High accuracy analog signal measurement with ultra low power MCU: Page 3 of 5

September 30, 2013 //By Alison Evans
High accuracy analog signal measurement with ultra low power MCU
Alison Evans, European Technical Marketing Avnet Memec looks at the numerous design considerations faced when optimizing a high precision analog design for low power consumption.
VPG precision resistors).   Additional circuitry is used to be able to attach various sensors and to allow for gain selection. These components are optional and can be removed for more optimal design if necessary.

DAQ on a stick with strain gauge

Figure 1: Simplified strain gauge schematic

The Intersil ISL28134 Chopper Stabilized Op Amp uses state of the art CMOS design techniques to achieve extremely offset drift and low noise at moderate current levels.

The complex input circuits needed for rail to rail operation often increase both the noise level and the current consumption of an operational amplifier.  In the ISL28134, this supply current overhead is minimal and the multiple input devices are exploited to achieve the 8 nV/rt(Hz) input noise level.  Low power design throughout the amplifier keeps the total supply current down to 675 microamps (typical).  The power can be reduced further to 1.7 mW by operating at 2.5 V supply.  The advantage of the chopper stabilized design of the ISL28134 is the near-absence of flicker noise.  In low noise, very low frequency applications the total noise is usually dominated by 1/f noise.  However in the ISL28134 chopper stabilization is extensively applied, giving a 1/f noise corner of 0.005 Hz (see Figure 2). 

The fact that the plot shows 12 nV/√Hz at 0.001 Hz (1000 seconds) shows the stability of the low offset design and performance. The actual data collection for this plot was taken over several hours, so this number at 0.001 Hz says the offset is very stable.  The ISL28134 is one of the best 'zero drift offset' op amps in the industry today.  Moreover, the ISL26102 Delta Sigma Converter also uses chopping techniques to remove 1/f noise and DC errors, preserving the unique 1/f noise performance of the ISL28134.  Consequently, the combination of the ISL28134 in differential configuration into the ISL26102 makes for one of the best implementations for precision, low noise design common in

Design category: 

Vous êtes certain ?

Si vous désactivez les cookies, vous ne pouvez plus naviguer sur le site.

Vous allez être rediriger vers Google.