EE 435

Lecture 39

DAC DesignString DACs – wrap up

Current Steering DACs

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 129 (4/18/18)

Review from Last Lecture

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

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,

Switch Implementation Issues

n-channel

p-channel

T-gate

Switch Implementation Issues

n-channel

p-channel

T-gate

End of Lecture 39