Hot Plug Circuit
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
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.
Hot Plug Circuit
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.
methods of controlling hot-plug damage, this
circuit is located on the source side of the mating connector instead
of on the load side.
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.
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
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. ...