/6/14)
Cited by 109 (4/5/16)
Cited by 130 (4/24/19)
Pelgrom Paper Assessment
Pelgrom Paper Assessment
Pelgrom Paper Assessment
Pelgrom Paper Assessment
Pelgrom Paper Assessment
Pelgrom Paper Assessment
Pelgrom Paper Assessment
Pelgrom Paper Assessment
Another key paper for matching-critical circuits:
2401 on Apr 7 2014
3452 on Apr 18 2018
Second most cited paper in the IEEE Journal of Solid State Circuits
Most cited basic research paper in IEEE Journal of Solid State Circuits
3528 on Apr 17 2019
Basic R-String DAC R
M1
R
M2
R
MN-2
R
MN-1
R
MN
VRFF
VOUT
n
XIN
Binary to
Thermometer
Decoder
2n
d1
d2
dN-2
dN-1
dN
CL
R
M1
R
M2
R
MN-2
R
MN-1
R
MN
VRFF
VOUT
n
XIN
Binary to
Thermometer
Decoder
2n
d1
d2
dN-2
dN-1
dN
CL
LATCH
CLK
Latching Boolean Signal Can Reduce/Eliminate Logic Transients which Cause Distortion
Load
Transfer
XIN
Basic R-String DAC
• Another Segmented DAC structure
• Can be viewed as a “dither” DAC
• Often n1 is much smaller than n2
• Dither can be used in other applications as well
R
R
R
R
R
R
R
R/4
R/4
R/4
R/4
1b
2b
R/4
R/4
R/4
1b
2b
VREF
Re
sis
tors
n1 b
its
n1 b
its
n2 b
its
2n2
-1
VOUT
RL
RU
RU+RL=RFor all b1 and b2,
End of Lecture 37