The Design Of Current-steering DAC For Digital Gyroscope

With more and more inertial systems are being used for military and civilian products, the requirements for gyroscope performance are also increasing. Digital circuits become the one of the important development direction of the gyroscope, and it has a bright future. This is because the digital circuit has faster algorithm processing capability and better stability. DAC is a bridge connecting digital and analog circuits, and it is a very important component of digital gyroscope drive circuit, the precision of the DAC directly affects the precision of gyroscope. Therefore, the study of the digital to analog converter has important research value and practical significance.The main content of this article is to design a 16-bit current-steering DAC. Through the analysis of current steering DAC structure, adopt the 6+6+4 sectional structure, the segmental structure can effectively reduce the chip area, enhance degree of linearity. In circuit design, in order to reduce the impact of the non-ideal effects such as the nonlinear of the circuit and mismatch, adopted the weighted data algorithm(DWA) to reduce current source mismatch in the current steering structure. On the time sequence, make the switch control signal synchronization by using the synchronous latch. To reduce the burr which produced by current source complementary switch open at the same time, make the clock control signal intersection reduced. In addition, in order to provide a stable reference current source for current source bias circuit, designed a band-gap reference circuit with self-starting function which had a low temperature coefficient, the reference voltage temperature coefficient is 15.47 ppm/ oC.When the current steering DAC sampling frequency is 500 KHZ, six separate current source module can realize stable output current which is 30 n A、60n A、120n A、240n A、480n A、30.72 u A. When digital gyro effective input signal frequency is 4 KHZ, the DNL is about 0.41 LSB, the INL is about 0.75 LSB, set up time is 0.4112 us, circuit output voltage range of 0 V to 4.5 V, SFDR is 62.5 DB. The design conforms to the design requirements.