All of the drivers I have seen which have both a voltage and a current adjustment aren't tailored for use with a laser diode, more commonly for LED's and never have a TTL input. The only reason I can think of to have a voltage range adjustment on a laser diode constant current regulator is to allow it to be used with different diodes; IR, red, blue and green which require different voltage ranges to operate, from lower to higher in that order of color.
I like the idea of a driver which has adjustment for voltage as well as current because then it can be set for use with any laser diode made, if the supply voltage is high enough and the driver components will handle the demand. However, I believe all of the drivers designed for laser diodes leave this adjustment off because they can be designed to automatically set the voltage to what ever it needs to be, within its design and supply limits, to produce the current you set the output to remain at but then these drivers usually can't drive all of the different color laser diodes available, not just because of the different current demands depending upon whether high or low power, but because it is more difficult to design a single driver in a small package which has the needed voltage and current ranges for all of the available laser diodes we use in pointers. Due to this, we have ended up with are drivers which are designed for the type of diode you will use, if you buy the correct driver for your diode you don't need to concern yourself with the actual output voltage, just the current, as the voltage will take care of itself depending upon the current set point and the diodes resistance, some diodes higher, some lower requiring more or less voltage for a given amount of current, but all of that taken care of through the regulator.
Some drivers are not designed for IR diodes, some are not designed for green diodes because the voltages needed for the two different technologies are so different, infrared requiring about 2 volts, green up to ~8 volts, for blue about midway between the two extremes. The choice for the kind of driver you need becomes more complex when using just one, or two of the common Li-On batteries we use for pointers because their single cell voltage ranges are 3 to 4.2 volts. Some diodes require more voltage than a single cell can produce and because of this, you either need to use two batteries in series, or a special "boost" driver which will increase the voltage beyond what a single cell can provide, through the magic of electronic circuitry, but at a cost, more current draw from the battery. Because high power blue and green diodes require over 4.2 volts, the maximum you can get out of a single celled Li-On battery, a single battery won't work to drive one of those laser diodes unless you buy a boost driver which can produce a higher voltage than one battery cell can provide.
So, now we have two basic types of driver designs, a regular or normal linear driver called a buck driver, and a boost driver. Buck drivers throw voltage away in the form of heat to keep too much current from flowing into your laser diode, boost drivers use more current from the battery to produce a higher voltage so you can supply enough current to your laser diode, two different methods of producing the voltage and current you need, depending upon whether your batteries are supplying too little voltage, or too much voltage for the device you want to regulate the current to. You do not need a boost driver for most of the laser diodes we use if the battery supply is two cells in series inside a pointer, as two cells usually produce enough voltage to drive just about any laser diode we use. In that case, why have a voltage adjustment when the driver can be designed to supply what ever voltage is needed to produce the amount of current a diode will draw? So, they leave the voltage control off, at a price, that pricing being some drivers are suited for IR, red and perhaps blue, but can't reach enough voltage to drive a green diode, so then you buy a different design.
I'd prefer all of the constant current regulators we use for laser diodes were designed for both a voltage as well as a current adjustment, that way all I would need to know is the min-max voltage and current ranges for both the input and outputs and be able to understand which driver I need just by a quick glance at their numbers. In the world of laser pointer drivers the designers of these devices approach things differently than I do, I want these input and output voltage and current figures but try to find them on any web page selling them, they aren't there. When I ask why not, I'm told most people just know what kind of driver they need for the battery and diode they want to drive... I base my choices upon knowing DC theory, as an electronics technician in my trade, so not having the figures right there seems uber stupid to me. If I had the figures, I wouldn't need to know which driver is better suited for which laser diode, I could figure it out myself from the specs. To make things even more confusing, the individuals selling these drivers often won't even put information showing which laser diodes they are good for, let alone color or whether you can use one or two batteries in series with them if you want to do so, such as I need to know for my tri-color laser diode pointer which uses red, green and blue laser diodes in it which operate across a large range of voltages, not to mention the next one I want to build which will also include an IR diode. Of course, my thinking it's stupid not to include this information is taken as being stupid not to be more familiar with the drivers offered. Their prices are high enough as it is to take a risk I'm buying the wrong driver, especially since my projects usually require lots of them, my next project over 24 of them so I want specs man, gimmie the specs!
OK, so there's some info I hope is helpful, thank you for bearing with my rant regarding the laser driver industry, they need to standardize their specs so we can figure things out easier, I've been working in electronics over 40 years now and find buying laser drivers too confusing, maybe because I'm a tech and know the possible gotcha's, not wanting to guess about any of the parameters.
