SLUAB16 March   2025 LMR51403 , TPS629203

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Input and Output Ripple of Buck Converter in DCM
  6. 3TPS629203 Design Consideration
  7. 4Experimental Results
    1. 4.1 VIN and VOUT Ripple Results
    2.     Efficiency
  8. 5Summary
  9. 6References

3 TPS629203 Design Consideration

The TPS629203 is a DCS control (COT), high-efficiency, easy-to-use, synchronous buck converter, and the typical Iq is 4uA. In VIN = 10V and Vout = 3.3V power rail, input and output capacitor of TPS629203 are chosen as CIN=1uF (GRM21BR71E105KA99L) and COUT = 10uF (GRM21BR61E106MA73L). Considering the DC bias effect and capacitance variation of ceramic capacitor, the actual capacitance can be considered as CIN = 0.9uF, Cout = 5.8uF. From the mode description in TPS629203 300mA, 3V to 17V Low IQ Buck Converter with DCS-Control data sheet, constant Ton time with AEE function is calculated by using Equation 9.

Equation 9. Ton=100×VINVIN-VOUT(ns)=150(ns)

To meet the target of ripple is 0.2% of input and output voltage in Table 1-2. The inductor can be calculated as L≤ 5.6uH from Equation 3 and Equation 8. Figure 3-1 is schematic for whole design. Considering the input capacitance is low, users can encounter oscillation problems, especially when the input trace is long. Therefore, TI recommends to add a 1 ohm resistor (R3) at input trace for damping.

TPS629203 Schematic DesignFigure 3-1 TPS629203 Schematic Design