Datasheet

ADuC7033
Rev. B | Page 43 of 140
16-BIT, Σ-Δ ANALOG-TO-DIGITAL CONVERTERS
The ADuC7033 incorporates two independent sigma-delta
(Σ-) analog-to-digital converters (ADCs), namely: the current
channel ADC (I-ADC) and the voltage/temperature channel ADC
(V/T-ADC). These precision measurement channels integrate
on-chip buffering, a programmable gain amplifier, 16-bit, Σ-
modulators, and digital filtering for precise measurement of
current, voltage, and temperature variables in 12 V automotive
battery systems.
CURRENT CHANNEL ADC (I-ADC)
The I-ADC converts battery current sensed through an external
100 Ω shunt resistor. On-chip programmable gain means that
the I-ADC can be configured to accommodate battery current
levels from ±1 A to ±1500 A.
As shown in Figure 17, the I-ADC employs a Σ- conversion
technique to realize 16 bits of no missing codes performance.
The Σ- modulator converts the sampled input signal into a
digital pulse train whose duty cycle contains the digital infor-
mation. A modified Sinc3, programmable, low-pass filter is
then employed to decimate the modulator output data stream
to give a valid 16-bit data conversion result at programmable
output rates from 4 Hz to 8 kHz in normal mode, and 1 Hz to
2 kHz in low power mode.
The I-ADC also incorporates counter, comparator, and
accumulator logic. This allows the I-ADC result to generate an
interrupt after a predefined number of conversions have elapsed
or if the I-ADC result exceeds a programmable threshold value.
A fast ADC overrange feature is also supported. When enabled,
a 32-bit accumulator automatically sums the 16-bit I-ADC results.
The time to a first valid (fully settled) result on the current
channel is three ADC conversion cycles with chop mode turned
off and two ADC conversion cycles with chop mode turned on.