The DAC874xH devices are a family of HART compliant modems that are also FOUNDATION™ Fieldbus and PROFIBUS® PA compatible. This family of devices are low-power modems design for industrial process control and industrial automation applications.

The DAC8740H is a HART modem that translates a HART FSK signal to UART signal and vice versa. The DAC8741H is register based and uses SPI instead of UART for communication. The DAC8741H uses a FIFO buffer for HART communication and data is transferred by reading and writing registers to exchange data with a FIFO buffer. The DAC8742H is able to use both UART and SPI for the transfer of HART data. Figure 3-4 shows a block diagram of the DAC874xH HART modem device. The HART modulated signal comes out of the MOD_OUT pin and the HART signal is received through either the RX_IN or RX_INF pin depending on external filtering.

The AFEx81H1 and AFEx82H1 devices are also HART modems but integrate a 16-bit or 14-bit voltage DAC. The output voltage can be used with a V-I stage to set the loop current for a remote transmitter.

With external gain, the output voltage of the DAC can be used to set the system to different voltage output ranges. The AFEx81H1 has a DAC output range of 0.15 V to 1.25 V and the AFEx82H1 has a DAC output range of 0 V to 2.5 V. Figure 3-5 shows a block diagram of these devices. The HART modulated signal comes out of the MOD_OUT pin and the HART signal is received through either the RX_IN or RX_INF pin depending on external filtering.