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PDF ACPL-7970 Data sheet ( Hoja de datos )
| Número de pieza | ACPL-7970 | |
| Descripción | Optically Isolated Sigma-Delta Modulator | |
| Fabricantes | AVAGO | |
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ACPL-7970
Optically Isolated Sigma-Delta Modulator
Data Sheet
Description
The ACPL-7970 is a 1-bit, second-order sigma-delta (∑-∆)
modulator converts an analog input signal into a high-
speed data stream with galvanic isolation based on optical
coupling technology. The ACPL-7970 operates from a 5 V
power supply with dynamic range of 78 dB with an appro-
priate digital filter. The differential inputs of ±200 mV (full
scale ±320 mV) are ideal for direct connection to shunt
resistors or other low-level signal sources in applications
such as motor phase current measurement.
The analog input is continuously sampled by a means of
sigma-delta over-sampling using an on-board clock. The
signal information is contained in the modulator data, as a
density of ones with data rate of 10 MHz, and the data are
encoded and transmitted across the isolation boundary
where they are recovered and decoded into high-speed
data stream of digital ones and zeros. The original signal
information can be reconstructed with a digital filter. The
serial interface for data and clock has a wide supply range
of 3 V to 5.5 V.
Combined with superior optical coupling technology,
the modulator delivers high noise margins and excellent
immunity against isolation-mode transients. With 0.5 mm
minimum distance through insulation (DTI), the ACPL‑7970
provides reliable reinforced insulation and high working
insulation voltage, which is suitable for fail-safe designs.
This outstanding isolation performance is superior to
alternatives including devices based on capacitive- or
magnetic-coupling with DTI in micro-meter range. Offered
in a DIP-8 package, the isolated ADC delivers the reliabil-
ity, small size, superior isolation and over-temperature
performance motor drive designers need to accurately
measure current at much lower price compared to tradi-
tional current transducers.
The external clock version modulator ACPL-796J (SO-16
package) is also available.
Features
• 10 MHz internal clock
• 1-bit, second-order sigma-delta modulator
• 16 bits resolution no missing codes (12 bits ENOB)
• 78 dB SNR
• 6 mV/°C maximum offset drift
• ±1% maximum gain error
• Internal reference voltage
• ±200 mV linear range with single 5 V supply (±320 mV
full scale)
• 3 V to 5.5 V wide supply range for digital interface
• -40° C to +105° C operating temperature range
• 25 kV/ms common-mode transient immunity
• Safety and regulatory approvals:
– IEC/EN/DIN EN 60747-5-5: 891 Vpeak working
insulation voltage
– UL 1577: 5000 Vrms/1min isolation voltage
– CSA: Component Acceptance Notice #5
Applications
• Motor phase and rail current sensing
• Power inverter current and voltage sensing
• Industrial process control
• Data acquisition systems
• General purpose current and voltage sensing
• Traditional current transducer replacements
Functional Block Diagram
VDD1
VIN+
VIN–
Σ-∆
MODULATOR/
ENCODER
LED
DRIVER
CLK
DECODER
SHIELD
VDD2
MCLK
MDAT
GND1
VREF
GND2
CAUTION: It is advised that normal static precautions be taken in handling and assembly
of this component to prevent damage and/or degradation which may be induced by ESD.
1 page  
Table 3. IEC/EN/DIN EN 60747-5-5 Insulation Characteristics [1]
Description
Symbol
Value
Units
Installation classification per DIN VDE 0110/1.89, Table 1
for rated mains voltage ≤ 150 Vrms
for rated mains voltage ≤ 300 Vrms
for rated mains voltage ≤ 450 V rms
for rated mains voltage ≤ 600 Vrms
I-IV
I-IV
I-IV
I-IV
Climatic Classification
55/105/21
Pollution Degree (DIN VDE 0110/1.89)
2
Maximum Working Insulation Voltage
Input to Output Test Voltage, Method b
VIORM x 1.875 = VPR, 100% Production Test with tm = 1 sec,
Partial Discharge < 5 pC
VIORM
VPR
891
1671
Vpeak
Vpeak
Input to Output Test Voltage, Method a
VIORM x 1.6 = VPR, Type and Sample Test, tm = 10 sec,
Partial Discharge < 5 pC
VPR
1426
Vpeak
Highest Allowable Overvoltage (Transient Overvoltage, tini = 60 sec)
VIOTM
8000
Vpeak
Safety-limiting values
(Maximum values allowed in the event of a failure)
Case Temperature
Input Current [2]
Output Power [2]
TS
IS,INPUT
PS,OUTPUT
175
400
600
°C
mA
mW
Insulation Resistance at TS, VIO = 500 V
RS
≥ 109
Ω
Notes:
1. Insulation characteristics are guaranteed only within the safety maximum ratings, which must be ensured by protective circuits within the
application.
2. Safety-limiting parameters are dependent on ambient temperature. The Input Current, IS,INPUT, derates linearly above 25° C free-air temperature at
a rate of 2.67 mA/°C; the Output Power, PS,OUTPUT, derates linearly above 25° C free-air temperature at a rate of 4 mW/°C.
Table 4. Insulation and Safety Related Specifications
Parameter
Symbol Value
Minimum External Air Gap
(External Clearance)
L(101) 7.4
Minimum External Tracking
(External Creepage)
Minimum Internal Plastic Gap
(Internal Clearance)
L(102)
8.0
0.5
Tracking Resistance
(Comparative Tracking Index)
Isolation Group
CTI
>175
IIIa
Units
mm
mm
mm
V
Conditions
Measured from input terminals to output terminals, shortest
distance through air
Measured from input terminals to output terminals, shortest
distance path along body
Through insulation distance, conductor to conductor,
usually the direct distance between the photoemitter and
photodetector inside the optocoupler cavity
DIN IEC 112/VDE 0303 Part 1
Material Group (DIN VDE 0110, 1/89, Table 1)
5
5 Page 
Definitions
Integral Nonlinearity (INL)
INL is the maximum deviation of a transfer curve from a
straight line passing through the endpoints of the ADC
transfer function, with offset and gain errors adjusted
out.
Differential Nonlinearity (DNL)
DNL is the deviation of an actual code width from the ideal
value of 1 LSB between any two adjacent codes in the ADC
transfer curve. DNL is a critical specification in closed-loop
applications. A DNL error of less than ±1 LSB guarantees
no missing codes and a monotonic transfer function.
Offset Error
Offset error is the deviation of the actual input voltage
corresponding to the mid-scale code (32,768 for a 16-bit
system with an unsigned decimation filter) from 0 V. Offset
error can be corrected by software or hardware.
Gain Error (Full-Scale Error)
Gain error includes positive full-scale gain error and
negative full-scale gain error. Positive full-scale gain error
is the deviation of the actual input voltage correspond-
ing to positive full-scale code (65,535 for a 16-bit system)
from the ideal differential input voltage (VIN+ – VIN– =
+320 mV), with offset error adjusted out. Negative full-
scale gain error is the deviation of the actual input voltage
corresponding to negative full-scale code (0 for a 16-bit
system) from the ideal differential input voltage (VIN+ –
VIN– = -320 mV), with offset error adjusted out. Gain error
includes reference error. Gain error can be corrected by
software or hardware.
Signal-to-Noise Ratio (SNR)
The SNR is the measured ratio of AC signal power to noise
power below half of the sampling frequency. The noise
power excludes harmonic signals and DC.
Signal-to-(Noise + Distortion) Ratio (SNDR)
The SNDR is the measured ratio of AC signal power to
noise plus distortion power at the output of the ADC. The
signal power is the rms amplitude of the fundamental
input signal. Noise plus distortion power is the rms sum
of all non-fundamental signals up to half the sampling
frequency (excluding DC).
Effective Number of Bits (ENOB)
The ENOB determines the effective resolution of an ADC,
expressed in bits, defined by ENOB = (SNDR − 1.76)/6.02
Isolation Transient Immunity (CMR)
The isolation transient immunity (also known as Common-
Mode Rejection or CMR) specifies the minimum rate-of-
rise/fall of a common-mode signal applied across the
isolation boundary beyond which the modulator clock or
data is corrupted.
Product Overview
Description
The ACPL-7970 isolated sigma-delta (∑-∆) modulator
converts an analog input signal into a high-speed (10
MHz typical) single-bit data stream by means of a sigma-
delta over-sampling modulator. The time average of the
modulator data is directly proportional to the input signal
voltage. The modulator uses internal clock of 10 MHz. The
modulator data are encoded and transmitted across the
isolation boundary where they are recovered and decoded
into high-speed data stream of digital ones and zeros. The
original signal information is represented by the density
of ones in the data output.
The other main function of the modulator (optocoupler)
is to provide galvanic isolation between the analog signal
input and the digital data output. It provides high noise
margins and excellent immunity against isolation-mode
transients that allows direct measurement of low-level
signals in highly noisy environments, for example mea-
surement of motor phase currents in power inverters.
With 0.5 mm minimum DTI, the ACPL-7970 provides
reliable double protection and high working insulation
voltage, which is suitable for fail-safe designs. This out-
standing isolation performance is superior to alternatives
including devices based on capacitive- or magnetic-
coupling with DTI in micro-meter range. Offered in an
DIP-8 package, the isolated ADC delivers the reliability,
small size, superior isolation and over-temperature perfor-
mance motor drive designers need to accurately measure
current at much lower price compared to traditional
current transducers.
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet ACPL-7970.PDF ] | |
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