Stepping down PWM
Project Colimbo
Posts: 1
I'm looking to use a National Semiconductor LM 3812 to measure current usage on my project. http://cache.national.com/ds/LM/LM3812.pdf for reference.
The currents I'm mearsuing are on voltages that are greater than the 5.25V limit, so I'm looking to use the circuit on page 9 for high side sensing of voltages greater than 5.25V. My understanding is that the PWM coming from the chip will now be referenced to a much higher voltage. So for example if the input voltage is 20V, the verner diode will allow 15V to pass and thus my PWM will range from 15V to 20V.
First question - am I understanding this correctly?
Second question - if so - what's the best way to step this back down to something·in the range of 0-5V so I·can read through standard digital i/o?
thanks much in advance,
Project Colimbo
The currents I'm mearsuing are on voltages that are greater than the 5.25V limit, so I'm looking to use the circuit on page 9 for high side sensing of voltages greater than 5.25V. My understanding is that the PWM coming from the chip will now be referenced to a much higher voltage. So for example if the input voltage is 20V, the verner diode will allow 15V to pass and thus my PWM will range from 15V to 20V.
First question - am I understanding this correctly?
Second question - if so - what's the best way to step this back down to something·in the range of 0-5V so I·can read through standard digital i/o?
thanks much in advance,
Project Colimbo