ICS8543BGILF Datasheet, PDF (14/18 Pages) Integrated Device Technology – Low Skew, 1-to-4, Differential-to-LVDS Fanout Buffer

ICS8543 Data Sheet
LOW SKEW, 1-to-4, DIFFERENTIAL-TO-LVDS FANOUT BUFFER
Power Considerations
This section provides information on power dissipation and junction temperature for the ICS8543.
Equations and example calculations are also provided.
1. Power Dissipation.
The total power dissipation for the ICS8543 is the sum of the core power plus the power dissipated in the load(s).
The following is the power dissipation for V_DD = 3.3V + 5% = 3.465V, which gives worst case results.
• Power (core)_MAX = V_{DD_MAX} * I_{DD_MAX} = 3.465V * 50mA = 173.25mW
2. Junction Temperature.
Junction temperature, Tj, is the temperature at the junction of the bond wire and bond pad directly affects the reliability of the device. The
maximum recommended junction temperature is 125°C. Limiting the internal transistor junction temperature, Tj, to 125°C ensures that the bond
wire and bond pad temperature remains below 125°C.
The equation for Tj is as follows: Tj = θ_JA * Pd_total + T_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_A = Ambient Temperature
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance θ_JA must be used. Assuming no air flow and
a multi-layer board, the appropriate value is 73.2°C/W per Table 6 below.
Therefore, Tj for an ambient temperature of 70°C with all outputs switching is:
70°C + 0.173W * 73.2°C/W = 82.7°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 (multi-layer).
Table 6. Thermal Resitance θ_JA for 20 Lead TSSOP, Forced Convection
θ_JA by Velocity
Linear Feet per Minute
0
Single-Layer PCB, JEDEC Standard Test Boards
114.5°C/W
Multi-Layer PCB, JEDEC Standard Test Boards
73.2°C/W
200
98.0°C/W
66.6°C/W
500
88.0°C/W
63.5°C/W
ICS8543BG REVISION E DECEMBER 17, 2010
14
©2010 Integrated Device Technology, Inc.