SLAS535F September 2007 – October 2018 DAC5652A
The architecture of the DAC5652A uses a current steering technique to enable fast switching and a high update rate. The core element within the monolithic DAC is an array of segmented current sources that are designed to deliver a full-scale output current of up to 20 mA. An internal decoder addresses the differential current switches each time the DAC is updated, and a corresponding output current is formed by steering all currents to either output summing node, IOUT1 or IOUT2. The complementary outputs deliver a differential output signal, which improves the dynamic performance through reduction of even-order harmonics, common-mode signals (noise), and doubles the peak-to-peak output signal swing by a factor of two, as compared to single-ended operation.
The segmented architecture results in a significant reduction of the glitch energy and improves the dynamic performance (SFDR) and DNL. The current outputs maintain a very high output impedance of greater
than 300 kΩ.
When pin 42 (GSET) is high (simultaneous gain set mode), the full-scale output current for DACs is determined by the ratio of the internal reference voltage (1.2 V) and an external resistor (RSET) connected to BIASJ_A. When GSET is low (independent gain set mode), the full-scale output current for each DAC is determined by the ratio of the internal reference voltage (1.2 V) and separate external resistors (RSET) connected to BIASJ_A and BIASJ_B. The resulting IREF is internally multiplied by a factor of 32 to produce an effective DAC output current that can range from 2 mA to 20 mA, depending on the value of RSET.
The DAC5652A is split into a digital and an analog portion, each of which is powered through its own supply pin. The digital section includes edge-triggered input latches and the decoder logic, while the analog section comprises both the current source array with its associated switches, and the reference circuitry.