HCPL-260L Datasheet, PDF (19/19 Pages) AVAGO TECHNOLOGIES LIMITED – High Speed LVTTL Compatible 3.3 Volt Optocouplers Low power consumption

Likewise for common-mode transients which occur
when the LED is off (i.e. CMR_H, since the output is “high”),
if an imbalance between I_LP and I_LN results in a transient
I_F equal to or greater than the switching threshold of the
optocoupler, the transient “signal” may cause the output
to spike below 2 V (which consti­tutes a CMR_H failure).
By using the recommended circuit in Figure 13, good
CMR can be achieved. The balanced I_LED-setting resistors
help equalize I_LP and I_LN to reduce the amount by which
I_LED is modulated from transient coupling through C_LA
and C_LC.
CMR with Other Drive Circuits
CMR performance with drive circuits other than that
shown in Figure 13 may be enhanced by following these
guidelines:
1. Use of drive circuits where current is shunted from the
LED in the LED “off” state (as shown in Figures 15 and
16). This is beneficial for good CMR_H.
2. Use of I_FH > 3.5 mA. This is good for high CMR_L.
Figure 15 shows a circuit which can be used with any
totem-pole-output TTL/LSTTL/HCMOS logic gate. The
buffer PNP transistor allows the circuit to be used with
logic devices which have low current-sinking capability.
It also helps maintain the driving-gate power-supply cur-
rent at a constant level to minimize ground shifting for
other devices connected to the input-supply ground.
When using an open-collector TTL or open-drain CMOS
logic gate, the circuit in Figure 16 may be used. When
using a CMOS gate to drive the optocoupler, the circuit
shown in Figure 17 may be used. The diode in parallel
with the R_LED speeds the turn-off of the optocoupler
LED.
74L504
(ANY
TTL/CMOS
GATE)
V_CC
420 Ω
(MAX)
HCPL-260L
1
2N3906
2
(ANY PNP)
3
LED
4
Figure 15. TTL interface circuit.
V_CC
HCPL- 261A fig 21
R
74HC00
(OR ANY
OPEN-COLLECTOR/
OPEN-DRAIN
LOGIC GATE)
HCPL-260L
1
2
LED
3
4
Figure 16. TTL open-collector/open drain gate drive circuit.
V_CC
74HC04
(OR ANY
TOTEM-POLE
OUTPUT LOGIC
GATE)
HCPL- 261A fig 22 ^HCPL-260L
1N4148
1
2
220 Ω
3
LED
4
Figure 17. CMOS gate drive circuit.
HCPL- 261A fig 23
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Data subject to change. Copyright © 2005-2013 Avago Technologies. All rights reserved. Obsoletes AV01-0581EN
AV02-0616EN - May 13, 2013