LP1111-00

Nov.-2017

Email: marketing@lowpowersemi.com

www.lowpowersemi.com

Page 7 of 8

Preliminary Datasheet

LP1111

Power Supply Decoupling

The LP1111 can source and sink relatively large

currents to the gate pins of the external MOSFETs.

In order to maintain a constant and stable supply

voltage (VCC) a low ESR capacitor should be placed

near the power and ground pins. A 1 μ F to 4.7 μ F

multilayer ceramic capacitor (MLCC) is usually

sufficient.

Input Pins

The PWM and the EN pins of the LP1111 have

internal protection for Electro Static Discharge (ESD),

but in normal operation they present relatively high

input impedance. If the PWM controller does not

have internal pull-down resistors, they should be

added externally to ensure that the driver outputs do

not go high before the controller has reached its

under voltage lockout threshold.

Bootstrap Circuit

The bootstrap circuit uses a charge storage capacitor

components can be done after the high-side

MOSFET has been chosen. The bootstrap capacitor

must have a voltage rating that is able to withstand

twice the maximum supply voltage. A minimum 50V

rating is recommended. The capacitance is

determined using the following equation:

the high-side MOSFET drive.

For example, an external MOSFET has a total gate

charge of about 30nC. For an allowed droop of

300mV, the required bootstrap capacitance is 100nF.

A good quality ceramic capacitor should be used.

The bootstrap diode must be rated to withstand the

maximum supply voltage plus any peak ringing

voltages that may be present on SWN. The average

forward current can be estimated by:

the controller. The peak surge current rating should

be checked in-circuit, since this is dependent on the

source impedance of the 12V supply and the ESR of