8T49N285 Datasheet, PDF (56/65 Pages) Integrated Circuit Systems – Open-drain Interrupt pin

8T49N285 DATA SHEET
Thermal Considerations
Once the total power consumption has been determined, it is necessary to calculate the maximum operating junction temperature for the device
under the environmental conditions it will operate in. Thermal conduction paths, air flow rate and ambient air temperature are factors that can
affect this. The thermal conduction path refers to whether heat is to be conducted away via a heatsink, via airflow or via conduction into the
PCB through the device pads (including the ePAD). Thermal conduction data is provided for typical scenarios in Table 13 below. Please contact
IDT for assistance in calculating results under other scenarios.
Table 13. Thermal Resistance _JA for 56-Lead VFQFN, Forced Convection
_JA by Velocity
Meters per Second
0
Multi-Layer PCB, JEDEC Standard Test Boards
16.0°C/W
1
12.14°C/W
2
11.02°C/W
Current Consumption Data and Equations
Table 14A. 3.3V LVPECL Output Calculation Table
Output
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
FQ_Factor (mA/MHz)
0.00593
0.01363
Base_Current (mA)
40.1
63.8
0.00591
42.9
Table 14D. 2.5V LVPECL Output Calculation Table
Output
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
FQ_Factor (mA/MHz)
0.00373
0.01134
Base_Current (mA)
32.8
56.5
0.00369
35.7
Table 14B. 3.3V HCSL Output Calculation Table
Output
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
FQ_Factor (mA/MHz)
0.00582
0.01358
Base_Current (mA)
40.1
63.8
0.00553
43.1
Table 14E. 2.5V HCSL Output Calculation Table
Output
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
FQ_Factor (mA/MHz)
0.00354
0.01125
Base_Current (mA)
32.9
56.5
0.00353
35.7
Table 14C. 3.3V LVDS Output Calculation Table
Output
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
FQ_Factor (mA/MHz)
0.00627
0.01404
Base_Current (mA)
48.6
72.5
0.00630
51.3
Table 14F. 2.5V LVDS Output Calculation Table
Output
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
FQ_Factor (mA/MHz)
0.00366
0.01148
Base_Current (mA)
40.8
64.5
0.00367
43.7
FEMTOCLOCK^® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR
56
REVISION 3 06/29/15