ADS9813 datasheet(22/66 Pages) TI

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6.3.1.2 Programmable Gain Amplifier (PGA)

The ADS9813 features a PGA at every analog input channel. The PGA supports single-ended and differential

inputs with a bipolar signal swing. Table 6-1 lists the supported analog input ranges. Configure the analog input

range independently for each channel with the RANGE_CHx register fields in address 0xC2 and address 0xC3.

Table 6-1. Analog Input Ranges

DIFFERENTIAL INPUTS

SINGLE-ENDED INPUTS

RANGE_CHx CONFIGURATION

±12V

±10V

±7V

±5V

±3.5V

±2.5V

Each analog input channel features an antialiasing, low-pass filter (LPF) at the output of the PGA. Table 6-2

lists the various programmable LPF options available in the ADS9813 corresponding to the analog input range.

Figure 5-12 and Figure 5-13 illustrate the frequency responses for low-bandwidth and wide-bandwidth LPF

configurations. Select the analog input bandwidth for the eight analog input channels with the ANA_BW[7:0] bits

in address 0xC0 of register bank 1.

Table 6-2. Low-Pass Filter Corner Frequency

LPF

ANALOG INPUT RANGE

CORNER FREQUENCY (–3dB)

Low-bandwidth

All input ranges

22.7kHz

Wide-bandwidth

±12V

664kHz

±10V

691kHz

±7V

700kHz

±5V

500kHz

±3.5V

325kHz

±2.5V

221kHz

6.3.1.3 Wide-Common-Mode Voltage Rejection Circuit

The ADS9813 features a common-mode (CM) rejection circuit at the analog inputs that supports CM voltages

up to ±12V. The CM voltage for differential inputs is given by Equation 1. On power-up or after reset, the

common-mode voltage range for the analog input channels is ±12V (CM_CTRL_EN = 0b). In all cases, make

sure the voltage at the analog inputs is within the Absolute Maximum Ratings.

Commonmodevoltage= VoltageonAINP + VoltageonAINM

(1)

As described in Table 6-3, optimize the CM voltage rejection circuit for various CM voltages for differential inputs.

Table 6-3. Wide Common-Mode Configuration for Differential Inputs

COMMON-MODE

(CM) RANGE

CM_CTRL_EN

ANALOG INPUT CHANNELS 1–4

ANALOG INPUT CHANNELS 5–8

CM_EN_CH[4:1]

CM_RNG_CH[4:1]

CM_EN_CH[8:5]

CM_RNG_CH[8:5]

CM ≤ ±1V

Don't care

CM ≤ ±RANGE / 2

CM ≤ ±6V

CM ≤ ±12V

ADS9813, ADS9811, ADS9810

SBASAQ6A – JULY 2024 – REVISED NOVEMBER 2024

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