1, application description
The VAS1085B is a wide input range constant current LED driver that provides a cost-effective solution for LED lighting applications such as advertising light boxes and landscape lighting. For most applications, the VAS1085B requires only one current setting resistor from SET to GND. A ceramic bypass capacitor from VIN to GND does not require an aluminum capacitor, Schottky diode or inductor. For high current applications, several VAS1085Bs can be connected in parallel to achieve high power output.
The vas1085b uses an external power supply resistor to reduce chip power consumption and poor quality power usage. At the same time, the vas1085b will automatically reduce the linear output current when the mold temperature reaches 120 ° C, this method avoids the LED stick flicker. Overheat protection can also be integrated.
Vas1085b is available with the dfn6l package.
2, features
Wide input range 2.7to40 V
Simple application circuit
Up to 120mA output current capability
Get a large output current in parallel
External power supply resistor to avoid overheating
±3% voltage accuracy
Over temperature protection
Dfn6l package
3, ordering instructions, ordering methods
4, pin diagram and pin function
5, the typical application circuit
6, structure diagram
7, electrical characteristics
8, typical performance characteristics
9, application information
(1) Set the LED current
The programmable LED current of the vas1085b feature is connected between the sleeve and the ground through a resistor. Calculate the sense resistor using the following formula:
Changing the RSET value gives the desired constant current. The chip consumes only *VD, and VD is the cathode voltage of the LED.
In order to obtain higher precision LED output current, a 1% or more high precision resistor comment. If the ambient temperature varies greatly, such as at 25 ° C to 85 ° C, use a low temperature coefficient resistor to ensure that the resistance is almost constant.
(2) Overheating problem
As the LED power supply rises, the LED cathode voltage will increase, which will cause the chip to overheat. Solve the problem with vas1085b:
If the vas1085b mold temperature rises to 120 ° C (IC surface temperature is about 80 ° C), the LED current begins to gradually decrease, when the temperature reaches 160 ° C, the LED current is reduced by half.
If the temperature continues to rise to 160 ° C, vas1085b enters thermal shutdown mode. When the temperature dropped to 120 ° C, vas1085b started working again.
(3) PCB layout
Careful PCB layout is critical to achieve low switching losses and stable operation. The input voltage between a 0.1uF ceramic capacitor and the ground is better for noise immunity. The SET pin is a high impedance. Pin, do not connect in parallel with any capacitor. Minimize ground pin noise to make the ground as wide and short as possible. A guard ring and a similar potential signal (such as GND) line around to prevent RSET interference.
10, the package
Stage Led Strobe Light ,Nine Eyes Laser Strobe Light,Stage Strobe Lights,Stage Led Strobe Lights
Guangzhou Cheng Wen Photoelectric Technology Co., Ltd. , https://www.cwledwall.com