5962-9755701HXA Avago Technologies US Inc., 5962-9755701HXA Datasheet - Page 14

• Manufacturer Part Number: 5962-9755701HXA
• Description: IC,Isolation Amplifier,HYBRID,DIP,8PIN,CERAMIC
• Manufacturer: Avago Technologies US Inc.

Specifications of 5962-9755701HXA

• Amplifier Type: Isolation
• Number Of Circuits: 1
• Output Type: Differential
• -3db Bandwidth: 100kHz
• Current - Input Bias: 570nA
• Voltage - Input Offset: 600µV
• Current - Supply: 10.7mA
• Current - Output / Channel: 11mA
• Voltage - Supply, Single/dual (±): 4.5 V ~ 5.5 V
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SMD Gull Wing
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Slew Rate: -
• Gain Bandwidth Product: -
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

As shown in Figure 24, a 0.1 F bypass capacitor (C2, C4)
should be located as close as possible to the input and
output power supply pins of the HCPL-7850. The bypass
capacitors are required because of the high-speed digital
nature of the signals inside the isolation amplifier. A 0.01
pin(s) due to the switched-capacitor nature of the input
circuit. The input bypass capacitor should be at least
1000 pF to maintain gain accuracy of the isolation amplifier.
Inductive coupling between the input power-supply
capacitor and the input circuit, including the input bypass
capacitor and the input leads of the HCPL-7850, can
introduce additional DC offset in the circuit. Several steps
can be taken to minimize the mutual coupling between
the two parts of the circuit, thereby improving the offset
performance of the design. Separate the two bypass
capacitors C2 and C3 as much as possible (even putting
them on opposite sides of the PC board), while keeping
the total lead lengths, including traces, of each bypass
capacitor less than 20 mm. PC board traces should be
made as short as possible and placed close together or
over ground plane to minimize loop area and pickup of
stray magnetic fields. Avoid using sockets, as they will
typically increase both loop area and inductance. And
finally, using capacitors with small body size and orienting
them perpendicular to each other on the PC board can
also help. For more information concerning this effect, see
Application Note 1078, Designing with Avago
Technologies Isolation Amplifiers.
Shunt Resistor Selections
The current-sensing shunt resistor should have low
resistance (to minimize power dissipation), low inductance
(to minimize di/dt induced voltage spikes which could
adversely affect operation), and reasonable tolerance (to
maintain overall circuit accuracy). The value of the shunt
should be chosen as a compromise between minimizing
power dissipation by making the shunt resistance smaller
and improving circuit accuracy by making it larger and
utilizing the full input range of the HCPL-7850. Avago
Technologies recommends four different shunts which can
be used to sense average currents in motor drives up to
35 A and 35 hp. Table 1 shows the maximum current and
horsepower range for each of the LVR-series shunts from
Dale. Even higher currents can be sensed with lower value
shunts available from vendors such as Dale, IRC, and Isotek
(Isabellenhuette). When sensing currents large enough to
cause significant heating of the shunt, the temperature
14
F bypass capacitor (C3) is also recommended at the input
coefficient of the shunt can introduce nonlinearity due to
the signal dependent temperature rise of the shunt. Using
a heat sink for the shunt or using a shunt with a lower
tempco can help minimize this effect. The Application
Note 1078, Designing with Avago Technologies
Isolation Amplifiers, contains additional information on
designing with current shunts.
The recommended method for connecting the isolation
amplifier to the shunt resistor is shown in Figure 24. Pin 2
(V
resistor, while pin 3 (V
the power-supply return path functioning as the sense
line to the negative terminal of the current shunt. This
allows a single pair of wires or PC board traces to connect
the isolation amplifier circuit to the shunt resistor. In some
applications, however, supply currents flowing through
the power-supply return path may cause offset or noise
problems. In this case, better performance may be
obtained by connecting pin 3 to the negative terminal of
the shunt resistor separate from the power supply return
path. When connected this way, both input pins should
be bypassed. Whether two or three wires are used, it is
recommended that twisted-pair wire or very close PC
board traces be used to connect the current shunt to the
isolation amplifier circuit to minimize electromagnetic
interference to the sense signal.
The 68
low-pass anti-aliasing filter with the input bypass capacitor
with a 200 kHz bandwidth. The resistor performs another
important function as well; it dampens any ringing which
might be present in the circuit formed by the shunt, the
input bypass capacitor, and the wires or traces connecting
the two. Undampened ringing of the input circuit near
the input sampling frequency can alias into the baseband
producing what might appear to be noise at the output
of the device. To be effective, the damping resistor should
be at least 39
PC Board Layout
In addition to affecting offset, the layout of the PC board
can also affect the common mode rejection (CMR)
performance of the isolation amplifier, due primarily to
stray capacitive coupling between the input and the
output circuits. To obtain optimal CMR performance, the
layout of the printed circuit board (PCB) should minimize
any stray coupling by maintaining the maximum possible
distance between the input and output sides of the circuit
IN+
) is connected to the positive terminal of the shunt
resistor in series with the input lead forms a
.
IN–
) is shorted to pin 4 (GND1), with