writer parameters training

© 2013 WESTERN DIGITAL TECHNOLOGIES, INC. ALL RIGHTS RESERVED

Writer Parameters Training

KhengKaitChannel Hardware

WD CONFIDENTIAL

Writer waveform

Writer Optimization

Writer optimization results vs big ARCO results

12345

Zone EM

TD

678

Backgrounds of writer path parameters

Agenda

How to manipulate writer parameters

Conclusion

3

Backgrounds of write path parameters

Objectives: provide optimized settings and results Failures type: EM combo, AC, 0 OTRC, DLG.

Employed in PTMs: Mini ARCO, TaKO, Full ARCO, Hot ARCO, BigTaKO, Big ARCO

Optimization functions: Taguchi, 1-D OSA/OSD/IW sweeping Influence on drive parameters: EM, OTRC, ATI, PMET OW/SNR

4

Topics to cover in this training

Write path

Basic

Writer waveform Algo.

Taguchi1-D

writer Opti.

Tub/XMMS review

Advance

RFPE & ATI

Write precom

Eqn. based IW

ISI, Seed & ITIC

Writer Waveform


Writer waveform: IW, OSA, OSD

WD CONFIDENTIAL

6

Writer Waveform: IW, OSA, OSD

Matching settings of different preamp. Link: http://exapps04.wdc.com/wdwwa/

7

Writer Waveform: IW, OSA, OSD

Matching settings of different preamp. Link: http://exapps04.wdc.com/wdwwa/

IW

Rise Time

OSAOSA

8

Write Current (IW)

Fix OSD 5 DAC, OSA 5 DAC, IW 40,45,50,60

IW 40IW 45IW 50IW 60

9

Overshoot Amplitude (OSA)

Fix IW 55 DAC, 5 OSD DAC and sweep OSA:1,5,10,15

OSA 1OSA 5OSA 10OSA 15

10

Overshoot Duration (OSD)

Fix IW 55 DAC, OSA 5 DAC and OSD:1,5,10,15

OSD 1OSD 5OSD 10OSD 15

11

Writer Waveform Analyzer

Settings matching for different preamps Link: http://exapps04.wdc.com/wdwwa/

Writer Optimization


Taguchi, 1-Dimension sweeping

WD CONFIDENTIAL

13

Optimization sequence

NLDOFF FIR & MRA

Boost & CutOff

VMJOG curvefit

SAT_OWTaguchi

OSA curvefit

OSD curvefit

IW curvefit

14

Know the TUBs: Head1 Zone 2 Writer TUBs

(1) Tub : TAGU_SDefault Dac : 2DHSelected Dac : 38H

DAC COUNT VALUE1123H 0014H 01FEFFH ***********************************************************2223H 001CH 01D113H ****************************************************4423H 0030H 00E2BCH ******************5523H 003CH 0070FAH **6623H 004AH 0063B1H *122AH 002CH 014D1BH *********************************242AH 0039H 007CD5H ****452AH 004CH 006373H *562AH 0059H 00698BH *612AH 0042H 0069A0H *1431H 0049H 006BAAH **2531H 0054H 006AC8H **4631H 0069H 006D57H **5131H 0053H 0067CCH *6231H 0060H 00669BH *1538H 0065H 00680AH *2638H 0072H 0068A2H *4138H 0066H 0066F0H *5238H 0073H 00654EH *6438H 0088H 006F1FH **163FH 0083H 006C0AH **213FH 0073H 006588H *423FH 0086H 0069F7H *543FH 009BH 0070F5H **653FH 00ABH 00744BH ***0001H 0001H 00E8C4H *******************0002H 0002H 00B492H ************0004H 0003H 0080E2H *****0005H 0004H 006B50H **0006H 0005H 006B11H **0001H 0001H 00B8FAH *************0002H 0002H 00DD9CH ******************0004H 0003H 0088A9H ******0005H 0004H 006BE8H **0006H 0005H 006973H *0023H 0001H 011B18H **************************002AH 0002H 0099B6H ********0031H 0003H 006A09H *0038H 0004H 0068CEH *003FH 0005H 006CF5H **

0006H 0005H 006B11H **

0006H 0005H 006973H *

0038H 0004H 0068CEH *

(2) Tub : OSAMPSDefault Dac : 6HSelected Dac : 1H

DAC COUNT VALUE0001H 0066H 007FAFH *0002H 006EH 0080C8H ***0003H 0076H 0089FFH ****************************0004H 007FH 008CE2H ************************************0005H 0088H 008F6EH ******************************************0006H 0092H 00955BH **********************************************************

(3) Tub : OSDURS

Default Dac : 6HSelected Dac : 4H

DAC COUNT VALUE0001H 0051H 00851DH **********************************************************0002H 0055H 00854DH ***********************************************************0003H 005AH 007D84H *0004H 005EH 007E3DH ******0005H 0062H 007F6CH ***************0006H 0066H 007EEDH ***********

(4) Tub : IW_SCEDefault Dac : 37HSelected Dac : 39H

DAC COUNT VALUE0023H 001EH 01C44CH **********************************************************0025H 0024H 01A407H *****************************************************0027H 002AH 01741BH *********************************************0029H 0030H 013324H ***********************************002BH 0036H 00F52FH *************************002DH 003CH 00A611H ************002FH 0043H 008DE6H ********0031H 0049H 00772DH ****0033H 0050H 00703FH ***0035H 0057H 0065ABH *0037H 005EH 0066F9H *0039H 0065H 006328H *003BH 006CH 0065E4H *003DH 0073H 0061D3H *003FH 007BH 006259H *

15

How L25 Taguchi defined = range / 5

WD Confidential

16

Taguchi TUB: DAC column & VMM(1) Tub : TAGU_SDefault Dac : 2DHSelected Dac : 38H

DAC COUNT VALUE

1123H 0014H 01FEFFH ***********************************************************2223H 001CH 01D113H ****************************************************4423H 0030H 00E2BCH ******************5523H 003CH 0070FAH **6623H 004AH 0063B1H *122AH 002CH 014D1BH *********************************242AH 0039H 007CD5H ****452AH 004CH 006373H *562AH 0059H 00698BH *612AH 0042H 0069A0H *1431H 0049H 006BAAH **2531H 0054H 006AC8H **4631H 0069H 006D57H **5131H 0053H 0067CCH *6231H 0060H 00669BH *1538H 0065H 00680AH *2638H 0072H 0068A2H *4138H 0066H 0066F0H *5238H 0073H 00654EH *6438H 0088H 006F1FH **163FH 0083H 006C0AH **213FH 0073H 006588H *423FH 0086H 0069F7H *543FH 009BH 0070F5H **653FH 00ABH 00744BH ***0001H 0001H 00E8C4H *******************0002H 0002H 00B492H ************0004H 0003H 0080E2H *****0005H 0004H 006B50H **0006H 0005H 006B11H **0001H 0001H 00B8FAH *************0002H 0002H 00DD9CH ******************0004H 0003H 0088A9H ******0005H 0004H 006BE8H **0006H 0005H 006973H *0023H 0001H 011B18H **************************002AH 0002H 0099B6H ********0031H 0003H 006A09H *0038H 0004H 0068CEH *003FH 0005H 006CF5H **0006H 0005H 006B11H **0006H 0005H 006973H *0038H 0004H 0068CEH *

1123H 0014H 01FEFFH ***********************************************************

1:OSA1:OSD23:IW

L25 taguchi sweep to reduce sweeping samples. Too time consuming If performing full permutation sweep.

Average by OSA

Average by OSD

Average by IW

Taguchi selection

Viterbi Margin Metrix (VMM). Treat VMM as error rate, lower value means better signal.

17

Taguchi tub


DAC COUNT VALUE

1123H 0014H 01FEFFH ***********************************************************2223H 001CH 01D113H ****************************************************4423H 0030H 00E2BCH ******************5523H 003CH 0070FAH **6623H 004AH 0063B1H *

122AH 002CH 014D1BH *********************************242AH 0039H 007CD5H ****452AH 004CH 006373H *562AH 0059H 00698BH *612AH 0042H 0069A0H *

1431H 0049H 006BAAH **2531H 0054H 006AC8H **4631H 0069H 006D57H **5131H 0053H 0067CCH *6231H 0060H 00669BH *

1538H 0065H 00680AH *2638H 0072H 0068A2H *4138H 0066H 0066F0H *5238H 0073H 00654EH *6438H 0088H 006F1FH **

163FH 0083H 006C0AH **213FH 0073H 006588H *423FH 0086H 0069F7H *543FH 009BH 0070F5H **653FH 00ABH 00744BH ***0001H 0001H 00E8C4H *******************0002H 0002H 00B492H ************0004H 0003H 0080E2H *****0005H 0004H 006B50H **0006H 0005H 006B11H **0001H 0001H 00B8FAH *************0002H 0002H 00DD9CH ******************0004H 0003H 0088A9H ******0005H 0004H 006BE8H **0006H 0005H 006973H *0023H 0001H 011B18H **************************002AH 0002H 0099B6H ********0031H 0003H 006A09H *0038H 0004H 0068CEH *003FH 0005H 006CF5H **0006H 0005H 006B11H **0006H 0005H 006973H *0038H 0004H 0068CEH *

Average by each OSA setting

Taguchi selection:IW : 0x38; OSA 0x6; OSD 0x6

Avg by OSA VMM(decimal) VMM (hex)

1 59588.8 E8C4

2 51284.5 C854

4 34461.5 869D

5 27111.75 69E7

6 26818.75 68C2

Min value is selected

18

Head1 Zone 2: Taguchi and 1-D sweeping



0006H 0005H 006B11H **

0006H 0005H 006973H *

0038H 0004H 0068CEH *



Default OSD (from Taguchi): 6H

Default IW (from Taguchi): 38H

OSA = 1HOSD = 6HIW = 38H

19

Head1 Zone 2 Writer TUBs



0006H 0005H 006B11H **

0006H 0005H 006973H *

0038H 0004H 0068CEH *



(3) Tub : OSDURS



Default OSA (from 1-D OSA): 1H

Default IW (from Taguchi): 38H

20

Head1 Zone 2 Writer TUBs



0006H 0005H 006B11H **

0006H 0005H 006973H *

0038H 0004H 0068CEH *



(3) Tub : OSDURS



(4) Tub : IW_SCEDefault Dac : 37HSelected Dac : 39H

DAC COUNT VALUE0023H 001EH 01C44CH **********************************************************0025H 0024H 01A407H *****************************************************0027H 002AH 01741BH *********************************************0029H 0030H 013324H ***********************************002BH 0036H 00F52FH *************************002DH 003CH 00A611H ************002FH 0043H 008DE6H ********0031H 0049H 00772DH ****0033H 0050H 00703FH ***0035H 0057H 0065ABH *0037H 005EH 0066F9H *0039H 0065H 006328H *003BH 006CH 0065E4H *003DH 0073H 0061D3H *003FH 007BH 006259H *

Default OSA (from 1-D OSA): 1H

Default OSD (from 1-D OSD): 4H

IW selected = median of 5 min value.

21

Trend of good settings


DAC COUNT VALUE

1123H 0014H 01FEFFH ***********************************************************2223H 001CH 01D113H ****************************************************4423H 0030H 00E2BCH ******************5523H 003CH 0070FAH **6623H 004AH 0063B1H *122AH 002CH 014D1BH *********************************242AH 0039H 007CD5H ****452AH 004CH 006373H *562AH 0059H 00698BH *612AH 0042H 0069A0H *1431H 0049H 006BAAH **2531H 0054H 006AC8H **4631H 0069H 006D57H **5131H 0053H 0067CCH *6231H 0060H 00669BH *1538H 0065H 00680AH *2638H 0072H 0068A2H *4138H 0066H 0066F0H *5238H 0073H 00654EH *6438H 0088H 006F1FH **163FH 0083H 006C0AH **213FH 0073H 006588H *423FH 0086H 0069F7H *543FH 009BH 0070F5H **653FH 00ABH 00744BH ***0001H 0001H 00E8C4H *******************0002H 0002H 00B492H ************0004H 0003H 0080E2H *****0005H 0004H 006B50H **0006H 0005H 006B11H **0001H 0001H 00B8FAH *************0002H 0002H 00DD9CH ******************0004H 0003H 0088A9H ******0005H 0004H 006BE8H **0006H 0005H 006973H *0023H 0001H 011B18H **************************002AH 0002H 0099B6H ********0031H 0003H 006A09H *0038H 0004H 0068CEH *003FH 0005H 006CF5H **0006H 0005H 006B11H **0006H 0005H 006973H *0038H 0004H 0068CEH *

Taguchi selects: 0x6 OSA; 0x6 OSD; 0x38(56) IW

1-D sweep select OSA 0x1; OSD 0x4; IW 57

22

Messages from Taguchi tub

Taguchi select IW 0x38, OSA 0x6, OSD 0x6

Taguchi sweep prefers higher OSA/OSD for optimum IW


23

Saturation trend in Taguchi tub

Taguchi select IW 0x38, OSA 0x6, OSD 0x6

Taguchi sweep prefers higher OSA/OSD for optimum IW


Writer optimization results vs big ARCO results


Result comparison

WD CONFIDENTIAL

Taguchi tub Taguchi selects IW

0x38, OSA 0x6, OSD 0x6 Taguchi sweep prefers

higher OSA/OSD for optimum IW

1-D sweep selects IW 0x39; OSA 0x1, OSD 0x4

Taguchi trend is matching with Big ARCO

Taguchi tub Taguchi select IW 0x38,

OSA 0x6, OSD 0x6 Taguchi sweep prefers

higher OSA/OSD for optimum IW


IW 56; OSD 6; sweep OSA

27

Taguchi tub Taguchi sweep

prefers higher OSA/OSD for optimum IW


4

IW 56; OSA 1; sweep OSD

28

Taguchi tub Taguchi sweep

prefers higher OSA/OSD for optimum IW


4

OSD4; OSA 1; sweep IW

Reason why BigARCO recommend settings is Fail


Explain via illustration & XMMS data analysis

WD CONFIDENTIAL

30

Big ARCO recommend settings

still possible for 1-D sweep to choose lower (bad) OSA/OSD settings

31

List out GIDs used in TaKO and FullARCOZone information (OD, MD, ID, Rsv) OD 1, MD 10, ID 20, reserve Table: 8 = cold, 9 = amb, 10= hot

WD Confidential

32

XMMS: IW, OSA & OSD in TaKO

New setting: saturated Old setting: bias to higher IW

OSA OSD

IW

New setting: possible to choose lower (bad) OSA/OSD combination

33

TaKO results

Old settings has more poor tilt end than new settings

34

TaKO results

Old settings has more poor tilt end than new settings

35

TaKO result analysis

Old settings has more poor tilt end than new settings Inspect from average perspective, new and old settings are comparable

(since higher IW/OSA/OSD) are able to obtain saturated result. only applicable to ambient but hot temperature.

1-D sweeping causing big ARCO recommend settings not suitable to use writer optimization unless the following is changed:

(Code change)Optimization sequence changed to IW OSD OSA Replace 1-D optimization with 2-level Taguchi or other equivalent design.

TaKO results

EM at OD: comparable. OSA/OSD of new settings at OD are higher than MD and ID.

TPI/KFCI are more dominant effect in EM DC shift. Writer parameters is just for saturated result but KFCI able to gives a big leap.

from another writer parameters evals(60L vs 60K), I takes same TPI/KFCI binning (less TPI/KFCI changes) of same drive, lower OSA/OSD tend to have poorer EM result.

Conclusion: with Codata with BigARCO recommend settings, it is still possible to select poor OSA/OSD settings which end up IW selects higher end settings.

New Codata with saturated choice


To illustrate the failure

WD CONFIDENTIAL

40

Big ARCO recommend settings

Selections will always fall into saturation(good) region --> all settings are good (if not ATI) bell-curve XMMS distribution.

Need to watch out ATI

41

Same drive XMMS review

JN.B.YA (baseline: old settings) vs JN.B.YN(new settings) Quantity of drive: 46 Hypothesis/expectation: comparable result with lower count on poor tilt-end

PMR: effect of writer parameters on EM/SNR is reduced compared to LMR. Sufficient writer energy will do in order to obtain saturated SNR. according to Marvel engineer.

Review result: TPI/KFCI: identical/comparable EM: comparable with lower poor tilt-end distribution

42

Same drive XMMS review: TaKO

TPI/KFCI: identical/comparable EM: comparable with new settings slightly better

Comments only applied for new settings

OSA: bias to lower mid range (5~10) not an signature of saturation

OSD: bias to median 10 ( sweep range 5~15, median 10=) normal distribution = signature of saturation.

IW: normal distribution = signature of saturation.

Conclusion: results look good in overall, need to monitor OSA

IMHO, less chance cos it is covered by OSD and IW.

It is always a plus if there is a way to lowering down IW (green tech).

There is one outlier at new settings consistently.

Need to know the SN for checking.

45

Same drive XMMS review: post TaKO

EM: comparable

46

Same drive XMMS review: post TaKO

Same comment as in TaKO

FA: 0 OTRC Failure


To illustrate the failure

WD CONFIDENTIAL

48

Failure Analysis - samples

Backgrounds: new head M11P is introduced in F2 & F3 build. Most failures are writer parameters related.

Failures type: EM combo, AC, 0 OTRC, DLG. Symptom: OSA/OSD selection are in contrast with Taguchi selection

Taguchi: clean tub and preferring higher OSA/OSD. low OSA/OSD yields poor result. 1-Dimension OSA/OSD: saturated and values selected << Taguchi selection 1-dimension IW: clean bath tub. Ambient performance is ok with low OSA/OSD but degrade in hot (SNR degraded)

Bench FA: increasing OSA/OSD able to pass the failure Big ARCO result: prefers higher OSA/OSD

49

0 OTRC failure

Run at hot

Amb performance is good.

Hot performance is poor

50

Writer parameters

51

Conclusion

XMMS results look good. New settings are OK to go. Things to watch-out: BI results and OSA optimization.

writer parameters training

Documents