HCPL-5301 Avago Technologies US Inc., HCPL-5301 Datasheet - Page 8

• Manufacturer Part Number: HCPL-5301
• Description: OPTOCOUPLER HERM CLASS H 8DIP
• Manufacturer: Avago Technologies US Inc.

Specifications of HCPL-5301

• Mounting Type: Through Hole
• Voltage - Isolation: 1500VDC
• Number Of Channels: 1, Unidirectional
• Current - Output / Channel: 15mA
• Data Rate: 2MBd
• Propagation Delay High - Low @ If: 180ns @ 10mA
• Current - Dc Forward (if): 25mA
• Input Type: DC
• Output Type: Open Collector
• Package / Case: 8-DIP (0.300", 7.62mm)
• No. Of Channels: 1
• Optocoupler Output Type: Gate Drive
• Input Current: 20mA
• Output Voltage: 30V
• Opto Case Style: DIP
• No. Of Pins: 8
• Body Material: Gold Plated
• Ctr Min: 30%
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

LED Drive Circuit Considerations For Ultra High CMR
Performance
Without a detector shield, the dominant cause of
optocoupler CMR failure is capacitive coupling from the
input side of the optocoupler, through the package, to
the detector IC as shown in Figure 14. The HCPL-530X
improves CMR performance by using a detector IC with
an optically transparent Faraday shield, which diverts the
capacitively coupled current away from the sensitive IC
circuitry. However, this shield does not eliminate the
capacitive coupling between the LED and the optocoupler
output pins and output ground as shown in Figure 15.
This capacitive coupling causes perturbations in the LED
current during common mode transients and becomes
the major source of CMR failures for a shielded
optocoupler. The main design objective of a high CMR
LED drive circuit becomes keeping the LED in the proper
state (on or off) during common mode transients. For
example, the recommended application circuit (Figure 13),
can achieve 10 kV/ s CMR while minimizing component
complexity. Note that a CMOS gate is recommended in
Figure 13 to keep the LED off when the gate is in the high
state.
Another cause of CMR failure for a shielded optocoupler is
direct coupling to the optocoupler output pins through
C
effect and magnitude of the direct coupling including: the
use of an internal or external output pull-up resistor, the
position of the LED current setting resistor, the connection
of the unused input package pins, and the value of the
capacitor at the optocoupler output (CL).
Techniques to keep the LED in the proper state and
minimize the effect of the direct coupling are discussed in
the next two sections.
CMR With The LED On (CMR
A high CMR LED drive circuit must keep the LED on during
common mode transients. This is achieved by overdriving
the LED current beyond the input threshold so that it is
not pulled below the threshold during a transient. The
recommended minimum LED current of 10 mA provides
adequate margin over the maximum I
Figure 1) to achieve 10 kV/ s CMR. Capacitive coupling is
8
LEDO1
and C
LEDO2
in Figure 15. Many factors influence the
L
)
TH
of 5.0 mA (see
higher when the internal load resistor is used (due to
C
CMR.
The placement of the LED current setting resistor affects
the ability of the drive circuit to keep the LED on during
transients and interacts with the direct coupling to the
optocoupler output. For example, the LED resistor in Figure
16 is connected to the anode. Figure 17 shows the AC
equivalent circuit for Figure 16 during common mode
transients. During a +dV
available at the LED anode (I
resistor. The LED current (I
by an amount equal to the current that flows through
C
current through C
output high (toward a CMR failure) at the same time the
LED current is being reduced. For this reason, the
recommended LED drive circuit (Figure 13) places the
current setting resistor in series with the LED cathode.
Figure 18 is the AC equivalent circuit for Figure 13 during
common mode transients. In this case, the LED current is
not reduced during a +dV
current flowing through the package capacitance is
supplied by the power supply. During a -dV
however, the LED current is reduced by the amount of
current flowing through C
performance is achieved since the current flowing in C
during a negative transient acts to keep the output low.
Coupling to the LED and output pins is also affected by
the connection of pins 1 and 4. If CMR is limited by
perturbations in the LED on current, as it is for the
recommended drive circuit (Figure 13), pins 1 and 4 should
be connected to the input circuit common. However, if
CMR performance is limited by direct coupling to the
output when the LED is off, pins 1 and 4 should be left
unconnected.
CMR With The LED Off (CMR
A high CMR LED drive circuit must keep the LED off
(V
during a +dV
through C
the LED and series resistor. As long as the voltage
LEDO2
LEDP
F
V
and C
) and an I
F(OFF)
LEDN
) during common mode transients. For example,
LEDO1
CM/dt
is supplied by the parallel combination of
. The situation is made worse because the
F
transient in Figure 18, the current flowing
= 16mA is required to obtain 10 kV/ s
LEDO1
has the effect of trying to pull the
CM/dt
H
F
)
) is reduced from its DC value
CM/dt
TOTAL
in Figure 17, the current
LEDN
) is limited by the series
transient because the
. But better CMR
CM/dt
transient,
LEDO1