Using ADI’s patented iCoupler™ technology, the ADP1031 integrates three isolated power rails, SPI and GPIO data isolation in a very small form factor of 7 mm X 9 mm. This high level of integration solves the PCB real estate challenges as it consolidates all channel isolation requirements into a very small area on the PCB. The ADP1031 also integrates a Power Good signal.
Drawing on Analog Devices power expertise, the AD5758 implements a technique called Dynamic Power Control (DPC) to minimize the power dissipation in the module under the worse case operating conditions when the part is configured for current output. It does this by continuously tracking the output voltage and using an integrated programmable high-efficiency buck converter to reduce the power supply voltage to the output driver to the minimum required to maintain the output load current. When DPC is enabled for current output modes, the AD5758 will automatically adjust the DPC voltage to minimize power dissipation under all load conditions. The ADP1031 is optimized to provide efficient isolated power for the AD5758 under worst-case load conditions so that the total channel power dissipation is minimized. The high-speed SPI channel integrated into the ADP1031 is also designed to reduce power dissipation when active and enters an ultra-low power state when inactive.
Because the ADP1031 integrates the feedback channel, the design of the flyback transformer is simplified resulting in a single primary and secondary winding required. This means the transformer form factor can be smaller and still meet the efficiency and isolation requirements. The recommended transformer for the ADP1031 has a footprint size of 8.6 mm X 8.26 mm and is less than 9.7 mm tall.
The high level of integration allows a 2 sided PCB design that will fit in an area of 400 mm2 per channel, including all passive components.
The AD5758 integrates advanced diagnostics to allow incorrect behavior and faults to be quickly detected. It integrates a digital diagnostic results register and an analog diagnostic results register, which contain error flags for the on-chip digital and analog diagnostic features. Some of the key diagnostics available are
For a complete list of diagnostics, see the AD5758 datasheet. The AD5758 also incorporates a 12-bit ADC to provide diagnostic measurements on user-selectable nodes, such as internal supplies and grounds, internal die temperature monitors, internal references among other signals. The AD5758 has a CHART pin, onto which a HART signal can be capacitively coupled. Once HART connectivity is enabled, the HART signal appears on the VIOUT pin. This functionality is only available when VIOUT is configured to output current.
The 3.3 V system power is generated by U3, an ADP2360 high efficiency buck converter. This takes an input supply from 4.5 V to 60 V and generated the 3.3 V supply rail which is used by the ADUCM3029, an ultra low-power ARM Cortex-M3 MCU with integrated power management and 256 KB of embedded flash memory.
The field power supply is connected to all 8 ADP1031s via a polarity protection diode, D2. This field power supply domain is fully isolated (300 V Basic) from the system domain, containing the ADUCM3029, and the eight field domain, where each AD5758's is located.
The board can be powered from a single 18 V to 32 V supply by inserting jumpers P5 & P6 which connects the system and field power domains together.
This page shows the connections to the ADUCM3029 and connections to the “Fault” and “Power Good” LEDs.
An FT232RQ, USB to Serial UART is used to connect the demo board to a PC or laptop via a standard USB connection. The FT232RQ is powered directly from the 5 V USB supply and U2 is used to level shift its output to 3.3 V logic levels.
This sheet shows the connectivity of each channel. The system domain and field power domain are common to all eight channels, but each channel has its own isolated field domain.
These pages show the connectivity for each output channel. Functionality is identical across all channels so only channel 0 (page 6) will be explained in detail.
U9, the ADP1031, generates a isolated 24 V (+24V_ISO) power supplies from the 18 V to 32 V field power supply using an integrated flyback converter and external transformer T3. The +24V_ISO, which is connected directly to the AD5758 AVDD1 supply. The +24V_ISO supply is also stepped down to 5.15 V using an integrated buck converter. This 5.15 V supply is connected to AVDD2 on the AD5758. A -15 V supply is also generated from the +24V_ISO which is used by the AD5758 in bipolar voltage output mode.