by heavy lines should be kept as short as possible. Single-
point grounding (as indicated) or ground plane construction
should be used for best results. When using the Adjustable
version, physically locate the programming resistors near the
regulator, to keep the sensitive feedback wiring short.
Test Circuit and Layout Guidelines
As in any switching regulator, layout is very important. Rapidly
switching currents associated with wiring inductance gener-
ate voltage transients which can cause problems. For minimal
inductance and ground loops, the length of the leads indicated
Fixed Output Voltage Versions
1147508
CIN — 100 μF, 75V, Aluminum Electrolytic
COUT — 330 μF, 25V, Aluminum Electrolytic
D1 — Schottky, 11DQ06
L1 — 330 μH, PE-52627 (for 5V in, 3.3V out, use 100 μH, PE-92108)
Adjustable Output Voltage Version
1147509
where VREF = 1.23V, R1 between 1k and 5k.
R1 — 2k, 0.1%
R2 — 6.12k, 0.1%
Note: Pin numbers are for the TO-220 package.
FIGURE 2.
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