I'm wondering if it is possible to cascade a number of AS1109 (DATASHEET HERE) but use only one resistor to set the current on all the drivers.
The AS1109 scales up the reference current (IREF) set by external resistor (REXT) to sink a current (IOUT) at each output port. As shown in
Figure 3 on page 7 the output current in the saturation region is extremely flat so that it is possible to define it as target current (IOUT TARGET).
IOUT TARGET can be calculated by:
VREXT = 1.253V
IREF = VREXT/REXT (if the other end of REXT is connected to ground)
IOUT TARGET = IREF*15 = (1.253V/REXT)*15
REXT is the resistance of the external resistor connected to pin REXT.
VREXT is the voltage on pin REXT.
If i just parallel all the current set pins would there be any problems because of small differences of the voltage (VREXT) ?