ICS8536I-33 Datasheet, PDF (14/19 Pages) Integrated Device Technology – LOW SKEW, 1-TO-6, CRYSTAL OSCILLATOR/LVCMOSTO-3.3V, 2.5V LVPECL/LVCMOS FANOUT BUFFER

ICS8536I-33
LOW SKEW, 1-TO-6, CRYSTAL OSCILLATOR/LVCMOS-TO-3.3V, 2.5V LVPECL/LVCMOS FANOUT BUFFER
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^TM devices is 125°C.
The equation for Tj is as follows: Tj = θ * Pd_total + T
JA
A
Tj = Junction Temperature
θ_JA = Junction-to-Ambient Thermal Resistance
Pd_total = Total Device Power Dissipation (example calculation is in section 1 above)
T = Ambient Temperature
A
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance θ must be used. Assuming no air
JA
flow and a multi-layer board, the appropriate value is 91.1°C/W per Table 7 below.
Therefore, Tj for an ambient temperature of 85°C with all outputs switching is:
85°C + 0.3993W * 91.1°C/W = 121.4°C. This is below the limit of 125°C.
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 7. THERMAL RESISTANCE θ FOR 20-PIN TSSOP, FORCED CONVECTION
JA
θ by Velocity (Linear Feet per Minute)
JA
Multi-Layer PCB, JEDEC Standard Test Boards
0
91.1°C/W
200
86.7°C/W
500
84.6°C/W
IDT^™ / ICS^™ 3.3V, 2.5V LVPECL/ LVCMOS FANOUT BUFFER
14
ICS8536CGI-33 REV. B OCTOBER 27, 2008