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Internal or External reference

Category: Hardware
Product Number: MAX191

I was looking to verify the reference setup on a MAX191 we use. I read the datasheet and noted that a logic high input on the /PD line places the chip in in normal operation with an internal reference compensation mode. Currently, the device is powered with VDD as +5vdc and Vss is set to power supply return (0 vdc). The /PD pin is tied to +5vdc. So, I assume it is set for normal operation with an internal reference.

I also see in our schematic diagram that the VREF is also tied to +5vdc. as is REFADJ.  When you connect the REFADJ pin to VDD, it indicates that an external reference is to be used at VREF.

So, I am a little confused as to how this chip is functioning. Am I using an internal reference or an external reference?

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