Browse Prior Art Database

Hot Plug Circuit

IP.com Disclosure Number: IPCOM000121431D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Egan, PK: AUTHOR

Abstract

Described is a method of allowing the mating of connector pins with voltage on them that will limit the mating current to prevent arcing damage of the connector pins and control the current to allow for capacitive loading.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 67% of the total text.

Hot Plug Circuit

      Described is a method of allowing the mating of connector
pins with voltage on them that will limit the mating current to
prevent arcing damage of the connector pins and control the current
to allow for capacitive loading.

      Unlike other methods of controlling hot-plug damage, this
circuit is located on the source side of the mating connector instead
of on the load side.

      The figure shows a schematic of the hot-plug circuit. The
circuit uses a P-junction FET Q1 in parallel with R1 as the pass
elements, which control the current in the connector J1.  C1, R2 and
R3 are used to turn Q1 on slowly.

      The control circuit is made up of OP-AMP M1 and its supporting
components, C2 and R4 through R9.  The control circuit's purpose is
to regulate the voltage drop across Q1. The concept that makes this
circuit work is choosing the Q1 regulation point between zero volts
and the voltage developed across Q1 when the load current is set at
minimum. This will give the wanted function in each mode of operation
explained below.

      With no connection (No Load), the drop across Q1 is zero.  This
will cause the control circuit to drive the gate of Q1 high, turning
Q1 completely off.

      When J1 is plugged to P1, Q1 is off, allowing a reduced mating
current limited by R1.  The drop across Q1 is now VIN.  C1 and R3 of
the control circuit are chosen to slowly drive Q1 through its linear
region, causing a soft turn on of Q1. ...