IEEE Solid-State Circuits Magazine - Summer 2015 - 44

stage (with no matching required
between the capacitors in one stage
and those in the next). Thus, highresolution SAR ADCs tend to occupy
a large area if the DAC unit capacitor
size is dictated by matching requirements rather than by kT/C noise.
Third, the lack of residue amplification means that the comparator
input noise can limit the performance, as is typical for resolutions
of 8 bits and above. A low-noise
comparator's response time and
power dissipation can far exceed
those of a standard design.
Pipelined and SAR architectures
also share some issues: the matching
of the capacitors must be commensurate with the resolution unless
digital calibration is employed, and
the circuit generating VREF must
exhibit fast settling and low noise.

Logic

Vin

VDAC1

VDAC2

VDAC3

DAC1

DAC2

DAC3

Register

Register

Register

Figure 11: Simple 2-bit/cycle SAR ADC.

response time, t comp, the logic
delay, t logic, and the settling of the
DAC, t DAC . In the 1-bit/cycle architecture studied thus far, one conversion period is approximately
equal to N (t comp + t logic + t DAC) . For
a given CMOS technology node,
each of these three components
has a lower bound regardless of (or
weakly dependent on) the power

dissipation, thereby limiting the
ADC's speed.
Second, the SAR ADC imposes
on its DAC both a high accuracy
and a high resolution. For example,
a 10-bit design requires 1,024 unit
capacitors, or 2,048 if the system
is fully differential. By comparison,
the pipelined topology of Figure 5(c)
incorporates only two capacitors per

SAR Speed Improvement
The conversion speed of SAR ADCs
can be improved through the use of
various techniques [16]-[24]. Three
are described here.
The first and most obvious approach
is to interleave two or more channels
and proportionally raise the conversion
rate. The generic interleaving issues
apply here as well, including area and
input capacitance penalty and the problem of interchannel mismatches. Also

Pipelined and SAR ADC architectures
date back to the mid-1900s.

32

32

31

33

28
24

VDAC (LSB)

VDAC (LSB)

Vin1 = 23.5 LSB

16

24

25
23

21
18

16

15

Vin1 = 12.5 LSB
8

8

t1

t2

t

t1

t2

(a)
Figure 12: (a) SAR response with incomplete DAC settling and (b) use of redundancy to correct the error.

44

s u m m E r 2 0 15

IEEE SOLID-STATE CIRCUITS MAGAZINE

t3
(b)

t



Table of Contents for the Digital Edition of IEEE Solid-State Circuits Magazine - Summer 2015

IEEE Solid-State Circuits Magazine - Summer 2015 - Cover1
IEEE Solid-State Circuits Magazine - Summer 2015 - Cover2
IEEE Solid-State Circuits Magazine - Summer 2015 - 1
IEEE Solid-State Circuits Magazine - Summer 2015 - 2
IEEE Solid-State Circuits Magazine - Summer 2015 - 3
IEEE Solid-State Circuits Magazine - Summer 2015 - 4
IEEE Solid-State Circuits Magazine - Summer 2015 - 5
IEEE Solid-State Circuits Magazine - Summer 2015 - 6
IEEE Solid-State Circuits Magazine - Summer 2015 - 7
IEEE Solid-State Circuits Magazine - Summer 2015 - 8
IEEE Solid-State Circuits Magazine - Summer 2015 - 9
IEEE Solid-State Circuits Magazine - Summer 2015 - 10
IEEE Solid-State Circuits Magazine - Summer 2015 - 11
IEEE Solid-State Circuits Magazine - Summer 2015 - 12
IEEE Solid-State Circuits Magazine - Summer 2015 - 13
IEEE Solid-State Circuits Magazine - Summer 2015 - 14
IEEE Solid-State Circuits Magazine - Summer 2015 - 15
IEEE Solid-State Circuits Magazine - Summer 2015 - 16
IEEE Solid-State Circuits Magazine - Summer 2015 - 17
IEEE Solid-State Circuits Magazine - Summer 2015 - 18
IEEE Solid-State Circuits Magazine - Summer 2015 - 19
IEEE Solid-State Circuits Magazine - Summer 2015 - 20
IEEE Solid-State Circuits Magazine - Summer 2015 - 21
IEEE Solid-State Circuits Magazine - Summer 2015 - 22
IEEE Solid-State Circuits Magazine - Summer 2015 - 23
IEEE Solid-State Circuits Magazine - Summer 2015 - 24
IEEE Solid-State Circuits Magazine - Summer 2015 - 25
IEEE Solid-State Circuits Magazine - Summer 2015 - 26
IEEE Solid-State Circuits Magazine - Summer 2015 - 27
IEEE Solid-State Circuits Magazine - Summer 2015 - 28
IEEE Solid-State Circuits Magazine - Summer 2015 - 29
IEEE Solid-State Circuits Magazine - Summer 2015 - 30
IEEE Solid-State Circuits Magazine - Summer 2015 - 31
IEEE Solid-State Circuits Magazine - Summer 2015 - 32
IEEE Solid-State Circuits Magazine - Summer 2015 - 33
IEEE Solid-State Circuits Magazine - Summer 2015 - 34
IEEE Solid-State Circuits Magazine - Summer 2015 - 35
IEEE Solid-State Circuits Magazine - Summer 2015 - 36
IEEE Solid-State Circuits Magazine - Summer 2015 - 37
IEEE Solid-State Circuits Magazine - Summer 2015 - 38
IEEE Solid-State Circuits Magazine - Summer 2015 - 39
IEEE Solid-State Circuits Magazine - Summer 2015 - 40
IEEE Solid-State Circuits Magazine - Summer 2015 - 41
IEEE Solid-State Circuits Magazine - Summer 2015 - 42
IEEE Solid-State Circuits Magazine - Summer 2015 - 43
IEEE Solid-State Circuits Magazine - Summer 2015 - 44
IEEE Solid-State Circuits Magazine - Summer 2015 - 45
IEEE Solid-State Circuits Magazine - Summer 2015 - 46
IEEE Solid-State Circuits Magazine - Summer 2015 - 47
IEEE Solid-State Circuits Magazine - Summer 2015 - 48
IEEE Solid-State Circuits Magazine - Summer 2015 - 49
IEEE Solid-State Circuits Magazine - Summer 2015 - 50
IEEE Solid-State Circuits Magazine - Summer 2015 - 51
IEEE Solid-State Circuits Magazine - Summer 2015 - 52
IEEE Solid-State Circuits Magazine - Summer 2015 - 53
IEEE Solid-State Circuits Magazine - Summer 2015 - 54
IEEE Solid-State Circuits Magazine - Summer 2015 - 55
IEEE Solid-State Circuits Magazine - Summer 2015 - 56
IEEE Solid-State Circuits Magazine - Summer 2015 - 57
IEEE Solid-State Circuits Magazine - Summer 2015 - 58
IEEE Solid-State Circuits Magazine - Summer 2015 - 59
IEEE Solid-State Circuits Magazine - Summer 2015 - 60
IEEE Solid-State Circuits Magazine - Summer 2015 - 61
IEEE Solid-State Circuits Magazine - Summer 2015 - 62
IEEE Solid-State Circuits Magazine - Summer 2015 - 63
IEEE Solid-State Circuits Magazine - Summer 2015 - 64
IEEE Solid-State Circuits Magazine - Summer 2015 - 65
IEEE Solid-State Circuits Magazine - Summer 2015 - 66
IEEE Solid-State Circuits Magazine - Summer 2015 - 67
IEEE Solid-State Circuits Magazine - Summer 2015 - 68
IEEE Solid-State Circuits Magazine - Summer 2015 - 69
IEEE Solid-State Circuits Magazine - Summer 2015 - 70
IEEE Solid-State Circuits Magazine - Summer 2015 - 71
IEEE Solid-State Circuits Magazine - Summer 2015 - 72
IEEE Solid-State Circuits Magazine - Summer 2015 - 73
IEEE Solid-State Circuits Magazine - Summer 2015 - 74
IEEE Solid-State Circuits Magazine - Summer 2015 - 75
IEEE Solid-State Circuits Magazine - Summer 2015 - 76
IEEE Solid-State Circuits Magazine - Summer 2015 - 77
IEEE Solid-State Circuits Magazine - Summer 2015 - 78
IEEE Solid-State Circuits Magazine - Summer 2015 - 79
IEEE Solid-State Circuits Magazine - Summer 2015 - 80
IEEE Solid-State Circuits Magazine - Summer 2015 - 81
IEEE Solid-State Circuits Magazine - Summer 2015 - 82
IEEE Solid-State Circuits Magazine - Summer 2015 - 83
IEEE Solid-State Circuits Magazine - Summer 2015 - 84
IEEE Solid-State Circuits Magazine - Summer 2015 - 85
IEEE Solid-State Circuits Magazine - Summer 2015 - 86
IEEE Solid-State Circuits Magazine - Summer 2015 - 87
IEEE Solid-State Circuits Magazine - Summer 2015 - 88
IEEE Solid-State Circuits Magazine - Summer 2015 - Cover3
IEEE Solid-State Circuits Magazine - Summer 2015 - Cover4
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2019
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2019
https://www.nxtbook.com/nxtbooks/ieee/mssc_2019summer
https://www.nxtbook.com/nxtbooks/ieee/mssc_2019winter
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018fall
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018summer
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018spring
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018winter
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2014
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2014
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2014
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2014
https://www.nxtbookmedia.com