HCPL-063A Ver la hoja de datos (PDF) - HP => Agilent Technologies

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HCPL-063A

HCMOS Compatible, High CMR, 10 MBd Optocouplers

HP => Agilent Technologies 

VCC BUS (FRONT)

N.C.

N.C.

N.C.

N.C.

SINGLE CHANNEL PRODUCTS

GND BUS (BACK)

0.1µF

0.1µF

ENABLE

(IF USED)

OUTPUT 1

ENABLE

(IF USED)

OUTPUT 2

10 mm MAX. (SEE NOTE 16)

Application Information

Common-Mode Rejection for

HCPL-261A/HCPL-261N

Families:

Figure 20 shows the recom-

mended drive circuit for the

HCPL-261N/-261A for optimal

common-mode rejection

performance. Two main points to

note are:

1. The enable pin is tied to VCC

rather than floating (this

applies to single-channel parts

only).

2. Two LED-current setting

resistors are used instead of

one. This is to balance ILED

variation during common-

mode transients.

VCC BUS (FRONT)

DUAL CHANNEL PRODUCTS

GND BUS (BACK)

0.1µF

OUTPUT 1

OUTPUT 2

10 mm MAX. (SEE NOTE 16)

Figure 19. Recommended Printed Circuit Board Layout.

VCC

*

HCPL-261A/261N

1

8

357 Ω

(MAX.)

2

7

357 Ω

(MAX.)

3

6

74LS04

OR ANY TOTEM-POLE

OUTPUT LOGIC GATE

4

5

SHIELD

*

GND1

0.01 µF

VCC+

350 Ω

VO

GND

GND2

* HIGHER CMR MAY BE OBTAINABLE BY CONNECTING PINS 1, 4 TO INPUT GROUND (GND1).

Figure 20. Recommended Drive Circuit for HCPL-261A/-261N Families for High-

CMR (Similar for HCPL-263A/-263N).

*Higher CMR May Be Obtainable by Connecting Pins 1, 4 to Input Ground (Gnd1).

If the enable pin is left floating, it

is possible for common-mode

transients to couple to the enable

pin, resulting in common-mode

failure. This failure mechanism

only occurs when the LED is on

and the output is in the Low

State. It is identified as occurring

when the transient output voltage

rises above 0.8 V. Therefore, the

enable pin should be connected

to either VCC or logic-level high

for best common-mode

performance with the output low

(CMRL). This failure mechanism

is only present in single-channel

parts (HCPL-261N, -261A,

-061N, -061A) which have the

enable function.

Also, common-mode transients

can capacitively couple from the

LED anode (or cathode) to the

output-side ground causing

current to be shunted away from

the LED (which can be bad if the

LED is on) or conversely cause

current to be injected into the

LED (bad if the LED is meant to

be off). Figure 21 shows the

parasitic capacitances which

exists between LED

1-178

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