DESIGN IDEAS Low Voltage PowerPath Driver
Switches from a 3.3V or 5V
by Peter Guan and
Supply to Battery Backup
Tim Skovmand
The LTC1473L solves the problem
of seamless power switching between
3.3V or 5V supplies and backup battery packs (3-or 4-cell NiMH) at high
current levels. By driving two sets of
back-to-back N-channel MOSFET
switches, the LTC1473L routes power
to the input of a low voltage (3.3V to
10V) system efficiently and inexpensively. An internal micropower boost
regulator is included to fully enhance
the external NMOS switches, even at
low operating voltages. An external
1mH inductor and 1ВµF capacitor
charge VGG to approximately 8.5V
above V+, providing ample drive for
the external MOSFETs. The LTC1473L
includes inrush-current limiting during supply switchover to produce
smooth transitions between the DC
supply and the battery backup and to …