SLAAE23 June 2021 DAC43204 , DAC53004 , DAC53204 , DAC63204

- The
*DACx3204 12-Bit, 10-Bit, and 8-Bit, Quad Voltage and Current Output Smart DACs With Auto-Detected I2C, PMBus™, or SPI Interface Data Sheet*recommends using a 100-nF decoupling capacitor for the VDD pin and a 1.5-µF or greater bypass capacitor for the CAP pin. The CAP pin is connected to the internal LDO. Place these capacitors close to the device pins. - The nominal voltage of the SMPS
is set by resistors R
_{1}and R_{2}. The SMPS uses an internal 600-mV reference voltage at the FB pin to determine the voltage at the output. Calculate R_{1}and R_{2}using the following equations:${R}_{1}=\frac{{V}_{NOMINAL}-{V}_{FB}}{{I}_{NOMINAL}}$${R}_{2}=\frac{{R}_{1}\times {V}_{FB}}{{V}_{NOMINAL}-{V}_{FB}}$A nominal current of 100µA through R_{1}and R_{2}and 3.3-V nominal output voltage is used. With these values the equations become:${R}_{1}=\frac{3.3V-0.6V}{100\mu A}=27k\Omega $${R}_{2}=\frac{27k\Omega \times 0.6V}{3.3V-0.6V}=6k\Omega $ - To achieve the desired margin,
the DAC43204 must sink or source additional current through R
_{1}. This current (I_{MARGIN}) is calculated by:${I}_{MARGIN}=\frac{{V}_{NOMINAL}\times \left(1+MARGIN\right)-{V}_{FB}}{{R}_{1}}-{I}_{NOMINAL}$For a ±10% margin, the equation becomes:

${I}_{MARGIN}=\frac{3.3V\times \left(1+0.10\right)-0.6V}{27k\Omega}-100\mu A=12\mu A$ - The DAC codes for
±I
_{MARGIN}are stored in the DAC-MARGIN-HIGH and DAC-MARGIN-LOW registers. The codes programmed to these registers, in decimal, is calculated using:$DAC\_MARGIN\_HIGH=\frac{{I}_{DAC,MAX}-{I}_{MIN}}{{I}_{MAX}-{I}_{MIN}}\times 256$$DAC\_MARGIN\_LOW=\frac{{I}_{DAC,MIN}-{I}_{MIN}}{{I}_{MAX}-{I}_{MIN}}\times 256$Using an I

_{OUT}range of ±25µA, the equation becomes:$DAC\_MARGIN\_HIGH=\frac{12\mu A-\left(-25\mu A\right)}{25\mu A-\left(-25\mu A\right)}\times 256=189.44d$$DAC\_MARGIN\_LOW=\frac{-12\mu A-\left(-25\mu A\right)}{25\mu A-\left(-25\mu A\right)}\times 256=66.56d$This is rounded to 189d and 67d to give a I

_{DAC,MAX}of 11.9µA and a I_{DAC,MIN}of –11.9µA. - In this design,
GPI is used for Margin High, Low function. A high on GPI sets the DAC output to
I
_{DAC,MAX}and the SMPS V_{OUT}to margin high, or 3.63V. A low on GPI sets the DAC output to I_{DAC,MIN}and the SMPS V_{OUT}to margin low, or 2.97V. - The DAC43204 can be programmed with the initial register settings described in the Register Settings section using I2C or SPI. Save the initial register settings in the NVM by writing a 1 to the NVM-PROG field of the COMMON-TRIGGER register. After programming the NVM, the device loads all registers with the values stored in the NVM after a reset or a power cycle.