ACPL-7970-500E Avago Technologies US Inc., ACPL-7970-500E Datasheet - Page 11

• Manufacturer Part Number: ACPL-7970-500E
• Description: IsolatedSigmaDelta Mod, TR+IEC+LF
• Manufacturer: Avago Technologies US Inc.
• Series: -r
• Type: Sigma-Delta Modulatorr

Specifications of ACPL-7970-500E

• Operating Supply Voltage: 5.5 V
• Supply Current: 8 mA at 5 V
• Operating Temperature Range: - 40 C to + 105 C
• Mounting Style: SMD/SMT
• Package / Case: DIP-8 Gull Wing
• Input Voltage Range (max): + 200 mV
• Voltage - Isolation: 5000Vrms
• Input Type: DC
• Voltage - Supply: 3 V ~ 5.5 V, 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Lead Free Status / Rohs Status: Details

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 (V
+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 (V
V
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).
11
IN
– = -320 mV), with offset error adjusted out. Gain error
IN
+ – V
IN
IN
– =
+ –
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.