Project of circuits for generation of voltage reference in receiving/transmitting RF systems. / Projeto de circuitos para geração de tensão de referência em sistemas receptores/transmissores RF.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

This work consists in the design of a CMOS Voltage Reference Source with a temperature coefficient inferior to 50 ppm/ºC. This voltage source should be applied in radio frequency receptor/transmitter but can be also applied in any analog system. The technology employed in the design is the CMOS 0.35 µm from the AMS (Austria Micro Systems) with four metal levels and two poly-silicon levels. The implemented voltage source is of the Bandgap type and uses MOS devices in weak inversion, a parasitic bipolar transistor, and resistors made with high resistive poly-silicon. The circuit produces a PTAT (Proportional to Absolute Temperature) voltage that is added to the bipolar transistor base-emitter voltage to build an output voltage independent of temperature. The project and the drawing of the layout of the circuit had been carried out. The netlists of the circuit were generated from the layout and they were employed in simulations done with the software ELDO and the BSIM3v3 MOS model, in typical, worst speed, and worst power conditions. Through these simulations it was verified that the circuit reached the initial specifications. The value of the output voltage, however, although being next to the desired value of 1.25 V, varied with the employed simulation conditions. Two different Bandgap circuits had been sent to the foundry: a circuit with integrated resistors (dimensions of 220 µm x 76 µm) and another one without the resistors (dimensions of 190 µm x 36 µm). This last one allows, with the adjustment of external resistor values, modifying, if necessary, the operation conditions of the circuit. The circuits had been characterized and the circuit with integrated resistors has a temperature coefficient inferior to 40 ppm/ºC, an output variation rate with the power supply close to 19 mV/V. The output voltage value at 50 ºC is between 1.1835 V and 1.2559 V (1.25 V ± 67 mV). The circuit without the resistors has a temperature coefficient as high as 90 ppm/ºC, an output variation rate with the power supply inferior to 28 mV/V. The output voltage value at 50 ºC is between 1.247 V and 1.2588 V (1.25 V ± 9 mV). The temperature range used in the measurements was from -30 ºC to 100 ºC. The current consumption of the circuits is approximately of 14 µA, and they operate with power supply voltages as low as 1.8 V.

ASSUNTO(S)

microeletronic integrated circuits circuitos integrados mos circuitos analógicos microeletrônica analog circuts

ACESSO AO ARTIGO

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