How to decide on the segmentation of current steering DAC ?

[rajanarender_suram]

How to decide on the segmentation of current steering DAC ?

Please give me insights

 

[analog_prodigy]

maximum glitch energy +current steering dac

I have some bookish idea on current steering dac.
but, what is segmentation?

 

[hzqziggy]

Re: DAC segmentation

you need to consider the tradeoff between binary and thermometer coded current steering DAC. what is the resolution bit do you want ?

 

[lladnar23]

DAC segmentation

Read the following paper:
C.-H. Lin, K. Bult, "A 10-b, 500MSample/s CMOS DAC in 0.6mm^2," IEEE JSSC, Vol 33, pp. 1948-1958, Dec 1998.

You arrange the segmentation according to your requirements for INL and DNL and area.
(thermometer has better INL, DNL, but binary has lower area due to the less complicated wiring)

 

[rajanarender_suram]

DAC segmentation

is the segmentation only area constraint??? or something other

 

[mahgoub]

DAC segmentation

what is segmentation

 

[rfsystem]

Re: DAC segmentation

Segmentation is the division of the encoding into first thermometer encoding and binary encoding.

For instance a "8-bit multiplying current DAC" is divided into 3bit thermometer encoded and 5bit binary encoded. So the first 3 MSB bits control the switches to 8 resistors and the 5LSB bits control the switches to the R2R ladder.

The decision is based on total area for given yield.

Work Procedure:

1. Design with a math tool e.g Matlab
2. Get the matching versus area coefficient
3. Design a component vector for each e.g resistor (1Ohm nominal resistance)
4. Assign area scaling variables to the thermometer and each branch of the binary encoded component
5. Write calculation procedure for DAC value depending on code
6. Write a procedure which measures INL and DNL, min, max, mean
7. Write a procedure which make mismatches to the components
8. Run many mismatched DAC's to estimate the yield for e.g. INL, DNL specs
9. Adjust the area scaling coeffcients to get a less area design

Finally:
You will get a area scaling with minimum total area for given total (MSB+LSB) number of bits.

The area scaling does not include spacing between components and fill or compaction losses. But is a good initial guess and runs in minutes after having the script.

 

[rajanarender_suram]

DAC segmentation

do any body have matlab code for this analysis

 

[tarun_taurus]

DAC segmentation

Segmentation of current steering DAC depends on :
1. area (can be estimated my calc no. of current cells)
2. power (what will be LSB,MSB etc current spec. for resolution)
3. matching (spl. lower than 130nm)
4.glitch energy--> critical in deciding upon segmentation.
5. resolution needed.(basically depends on matching)

 

[rajanarender_suram]

DAC segmentation

i have a dac Ip in our company 10bit(7+3 segmentation)

lsb current =18uA
INL=+-2LSB
DNL=+-1/2 LSB
Rload=37.5 Ohm
330Mhz clock freq
glitch dont remember???
Now can any one explain how they have arrived to the segmentation plan? also 7 MSB is 2-d thermometer coded and 3LSB is 1-d Thermometer coded...

 

[ashish_chauhan]

Re: DAC segmentation

I have some idea about segmentation and thermometer encoding , but can you please elaborate on what is 2d or 3d encoding... please give a small exmaple if possible

thanx

 

[rfsystem]

Re: DAC segmentation

2d and 1d is possible referring the layout structure.

So there is no segmentation in schematic but only in layout.

 

[shriraj19]

Re: maximum glitch energy +current steering dac

I have some bookish idea on current steering dac.
but, what is segmentation?

segmentation means the main dac is consist of different sub dacs working parally..

---------- Post added at 07:28 ---------- Previous post was at 07:24 ----------

paper referenced above ,doesn't tells how INL is related to unit area(table1)?can anyone tell me that how INL/DNL of a DAC is related to area of unit current cell?