Prototype GW11

a few proto GW11's have been made - to test all the elements

Amps:

AD8553 should replace the AD623 for rail-rail output

Vref - need to install Vref chip?

Measurements of sleep/wake current use

conclusion: Some main changes on final PCB

 i)  add a switch to control the battery and external power supply, and two diodes

 ii) add battery monitor unit 

 iii) add one voltage reference chip in case the sensor needs high precision supply

 iv) change the signal pinout of CON to radio modem

 v) change the package of TPS76850 from D to PWP!