MPC9443 REVISION 6 3/14/16

9

©2016 Integrated Device Technology, Inc.

MPC9443 Data Sheet

2.5V, 3.3V LVCMOS CLOCK FANOUT BUFFER

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 temperature, 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

Freescale application note AN1545. According the AN1545, the

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

temperature.

Increased power consumption will increase the die junction

temperature and impact the device reliability (MTBF). According

to the system-defined tolerable MTBF, the 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 is represented in Equation

1.

Where ICCQ is the static current consumption of the MPC9443,

CPD is the power dissipation capacitance per output. CL

represents the external capacitive output load, and N is the

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

MPC9443). The MPC9443 supports driving transmission lines to

maintain high signal integrity and tight timing parameters. Any

transmission line will hide the lumped capacitive load at the end of

the board trace; therefore,

C

L is zero for controlled transmission

line systems and can be eliminated from Equation 1. Using

parallel termination output termination results in Equation 2 for

power dissipation.

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

cycle. If transmission lines are used,

C

L 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.

If the calculated maximum frequency is below 250 MHz, it

becomes the upper clock speed limit for the given application

conditions. The following eight derating charts describe the safe

frequency operation range for the MPC9443. The charts were

calculated for a maximum tolerable die junction temperature of

110

C (120C), corresponding to an estimated MTBF of 9.1 years

(4 years), a supply voltage of 3.3 V and series terminated

transmission line or capacitive loading. Depending on a given set

of these operating conditions and the available device convection

a decision on the maximum operating frequency can be made.

Table 13. Die Junction Temperature and MTFBF

Junction Temperature (

C)

MTBF (Years)

100

20.4

110

9.1

120

4.2

130

2.0

Table 14. Thermal Package Impedance of the 48 ld LQFP

Convection,

LFPM

Rthja (1P2S board),

K/W

Rthja (2P2S board),

K/W

Still air

69

53

100 lfpm

200 lfpm

64

50

300 lfpm

400 lfpm

500 lfpm

PTOT = [ ICCQ + VCC · fCLOCK · ( N · CPD +  CL ) ] · VCC

M

PTOT = VCC · [ ICCQ + VCC · fCLOCK · ( N · CPD +  CL ) ] +  [ DCQ · IOH · (VCC – VOH) + (1 – DCQ) · IOL · VOL ]

MP

TJ = TA + PTOT · Rthja

fCLOCK,MAX =

CPD · N · V

2

CC

1

·

[

– (ICCQ · VCC)

]

Rthja

Tj,MAX – TA

Equation 1

Equation 2

Equation 3

Equation 4