A color-temperature-tunable device comprises a first light emitting diode (LED) chip group comprising at least one first blue LED chip that emits a first light having a first peak wavelength, a second LED chip group comprising at least one second blue LED chip that emits a second light having a second peak wavelength different from the first peak wavelength, and a wavelength converting layer above at least a portion of the first LED chip group and a portion of the second LED chip group. The first LED chip group and the second LED chip group are driven by a first driving current and a second driving current, respectively.