Description

In HVAC (heating: ventilation: and air conditioning) HMI (human machine interface) the displays and buttons are illuminated with many of LEDs. The drive circuit for these LEDs are traditionally realized in a discreet way so that an MCU drives external low side BJTs that sink current: limited by series resistor: to the LEDs. The BJTs may be driven with a PWM signal in order to get the dimming effect or they could be used simply like an on/off switch. This reference design is an alternative cost-effective LED driver solution capable of driving multiple LEDs without using current-limiting resistors. The reference design allows the designer to individually adjust the current: as well as the PWM-dimming signal: in each diode excluding those that are connected in series to one pin.