NB2DSK01 - Power

The NB2DSK01 is powered by a 5V regulated supply, the power module for which is supplied in the box. If the total power consumption of a given NanoBoard configuration – i.e. daisy-chained and/or with connected expansion devices/user boards – exceeds 4A, then a higher current capacity power supply may be required. Such a power source must provide a regulated 5V supply.

Three power connector jacks are provided. Two of these are connected in parallel allowing one of the jacks to be used to supply power to the next NanoBoard in a series of daisy-chained NanoBoards.

Figure 1. 5V power input connectors and
toggle switch.

The third power connector jack is used for outputting the board's 5V supply to an external user board.

Figure 2. 5V power output connector.

Power to the board is controlled through a power toggle switch. The board is powered when the switch is in the downward position. This switch controls power to the NB2DSK01 and also power at the output power jack. It does not toggle the power to other NanoBoards in a daisy-chain configuration.

The NB2DSK01 has on-board fixed-voltage regulators that provide 3.3V, 2.5V, 1.8V and 1.2V for the Xilinx Spartan-3 controller FPGA, and a programmable voltage regulator (1.25V to 3.3V) to provide an appropriate voltage (VCCX) for the FPGA device on a plug-in daughter board. Each daughter board module automatically programs the regulator (where applicable) to suit its own internal voltage requirements.
 

 
For the TFT LCD panel a further three voltage levels are produced by the NB2DSK01, based on the regulated 5V input. These are: -7.5V, 9V and 16.5V.

The NB2DSK01 provides an array of test points for checking the integrity of each of the board's power supplies, including four dedicated GND points (0V).

Figure 3. Test points are available for all power supplies
on the NB2DSK01, in the one convenient location.

Power required for a daughter board (3.3V, 5V) and each peripheral board (1.2V, 1.8V, 2.5V, 3.3V, 5V) is routed to the corresponding docking connector(s) for those boards. Both the 3.3V and 5V supply buses can also be selected to power various expansion devices that can be connected to the NB2DSK01, via the 'User Header A' and 'User Header B' connectors.

Current monitoring is in place for each of these power lines (19 in total) through use of a MAX4372T high-side current sense amplifier (from Maxim). Each power line is routed to its destination connector through a 47mΩ resistor, which serves as the external sense resistance for the associated MAX4372T device. Powered by the NB2DSK01's 9V supply, this device provides a voltage output that is proportional to the voltage across this sense resistance, and has a fixed gain of 20. For current passing through the 47mΩ resistor, the voltage across the device's input is 47uV/mA. The output of the device is therefore 940uV/mA (applying the x20 gain).

Two low-power, 12-channel, 12-bit ADC devices (MAX1229, from Maxim) collect together the analog voltage outputs from all current sense amplifiers, for transmission back to the NB2DSK01's Xilinx Spartan-3 Controller FPGA, over an SPI bus. The output of each ADC, which has an internal reference voltage of 2.5V is:
 
ADC output = (2.5V/4096) / 940uV = 0.64931mA/bit (=2.65957A full scale)
 

Location on Board

The parallel-connected 5V power connectors (designated J1 and J3) and power toggle switch (designated SW6) are located on the component side of the board, towards the top-right corner. The 5V power output connector (designated J2) is located on the solder side, at the bottom-left edge of the board.

The power supply test points (designated TP1, TP5-TP12, and TP15) and GND points (designated 0V) are also located on the component side of the board, directly below the parallel-connected power jacks.

The MAX4372T devices for power routed to the 'PERIPHERAL BOARD A' connector (designated U31, U34, U37, U40, U43), 'PERIPHERAL BOARD B' connector (designated U29, U32, U35, U38, U41), 'PERIPHERAL BOARD C' connector (designated U30, U33, U36, U39, U42), the relevant daughter board connectors (designated U44, U46), and the User Board headers (designated U45, U47), are all located on the solder-side of the board.

The MAX1229 devices (designated U48 and U49) are also located on the solder-side of the board.

Figure 4. Current sense circuitry on the NB2DSK01. Top - MAX4372T devices associated with peripheral board monitoring and the
MAX1229 devices. Bottom-Left - MAX4372T devices associated with daughter board monitoring. Bottom-Right - MAX4372T devices
associated with user board monitoring.

Schematic Reference

Power supply-related circuitry can be found on the following sheets of the motherboard schematics:

• Sheet 2 (NB2_PSU.SchDoc, entitled NB2DSK01 POWER SUPPLIES) - top sheet for all power supplies on the NB2DSK01.

• Sheet 3 (PSU_BZX84C7V5_-7V5.SchDoc, entitled PSU BZX84C7V5 -7V5) – TFT LCD panel's -7.5V supply.

• Sheet 4 (PSU_MAX1831_1V2.SchDoc, entitled PSU MAX1831 1V2) – Primary 1.2V supply.

• Sheet 5 (TPS75501_1V8.SchDoc, entitled PSU TPS75501 1V8) – Primary 1.8V supply.

• Sheet 6 (TPS75501_2V5.SchDoc, entitled PSU TPS75501 2V5) – Primary 2.5V supply.

• Sheet 7 (TPS75501_3V3.SchDoc, entitled PSU TPS75501 3V3) – Primary 3.3V supply.

• Sheet 8 (PSU_LM317_9V0.SchDoc, entitled PSU LM317 9V0) – TFT LCD panel's 9V supply.

• Sheet 9 (PSU_LM2704_16V5.SchDoc, entitled PSU LM2704 16V5) – TFT LCD panel's 16.5V supply.

• Sheet 10 (PSU_LM1084_ADJ.SchDoc, entitled PSU LM1084 ADJ) – Daughter board VCCX supply.

• Sheet 11 (PWJACK+SWITCH.SchDoc, entitled Power Jack & Switch) – 5V power jacks and toggle switch.

• Sheet 12 (CURRENT_SENSE.SchDoc, entitled DB/PB Current Sense) – Current sense circuitry.

Further Device Information

For more information on the MAX4372T and MAX1229 devices, refer to the datasheets (MAX4372-MAX4372T.pdf and MAX1227-MAX1231.pdf) available at www.maxim-ic.com.