AMD LX 900@1.5W User Manual

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The data bus on the DDR SDRAM has a low voltage swing
when actively terminated (terminated topology). The termi-
nated topology supports higher data transfer rates and is
less constrained, but it consumes more power. Many
designs should be able to operate reliably without active
termination (unterminated topology). The design con-
straints are smaller memory subsystems and tight control
on routing. See the application note, AMD Geode™ LX
Processor and CS5535/CS5536 Companion Device Layout
Recommendations (publication ID #32739), for more infor-
mation.

When series termination resistors are used, as specified in
the  AMD Geode™ LX Processor and CS5535/CS5536
Companion Device Layout Recommendations, the actual
power provided by the V

MEMLX

 supply is split between the

processor and the series and parallel termination (see Fig-
ure 7-1). Therefore, it is impossible to specify the power
used by the processor’s memory subsystem with one hun-
dred percent accuracy. A conservative estimate, is that
32.5% of the power is consumed by the processor and

67.5% by the termination resistors. See the AMD Geode™
LX Processor Determining Memory Interface I/O Power
Consumption document (publication ID #40554) for the
detailed analysis. This number is used for the results in DC
Current tables (Tables 7-3, 7-4, and 7-5).

 

V

MEMLX

V

MEMDIMM

V

TT

Connector

or

Device

MEM

LX

R

P1

R

P2

R

S

I

CC3ON

 - CRT Display

Power State: 
On (S0/C0)

85

100

mA

I

CC3ON

 - TFT Display

37

45

I

COREON

1420

3140

I

MEMON

 - Terminated

150

165

Note 2, Note 3

I

MEMON

 - Unterminated

90

100

I

MEMDDR2ON

80

95

I

CC3IDLE

 - CRT Display

Power State: 
Active Idle (S0/C1)

85

mA

I

CC3IDLE

- TFT Display

37

I

COREIDLE

1250

I

MEMIDLE

 - Terminated

150

I

MEMIDLE

 - Unterminated

80

I

CC3SLP

 - CRT Display

Power State: 
Sleep (S1)

4

mA

I

CC3SLP

 - TFT Display

4

I

CORESLP

600

I

MEMSLP

 - Terminated

100

I

MEMSLP

 - Unterminated

35

Note 1. The AMD Geode LX 900@1.5W processor operates at 600 MHz. Model numbers reflect performance as described 

here: 

.

T = Terminated and U = Unterminated.

Note 2. Calculations are based on a 32.5/67.5 split between V

MEMLX

 used by the AMD Geode LX processor and series 

termination resistors. See Section 7.4.3 on page 599 for more details.

Note 3. V

MEM

 is 2.6V for the LX 900@1.5W processor.