AMC7832IPAPR.A datasheet(28/74 Pages) TI2

28 / 74 page

CODE × 5

Voltage = 5

- 2.5

4096

LV_ADC12

AVDD

LV_ADC16

AGND

SW is closed during sampling.

SW is open during conversion.

CSAMPLE

ADC_0

ADC_11

RMUX

3.125V

Scaling Network

AMC7832

SLAS836 – MARCH 2014

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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.

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-k

Ω.

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,

(1)

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