34652_07 Datasheet, PDF (11/26 Pages) Freescale Semiconductor, Inc – 2.0 A Negative Voltage Hot Swap Controller with Enhanced Programmability

FUNCTIONAL DESCRIPTION
FUNCTIONAL PIN DESCRIPTION
POWER GOOD OUTPUT (ACTIVE LOW) (PG)
The PG pin is the active low 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.
OUTPUT VOLTAGE (VOUT)
The VOUT pin is the drain of the internal Power MOSFET
and supplies a current-limited voltage to the load. The load
connects between the VOUT and VPWR pins.
START-UP AND RETRY DELAY TIMER (TIMER)
This input is used to control the time-base used to
generate the timing sequences at start-up and the retry delay
when the device experiences any fault. The TIMER pin can
be left unconnected for a default timer value of 200 ms or the
user can connect a resistor between this pin and the VIN pin
to set the timer value externally. The timer value can vary
between 100 ms and 1000 ms.
OVERVOLTAGE CONTROL (OV)
The OV pin is used to set the upper limit of the input
voltage operation range. If the OV pin voltage goes above the
overvoltage threshold value, the device turns off the internal
Power MOSFET and deactivates the two power good
outputs, PG and PG. The Power MOSFET stays off until the
OV drops below the threshold value. The overvoltage
detection circuit has a 1.0 ms filter timer.
The OV pin can be left unconnected for the typical default
threshold value of 78 V or the user can set the threshold
value externally with a simple voltage divider using resistors
between the VPWR and VIN pins.
UNDERVOLTAGE CONTROL (UV)
The UV pin is used to set the lower limit of the input voltage
operation range. If the UV pin voltage goes below the
undervoltage threshold value, the device turns off the internal
Power MOSFET and deactivates the two power good
outputs, PG and PG. The Power MOSFET stays off until the
UV rises above the threshold value. The undervoltage
detection circuit has a 1.0 ms filter timer.
The UV pin can be left unconnected for the typical default
threshold value of 37 V or the user can set the threshold
value externally with a simple voltage divider using resistors
between the VPWR and VIN pins.
POSITIVE SUPPLY VOLTAGE INPUT (VPWR)
The VPWR pin is the most-positive power supply input.
The load connects between the VPWR and VOUT pins.
DISABLE INPUT CONTROL (DISABLE)
The DISABLE pin is used to easily disconnect or connect
the load from the main power line by disabling or enabling the
34652. It can also be used to reset the fault conditions that
cause a “Power No Good” signal.
If left open or connected to VPWR, the DISABLE pin is
inactive and the device is enabled. If a positive voltage
(above V_PWR) or a negative voltage (below V_PWR) is applied
to DISABLE, it is active and the device is disabled. The
disable function has a 1.0 ms filter timer.
This pin is referenced to VPWR.
CURRENT LIMIT CONTROL (ILIM)
The ILIM pin is used to set the overcurrent limit during
normal operation. This pin can be left unconnected for a
default overcurrent limit value of 1.0 A or the user can
connect an external resistor between the ILIM and VIN pins
to set the overcurrent limit value. This value can vary
between 0.35 A and 2.25 A. The overcurrent detection circuit
has a 100 µs filter timer.
CHARGING CURRENT LIMIT CONTROL (ICHG)
The ICHG pin is used to set the current limit that is used to
charge the load’s input capacitor, hence limiting the inrush
current to a known constant value. This pin can be left
unconnected for a default charging current limit value of 0.1 A
and a default I_CHG rise time of 1.0 ms. Or the user can
connect an external resistor between the ICHG and VIN pins
to set the current limit value between 0.05 A and 0.5 A and an
Analog Integrated Circuit Device Data
Freescale Semiconductor
34652
11