Tag
switching regulators
7 articles.
- MOSFET gate resistor: what value, and what it actually sets
The gate resistor sets one thing, how fast the drain slews during the Miller plateau, and costs one thing in return. TI's design: 10.5 Ω for a 2.3 kV/µs edge.
- Switch-node ringing: measure it, then size the snubber
Two scope readings give the loop inductance and the parasitic capacitance. From those the snubber values follow, and so does the reason to fix the layout first.
- Choosing a buck inductor: ripple, saturation and heat
Size the inductance from the ripple target, then check the peak against saturation and the RMS against heating — two different ratings that fail differently.
- Measuring supply ripple: the ground clip is the antenna
A 3-inch probe ground lead turns a switching spike into ringing that is not on the rail. Tip-and-barrel, coax, bandwidth limits, and the null test.
- Buck converter input filter design for conducted EMI
Size a buck converter's LC input filter from the required attenuation at the switching fundamental, damp the resonant peak, and keep the control loop stable.
- Buck converter PCB layout: find the hot loop first
The two switch-state current loops differ by one small loop carrying chopped current. Its area sets the EMI, and the input capacitor's placement sets its area.
- Where the buck ripple comes from, and why more capacitance didn't help
The textbook ΔV = I/(8Cf) is the special case where ESR is zero. Where most real designs sit, output ripple is I·ESR, independent of capacitance and frequency.