Short Pulse Reading Concept An initial voltage (V+,V-) can be setup by the sensing

stage for the S.A. After the S.A is enabled, all initial points in the blue

region above MSL will be latched as “1”, all those in the red region below MSL will be latched as “0”.

However, MSL can vary widely due to mismatch, process and temperature variation, so any initial point in the MSLregion may result in reading error.

The key of short pulse reading is to effectively setup initial voltage points accordingly for the S.A, which should be as far way from the MSL region as possible.

The distance from initial voltage to the boundary of MSLregion is defined as noise margin.

1

Simulated MSL Variation

Direct sensing

Need to add capacitance to the input nodes of dynamic latch.

2

Visualization of Sensing Stage

TMR v.s. RM

Rp = 2.9kΩ, VDD=1V Increasing TMR can increase NM very effectively. For

practical TMR the NM is very small.

30 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

V+

V-

TMR= 50TMR= 75

TMR=100

TMR=150TMR=200

TMR=300

TMR=400

TMR=500TMR=600

TMR=700

TMR=800TMR=900

0 100 200 300 400 500 600 700 800 900-200

-150

-100

-50

0

50

100

150

TMR(%)

Noi

se M

argi

n (m

V)

Vp

Vap

Vap

Vp

Rpv.s. RM

TMR = 110%, VDD=1V

Only increasing Rp won’t help NM, since both Ip and Iap are affected.

40 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0

0.1

0.2

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1

V+

V-

Rp=0.5k

Rp= 1k

Rp=1.5k

Rp= 2k

Rp=2.5k

Rp= 3k

Rp=3.5k

Rp= 4k

Rp=4.5k

Rp= 5k

Rp= 6k

Rp= 7k

Rp= 8k

Rp= 9k

Rp= 10k

0 1 2 3 4 5 6 7 8 9 10-50

-40

-30

-20

-10

0

10

20

30

40

Rp(k)

Noi

se M

argi

n (m

V)

Sizing v.s. RM

Rp = 2.9kΩ, TMR = 110%, VDD=1V Purely increase the read current (e.g. by sizing the mirror

transistor), won’t help RM.

50 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0

0.1

0.2

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0.5

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1

V+

V-

W= 5umW= 7.5um

W= 10um

W=12.5um

W= 15um

W=17.5umW= 20um

W=22.5um

W= 25um

W=27.5umW= 30um

5 10 15 20 25 30-40

-30

-20

-10

0

10

20

30

40

W(m)

Noi

se M

argi

n (m

V)

Differential Sensing

Need to minimize the capacitance to the input nodes of dynamic latch.– The longer the sensing state is, the better.

6

Visualization of Sensing Stage

Reverse Sensing

Need to minimize the capacitance to the input nodes of dynamic latch.– The longer the sensing state is, the better.

7

Visualization of Sensing Stage

Differential Sensing NM

Need at least 2.5 ns to have worst case NM>0

8

1 2 3 4 5 6 7 8 9 10-250

-200

-150

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-50

0

50

100

150

200

250

Sensing Time (ns)

Noi

se M

argi

n (m

V)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

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1

V+

V-

1ns

2ns 3ns

4ns

5ns

6ns

7ns

8ns 9ns

10ns

Vap Vp

Vap

Vp

Reverse Sensing NM

NM is not symmetric, need to be optimized Need at least 2 ns to have worst case NM>0

9

1 2 3 4 5 6 7 8 9 10-500

-400

-300

-200

-100

0

100

200

300

400

500

Sensing Time (ns)

Noi

se M

argi

n (m

V)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0.5

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0.7

0.8

0.9

1

V+

V-

1ns

2ns 3ns

4ns

5ns

6ns

7ns

8ns 9ns

10nsVap

Vp

Vp

Vap

DS v.s. RS

10

1 2 3 4 5 6 7 8 9 10-150

-100

-50

0

50

100

150

200

250

300

Sensing Time (ns)

Noi

se M

argi

n (m

V)

NM of Vp (DS)

NM of Vap (DS)

NM of Vp (RS)

NM of Vap (RS)

1 2 3 4 5 6 7 8 9 10-150

-100

-50

0

50

100

150

200

Sensing Time (ns)

Noi

se M

argi

n (m

V)

NM of Vp (DS)

NM of Vap (DS)

NM of Vp (RS)

NM of Vap (RS)

Differential Sensing Improves NM

11

Direct Sensing Differential Sensing

Visualization of Sensing Stage Simulated NM for the same setting

Current Work

Optimizing and getting data from differential sensing.

Will try dual differential sensing, which should work even better.

12