MPC9443 데이터 시트보기 (PDF) - Motorola => Freescale

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MPC9443

2.5V and 3.3V LVCMOS Clock Fanout Buffer

Motorola => Freescale 

Freescale Semiconductor, Inc.

MPC9443

Power Consumption of the MPC9443 and Thermal

Management

The MPC9443 AC specification is guaranteed for the

entire operating frequency range up to 350 MHz. The

MPC9443 power consumption and the associated long-term

reliability may decrease the maximum frequency limit,

depending on operating conditions such as clock frequency,

supply voltage, output loading, ambient temperture, vertical

convection and thermal conductivity of package and board.

This section describes the impact of these parameters on the

junction temperature and gives a guideline to estimate the

MPC9443 die junction temperature and the associated

device reliability. For a complete analysis of power

consumption as a function of operating conditions and

associated long term device reliability please refer to the

application note AN1545. According the AN1545, the

long-term device reliability is a function of the die junction

temperature:

Table 13: Die junction temperature and MTBF

Junction temperature (°C)

MTBF (Years)

100

20.4

In equation 2, P stands for the number of outputs with a

parallel or thevenin termination, VOL, IOL, VOH and IOH are a

function of the output termination technique and DCQ is the

clock signal duty cyle. If transmission lines are used ΣCL is

zero in equation 2 and can be eliminated. In general, the use

of controlled transmission line techniques eliminates the

impact of the lumped capacitive loads at the end lines and

greatly reduces the power dissipation of the device. Equation

3 describes the die junction temperature TJ as a function of

the power consumption.

Where Rthja is the thermal impedance of the package

(junction to ambient) and TA is the ambient temperature.

According to Table 13, the junction temperature can be used

to estimate the long-term device reliability. Further, combining

equation 1 and equation 2 results in a maximum operating

frequency for the MPC9443 in a series terminated

transmission line system.

TJ,MAX should be selected according to the MTBF system

requirements and Table 13. Rthja can be derived from Table

14. The Rthja represent data based on 1S2P boards, using

2S2P boards will result in a lower thermal impedance than

indicated below.

110

9.1

Table 14: Thermal package impedance of the 48ld LQFP

120

4.2

Convection, LFPM

Rthja (1P2S

Rthja (2P2S

130

2.0

board), K/W

board), K/W

Increased power consumption will increase the die

Still air

69

53

junction temperature and impact the device reliability

100 lfpm

(MTBF). According to the system-defined tolerable MTBF, the

200 lfpm

64

50

die junction temperature of the MPC9443 needs to be

controlled and the thermal impedance of the board/package

should be optimized. The power dissipated in the MPC9443

300 lfpm

400 lfpm

is represented in equation 1.

500 lfpm

Where ICCQ is the static current consumption of the

If the calculated maximum frequency is below 250 MHz, it

MPC9443, CPD is the power dissipation capacitance per

becomes the upper clock speed limit for the given application

output, (Μ)ΣCL represents the external capacitive output

conditions. The following eight derating charts describe the

load, N is the number of active outputs (N is always 16 in case

safe frequency operation range for the MPC9443. The charts

of the MPC9443). The MPC9443 supports driving

were calculated for a maximum tolerable die junction

transmission lines to maintain high signal integrity and tight

temperature of 110°C (120°C), corresponding to an

timing parameters. Any transmission line will hide the lumped

estimated MTBF of 9.1 years (4 years), a supply voltage of

capacitive load at the end of the board trace, therefore, ΣCL is

3.3V and series terminated transmission line or capacitive

zero for controlled transmission line systems and can be

loading. Depending on a given set of these operating

eliminated from equation 1. Using parallel termination output

termination results in equation 2 for power dissipation.

conditions and the available device convection a decision on

the maximum operating frequency can be made.

+ƪ ) @ @ǒ @ )ȍ Ǔƫ@ PTOT

ICCQ VCC fCLOCK

N CPD

CL

M

VCC

Equation 1

+ @ƪ ) @ @ǒ @ )ȍ Ǔƫ)ȍƪ @ @ǒ * Ǔ)ǒ * Ǔ@ @ ƫ PTOT VCC

ICCQ VCC fCLOCK

N CPD

CL

DCQ IOH VCC VOH 1 DCQ IOL VOL Equation 2

M

P

+ ) @ TJ TA PTOT Rthja

+ @ @ @ ƪ * * ǒ @ Ǔƫ fCLOCK,MAX

1

CPD N V2CC

TJ,MAX TA

Rthja

ICCQ VCC

Equation 3

Equation 4

TIMING SOLUTIONS

For More Informa9tion On This Product,

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MOTOROLA

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