Daughter Board Power (Including 1.2V and 2.5V)

In addition to the 3.3V and 5V supply voltages and ground signals fed to the daughter board from the NB2DSK01 motherboard, the daughter board also has its own 1.2V and 2.5V supplies.

The 1.2V supply is generated by passing the regulated 5V supply through a low-voltage step-down regulator – a MAX1831 device, from Maxim.

Figure 1. MAX1831 device (as seen on the
DB30).

The 2.5V supply is sourced from the output of an adjustable linear voltage regulator – a MAX8860 device, from Maxim. Powered by the daughter board's 5V supply, the output level is determined by the resistance between the device's OUT and SET pins, and is calculated using the following formula:

VOUT = 1.25 * (1 + RA/100K)

Where,

VOUT is the voltage output of the device

RA is the resistance between the device's OUT and SET pins.

On the daughter board, a resistance of 100K is used, giving a nominal analog power supply of 2.5V.

The daughter board provides an array of test points for checking the integrity of each of the board's power supplies, as well as GND.

Figure 2. Power supply test points.

Location on Board

The MAX1831 device is located on the component side of the board, to the right of the FPGA device.

The MAX8860 device is located on the solder side of the board.
 

 
The power supply test points (designated TP0 – TP4) are also located on the component side of the board, to the right of the Flash memory device (U1_CM).

Schematic Reference

The power supply-related circuitry can be found on the following sheets of the daughter board schematics.

• PSU.SchDoc (entitled Power Supply Top Level)

• PSU_MAX1831_1V2_ALT.SchDoc (entitled Power Supply MAX1831 (1V2))

• PSU_MAX8860_ADJ.SchDoc (entitled Power Supply MAX8860 (2V5))

Further Device Information

For more information on the MAX1831 and MAX8860 devices, refer to the datasheets (MAX1830-MAX1831.pdf and MAX8860.pdf) available at www.maxim-ic.com.