Low Voltage Hot Swap Controller Ignores Backplane Noise
and Surges – Design Note 319
Mitchell Lee
First generation single supply Hot Swapв„ў controllers,
such as the LTC В®1422, combine the features of various
discrete inrush limiting circuits into a single IC, including
an electronic circuit breaker, adjustable power-up rate,
reset output, high side MOSFET gate drive, undervoltage
lockout and a wide operating voltage range. The LTC4211
advances these features by adding a dual level, dual
response time electronic circuit breaker, adjustable softstart with inrush current limiting, fault detection, faster
response time to severe overloads and operation from
2.5V to 16.5V—all in a small 10-lead MSOP package.
Control 25W with a 10-Lead MS Package
Figure 1 shows a 5V, 5A Hot Swap application designed
for inclusion on a removable circuit board. As is customary, the circuit board ground and VCC planes are wired
to long connector pins, eliminating reliability problems
associated with pin-to-receptacle arcing. Until the PC
board is п¬Ѓrmly seated in the backplane, the MOSFET
switch remains safely off and isolates CLOAD (typically
100ОјF or more) from the backplane. Once the connector
is fully seated, the R1-R2 divider which serves both as a
connection sense and an undervoltage lockout, activates …