Datasheet

ADSP-2185
–15–
REV. 0
ENVIRONMENTAL CONDITIONS
Ambient Temperature Rating:
T
AMB
= T
CASE
– (PD x θ
CA
)
T
CASE
= Case Temperature in °C
PD = Power Dissipation in W
θ
CA
= Thermal Resistance (Case-to-Ambient)
θ
JA
= Thermal Resistance (Junction-to-Ambient)
θ
JC
= Thermal Resistance (Junction-to-Case)
Package u
JA
u
JC
u
CA
TQFP 50°C/W 2°C/W 48°C/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
DD
= 5.0 V and t
CK
= 30 ns.
Total Power Dissipation = P
INT
+ (C × V
DD
2
× f)
P
INT
= internal power dissipation from Power vs. Frequency
graph (Figure 8).
(C × V
DD
2
× f) is calculated for each output:
# of
Pins 3 C 3 V
DD
2
3f
Address, DMS 8 × 10 pF × 5
2
V × 33.3 MHz = 66.6 mW
Data Output, WR 9 × 10 pF × 5
2
V × 16.67 MHz = 37.5 mW
RD 1 × 10 pF × 5
2
V × 16.67 MHz = 4.2 mW
CLKOUT 1 × 10 pF × 5
2
V × 33.3 MHz = 8.3 mW
116.6 mW
Total power dissipation for this example is P
INT
+ 116.6 mW.
1/ t
CK
– MHz
POWER (P
INT
) – mW
440
340
280
28 34
29 30 31 32 33
420
360
320
300
400
380
260
240
220
200
2185 POWER, INTERNAL
1, 3, 4
V
DD
= 5.5V
V
DD
= 5.0V
V
DD
= 4.5V
396mW
315mW
243mW
349mW
277mW
214mW
1/f
CK
– MHz
95
60
45
28 34
29 30 31 32 33
90
65
55
50
85
75
80
70
40
POWER, IDLE
1, 2
POWER (P
IDLE
) – mW
83mW
62mW
45mW
40mW
56mW
75mW
V
DD
= 5.5V
V
DD
= 5.0V
V
DD
= 4.5V
1/f
CK
– MHz
75
40
30
28 3429 30 31 32 33
70
45
35
65
55
60
50
25
POWER, IDLE n MODES
3
62mW
38mW
36mW
34mW
36mW
56mW
IDLE
IDLE (16)
IDLE (128)
POWER (P
IDLE
n
) – mW
VALID FOR ALL TEMPERATURE GRADES.
1
POWER REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.
2
IDLE REFERS TO ADSP-2185 STATE OF OPERATION DURING EXECUTION OF IDLE
INSTRUCTION. DEASSERTED PINS ARE DRIVEN TO EITHER V
DD
OR GND.
3
TYPICAL POWER DISSIPATION AT 5.0V V
DD
AND 25°C EXCEPT WHERE SPECIFIED.
4
I
DD
MEASUREMENT TAKEN WITH ALL INSTRUCTIONS EXECUTING FROM INTERNAL
MEMORY. 50% OF THE INSTRUCTIONS ARE MULTIFUNCTION (TYPES 1, 4, 5, 12, 13, 14),
30% ARE TYPE 2 AND TYPE 6, AND 20% ARE IDLE INSTRUCTIONS.
Figure 8. Power vs. Frequency