The AD7779 is an 8-channel simultaneous sampling
Analog-to-digital converters。 There are 8 complete Σ-Δ ADCs on the chip. The AD7779 provides input impedance up to 10 MOhm for direct sensor connection. Each input channel has a programmable gain stage for gains of 1, 2, 4, and 8 to map the low amplitude sensor output into the full-scale ADC input range to maximize the dynamic range of the signal chain. At an analog supply voltage of 3.3V or ±1.65V, the analog inputs accept unipolar 0 to 2.5V or true bipolar ± 1.25V analog input signals, respectively. The analog inputs can be configured to accept true differential or single-ended signals to match different sensor output configurations.
Each channel contains an ADC modulator and a Sinc 3 low-latency digital filter. A sample rate converter (SRC) is used to fine-tune resolution control of the AD7779 output data rate (ODR). This device can be used in power quality applications where ODR resolution and 0.01Hz line frequency variation are required. The SRC can be programmed through the SPI interface. The AD7779 implements two different interfaces, a data output interface and an SPI control interface. The ADC data output interface is designed to send ADC conversion results from the AD7779 to the processor. The SPI interface is used to read and write to the AD7779 configuration registers and to control and read data from the SAR ADC. The SPI interface can also be configured to output sigma-delta conversion data.
The AD7779 includes a 12-bit SAR ADC. The ADC can be used for AD7779 diagnostics, eliminating the need to free up a sigma-delta ADC channel dedicated to system measurements. By employing an external multiplexer and signal conditioning, SAR ADCs can be used to verify sigma-delta ADC measurements in applications with functional safety requirements. In addition, the AD7779 provides three GPIOs that can be used to control an external multiplexer.
The AD7779 contains a 2.5V reference and reference buffer. The temperature coefficient of the reference is 20 ppm/°C maximum.
The AD7779 offers two modes of operation: high resolution and low power. The high-resolution mode provides high dynamic range while consuming 13 mW/ch, while the low-power mode consumes only 5 mW/ch by reducing the dynamic range.
The specified operating temperature range is -40°C to +105°C, while this section can operate up to +125°C.