IR2114SS datasheet(16/21 Pages) IRF

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IR2114/IR21141/IR2214/IR22141

it and the outputs go back to follow the

inputs.

D. The DSH goes high but this is not read

because HO is off.

E. The LO signal is on and the low side

IGBT desaturates, the low side behaviour

is the same as described in point B.

F. The DSL goes high but this is not read

because LO is off.

G. As point A (anti-shoot through).

Referred to timing diagram figure 18:

A. The device is in hold state, regardless of

input variations. Hold state is forced by

SY_FLT forced low externally

B. The device outputs goes off by hard

shutdown,

externally

commanded.

through B is the same sequence adopted

by another IR2x14x device in SSD

procedure.

C. Externally

driven

low

FAULT/SD

(shutdown state) cannot be disabled by

forcing

FLT_CLR

(see

FAULT/SD

section).

D. The FAULT/SD is released and the

outputs go back to follow the inputs.

E. Externally driven low FAULT/SD: outputs

go off by hard shutdown (like point B).

F. As point A and B but for the low side

output.

Sizing tips

Bootstrap supply

The VBS voltage provides the supply to the high

side driver circuitry of the gate driver. This supply

sits on top of the VS voltage and so it must be

floating.

The bootstrap method to generate VBS supply can

be used with any of the IR2114,

IR21141,

IR2214, IR22141. The bootstrap supply is formed

by a diode and a capacitor connected as in figure

19.

bootstrap

diode

bootstrap

capacitor

VCC

HOP

HON

SSDH

DC+

bootstrap

resistor

COM

VCC

VBS

VGE

VCEon

VFP

ILOAD

motor

Rboot

Figure 19: bootstrap supply schematic

This method has the advantage of being simple

and low cost but may force some limitations on

duty-cycle and on-time since they are limited by

the requirement to refresh the charge in the

bootstrap capacitor.

Proper capacitor choice can reduce drastically

these limitations.

Bootstrap capacitor sizing

To size the bootstrap capacitor, the first step is to

establish the minimum voltage drop (∆VBS) that

we have to guarantee when the high side IGBT is

on.

If VGEmin is the minimum gate emitter voltage we

want to maintain, the voltage drop must be:

CEon

−

≤

∆

min

under the condition:

−

BSUV

min

where VCC is the IC voltage supply, VF is bootstrap

diode forward voltage, VCEon is emitter-collector

voltage of low side IGBT and VBSUV- is the high-

side

supply

undervoltage

negative

going

threshold.

Now we must consider the influencing factors

contributing VBS to decrease:

− IGBT turn on required Gate charge (QG);

− IGBT gate-source leakage current (ILK_GE);

− Floating section quiescent current (IQBS);

− Floating section leakage current (ILK)

− Bootstrap diode leakage current (ILK_DIODE);

− Desat diode bias when on (IDS- )

− Charge required by the internal level shifters

(QLS); typical 20nC

− Bootstrap

capacitor

leakage

current

(ILK_CAP);

− High side on time (THON).

ILK_CAP is only relevant when using an electrolytic

capacitor and can be ignored if other types of

capacitors are used. It is strongly recommend

using at least one low ESR ceramic capacitor

(paralleling electrolytic and low ESR ceramic may

result in an efficient solution).

Then we have:

QBS

TOT

(

HON

CAP

DIODE

⋅

− )

The minimum size of bootstrap capacitor is:

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