Esto lo leiste en el ULN2803
10.2.2.3 Power Dissipation & Temperature The number of coils driven is dependent on the coil current and on-chip power dissipation. To determine the number of coils possible, use the below equation to calculate ULN2803A on-chip power dissipation PD: Where: N is the number of channels active together. VOLi is the OUTi pin voltage for the load current ILi. This is the same as VCE(SAT) (2) In order to guarantee reliability of ULN2803A and the system the on-chip power dissipation must be lower that or equal to the maximum allowable power dissipation (PD(MAX)) dictated by below equation Equation 3. Where: TJ(MAX) is the target maximum junction temperature. TA is the operating ambient temperature. θJA is the package junction to ambient thermal resistance. (3) It is recommended to limit ULN2803A IC’s die junction temperature to less than 125°C. The IC junction temperature is directly proportional to the on-chip power dissipation.
500mA por salida, pero no puedes usar todas las salidas sin que el integrado se caliente.
Ten cuidado y haz los calculos
Pagina 12 del datasheet ULN2803 de Texas Instrument
Bueno mas allá de eso. Porque no piensas en usar un driver MOSFET.
Que tal algo asi como idea
