ISO5452 datasheet(27/37 Pages) TI

27 / 37 page

DESAT

GND2

VCC2

15V

DDST

VEE2

220

CLAMP

1, 8

15V

RGL

OUTH

OUTL

ISO5452

VFW

VFW-Inst

RGH

ISO5452

www.ti.com

SLLSEQ4A – AUGUST 2015 – REVISED SEPTEMBER 2015

Figure 54. DESAT Pin Protection with Series Resistor and Schottky Diode

10.2.2.8 DESAT Diode and DESAT Threshold

The DESAT diode’s function is to conduct forward current, allowing sensing of the IGBT’s saturated collector-to-

emitter voltage, V(DESAT), (when the IGBT is "on") and to block high voltages (when the IGBT is "off"). During the

short transition time when the IGBT is switching, there is commonly a high dVCE/dt voltage ramp rate across the

IGBT. This results in a charging current ICHARGE = C(D-DESAT) x dVCE/dt, charging the blanking capacitor. C(D-DESAT)

is the diode capacitance at DESAT.

To minimize this current and avoid false DESAT triggering, fast switching diodes with low capacitance are

recommended. As the diode capacitance builds a voltage divider with the blanking capacitor, large collector

voltage transients appear at DESAT attenuated by the ratio of 1+ C(BLANK) / C(D-DESAT).

Because the sum of the DESAT diode forward-voltage and the IGBT collector-emitter voltage make up the

voltage at the DESAT-pin, VF + VCE = V(DESAT), the VCE level, which triggers a fault condition, can be modified by

adding multiple DESAT diodes in series: VCE-FAULT(TH) = 9 V – n x VF (where n is the number of DESAT diodes).

When using two diodes instead of one, diodes with half the required maximum reverse-voltage rating may be

chosen.

10.2.2.9 Determining the Maximum Available, Dynamic Output Power, POD-max

The ISO5452 maximum allowed total power consumption of PD = 251 mW consists of the total input power, PID,

the total output power, POD, and the output power under load, POL:

PD = PID + POD + POL

(1)

With:

PID = VCC1-max × ICC1-max = 5.5 V × 4.5 mA = 24.75 mW

(2)

and:

POD = (VCC2 – VEE2) x ICC2-max = (15V – ( –8V)) × 6 mA = 138 mW

(3)

then:

POL = PD – PID – POD = 251 mW – 24.75 mW – 138 mW = 88.25 mW

(4)

Submit Documentation Feedback

Product Folder Links: ISO5452

ISO5452 Datasheet(PDF) 27 Page - Texas Instruments

ISO5452 Datasheet(HTML) 27 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

Datasheet Download

Link URL