ACPL-C797 Datasheet, PDF (1/16 Pages) AVAGO TECHNOLOGIES LIMITED – Optically Isolated Sigma-Delta Modulator

ACPL-C797
Optically Isolated Sigma-Delta Modulator
Data Sheet
Description
The ACPL-C797 is a 1-bit, second-order sigma-delta (Σ-∆)
modulator converts an analog input signal into a high-
speed data stream with galvanic isolation based on optical
coupling technology. The ACPL-C797 operates from a 5 V
power supply with dynamic range of 80 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-C797 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 ca-
pacitive- or magnetic-coupling with DTI in micro-meter
range. Offered in a Stretched SO-8 (SSO-8) package, the
isolated ADC delivers the reliability, small size, superior
isolation and over-temperature performance motor drive
designers need to accurately measure current at much
lower price compared to traditional current transducers.
The external clock version modulator ACPL-796J (SO-16
package) is also available.
Features
• Superior Optical Isolation and Insulation
• 10 MHz internal clock
• 1-bit, second-order sigma-delta modulator
• 16 bits resolution no missing codes (12 bits ENOB)
• 78 dB SNR
• 3.5 µV/°C maximum offset drift
• ±1% 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
• SSO-8 package
• 25 kV/µs common-mode transient immunity
• Safety and regulatory approval:
– IEC/EN/DIN EN 60747-5-5: 1414 Vpeak working insu-
lation 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
V_DD1
VDD2
VIN+
V_IN–
Σ-∆
MODULATOR/
ENCODER
LED
DRIVER
MCLK
DECODER
SHIELD
MDAT
CLK
GND1
VREF
GND2
Figure 1.
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.