9DB306 Data Sheet
©2016 Integrated Device Technology, Inc Revision C February 18, 201611
POWER CONSIDERATIONS
This section provides information on power dissipation and junction temperature for the 9DB306.
Equations and example calculations are also provided.
1. Power Dissipation.
The total power dissipation for the 9DB306 is the sum of the core power plus the power dissipated in the load(s).
The following is the power dissipation for V
CC
= 3.3V + 10% = 3.63V, which gives worst case results.
NOTE: Please refer to Section 3 for details on calculating power dissipated in the load.
• Power (core)
MAX
= V
CC_MAX
* I
EE_MAX
= 3.63V * 135mA = 490.1mW
• Power (outputs)
MAX
= 30mW/Loaded Output pair
If all outputs are loaded, the total power is 6 * 30mW = 180mW
Total Power
_MAX
(3.63V, with all outputs switching) = 490.1mW + 180mW = 670.1mW
2. Junction Temperature.
Junction 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 = θJA * Pd_total + TA
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 a
moderate air fl ow of 200 linear feet per minute and a multi-layer board, the appropriate value is 43.9°C/W per Table 6 below.
Therefore, Tj for an ambient temperature of 70°C with all outputs switching is:
70°C + 0.670W * 43.9°C/W = 99.4°C. This is well 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 fl ow, and the
type of board (single layer or multi-layer).
θ
JA
by Velocity (Linear Feet per Minute)
0 200 500
Single-Layer PCB, JEDEC Standard Test Boards 82.9°C/W 68.7°C/W 60.5°C/W
Multi-Layer PCB, JEDEC Standard Test Boards 49.8°C/W 43.9°C/W 41.2°C/W
NOTE: Most modern PCB designs use multi-layered boards. The data in the second row pertains to most designs.
TABLE 6. THERMAL RESISTANCE θ
JA
FOR 28-PIN TSSOP, FORCED CONVECTION
