ADSP2181 datasheet(25/32 Pages) AD

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ADSP-2181

–25–

REV. D

OUTPUT DRIVE CURRENTS

Figure 19 shows typical I-V characteristics for the output drivers

of the ADSP-2181. The curves represent the current drive

capability of the output drivers as a function of output voltage.

SOURCE VOLTAGE – Volts

120

–80

100

–20

–40

–60

5.5V, –40 C

5.0V, +25 C

4.5V, +85 C

5.0V, +25 C

5.5V, –40 C

Figure 19. Typical Drive Currents

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

× V

× f )

PINT = internal power dissipation from Power vs. Frequency

graph (Figure 20).

TEMPERATURE –

°C

1000

100

585

–5

VDD = 5.5V

VDD = 5.0V

VDD = 4.5V

NOTES:

1. REFLECTS ADSP-2181 OPERATION IN LOWEST POWER MODE.

(SEE “SYSTEM INTERFACE" CHAPTER OF THE

ADSP-2100 FAMILY

USER'S MANUAL, THIRD EDITION, FOR DETAILS.)

2. CURRENT REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.

Figure 20. Power-Down Supply Current (Typical)

× 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.

1/tCK – MHz

220

420

370

320

270

570

470

520

2181 POWER, INTERNAL1, 3, 4

VDD = 5.5V

VDD = 5.0V

VDD = 4.5V

410mW

325mW

250mW

550mW

425mW

330mW

1/tCK – MHz

100

POWER, IDLE1, 2, 3

VDD = 5.5V

VDD = 5.0V

VDD = 4.5V

77mW

60mW

45mW

95mW

75mW

54mW

1/tCK – MHz

POWER, IDLE

n MODES3

IDLE

IDLE (16)

IDLE (128)

60mW

35mW

34mW

39mW

37mW

75mW

VALID FOR ALL TEMPERATURE GRADES.

4IDD 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.

3TYPICAL POWER DISSIPATION AT 5.0V VDD AND 25 C EXCEPT WHERE SPECIFIED.

2IDLE REFERS TO ADSP-2181 STATE OF OPERATION DURING EXECUTION OF IDLE

1POWER REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.

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

Figure 21. Power vs. Frequency

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