ADSP-2185 Datasheet, PDF (15/32 Pages) Analog Devices – DSP Microcomputer

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
TQFP
␪_JA
50°C/W
␪_JC
2°C/W
␪_CA
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_DD2 × 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_DD² × f)
P_INT = internal power dissipation from Power vs. Frequency
graph (Figure 8).
(C × V_DD² × f) is calculated for each output:
# of
Pins ؋ C
؋ V_DD2 ؋f
Address, DMS 8
Data Output, WR 9
RD
1
CLKOUT
1
× 10 pF × 5² V
× 10 pF × 5² V
× 10 pF × 5² V
× 10 pF × 5² V
× 33.3 MHz = 66.6 mW
× 16.67 MHz = 37.5 mW
× 16.67 MHz = 4.2 mW
× 33.3 MHz = 8.3 mW
116.6 mW
Total power dissipation for this example is P_INT + 116.6 mW.
ADSP-2185
2185 POWER, INTERNAL^{1, 3, 4}
440
420
400
396mW
380
V_DD = 5.5V
360 349mW
340
320
300
280 ^277mW
V_DD = 5.0V
315mW
260
240
220 _214mW
200
28 29
95
90
85
80
V_DD = 4.5V
30 31 32
1/t_CK – MHz
POWER, IDLE^{1, 2}
V_DD = 5.5V
243mW
33 34
83mW
75
75mW
70
65
60 _56mW
55
V_DD = 5.0V
62mW
50
45
40mW
40
28 29
V_DD = 4.5V
30 31 32
1/f_CK – MHz
45mW
33 34
POWER, IDLE n MODES³
75
70
65
60
56mW
55
62mW _IDLE
50
45
40 _36mW
35
34mW
30
38mW
36mW
IDLE (16)
IDLE (128)
25
28 29 30 31 32 33 34
1/f_CK – MHz
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 VDD AND 25°C EXCEPT WHERE SPECIFIED.}
4_{IDD 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
REV. 0
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