14©2016 Integrated Device Technology, Inc Revision A April 14, 2016
840S07I Data Sheet
Power Considerations
This section provides information on power dissipation and junction temperature for the 840S07I.
Equations and example calculations are also provided.
1. Power Dissipation.
The total power dissipation for the 840S07I is the sum of the core power plus the analog power plus the power dissipation in the load(s). The
following is the power dissipation for V
DD
= 3.3V + 5% = 3.465V, which gives worst case results.
The maximum current at 85°C is as follows:
I
DD_MAX
= 168.5mA
I
DDA_MAX
= 20.96mA
I
DDO_MAX
= 74.11mA
Core Output Power Dissipation
• Power (core)
MAX
= V
DD_MAX
* (I
DD
+ I
DDA
) = 3.465V *(168.5mA + 20.96mA) = 656.51mW
• Power (output)
MAX
= V
DDO_MAX
* I
DDO
= 3.465V *74.11mA = 256.80mW
LVCMOS Output Power Dissipation
• Output Impedance R
OUT
Power Dissipation due to Loading 50 to V
DD
/2
Output Current I
OUT
= V
DD_MAX
/ [2 * (50 + R
OUT
)] = 3.465V / [2 * (50 + 35)] = 20.38mA
• Power Dissipation on the R
OUT
per LVCMOS output
Power (R
OUT
) = R
OUT
* (I
OUT
)
2
= 35 * (20.38mA)
2
= 14.54mW per output
• Total Power Dissipation on the R
OUT
Total Power (R
OUT
) = 14.54mW * 7 = 101.8mW
• Dynamic Power Dissipation at 25MHz
Power (25MHz) = C
PD
* Frequency * (V
DDO
)
2
= 10pF * 25MHz * (3.465V)
2
= 3mW per output
Total Power (25MHz) = 3mW * 2 = 6mW
• Dynamic Power Dissipation at 166.67MHz
Power (166.67MHz) = C
PD
* Frequency * (V
DDO
)
2
= 10pF * 166.67MHz * (3.465V)
2
= 20mW per output
Total Power (166.67MHz) = 20mW * 5 = 100.1mW
Total Power Dissipation
• Total Power
= Power (core) + Power (output) + Total Power (25MHz + Total Power (166.67MHz)
= 656.51mW + 256.80mW + 101.8mW + 6.0mW + 100.1mW
= 1121.15mW
