UM0240 datasheet(13/39 Pages) STMICROELECTRONICS

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UM0240

10-bit digital-to-analog converter (DAC)

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10-bit digital-to-analog converter (DAC)

The Industrial Communication Board embeds a 10(12)-bit buffered voltage-output DAC

implemented by the AD5317 (AD5327) converter from Analog Devices. The IC provides four

buffered rail-to-rail outputs, in the range 0 ÷ Vcc, with a slew rate of 0.7 V/µs.

The DAC is controlled by the Microcontroller (PC2, PC3, PC4) through a 3-wires serial

interface and is compatible with SPI, QSPI, MICROWIRE and DSP interface standards.

The AD5317 is connected to the microcontroller through its SPI interface (MOSI to DIN and

SCK to SCLK). The references for the four DACs are derived from two reference pins:

VrefAB for VoutA and VoutB, VrefCD for VoutC and VoutD. These reference inputs can be

configured as buffered or unbuffered inputs, through interface command.

On the Industrial board the reference for the output pair AB is connected directly to Vcc

supply, while the VrefCD is available in a double option configuration, thanks to the jumper

JP3:

Connected to the VCC supply

Connected to the DAC output VoutB. This option is designed in order to provide a fine

voltage adjustment for the CD output pair DAC reference: this function is suitable, e.g.,

in Motor Control Applications using Micro-stepping technique, for the synthesis of

discrete sinusoidal waveforms. In fact, while the DAC output VoutC or VoutD can

generate a discrete sinusoidal waveform, the DAC output VoutB is able to control the

amplitude of the said signal, in order to control finely the torque of the stepper motor.

The AD5317(AD5327) DACs incorporate a power-on reset circuit, which ensures that the

DAC outputs power up to 0 V and remain there until a valid write to the device takes place.

There is also an asynchronous active low CLR pin, connected to the RES line of Industrial

board, that clears all DACs to 0 V. The outputs of all DACs may be updated simultaneously

using the asynchronous LDAC input, controlled by the MCU pin PD1.

The DAC IC contains a power-down feature that reduces the current consumption of the

devices to 300 nA @ 5 V, by setting all outputs in high impedance state. The devices goes

into power-down mode when the pin PD connected to the PD2 MCU line is tied low.

On the PLM connector, the four DAC outputs VOUTA, VOUTB, VOUTC and VOUTD are

available directly, while on the Motor connector, VREF_A and VREF_B are available. These

two signals are provided by the two difference amplifiers U3A and U3B implemented by

LM358.

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