CM3106-12SB Ver la hoja de datos (PDF) - California Micro Devices Corp

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CM3106-12SB

2 Amp Source/ Sink Bus Termination Regulator

California Micro Devices Corp 

CM3106

Performance Information (cont’d)

Typical Thermal Characteristics (nominal conditions unless otherwise specified)

The overall junction to ambient thermal resistance

(θJA) for device power dissipation (PD) consists prima-

rily of two paths in series. The first path is the junction

to the case (θJC) which is defined by the package style,

and the second path is case to ambient (θCA) thermal

resistance which is dependent on board layout. The

final operating junction temperature for any set of con-

ditions can be estimated by the following thermal equa-

tion:

increases from 0.42A to 0.58A for the CM3106-12SN

and a maximum instantaneous current of 2A should

not be exceeded for more than 29% of the time. For

CM3106-12SB, the maximum RMS current increases

from 1.3A to 2.2A. Thus, the maximum continuous cur-

rent can be 2A all the time.

TJUNC = TAMB + PD (θJC) + PD (θCA)

= TAMB + PD (θJA)

When a CM3106-12SN is mounted on a double sided

printed circuit board with two square inches of copper

allocated for "heat spreading", the resulting θJA is

151°C/W. Based on the over temperature limit of 150°C

with an ambient of 70°C, the available power of this

package will be:

PD = (150°C - 85°C) / 151°C/W = 0.43W

Since the θJA of the CM3106-12SB (PSOP) is 40°C/W,

the available power for this package will be:

PD = (150°C - 85°C) / 40°C/W = 1.625W

Figure 10. Duty Cycle vs. Ambient

Temperature (ILOAD=2.0A)

DDR Memory Application

Since the output voltage is 1.25V, and the device can

either source current from VDD or sink current to

Ground, the power dissipated in the device at any time

is 1.25V times the current load. This means the the

maximum average RMS current (in either direction) is

0.344A for the CM3106-12SN and 1.3A for the

CM3106-12SB. The maximum instantaneous current is

specified at 2A, so this condition should not be

exceeded for more than 17% of the time for the

CM3106-12SN and 65% of the time for the CM3106-

12SB. It is highly unlikely in most usage of DDR mem-

ory that this might occur, because it means the DDR

memory outputs are either all high or all low for 17%

(SOIC) and 65% (PSOP) of the time.

If the ambient temperature is 40°C instead of 85°C,

which is typically the maximum in most DDR memory

applications, the power dissipated (PD) can be 0.73W,

for the CM3106-12SN and 2.75W for the CM3106-

12SB. So the maximum average RMS current

Figure 11. Duty Cycle vs. Output

Current (Temp=70°C)

© 2004 California Micro Devices Corp. All rights reserved.

02/02/04 430 N. McCarthy Blvd., Milpitas, CA 95035-5112

L Tel: 408.263.3214 L Fax: 408.263.7846 L www.calmicro.com

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