JAJSTM8 April 2024 AFE20408
PRODUCTION DATA
The AFE20408 facilitates rapid turn-on and turn-off of the voltage at the device OUT outputs. The OUT0 and OUT2 outputs (from groups A and B) can be switched on or off by the DRVEN inputs or alternatively through software. The ON voltages are set by the DAC0 and DAC2 outputs of each respective DAC group, while the OFF voltages are set by either VSS or a specified clamp voltage for each DAC. The OUT0 and OUT2 pins are driven by DAC0 and DAC2 when the corresponding switch control pin or bit is asserted high (drive enabled). Otherwise, the OUT pins are in drive disabled state and driven to either VSS or the corresponding clamp DAC.
Additionally, the DAC1 and DAC3 outputs from each group include a simplified switch network that facilitates fast turnoff. The DAC1 and DAC3 pins can be switched on or off, either through one of the DRVEN pins or through software. The DAC1 and DAC3 output pins are driven by the DAC1 and DAC3 buffers when on, and to VSS when off. While fast turnoff is possible, turn-on time is limited by the DAC1 and DAC3 buffer bandwidth, and also DAC1 and DAC3 have to exit the power-down state.
The switches are designed to be bidirectional, allowing for two-way current when powered ON and blocking voltage when powered OFF. The switch control is optimized for minimum delay between the DRVEN input and the output pins voltage switching. The switches default to the off (drive disabled) state at start-up or after an alarm event. Along with a VDD supply collapse, there are three additional reset events: a logic low on the RESET pin, a software reset command, or an I2C general-call reset. All reset events generate a power-down, drive disable sequence. At reset, the DAC and OUT outputs go to VSS.
Figure 6-8 shows the configuration of switching channels in the AFE20408, for both DAC output groups.