Datasheet

REV. 0
ADSP-2188M
–21–
• 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
= 30 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 ⴛ C ⴛ V
DDEXT
2
ⴛ fPD
Parameters Pins pF V MHz mW
Address 7 10 3.3
2
16.67 12.7
Data Output, WR 9 10 3.3
2
16.67 16.3
RD 1 10 3.3
2
16.67 1.8
CLKOUT, DMS 2 10 3.3
2
33.3 7.2
38.0
Total power dissipation for this example is P
INT
+ 38.0 mW.
Output Drive Currents
Figure 14 shows typical I-V characteristics for the output drivers
on the ADSP-2188M. 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
FREQUENCY DEPENDENCY FOR TIMING
SPECIFICATIONS
t
CK
is defined as 0.5 t
CKI
. The ADSP-2188M uses an input clock
with a frequency equal to half the instruction rate. For example,
a 37.50 MHz input clock (which is equivalent to 26.6 ns) yields
a 13.3 ns processor cycle (equivalent to 75 MHz). t
CK
values
within the range of 0.5 t
CKI
period should be substituted for all
relevant timing parameters to obtain the specification value.
Example: t
CKH
= 0.5 t
CK
– 2 ns = 0.5 (15 ns) – 2 ns = 5.5 ns
ENVIRONMENTAL CONDITIONS
1
Rating
Description Symbol LQFP Mini-BGA
Thermal Resistance θ
CA
48°C/W 63.3°C/W
(Case-to-Ambient)
Thermal Resistance θ
JA
50°C/W 70.7°C/W
(Junction-to-Ambient)
Thermal Resistance θ
JC
2°C/W 7.4°C/W
(Junction-to-Case)
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.