34652_07 Datasheet, PDF (10/26 Pages) Freescale Semiconductor, Inc – 2.0 A Negative Voltage Hot Swap Controller with Enhanced Programmability

FUNCTIONAL DESCRIPTION
INTRODUCTION
FUNCTIONAL DESCRIPTION
INTRODUCTION
Most telecom and data transfer networks require that
circuit boards be inserted and removed from the system
without powering down the entire system. When a circuit
board is inserted into or removed from a live backplane, the
filter or bypass capacitors at the input of the board’s power
module or switching power supply can cause large transient
currents when being charged or discharged. These currents
can cause severe and permanent damage to the boards, thus
making the system unstable. Figure 4 displays the inrush
current to the filter capacitor if a hot swap device is absent.
The inrush current reached an unsafe value of more than
55 A.
voltages in a controlled manner and regulating the inrush
current to a user-programmable limit, thus allowing the
system to safely stabilize (see Figure 5). The 34652 provides
protection against overcurrent, undervoltage, overvoltage,
and overtemperature. Furthermore, it protects the system
from short circuits.
Figure 5. Circuit Board Insertion With the Hot Swap
Device, Inrush Current Limited
Figure 4. Circuit Board Insertion Without a
Hot Swap Device, Inrush Current Not Limited
The 34652 is an integrated negative voltage hot swap
controller with an internal Power MOSFET. The 34652
resides on the plug-in boards and allows the boards to be
safely inserted or removed by powering up the supply
By integrating the control circuitry and the Power MOSFET
switch into a space-efficient package, the 34652 offers a
complete, cost-effective, and simple solution that takes much
less board space than a similar part with an external Power
MOSFET requires.
The 34652 can be used in - 48 V telecom and networking
systems, servers, electronic circuit breakers, - 48 V
distributed power systems, negative power supply control,
and central office switching.
FUNCTIONAL PIN DESCRIPTION
NEGATIVE SUPPLY INPUT VOLTAGE (VIN)
The VIN pin is the most negative power supply input. All
pins except the DISABLE pin are referenced to this input.
POWER GOOD OUTPUT (ACTIVE HIGH) (PG)
The PG pin is the active high power good output signal that
is used to enable or disable a load. This signal goes active
after a successful power-up sequence and stays active as
long as the device is in normal operation and is not
experiencing any faults.
The signal is deactivated under the following conditions:
• Power is turned off.
• The device is disabled for more than 1.0 ms.
• The device exceeded its thermal shutdown threshold for
more than 12 µs.
• The device is in overvoltage or undervoltage mode for
more than 1.0 ms.
• Load current exceeded the overcurrent limit for more than
3.0 ms.
This pin is referenced to VIN.
34652
10
Analog Integrated Circuit Device Data
Freescale Semiconductor