AMC7832 Datasheet, PDF (28/70 Pages) Texas Instruments – AMC7832 12-Bit Analog Monitor and Control Solution with Multi-Channel ADC, Bipolar DACs, Temperature Sensor and GPIO Ports

AMC7832
SLAS836 – MARCH 2014
www.ti.com
8.3.2 Analog-to-Digital Converter (ADC)
The AMC7832 features a monitoring system centered on a 12-bit successive approximation register (SAR) ADC
fronted by an 18-channel multiplexer and an on-chip track-and-hold. The monitoring systems is capable of
sensing up to 12 external bipolar inputs (-12.5-V to +12.5-V range), 5 external unipolar inputs (0 to +5-V range)
and an internal analog temperature sensor.
The ADC operates from an internal 2.5-V reference and its input range is 0-V to 2 × VREF. The external bipolar
inputs to the ADC are internally mapped to this range. The ADC timing signals are derived from an on-board
temperature compensated oscillator. The conversion results can be accessed through the device serial interface.
8.3.2.1 Analog Inputs
The AMC7832 has 17 uncommitted analog inputs for external voltage sensing. Twelve of these inputs (ADC_0 to
ADC_11) are bipolar and the other five (LV_ADC12 to LV_ADC16) unipolar. Figure 43 shows the equivalent
circuit for the external analog input terminals. All switches are open while the ADC is in idle state.
Scaling Network
3.125V
ADC_0
3.125V
R_MUX
S_W
R_S
C_SAMPLE
SW is closed during sampling.
SW is open during conversion.
ADC_11
AV_DD
LV_ADC12
AV_DD
LV_ADC16
AGND
Figure 43. ADC External Inputs Equivalent Circuit
In order to achieve specified performance, especially at higher input frequencies, it is recommended to drive
each analog input terminal with a low impedance source. An external amplifier can also be used to drive the
input terminals.
8.3.2.1.1 Bipolar Analog Inputs
The AMC7832 supports up to twelve bipolar analog inputs. The analog input range for these channels is -12.5-V
to +12.5-V. The bipolar signal is scaled internally through a resistor divider so that it maps to the native input
range of the ADC (0-V to 2 × VREF). The input resistance of the scaling network is 175-kΩ.
The bipolar analog input conversion values are stored in straight binary format in the ADC-Data registers
(address 0x20 – 0x37). The LSB size for these channels is 10 × VREF/4096. With the internal reference equal to
2.5-V the voltage value is given by,
Voltage
=
5
éCODE ×
êë ₄₀₉₆
5
-
ù
2.5_úû
(1)
28
Submit Documentation Feedback
Product Folder Links: AMC7832
Copyright © 2014, Texas Instruments Incorporated