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ADSP-2185

–15–

REV. 0

ENVIRONMENTAL CONDITIONS

Ambient Temperature Rating:

TAMB = TCASE – (PD x

CA)

TCASE = Case Temperature in

°C

PD = Power Dissipation in W

CA = Thermal Resistance (Case-to-Ambient)

JA = Thermal Resistance (Junction-to-Ambient)

JC = Thermal Resistance (Junction-to-Case)

Package

TQFP

°C/W

POWER DISSIPATION

To determine total power dissipation in a specific application,

the following equation should be applied for each output:

× V

× 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 VDD = 5.0 V and tCK = 30 ns.

Total Power Dissipation = PINT + (C × VDD

× f)

PINT = internal power dissipation from Power vs. Frequency

graph (Figure 8).

× V

× f) is calculated for each output:

# of

Pins

VDD

Address,

DMS

× 10 pF × 52 V × 33.3 MHz = 66.6 mW

Data Output,

WR 9

× 10 pF × 52 V × 16.67 MHz = 37.5 mW

× 10 pF × 52 V × 16.67 MHz = 4.2 mW

CLKOUT

× 10 pF × 52 V × 33.3 MHz = 8.3 mW

116.6 mW

Total power dissipation for this example is PINT + 116.6 mW.

tCK – MHz

440

340

280

420

360

320

300

400

380

260

240

220

200

2185 POWER, INTERNAL1, 3, 4

VDD = 5.5V

VDD = 5.0V

VDD = 4.5V

396mW

315mW

243mW

349mW

277mW

214mW

1/fCK – MHz

POWER, IDLE1, 2

83mW

62mW

45mW

40mW

56mW

75mW

VDD = 5.5V

VDD = 5.0V

VDD = 4.5V

1/fCK – MHz

POWER, IDLE

n MODES3

62mW

38mW

36mW

34mW

36mW

56mW

IDLE

IDLE (16)

IDLE (128)

VALID FOR ALL TEMPERATURE GRADES.

1POWER REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.

2IDLE REFERS TO ADSP-2185 STATE OF OPERATION DURING EXECUTION OF IDLE

INSTRUCTION. DEASSERTED PINS ARE DRIVEN TO EITHER VDD OR GND.

3TYPICAL POWER DISSIPATION AT 5.0V V

DD AND 25°C EXCEPT WHERE SPECIFIED.

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

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