7721 datasheet(568/577 Pages) RENESAS

568 / 577 page

7721 Group User’s Manual

17–105

Appendix 11. Electrical characteristics

APPENDIX

Table 5 Calculation formulas for DRAM control bus timing depending of f(XIN)

(Vcc = 5 V ± 10 %, Vss = 0 V, Ta = –20 to 85 °C)

Read

Symbol

tw(RASL)

tw(CASL)

tw(RASH)

td(RAS–CAS)

td(RA–RAS)

th(RAS–RA)

Calculation formula

Unit

3 ! 109

f(XIN)

4 ! 109

f(XIN)

2 ! 109

f(XIN)

– 40

– 27.5

– 20

1 ! 109

f(XIN)

1 ! 109

f(XIN)

1 ! 109

f(XIN)

– 12

– 22

– 35

Unit

1 ! 109

f(XIN)

4 ! 109

f(XIN)

1 ! 109

f(XIN)

– 60

– 22

1 ! 109

f(XIN)

+ 25

Symbol

th(CAS–CA)

td(R/W–RAS)

th(CAS–R/W)

td(E–CA)

td(E–CASL)

Calculation formula

1 ! 109

f(XIN)

+ 37.5

Write

Symbol

tw(RASL)

tw(CASL)

tw(RASH)

td(RAS–CAS)

td(RA–RAS)

th(RAS–RA)

Unit

2 ! 109

f(XIN)

4 ! 109

f(XIN)

2 ! 109

f(XIN)

– 40

– 25

– 20

1 ! 109

f(XIN)

2 ! 109

f(XIN)

1 ! 109

f(XIN)

– 20

– 22

– 35

Unit

3 ! 109

f(XIN)

1 ! 109

f(XIN)

1 ! 109

f(XIN)

– 30

– 60

– 22

1 ! 109

f(XIN)

– 22

Symbol

td(CA–CAS)

th(CAS–CA)

td(R/W–RAS)

th(CAS–R/W)

td(E–CASL)

Calculation formula

2 ! 109

f(XIN)

+ 35(0)V

V The value within ( ) is for the minimum value.

Refresh

Symbol

tw(RASL)

tw(CASL)

Unit

2 ! 109

f(XIN)

4 ! 109

f(XIN)

– 40

Unit

1 ! 109

f(XIN)

1 ! 109

f(XIN)

Symbol

td(CAS–RAS)

th(RAS–CAS)

Calculation formula

– 25

Calculation formula

– 22.5

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