DM3725CBC datasheet(188/280 Pages) TI

188 / 280 page

OMAP

DM3730, DM3725

SPRS685D

– AUGUST 2010 – REVISED JULY 2011

www.ti.com

Table 6-19. LPDDR Signal Terminations

NO.

PARAMETER

MIN

TYP

MAX

UNIT

NOTES

CK Net Class

Ω

See Note(1)

ADDR_CTRL Net Class

Ω

See Notes(1),(2),(3)

Data Byte Net Classes

Ω

See Notes(1),(2),(3)

(DQS0-DQS3, DQ0-DQ3)

(1) Only series termination is permitted, parallel or SST specifically disallowed.

(2) Terminator values larger than typical only recommended to address EMI issues.

(3) Termination value should be uniform across net class.

6.4.2.6

LPDDR CK and ADDR_CTRL Routing

Figure 6-21 shows the topology of the routing for the CK and ADDR_CTRL net classes. The route is a

balanced T as it is intended that the length of segments B and C be equal. In addition, the length of A

should be maximized.

Figure 6-21. CK and ADDR_CTRL Routing and Topology

Table 6-20. CK and ADDR_CTRL Routing Specification (5)

NO.

PARAMETER

MIN

TYP

MAX

UNIT

NOTES

Center to Center CK-CK spacing

CK Differential Pair Skew Length Mismatch(4)

Mils

See Note(1)

CK B to C Skew Length Mismatch

Mils

Center to Center CK to other

See Note(2)

LPDDR trace spacing

CK/ADDR_CTRL nominal trace length

CACLM-50

CACLM

CACLM+50

Mils

See Note(3)

ADDR_CTRL to CK Skew Length Mismatch

100

Mils

ADDR_CTRL to ADDR_CTRL

100

Mils

Skew Length Mismatch

Center to Center ADDR_CTRL to other

See Note(2)

LPDDR trace spacing

Center to Center ADDR_CTRL to other

See Note(2)

ADDR_CTRL trace spacing

ADDR_CTRL A to B, ADDR_CTRL A to C

100

Mils

See Note(1)

Skew Length Mismatch

ADDR_CTRL B to C Skew Length Mismatch

100

Mils

(1) Series terminator, if used, should be located closest to DM37x.

(2) Center to center spacing is allowed to fall to minimum (w) for up to 500 mils of routed length to accommodate BGA escape and routing

congestion.

(3) CACLM is the longest Manhattan distance of the CK and ADDR_CTRL net classes.

(4) Differential impedance should be 100 ohms.

(5) Specific routing guidelines for the CUS package can be found in the AM37x CUS Routing Guidelines (SPRABD4) application note.

188

Timing Requirements and Switching Characteristics

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