Innovations in low-noise and low-power voltage references

One way to lower noise is to increase the power in the system, but there is often a power budget, making it necessary to maximize noise performance with limited power. TI’s low-noise voltage reference portfolio includes low-power options such as the REF33, REF34 and REF35 families, which push the boundary between power and noise for low-power ADCs with high precision. A lower quiescent current (I_Q) voltage reference is beneficial for portable or edge applications, such as two-wire transmitters, that have a limited power budget.

Innovations in efficient band-gap circuits and output buffers have improved the power-to-noise ratio of voltage references. The REF33, REF34 and REF35 are staple devices in TI’s voltage reference portfolio for low noise and low power. Figure 7 compares their noise and power and highlights the innovation of the REF35.

One common application for low noise is portable medical equipment such as portable electrocardiogram machines. The ADS124S08 family of 24-bit ADCs has power consumption as low as 280 μA to minimize power draw in field instruments and edge devices that have limited power budgets. Table 1 compares the REF35 with the internal ADS124S08 voltage reference and highlights the improved accuracy with I_Q. The REF35’s low noise and high accuracy improves both quantization and gain errors while lowering system power. The benefit of a flexible voltage reference voltage enables further optimization for maximizing the full-scale range of the ADS124S08.

The REF35 also pairs with the ADS127L11, which is an ADC focused on DC precision with low power consumption. The REF35 offers a 10x reduction in supply current compared to the REF34 which makes it a stronger pairing with the ADS127L11 in low-speed mode. This pairing enables the ADS127L11 to achieve accuracy in power quality analyzer systems that require high precision, or machine vibration systems that need low power in order to balance solution size, resolution and bandwidth.