AFE639D2 consists of a 12-bit digital-to-analog converter (DAC) with string architecture, followed by a voltage-output amplifier. Similarly, AFE539A4 consists of a 10-bit DAC. Figure 7-3 and Figure 7-2 show the DAC architecture within the block diagram, which operates from a 1.8-V to 5.5-V power supply.

AFE439A2 supports 7-bit duty-cycle pulse-width modulation (PWM) output on the SDA/SCLK/PWM pin. Pull the VREF/MODE pin high to enable the PWM function. AFE439A2 also supports a DIR output to provide bidirectional control of TEC elements.

The AFEx39xx have an internal voltage reference of 1.21 V. There is an option to select an external reference on the VREF/MODE pin or use the power supply as a reference. These devices use one of these three reference options.

The AFEx39xx support an independent programmable comparator for fault management. The architecture supports inversion of the comparator output using register settings. The comparator outputs can be push-pull or open-drain. The comparator outputs are accessible internally by the device to force the PI controller output to a predefined value in case of a fault.

The AFE439A2 and AFE539A4 feature an ADC to sense the input for the PI controller. AFE639D2 provides an I²C controller interface to interface to external digital temperature sensors.

The AFEx39xx feature a programmable state machine supporting arithmetic, logic, and timing operations, as shown in Figure 7-4. This state machine has been pre-programmed as a proportional-integral (PI) controller allowing the user to program the coefficients and input-output parameters. The details of the PI controller are discussed in Section 7.4.6. The user configurations are stored in the NVM and the state machine can be operated in standalone mode without interfacing to a processor (processor-less operation)

Figure 7-4 Smart AFE Architecture