add XL2596 buck/step down converter

vreg/buck_xl2596.yaml

@@ -0,0 +1,45 @@
+name: XL2596
+variations: TO263-5L, TO220-5L # suffix: S, T
+description: step-down voltage regulator
+keywords: IC, regulator, buck
+datasheet: http://www.xlsemi.com/datasheet/XL2596%20datasheet-English.pdf
+
+pinout:
+  VIN: 1
+  SW: 2
+  GND: 3
+  FB: 4
+  EN: 5
+  GND_TAB: 6
+
+properties:
+  power: VIN
+  output: SW
+  input: FB, EN
+  ground: GND, GND_TAB
+
+schematic:
+  symbol: IC
+  left: VIN, EN
+  right: SW
+  top: FB
+  bottom: GND, GND_TAB
+
+housing@TO263-5L:
+  outline: JEDEC TO-263 BA
+  suffix: S
+
+housing@TO220-5L:
+  pattern: custom
+  suffix: T
+  bodyWidth: 9.78-10.54 # E
+  bodyLength: 4.06-4.83 # A
+  height: 14.22-15.49 # D
+  pitch: 1.71 # e (1.57+1.85)/2
+  leadHeight: 14.22-15.49 # D
+  leadWidth: 0.76-1.02 # b
+  leadLength: 0.36-0.64 # C
+  holeDiameter: 1.2
+  columnCount: 5
+  rowCount: 1
+  rowDY: 1.21 # (4.83+4.06)/2 - (2.29+3.18)/2 - (0.36+0.64)/2