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AN2785: DescriptionL6393 half bridge gate driver; File Size2MB，51 Pages; ManufacturerSTMicroelectronics; Websitehttp://www.st.com/

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AN2785 Overview

L6393 half bridge gate driver

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AN2785

Application note

L6393 half bridge gate driver

Introduction

The L6393 is a versatile high-voltage gate driver IC particularly suited to motor driving

applications. It simplifies the design of control systems for a wide range of motor

applications such as home appliances, industrial drives, DC motors and fans.

Developed using BCD offline technology, the device can operate with voltage rails up to

600 V. The gate driver provides all the functions and current capability necessary for

high-side and low-side power MOS and IGBT driving.

The L639x are high voltage half-bridge gate drivers. These devices can be used in all

applications where high voltage shifted control is necessary. The devices have a driver

current capability best suited for motor driving ratings and they are also equipped with

patented internal circuitry which replaces the external bootstrap diode. This feature is

achieved by means of a high-voltage DMOS synchronously driven with the low-side gate

driver.

The L6393 is an half-bridge driver with several functionalities such as externally adjustable

dead-time, shut-down function and an uncommitted comparator. The outputs can be driven

by a special logic input interface particularly suitable for phase/brake functions. The device

is available in DIP-14 or SO-14 packages.

Figure 1.

DETECTION

from LVG

L6393 application block diagram

BOOTSTRAP DRIVER

FLOATING STRUCTURE

BOOT

DETECTION

HVG

DRIVER

H.V.

HVG

Cboot

PHASE

LEVEL

SHIFTER

LOGIC

SHOOT

THROUGH

PREVENTION

LVG

DRIVER

CPOUT

COMPARATOR

CP-

CP+

BRAKE

OUT

TO LOAD

LVG

DEAD

TIME

GND

December 2009

Doc ID 14785 Rev 1

1/51

www.st.com

Contents

AN2785

Contents

Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Logic inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

UVLO function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Dead time function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Bootstrap driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5.1

CBOOT selection and charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Application examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6.1

Basic topology: single half-bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6.1.1

6.1.2

6.1.3

6.1.4

6.1.5

6.1.6

VCC supply pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

BOOT (floating) supply pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Logic input pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Dead time pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Comparator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Gate driver outputs: gate lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

6.2

Full-bridge topology: single-phase fan motor driver . . . . . . . . . . . . . . . . . 15

6.2.1

6.2.2

6.2.3

Current mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Voltage mode - example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Voltage mode - example 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

6.3

6.4

Full-bridge topology: brush DC motor driver . . . . . . . . . . . . . . . . . . . . . . 21

Gate driving: principle of working with inductive loads . . . . . . . . . . . . . . . 23

Induced turn-on phenomenon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

How to increase the gate driver output current capability . . . . . . . . . 34

Below-ground voltage on the OUT pin . . . . . . . . . . . . . . . . . . . . . . . . . 36

9.1

9.2

9.3

Below-ground voltage phenomenon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

How to reduce the below ground spike voltage . . . . . . . . . . . . . . . . . . . . 38

Issues related to the below-ground voltage phenomenon . . . . . . . . . . . . 41

2/51

Doc ID 14785 Rev 1

List of figures

AN2785

List of figures

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

Figure 10.

Figure 11.

Figure 12.

Figure 13.

Figure 14.

Figure 15.

Figure 16.

Figure 17.

Figure 18.

Figure 19.

Figure 20.

Figure 21.

Figure 22.

Figure 23.

Figure 24.

Figure 25.

Figure 26.

Figure 27.

Figure 28.

Figure 29.

Figure 30.

on OUT pin

Figure 31.

Figure 32.

Figure 33.

Figure 34.

Figure 35.

Figure 36.

Figure 37.

L6393 application block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Input configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

L6393 gate driver outputs in UVLO condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Timing waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Typical dead time vs DT resistor value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Bootstrap driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

External charge pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Typical schematic of power half-bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Layout suggestions for the gate driving circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Application circuit for current mode FAN controller using two L6393 drivers . . . . . . . . . . . 16

Current modulation (flowing in the shunt resistor) changing the Vth signal . . . . . . . . . . . . 17

L6393 application circuit for voltage mode FAN controller (logic output hall sensor) . . . . . 19

L6393 application circuit for voltage mode FAN controller (linear hall sensor) . . . . . . . . . . 20

Waveform related to the VM application circuit with linear hall sensor . . . . . . . . . . . . . . . . 21

L6393 application circuit for brush DC motor controller (current mode) . . . . . . . . . . . . . . . 22

Gate driver output buffers: equivalent circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Hard and soft switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Turn-ON hard switching details with induction load: gate charge and plateau phase . . . . 26

Total equivalent circuit for turn-ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Turn-OFF hard switching details with induction load: gate charge and plateau phase. . . . 28

Total equivalent circuit for turn-OFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Power dissipation during switching (approximation) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Rgate dimensioning criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Induced turn ON phenomenon - circuital description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Block diagram of output current capability enhancement using external current buffers . . 34

Example of a gate driving circuit with current buffers to increase current capability. . . . . . 35

Below-ground voltages in L6393 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Transient peak forward voltage vs. dI

/dt of STTH1L06 diode . . . . . . . . . . . . . . . . . . . . . . 37

Use of OUT resistor to limit the below ground voltage spike on OUT pin. . . . . . . . . . . . . . 39

Use of combination of OUT resistor and OUT diode to limit the below ground voltage spike

Bootstrap overcharging due to below-ground voltage on OUT pin . . . . . . . . . . . . . . . . . . . 42

Different bootstrap network characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

L6393 safe operating range when OUT pin is below ground voltage (in steady state). . . . 44

Driver functionality in below-ground voltage condition on OUT pin . . . . . . . . . . . . . . . . . . 44

OUT below-ground voltage in transient conditions: limited boot overcharging . . . . . . . . . 46

Example of below-ground voltage spike . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Layout suggestion for a H-bridge power system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4/51

Doc ID 14785 Rev 1

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