AMC7832_15 Datasheet, PDF (56/72 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
Typical Application (continued)
9.2.2 Design Requirements
The AMC7832 Example Schematic uses most of the following design parameters.
DESIGN PARAMETER
AV_CC
AV_EE
IOV_DD
DV_DD
AV_DD
ADC Bipolar inputs
ADC Unipolar inputs
DAC Output voltage Ranges
Remote temperature sensing
Table 54. Design Parameters
EXAMPLE VALUE
5V
-12V
3.3V
5V
5V
(ADC0 – ADC11)
(LV_ADC12 – LV_ADC16)
VRANGE_A: GND
VRANGE_B: GND
VRANGE_C: 2.5V (REF_OUT2)
VRANGE_D: 2.5V (REF_OUT2)
IC Temperature sensor (LM50) or thermistor
-12.5 to +12.5-V input range
0 to +5-V range
[0 to +5-V Range]
[0 to +5-V Range]
[-10 to 0-V Range]
[-10 to 0-V Range]
9.2.3 Detailed Design Procedure
The following displays a set of parameters and concepts that will facilitate the design process:
• AV_CC and AV_EE voltage values
• ADC input voltage range
• DAC Output voltage Ranges
• Remote temperature applications
9.2.3.1 ADC Input Conditioning
The AMC7832 has a single ADC core that features a multi-channel multiplexer input stage to a successive
approximation register (SAR) ADC. The analog inputs are separated into two input classes: bipolar ADC inputs
(high-voltage) and unipolar ADC Inputs (low-voltage). The high-voltage analog inputs (ADC_0 – ADC_11) feature
a -12.5-V to +12.5-V input range, while the low-voltage analog inputs (LV_ADC12 – LV_ADC16) accept a full-
scale range of 0 to 2 x V_REF (V_REF corresponds to a +2.5-V internal reference to the ADC block, and is externally
available on the REF_CMP pin). For additional noise filtering, a 4.7-µF capacitor is recommended between the
REF_CMP and GND. The value of this cap must exceed 470nF to ensure reference stability. A high-quality
ceramic type NP0 or X7R is recommended for its optimal performance across temperature, and very low
dissipation factor.
During conversion the input current per channel will vary with the total update time which is determined by the
number and type of channels (NCH) and the conversion rate setting CONV-RATE in the ADC Configuration
register (address 0x10). This information is displayed in Table 55.
I_IN = F_S × DV × C_IN
(5)
Where:
C_IN: Internal ADC input channel capacitance
ΔV : The maximum voltage difference between analog inputs
F_S = f(CONV_RATE, NCH_BIPOLAR, NCH_UNIPOLAR) = 1/T_S
The total update time (T_S) can be determined from Table 55.
CONV-RATE[1:0]
00
01
10
11
Table 55. ADC Update Time per Input Channel
T_S (μs) / CHANNEL
UNIPOLAR INPUT CHANNEL
11.5
23
34.5
69
T_S (μs) / CHANNEL
BIPOLAR INPUT CHANNEL
34.5
34.5
34.5
69
T_S (μs)
TEMPERATURE SENSOR CHANNEL
256
256
256
256
56
Submit Documentation Feedback
Product Folder Links: AMC7832
Copyright © 2014, Texas Instruments Incorporated