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L6911E

PIN FUNCTION

N

Name

Description

1

VSEN

Connected to the output voltage is able to manage over-voltage conditions and the PGOO D signal.

2

OCSET

A resistor connected from this pin and the upper Mos Drain sets the current limit protection.

The internal 200

µA current generator sinks a current from the drain through the external resistor.

The Over-Current threshold is due to the following equation:

3

SS/INH

The soft start time is programmed connecting an external capacitor from this pin and GND. The

internal current generator forces through the capacitor 10

µA.

This pin can be used to disable the device forcing a voltage lower than 0.4V

4 - 8

VID0 - 4

Voltage Identification Code pins. These input are internally pulled-up and TTL compatible. They are

used to program the output voltage as specified in Table 1 and to set the overvoltage and power

good thresholds.

Connect to GND to program a ‘0’ while leave floating to program a ‘1’.

9

COMP

This pin is connected to the error amplifier output and is used to compensate the voltage control

feedback loop.

10

FB

This pin is connected to the error amplifier inverting input and is used to compensate the voltage

control feedback loop.

11

GND

All the internal references are referred to this pin. Connect it to the PCB signal ground.

12

PGOO D This pin is an open collector output and is pulled low if the output voltage is not within the above

specified threshlds.

If not used may be left floating.

13

PHASE

This pin is connected to the source of the upper mosfet and provides the return path for the high side

driver. This pin monitors the drop across the upper mosfet for the current limit.

14

UGATE

High side gate driver output.

15

BOOT

Bootstrap capacitor pin. Through this pin is supplied the high side driver and the upper mosfet.

Connect through a capacitor to the PHASE pin and through a diode to Vcc (catode vs boot).

16

PGND

Power ground pin. This pin has to be connected closely to the low side mosfet source in order to

reduce the noise injection into the device

17

LGATE

This pin is the lower mosfet gate driver output

18

VCC

Device supply voltage. The operative supply voltage range is from 4.5 to 12V.

19

OVP

Over voltage protection. If the output voltage reach the 15% above the programmed voltage this pin

is driven high and can be used to drive an external SCR that crowbar the supply voltage.

If not used, it may be left floating.

20

RT

Oscillator switching frequency pin. Connecting an external resistor from this pin to GND, the external

frequency is increased according to the equation:

Connecting a resistor from this pin to Vcc (12V), the switching frequency is reduced according to the

equation:

If the pin is not connected, the switching frequency is 200KHz.

The voltage at this pin is fixed at 1.23V. Forcing a 50

µA current into this pin, the built in oscillator

stops to switch.

I

OCSET

R

OCSET

R

DSon

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

=

f

S

200kHz

510

6

⋅

R

()

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

+

=

f

S

200kHz

410

7

⋅

R

()

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

–

=