8T49N281_16 Datasheet, PDF (59/67 Pages) Integrated Device Technology – FemtoClock NG Octal Universal Frequency Translator

8T49N281 Datasheet
Example Calculations
Example 1. Common Customer Configuration (3.3V Core Voltage)
Output
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Output Type
LVPECL
LVPECL
LVPECL
LVPECL
LVDS
LVDS
LVCMOS
LVCMOS
Frequency (MHz)
625
625
212.5
212.5
25
25
125
125
V_CCO
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
• Core Supply Current, I_CC = 90mA (max)
• Analog Supply Current, I_CCA = 187mA (max)
Q0 Current = 0.00624x625 + 40.3 = 44.2mA
Q1 Current = 0.00624x625 + 40.3 = 44.2mA
Q2 Current = 0.01445x212.5 + 63.6 = 66.67mA
Q3 Current = 0.01445x212.5 + 63.6 = 66.67mA
Q4 Current = 0.00646x25 + 51.5 = 51.66mA
Q5 Current = 0.00646x25 + 51.5 = 51.66mA
Q6 Current = 40.1mA
Q7 Current = 40.1mA
• Total Output Current = 405.26mA (max)
Total Device Current = 90mA + 187mA + 405.26mA = 682.26mA
Total Device Power = 3.465V * 682.26mA = 2364mW
• Power dissipated through output loading:
LVPECL = 27.95mW * 4 = 111.8mW
LVDS = already accounted for in device power
LVCMOS = 14.5pF * 125MHz * 3.465V² * 2 output pairs = 43.5mW
• Total Power = 2364mW + 111.8mW + 43.5mW = 2519.3mW or 2.52W
With an ambient temperature of 85°C and no airflow, the junction temperature is:
T_J = 85°C + 16.0°C/W * 2.52W = 125.3°C
This junction temperature is above the maximum allowable. In instances where maximum junction temperature is exceeded adjustments need
to be made to either airflow or ambient temperature. In this case, adjusting airflow to 1m/s (_JA = 12.14°C/W) will reduce junction temperature
to 115.6°C. If no airflow adjustments can be made, the maximum ambient operating temperature must be reduced by a minimum of 0.3°C.
©2016 Integrated Device Technology, Inc.
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Revision 7, October 26, 2016