
200
www.newnespress.com
Chapter 6
switches following the regulated supply. To avoid losing regulation while delivering peak
load currents, the FETs ’
on-resistance must be suffi ciently low to ensure that the load-side
voltage remains above the minimum level specifi ed.
This switch-resistance problem is further complicated in low-voltage systems of 3.3 V and
below, because the low gate drive may not suffi ciently minimize the FET ’ s on-resistance.
The cost of low-gate-threshold FETs is declining. However, in many cases, the use of
multiple linear regulators offers a better approach. Many new linear regulators have a
logic-level shutdown capability ...