ICS8521 ICST [Integrated Circuit Systems], ICS8521 Datasheet - Page 9

• Manufacturer Part Number: ICS8521
• Description: LOW SKEW, 1-TO-9 DIFFERENTIAL-TO-LVHSTL FANOUT BUFFER
• Manufacturer: ICST [Integrated Circuit Systems]

This section provides information on power dissipation and junction temperature for the ICS8521.
Equations and example calculations are also provided.
1. Power Dissipation.
The total power dissipation for the ICS8521 is the sum of the core power plus the power dissipated in the load(s).
The following is the power dissipation for V
NOTE: Please refer to Section 3 for details on calculating power dissipated in the load.
2. Junction Temperature.
Junction temperature, Tj, is the temperature at the junction of the bond wire and bond pad and directly affects the reliability of the
device. The maximum recommended junction temperature for HiPerClockS
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance
moderate air flow of 200 linear feet per minute and a multi-layer board, the appropriate value is 42.1°C/W per Table 6 below.
Therefore, Tj for an ambient temperature of 70°C with all outputs switching is:
This calculation is only an example. Tj will obviously vary depending on the number of loaded outputs, supply voltage, air flow,
and the type of board (single layer or multi-layer).
Table 6. Thermal Resistance q
8521BY
Single-Layer PCB, JEDEC Standard Test Boards
Multi-Layer PCB, JEDEC Standard Test Boards
NOTE: Most modern PCB designs use multi-layered boards. The data in the second row pertains to most designs.
Power (core)
Power (outputs)
If all outputs are loaded, the total power is 9 * 32mW = 288mW
The equation for Tj is as follows: Tj =
Tj = Junction Temperature
Pd_total = Total device power dissipation (example calculation is in section 1 above)
T
70°C + 0.565W * 42.1°C/W = 93.8°C. This is well below the limit of 125°C
JA
A
= Ambient Temperature
= junction-to-ambient thermal resistance
MAX
MAX
= V
= 32mW/Loaded Output pair
DD_MAX
* I
JA
DD_MAX
q
for 32-pin LQFP, Forced Convection
JA
P
DD
= 3.465V * 80mA = 277.2mW
by Velocity (Linear Feet per Minute)
= 3.3V + 5% = 3.465V, which gives worst case results.
www.icst.com/products/hiperclocks.html
OWER
JA
* Pd_total + T
C
ONSIDERATIONS
A
9
67.8°C/W
47.9°C/W
D
IFFERENTIAL
0
TM
devices is 125°C.
55.9°C/W
42.1°C/W
-
TO
200
-LVHSTL F
JA
must be used . Assuming a
L
50.1°C/W
39.4°C/W
OW
500
ANOUT
S
ICS8521
KEW
REV. B JULY 31, 2001
, 1-
B
UFFER
TO
-9