L6732_08 datasheet(8/37 Pages) STMICROELECTRONICS

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Pin connection and function

L6732

8/37

Pin n.

Name

Function

EAREF

By setting the voltage at this pin is possible to select the internal/external

reference and the switching frequency:

VEAREF 0-80 % of VCCDR -> external reference/FSW = 250 kHz

VEAREF = 80 %-95 % of VCCDR -> VREF = 0.6 V/FSW = 500 kHz

VEAREF = 95 %-100 % of VCCDR -> VREF = 0.6 V/FSW = 250 kHz

An internal clamp limits the maximum VEAREF at 2.5 V (typ.). The device

captures the analog value present at this pin at the start-up when VCC

meets the UVLO threshold.

OCL

A resistor connected from this pin to ground sets the valley- current-limit.

The valley current is sensed through the low-side MOSFET(s). The internal

current generator sources a current of 100 µA (IOCL) from this pin to ground

through the external resistor (ROCL). The over-current threshold is given by

the following equation:

Connecting a capacitor from this pin to GND helps in reducing the noise

injected from VCC to the device, but can be a low impedance path for the

high-frequency noise related to the GND. Connect a capacitor only to a

“clean” GND.

OCH

A resistor connected from this pin and the high-side MOSFET(s) drain sets

the peak-current-limit. The peak current is sensed through the high-side

MOSFET(s). The internal 100 µA current generator (IOCH) sinks a current

from the drain through the external resistor (ROCH). The over-current

threshold is given by the following equation:

PHASE

This pin is connected to the source of the high-side MOSFET(s) and

provides the return path for the high-side driver. This pin monitors the drop

across both the upper and lower MOSFET(s) for the current limit together

with OCH and OCL.

HGATE

This pin is connected to the high-side MOSFET(s) gate.

BOOT

Through this pin is supplied the high-side driver. Connect a capacitor from

this pin to the PHASE pin and a diode from VCCDR to this pin (cathode

versus BOOT).

PGND

This pin has to be connected closely to the low-side MOSFET(s) source in

order to reduce the noise injection into the device.

LGATE

This pin is connected to the low-side MOSFET(s) gate.

VCCDR

5 V internally regulated voltage. It is used to supply the internal drivers.

Filter it to ground with at least 1 µF ceramic cap.

VCC

Supply voltage pin.

The operative supply voltage range is from 4.5 V to 14 V.

Table 4.

Pin functions (continued)

VALLEY

OCL

•

DSONLS

•

----------------------------------

PEAK

OCH

•

DSONHS

----------------------------------

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