UC2845D8G4 datasheet by Texas Instruments

UC2845D8G4 Frequently Asked Questions (FAQs)

• What is the recommended layout and PCB design considerations for the UC2845D8G?
  The UC2845D8G is a high-frequency switching regulator, and as such, it requires careful PCB design and layout to minimize noise, EMI, and parasitic inductance. TI recommends using a 4-layer PCB with a solid ground plane, separating the high-current and low-current loops, and using short, wide traces for the power lines. Additionally, it's essential to place the input and output capacitors close to the IC and use a common ground point for the input and output returns.
• How do I choose the right inductor for my UC2845D8G design?
  Choosing the right inductor for the UC2845D8G involves considering factors such as inductance value, current rating, and core material. TI recommends using an inductor with a value between 1.5uH to 3.3uH, a current rating of at least 1.5 times the maximum output current, and a core material with low core loss at high frequencies. Additionally, the inductor should be placed close to the IC and oriented to minimize mutual inductance.
• What is the maximum input voltage that the UC2845D8G can handle?
  The UC2845D8G has an absolute maximum input voltage rating of 18V, but the recommended maximum input voltage is 15V to ensure reliable operation and minimize the risk of damage. Exceeding the recommended maximum input voltage can lead to reduced performance, increased power dissipation, and potentially even damage to the IC.
• How do I compensate for the UC2845D8G's voltage feedback loop?
  The UC2845D8G's voltage feedback loop requires compensation to ensure stability and prevent oscillations. TI recommends using a Type II compensation network, which consists of a series resistor and capacitor connected between the VFB pin and the output voltage. The values of the resistor and capacitor depend on the specific application and can be calculated using TI's compensation calculator or by following the guidelines in the datasheet.
• What is the purpose of the UC2845D8G's soft-start pin, and how do I use it?
  The UC2845D8G's soft-start pin (SS) allows the user to control the startup sequence of the converter. By connecting a capacitor from the SS pin to ground, the user can slow down the startup sequence and reduce the inrush current. The value of the capacitor determines the soft-start time, and TI recommends a value between 10nF to 100nF. The soft-start feature helps to reduce the stress on the input power source and the converter itself during startup.