ADSP-2173 datasheet(29/52 Pages) AD

29 / 52 page

ADSP-2171/ADSP-2172/ADSP-2173

REV. A

–29–

ADSP-2171/ADSP-2172

ENVIRONMENTAL CONDITIONS

Ambient Temperature Rating:

TAMB = TCASE – (PD × θCA)

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

PQFP

°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 V

DD = 5.0 V and tCK = 30 ns.

Total Power Dissipation = PINT + (C × VDD

× f )

PINT = internal power dissipation from Power vs. Frequency

graph (Figure 18).

× V

× f ) is calculated for each output:

# of

Pins

× C

× V

× f

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.

VALID FOR ALL TEMPERATURE GRADES.

1 POWER REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.

2 IDLE REFERS TO ADSP-2171 STATE OF OPERATION DURING

EXECUTION OF IDLE INSTRUCTION. DEASSERTED PINS ARE

DRIVEN TO EITHER V

DD OR GND. POWER REFLECTS DEVICE

OPERATING WITH CLKOUT DISABLED.

3 TYPICAL POWER DISSIPATION AT 5.0V V

DD DURING EXECUTION

IDLE N INSTRUCTION (CLOCK FREQUENCY REDUCTION).

POWER REFLECTS DEVICE OPERATING WITH CLKOUT DISABLED.

POWER, INTERNAL

= 4.5V

186mW

382mW

229mW

148mW

110mW

= 5.0V

= 5.5V

225

175

200

300

250

275

325

375

350

400

150

125

301mW

/ t

– MHz

POWER, IDLE

/ t

– MHz

48mW

37mW

26mW

82mW

48mW

64mW

= 4.5V

= 5.0V

= 5.5V

IDLE;

IDLE (16)

IDLE (128)

/ t

– MHz

POWER,

IDLE n MODES

82mW

20mW

37mW

23mW

31mW

64mW

28mW

1, 2

Figure 18. Power vs. Frequency

ADSP-2173 Datasheet(PDF) 29 Page - Analog Devices

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