ADSP-2187NBST-320 View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

ADSP-2187NBST-320

DSP Microcomputer

Analog Devices 

ADSP-218xN Series

Environmental Conditions

Table 14. Thermal Resistance

Rating Description1

LQFP

Symbol (°C/W)

Thermal Resistance

θCA

48

(Case-to-Ambient)

Thermal Resistance

θJA

50

(Junction-to-Ambient)

Thermal Resistance

θJC

2

(Junction-to-Case)

1Where the Ambient Temperature Rating (TAMB) is:

TAMB = TCASE – (PD × θCA)

TCASE = Case Temperature in °C

PD = Power Dissipation in W

Mini-

BGA

(°C/W)

63.3

70.7

7.4

Test Conditions

INPUT

1.5V

OUTPUT

2.0V

1.5V

0.8V

Figure 16. Voltage Reference Levels for AC

Measurements (Except Output Enable/Disable)

IOL

TO

OUTPUT

PIN

50pF

1.5V

IOH

Figure 17. Equivalent Loading for AC Measurements

(Including All Fixtures)

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 18. 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

output 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 18. The time is the interval from

when a reference signal reaches a high or low voltage level

to when the output voltages have changed by 0.5 V from the

measured output 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

approximated by the following equation:

tDECAY

=

C-----L-----×----0---.--5---V---

iL

from which

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 18. If multiple pins (such as

the data bus) are enabled, the measurement value is that of

the first pin to start driving.

–24–

REV. 0

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