ADSP-2184L 데이터 시트보기 (PDF) - Analog Devices

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ADSP-2184L

DSP Microcomputer

Analog Devices 

ADSP-2184L/ADSP-2185L/ADSP-2186L/ADSP-2187L

TEST CONDITIONS

Figure 44 shows voltage reference levels for all ac measurements

(except output disable/enable).

INPUT

OR

OUTPUT

1.5V

1.5V

Figure 44. Voltage Reference Levels for AC Measurements (Except Output

Enable/Disable)

Output Disable Time

Output pins are considered to be disabled when they have

stopped driving and started a transition from the measured out-

put high or low voltage to a high impedance state. The output

disable time (tDIS) is the difference of tMEASURED and tDECAY, as

shown in Figure 45. The time is the interval from when a refer-

ence signal reaches a high or low voltage level to when the

output voltages have changed by 0.5 V from the measured out-

put high or low voltage.

The decay time, tDECAY, is dependent on the capacitive load, CL,

and the current load, iL, on the output pin. It can be approxi-

mated by the following equation:

from which

tDECAY

=

C-----L---×-----0---.-5----V--

iL

tDIS = tMEASURED – tDECAY

is calculated. If multiple pins (such as the data bus) are disabled,

the measurement value is that of the last pin to stop driving.

Output Enable Time

Output pins are considered to be enabled when they have made

a transition from a high-impedance state to when they start

driving. The output enable time (tENA) is the interval from when

a reference signal reaches a high or low voltage level to when the

output has reached a specified high or low trip point, as shown

in Figure 45. If multiple pins (such as the data bus) are enabled,

the measurement value is that of the first pin to start driving.

REFERENCE

SIGNAL

tMEASURED

VOH tDIS

(MEASURED)

OUTPUT

VOL

(MEASURED)

VOH (MEASURED) – 0.5V

VOL (MEASURED) + 0.5V

tDECAY

tENA

VOH

(MEASURED)

2.0V

1.0V

VOL

(MEASURED)

OUTPUT STOPS

DRIVING

OUTPUT STARTS

DRIVING

HIGH-IMPEDANCE STATE. TEST CONDITIONS CAUSE

THIS VOLTAGE LEVEL TO BE APPROXIMATELY 1.5V.

Figure 45. Output Enable/Disable

IOL

TO

OUTPUT

PIN

50pF

1.5V

IOH

Figure 46. Equivalent Loading for AC Measurements (Including All Fixtures)

ENVIRONMENTAL CONDITIONS

Table 28. Thermal Resistance

Rating Description1

LQFP

Symbol (°C/W)

Thermal Resistance (Case- θCA

48

to-Ambient)

Thermal Resistance

θJA

50

(Junction-to-Ambient)

Thermal Resistance

θJC

2

(Junction-to-Case)

1 Where the ambient temperature rating (TAMB) is:

TAMB = TCASE – (PD × θCA)

TCASE = case temperature in °C

PD = power dissipation in W

BGA

(°C/W)

63.3

70.7

7.4

Rev. C | Page 43 of 48 | January 2008

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