HCPL-7560 Datasheet, PDF (13/18 Pages) Agilent(Hewlett-Packard) – Optically Isolated Sigma-Delta Modulator

Product Description
The HCPL-7560 Isolated
Modulator (optocoupler) uses
sigma-delta modulation to
convert an analog input signal
into a high-speed (10 MHz)
single-bit digital data stream;
the time average of the
modulator’s single-bit data is
directly proportional to the
input signal. The isolated
modulator’s other main
function is to provide galvanic
isolation between the analog
input and the digital output.
An internal voltage reference
determines the full-scale
analog input range of the
modulator (approximately ±
320 mV); an input range of ±
200 mV is recommended to
achieve optimal performance.
HCPL-7560 can be used
together with HCPL-0872,
Digital Interface IC or a digital
filter. The primary functions of
the HCPL-0872 Digital
Interface IC are to derive a
multi-bit output signal by
averaging the single-bit
modulator data, as well as to
provide a direct micro-
controller interface. The
effective resolution of the
multi-bit output signal is a
function of the length of time
(measured in modulator clock
cycles) over which the average
is taken; averaging over longer
periods of time results in
higher resolution. The Digital
Interface IC can be configured
for five conversion modes,
which have different
combinations of speed and
Table 1. Input Full-Scale Range and Code Assignment.
Analog Input
Voltage Input
Digital Output
Full Scale Range
Minimum Step Size
640 mV
20 µV
32768 LSBs
1 LSB
+Full Scale
+320 mV
111111111111111
Zero
-Full Scale
0 mV
-320 mV
100000000000000
000000000000000
resolution to achieve the
desired level of performance.
Other functions of the HCPL-
0872 Digital Interface IC
include a Phase Locked Loop
based pre-trigger circuit that
can either give more precise
control of the effective
sampling time or reduce
conversion time to less than
1µs, a fast over-range
detection circuit that rapidly
indicates when the magnitude
of the input signal is beyond
full-scale, an adjustable
threshold detection circuit that
indicates when the magnitude
of the input signal is above a
user adjustable threshold level,
an offset calibration circuit,
and a second multiplexed
input that allows a second
Isolated Modulator to be used
with a single Digital Interface
IC.
The digital output format of
the Isolated A/D Converter is
15 bits of unsigned binary
data. The input full-scale range
and code assignment is shown
in Table 1 below. Although the
output contains 15 bits of
data, the effective resolution is
lower and is determined by
selected conversion mode as
shown in Table 2 below.
Table 2. Isolated A/D Converter Typical Performance Characteristics.
Conversion Mode
Signal-to-- Effective
Noise Ratio Resolution
(dB)
(bits)
Conversion Time (µs)
Pre-Trigger Mode
0
1
2
Signal
Delay(µs)
Signal
Bandwidth
(kHz)
1
83
13.5
205
102
102
3.4
2
79
12.8
103
51
51
6.9
3
73
11.9
39
19
0.2
19
22
4
66
10.7
20
10
10
45
5
53
8.5
10
5
5
90
Notes: Bold italic type indicates Default values.
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