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© Koninklijke Philips Electronics N.V. 2005. All rights reserved.

Product data sheet

Rev. 01 — 29 November 2005

12 of 20

Philips Semiconductors

PCK9448

3.3 V/2.5 V LVCMOS 1 : 12 clock fan-out buffer

9.2 Power consumption of the PCK9448 and thermal management

The PCK9448 dynamic electrical (AC) specification is guaranteed for the entire operating

frequency range up to 350 MHz. The PCK9448 power consumption and the associated

long-term reliability may decrease the maximum frequency limit, depending on operating

condition 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 PCK9448 die junction temperature and the associated device reliability. The

long-term device reliability is a function of the die temperature; refer to Table 10.

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 PCK9448 needs to be controlled and the thermal impedance of the

board/package should be optimized. The power dissipated in the PCK9448 is represented

in Equation 1.

(1)

dissipation capacitance per output, (M)

ΣC

N is the number of active outputs (N is always 12 in the case of the PCK9448). The

PCK9448 supports driving transmission lines to maintain high signal integrity and tight

timing parameters. Any transmission line will hide the limped capacitive load at the end of

the board trace, therefore,

ΣC

eliminated from Equation 1. Using parallel termination output termination results in

Equation 2 for power dissipation.

Fig 14. Optimized dual line termination

Zo = 50 Ω

002aaa723

Rs = 16 Ω

Zo = 50 Ω

Rs = 16 Ω

PCK9448

OUTPUT

BUFFER

17

Ω

IN

Zo = 50 Ω

Ro

17

Ω 16 Ω 16 Ω

||

+

50

Ω 50 Ω

||

=

25

Ω

25

Ω

=

Table 10:

Die junction temperature and MTBF

Junction temperature (

°C)

MTBF (years)

100

20.4

110

9.1

120

4.2

130

2.0

P

tot

I

q max

()

V

CC

f

clk

×

+

NC

PD

C

L

M

∑

+

×





×

V

CC

×

=