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L6911C

5 BIT PROGRAMMABLE STEP DOWN CONTROLLER WITH SYNCHRONOUS RECTIFICATION

STMicroelectronics 

L6911C

PIN FUNCTION

Pin

Num.

Name

Description

1

VSEN Connected to the output voltage is able to manage over-voltage conditions and the PGOOD

signal.

2

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

The internal 200µA current generator sinks a current from the drain through the external resistor.

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

IP

=

I--O----C----S----E---T-----⋅--R-----O----C----S---E----T-

RDSon

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 10µA.

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

specified thresholds.

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 (cathode 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 nominal supply voltage ranges from 5 to 12V.

DO NOT CONNECT VIN TO A VOLTAGE GREATER THAN VCC.

19

OVP Over voltage protection. If the output voltage reaches the 17% 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:

fS = 200kHz + -4--R-.-9---T-4--(--k-⋅---1Ω---0--)--6-

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

the equation:

fS = 200kHz – 4----.-R3----0T---6(---k--⋅-Ω--1---0)----7-

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

The voltage at this pin is fixed at 1.23V (typ). Forcing a 50µA current into this pin, the built in

oscillator stops to switch.

3/20

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