ICS8535-31 ICST [Integrated Circuit Systems], ICS8535-31 Datasheet - Page 9

• Manufacturer Part Number: ICS8535-31
• Description: LOW SKEW, 1-TO-4, CRYSTAL OSCILLATOR/ LVCMOS-TO-3.3V LVPECL FANOUT BUFFER
• Manufacturer: ICST [Integrated Circuit Systems]

This section provides information on power dissipation and junction temperature for the ICS8535-31.
Equations and example calculations are also provided.
1. Power Dissipation.
The total power dissipation for the ICS8535-31 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 66.6°C/W per Table 7 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).
T
8535AG-31
ABLE
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.
7. T
Power (core)
Power (outputs)
If all outputs are loaded, the total power is 4 * 30mW = 120mW
Total Power
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 + 0.328W * 66.6°C/W = 92°C. This is well below the limit of 125°C.
JA
A
= Ambient Temperature
= Junction-to-Ambient Thermal Resistance
HERMAL
Integrated
Circuit
Systems, Inc.
R
MAX
ESISTANCE
_MAX
MAX
= V
(3.465V, with all outputs switching) = 207.9mW + 120mW = 327.9mW
= 30mW/Loaded Output pair
CC_MAX
* I
JA
EE_MAX
FOR
JA
P
CC
= 3.465V * 60mA = 207.9mW
20-
by Velocity (Linear Feet per Minute)
= 3.3V + 5% = 3.465V, which gives worst case results.
www.icst.com/products/hiperclocks.html
OWER
PIN
JA
* Pd_total + T
TSSOP, F
C
ONSIDERATIONS
LVCMOS-
ORCED
A
9
114.5°C/W
73.2°C/W
L
C
0
OW
ONVECTION
TM
S
devices is 125°C.
TO
KEW
-3.3V LVPECL F
, 1-
98.0°C/W
66.6°C/W
200
TO
-4, C
JA
must be used. Assuming a
RYSTAL
ICS8535-31
88.0°C/W
63.5°C/W
500
ANOUT
O
REV. B APRIL 29, 2005
SCILLATOR
B
UFFER
/