AD7195 with MIC4427

Hi, 

You have to used all of the excitation logic pins. Please take note that in ac excitation, the polarity of the excitation voltage to the bridge is reversed on alternate cycles. When the ac excitation is enabled, the reference inputs along with the analog inputs are inverted. 

Phase 1: The excitation voltage is applied to the top of the loadcell. 

Phase 2: The polarity is changed so that the excitation voltage is applied to the bottom of the loadcell and the analog inputs and reference inputs to the ADC are inverted. 

These 2 conversions are then averaged within the ADC and the averaged result is loaded into the data register.

Please refer to Figure 50. of the datasheet or to the CN-0155 on how to connect it to the bridge sensor and to the ADC. Please also refer to the same materials on how to configure the AC excitation bits.

Thanks,

Jellenie

Hi, 

You have to used all of the excitation logic pins. Please take note that in ac excitation, the polarity of the excitation voltage to the bridge is reversed on alternate cycles. When the ac excitation is enabled, the reference inputs along with the analog inputs are inverted. 

Phase 1: The excitation voltage is applied to the top of the loadcell. 

Phase 2: The polarity is changed so that the excitation voltage is applied to the bottom of the loadcell and the analog inputs and reference inputs to the ADC are inverted. 

These 2 conversions are then averaged within the ADC and the averaged result is loaded into the data register.

Please refer to Figure 50. of the datasheet or to the CN-0155 on how to connect it to the bridge sensor and to the ADC. Please also refer to the same materials on how to configure the AC excitation bits.

Thanks,

Jellenie

Yes, I understand the excitation principle.

I looked at CN-0155, but as the datasheet mention, I'd like to use a MIC4427 instead of four transistors. The MIC4427 having only two inputs.

If I get it right, the attached schematic should be correct.

Hi, 

I see. I think that should be fine. I think the advantage of having ACX1 and ACX2 instead of ACX1 and !ACX1 is that the signals ACX1 and ACX2 are non overlapping meaning no potential short circuiting will occur when switching on/off. Though 1Mohm pull-up/down resistors is recommended to prevent short circuiting during power. 

Thanks,

Jellenie 

Ok, I did understand it correctly then.

I will add pull up on ACX1 and a pull down on AXC2 per your recommendation.