dsp56167 Freescale Semiconductor, Inc, dsp56167 Datasheet - Page 86

• Manufacturer Part Number: dsp56167
• Description: Advance Information 16-bit Digital Signal Processor
• Manufacturer: Freescale Semiconductor, Inc

Design Considerations
Power Consumption
POWER CONSUMPTION
4-10
Equation 3:
Equation 4:
Power dissipation is a key issue in portable DSP applications. The following describes
some factors which affect current consumption. Current consumption is described by
the formula:
where:
For example, for an address pin loaded with a 50 pF capacitance and operating at 5.5
V with a 60 MHz clock, toggling at its maximum possible rate (which is 15 MHz), the
current consumption is:
The maximum internal current value (I
when running a test code. This represents “typical” internal activity, and is included
as a point of reference. Some applications may consume more or less current
depending on the code used. The typical internal current value (I
what is typically seen when running the given code.
The following steps are recommended for applications requiring very low current
consumption:
1. Minimize external memory accesses; use internal memory accesses instead.
2. Minimize the number of pins that are switching.
3. Minimize the capacitive load on the pins.
4. Connect unused digital inputs to V
5. All Port A input pins and bidirectional pins must have a valid state at all times
6. When the codec is not used, connect V
through 10 k resistors to V
when Port A is released to minimize power consumption; therefore the pins
must be pulled up or down or driven by another device.
decouple VRAD and VARD. Leave all other codec pins floating.
C = node/pin capacitance in F
V = voltage swing in V
I
I = current in A
f = frequency of node/pin toggle (in Hz)
I
=
=
C V f
50 10
–
12
5.5 15 10
DSP56167/D, Rev. 1
6
DD
=
4.125mA
CCI
or V
-max), reflects the maximum I
DD
SS
.
or V
DDA
SS
to V
. Connect unused I/O pins
DD
and V
SSA
CCI
to V
-typ) reflects
MOTOROLA
SS
CC
and
expected