Specifications

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SLWS142J − JANUARY 2003 − REVISED AUGUST 2007
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5
9 POWER CONSUMPTION
The maximum power consumption depends on the operating mode of the chip. The following equation estimates the
typical power supply current for the chip. Chip-to-chip variation is typically ±5%. The AC Characteristics provides the
production test limit for current in a maximum configuration. It is 10% over the typical value.
Icore = (f
CK
/100 MHz) (Vcore/1.8 V) (Number_of_Active_Channels/4) (0.75 + FIRDutyCycle) 220 mA
The FIRDutyCycle is calculated in the cmd5016 programming software. The ’.ANL’ extension of the user
programming file contains the power analysis value.. It can be estimated by:
Down Converter Mode:
FIRDutyCycle = 1 for f
CK
/Fout ≤ 16
16 x Fout/f
CK
otherwise
Up Converter Mode:
FIRDutyCycle = 1 for f
CK
/Fin ≤ 32
32 x Fin/f
CK
otherwise
Current consumption on the pad supply is primarily due to the external loads and follows C x V x F. Internal loads
are estimated at 2 pF per pin. Data outputs transition from a zero to a one once per four clocks, while clock outputs
transition every cycle. The frame strobes consume negligible power due to the low transition frequency. In general:
Ipad = Σ DataPad/4 x C x F x V + Σ ClockPad x C x F x V
Typically loads are 20 pF per pin. A worst case current would be all four output ports operating at 125 MHz and the
four output clocks with [A−D]CK active at 125 MHz.
Ipad = (64/4 + 4) x (C+2pF) x Fout x Vpad = 20 x 22 pF x 125 MHz x 3.3 V = 180 mA