L6911E Просмотр технического описания (PDF) - STMicroelectronics

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L6911E

5-Bit programmable step down controller with synchronous rectification

STMicroelectronics 

Pin settings

L6911E

Table 2. Pin description (continued)

N°

Name

Description

11

GND

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

ground.

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

12 PGOOD within the above specified threshlds.

If not used may be left floating.

This pin is connected to the source of the upper mosfet and provides the return

13 PHASE 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.

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

15

BOOT 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

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

18

VCC

DO NOT CONNECT VIN to 12V if VCC IS 5V.

Over voltage protection. If the output voltage reach the 15% above the

19

OVP

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.

Oscillator switching frequency pin. Connecting an external resistor from this pin

to GND, the external frequency is increased according to the equation:

fS

=

200kHz + --5-----⋅---1---0----6--

RT(kΩ)

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

20

RT

reduced according to the equation:

fS

=

200kHz – --4-----⋅---1---0----7--

RT(kΩ)

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

The voltage at this pin is fixed at 1.23V. Forcing a 50µA current into this pin, the

built in oscillator stops to switch.

6/34

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