ACSL datasheet(16/17 Pages) AVAGO

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With a CMOS gate to drive the optocoupler, the circuit

shown in Figure 19 can be used. The diode in parallel to

the current limiting resistor speeds the turn-off of the

optocoupler LED. Any HC or HCT series CMOS gate can

be used in this circuit.

For high common-mode rejection applications, the drive

circuit shown in Figure 20 is recommended. In this circuit,

only an open-collector TTL, or an open drain CMOS gate

can be used. This circuit drives the optocoupler LED with

a 220 ohm current-limiting resistor to ensure that an I

of 7 mA is applied under worst case conditions and thus

guarantee the 10,000 V/µs optocoupler common mode

rejection rating. The designer can obtain even higher

common-mode rejection performance than 10,000 V/µs

by driving the LED harder than 7 mA.

Phase Relationship to Input

The output of the optocoupler is inverted when

compared to the input. The input is defined to be logic

HIGH when the LED is ON. If there is a design that requires

the optocoupler to behave as a non-inverting gate, then

Figure 20. High CMR drive circuit for the ACSL-6xx0.

Figure 21. High voltage switching with ACSL-6xx0.

Figure 22. High voltage and high current switching

with ACSL-6xx0.

Figure 19. CMOS drive circuit for the ACSL-6xx0.

the series input drive circuit shown in Figure 19 can be

used. This input drive circuit has an inverting function,

and since the optocoupler also behaves as an inverter,

the total circuit is non-inverting. The shunt drive circuits

shown in Figures 18 and 20 will cause the optocoupler to

function as an inverter.

Current and Voltage Limitations

The absolute maximum voltage allowable at the output

supply voltage pin and the output voltage pin of the opt-

ocoupler is 7 volts. However, the recommended maximum

voltage at these two pins is 5.5 volts. The output sinking

current should not exceed 13 mA in order to make the

Low Level Output Voltage be less than 0.6 volt. If the

output voltage is not a consideration, then the absolute

maximum current allowed through the ACSL-6xx0 is 50

mA. If the output requires switching either higher currents

or voltages, output buffer stages as shown in Figures 21

and 22 are suggested.

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