REV. A
ADSP-2189M
–16–
FREQUENCY DEPENDENCY FOR TIMING
SPECIFICATIONS
tCK is defined as 0.5tCKI. The ADSP-2189M uses an input clock
with a frequency equal to half the instruction rate: a 37.50 MHz
input clock (which is equivalent to 28 ns) yields a 13 ns proces-
sor cycle (equivalent to 75 MHz). tCK values within the range of
0.5tCKI period should be substituted for all relevant timing pa-
rameters to obtain the specification value.
Example: tCKH = 0.5tCK – 7 ns = 0.5 (15 ns) – 7 ns = 0.5 ns
ENVIRONMENTAL CONDITIONS
1
Rating Description
Symbol
Value
Thermal Resistance
(Case-to-Ambient)
θ
CA
48
°C/W
(Junction-to-Ambient)
θJA
50
°C/W
(Junction-to-Case)
θJC
2
°C/W
NOTE
1Where the ambient temperature rating (T
AMB) is:
TAMB = TCASE – (PD
× θCA)
TCASE = Case temperature in
°C
PD = Power dissipation in W.
POWER DISSIPATION
To determine total power dissipation in a specific application,
the following equation should be applied for each output:
C
× VDD2 × f
C = load capacitance, f = output switching frequency.
Example:
In an application where external data memory is used and no
other outputs are active, power dissipation is calculated as follows:
Assumptions:
External data memory is accessed every cycle with 50% of
the address pins switching.
External data memory writes occur every other cycle with
50% of the data pins switching.
Each address and data pin has a 10 pF total load at the pin.
The application operates at VDDEXT = 3.3 V and tCK = 15 ns.
Total Power Dissipation = PINT + (C
× VDDEXT2 × f)
PINT = internal power dissipation from Power vs. Frequency
graph (Figure 15).
(C
× VDDEXT2 × f) is calculated for each output:
# of
Parameters
Pins C
VDDEXT
2
fPD
Address,
DMS
8
10 pF
3.3
2 V
33.3 MHz
29.0 mW
Data Output,
WR 9
10 pF
3.3
2 V
16.67 MHz
16.3 mW
RD
1
10 pF
3.3
2 V
16.67 MHz
1.8 mW
CLKOUT
1
10 pF
3.3
2 V
33.3 MHz
3.6 mW
50.7 mW
Total power dissipation for this example is PINT + 50.7 mW.
Output Drive Currents
Figure 14 shows typical I-V characteristics for the output drivers
on the ADSP-2189M. The curves represent the current drive
capability of the output drivers as a function of output voltage.
VOH
VOL
SOURCE VOLTAGE – V
0
0.5
1.0
SOURCE
CURRENT
–
mA
60
0
–20
–40
–60
40
20
VDDEXT = 3.6V @ –40 C
VDDEXT = 3.3V @ +25 C
VDDEXT = 2.5V @ +85 C
VDDEXT = 3.3V @ +25 C
VDDEXT = 3.6V @ –40 C
80
–80
1.5
2.0
2.5
3.0
3.5
4.0
Figure 14. Typical Output Driver Characteristics