HCPL-810J Datasheet, PDF (13/16 Pages) Agilent(Hewlett-Packard) – PLC Powerline DAA IC

Applications Information
Tx-en
Tx-in
Rx-out
Status
C1
100 nF
R3
2 kΩ
R1
100 nF
5 kΩ
R2
10 kΩ
VCC1
100 nF
GND1
1 _Tx-en
2 _Tx-in
3 _Rx-PD-out
4
Rx-Amp-in
5 _Status
6 _Rx-out
7
VCC1
8
GND1
HCPL-810J
GND2
Tx-out
VCC2
Tx-PD-out
Tx-LD-in
Cext
Rx-in
Rref
16
GND2
15
R4
2Ω
14
13
12
11
10 ^{1 µF}
9
Filter
GND2
Filter
Rref
24 kΩ
VCC2
100 nF
100 µF
GND2 GND2
1 µF
L2
D1
C2
L
X2
L1
330 µH
N
GND1
GND2
GND2
Figure 17. Schematic of HCPL-810J application for FSK modulation scheme.
Typical application for FSK modulation
scheme
The HCPL- 810J is designed to
work with various transceivers
and can be used with a variety
of modulation methods
including ASK, FSK and BPSK.
Figure 17 shows a typical
application in a powerline
modem using Frequency Shift
Keying (FSK) modulation
scheme.
Transmitter
The analogue Tx input pin is
connected to the modulator via
an external coupling capacitor
C1 and a series resistor R3 (see
Figure 17). Optimal performance
is obtained with an input signal
of 250 µA_PP. E.g., for a
modulator with an output signal
of 0.5 V_PP using a coupling
capacitor of 100 nF, the optimal
series resistor R3 would be 2
kΩ.
Tx AGC
To ensure a stable and constant
output voltage at Tx- PD- out, the
HCPL- 810J includes an
Automatic Gain Control (AGC)
circuit in the isolated transmit
signal path.
This AGC circuit compensates
for variations in the input signal
level presented at Tx- in and
variations in the optical channel
over temperature and time. The
Tx- PD- out output signal is
effectively stabilized for input
Tx- in signals of between 150
µA_PP and 250 µA_PP (see Figure
8). The AGC circuit starts to
function 10 µs after the Tx- en
signal is set to logic high. After
a period of 180 µs the Tx- PD-
out signal typically reaches 66%
of its steady state level (see
Figure 18). To ensure correct
operation of the internal
circuitry, an external 1 µF
capacitor needs to be connected
from pin 11 to GND2.
Tx-en 5 V/Div
Tx-PD-out 1 V/Div
The optical signal coupling
technology used in the HCPL-
810J transmit path achieves
very good harmonic distortion,
which is usually significantly
better than the distortion
performance of the modulated
input signal. However to meet
the requirements of some
international EMC regulations it
is often necessary to filter the
modulated input signal. The
optimal position for such a
filter is between pins 13 and 12
as shown in Figure 17. A
possible band- pass filter
topology is shown in Figure 19,
some typical values of the
components in this filter are
listed in Table 1.
5 0 µs/Div
ts, Tx
tAGC
Figure 18. Tx-PD-out AGC response time.
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