JAJSSV2G March 2011 – January 2024 DAC3482
PRODUCTION DATA
The DAC3482 uses a bandgap reference and control amplifier for biasing the full-scale output current. The full-scale output current is set by applying an external resistor RBIAS to pin BIASJ. The bias current IBIAS through resistor RBIAS is defined by the on-chip bandgap reference voltage and control amplifier. The default full-scale output current equals 64 times this bias current and can thus be expressed as:
The DAC3482 has a 4-bit coarse gain control coarse_dac(3:0) in the config3 register. Using gain control, the IOUTFS can be expressed as:
where VEXTIO is the voltage at terminal EXTIO. The bandgap reference voltage delivers an accurate voltage of 1.2V. This reference is active when extref_ena = 0b in config27. An external decoupling capacitor CEXT of 0.1µF should be connected externally to terminal EXTIO for compensation. The bandgap reference can additionally be used for external reference operation. In that case, an external buffer with high impedance input should be applied to limit the bandgap load current to a maximum of 100nA. The internal reference can be disabled and overridden by an external reference by setting the extref_ena control bit. Capacitor CEXT may hence be omitted. Terminal EXTIO thus serves as either input or output node.
The full-scale output current can be adjusted from 30mA down to 10mA by varying resistor RBIAS, programming coarse_dac(3:0), or changing the externally applied reference voltage.
With internal reference, the minimum Rbias resistor value is 1.28kΩ. Resistor value below 1.28kΩ is not recommended since it programs the full-scale current to go above 30mA and potentially damages the device.