REV. A
ADSP-2189M
–16–
FREQUENCY DEPENDENCY FOR TIMING
SPECIFICATIONS
t
CK
is
defined as 0.5t
CKI
. 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). t
CK
values within the range of
0.5t
CKI
period should be substituted for all relevant timing pa-
rameters to obtain the specification value.
Example: t
CKH
= 0.5t
CK
– 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) θ
JA
50°C/W
(Junction-to-Case) θ
JC
2°C/W
NOTE
1
Where the ambient temperature rating (T
AMB
) is:
T
AMB
= T
CASE
– (PD × θ
CA
)
T
CASE
= 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 × V
DD
2
× 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 V
DDEXT
= 3.3 V and t
CK
= 15 ns.
Total Power Dissipation = P
INT
+ (C × V
DDEXT
2
× f)
P
INT
= internal power dissipation from Power vs. Frequency
graph (Figure 15).
(C × V
DDEXT
2
× f) is calculated for each output:
# of ⴛⴛ ⴛ
Parameters Pins C V
DDEXT
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 P
INT
+ 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.
V
OH
V
OL
SOURCE VOLTAGE – V
0
0.5 1.0
SOURCE CURRENT – mA
60
0
–20
–40
–60
40
20
V
DDEXT
= 3.6V @ –40ⴗC
V
DDEXT
= 3.3V @ +25ⴗC
V
DDEXT
= 2.5V @ +85ⴗC
V
DDEXT
= 2.5V @ +85ⴗC
V
DDEXT
= 3.3V @ +25ⴗC
V
DDEXT
= 3.6V @ –40ⴗC
80
–80
1.5 2.0 2.5 3.0 3.5 4.0
Figure 14. Typical Output Driver Characteristics
