34652 datasheet(11/26 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34652

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 VPWR) or a negative voltage (below VPWR) 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 ICHG 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

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