HCPL316J datasheet(29/33 Pages) HP

29 / 33 page

Figure 75. Current Buffer for Increased Drive Current.

Power/Layout

Considerations

Operating Within the

Maximum Allowable Power

Ratings (Adjusting Value of

RG):

When choosing the value of RG,

it is important to confirm that the

power dissipation of the

HCPL-316J is within the

maximum allowable power

rating.

The steps for doing this are:

1. Calculate the minimum desired

RG;

2. Calculate total power

dissipation in the part

referring to Figure 77.

Figure 74. Use of RC to Further Limit

ION,PEAK.

Higher Output Current Using

an External Current Buffer:

To increase the IGBT gate drive

current, a non-inverting current

buffer (such as the npn/pnp

buffer shown in Figure 75) may

be used. Inverting types are not

compatible with the desaturation

fault protection circuitry and

should be avoided. To preserve

the slow IGBT turn-off feature

during a fault condition, a 10 nF

capacitor should be connected

from the buffer input to VEE and

a 10

Ω resistor inserted between

the output and the common npn/

pnp base. The MJD44H11 /

MJD45H11 pair is appropriate

for currents up to 8A maximum.

The D44VH10 / D45VH10 pair is

appropriate for currents up to 15

A maximum.

DESAT Diode and DESAT

Threshold

The DESAT diode’s function is to

conduct forward current,

VLED2+

DESAT

VCC2

VOUT

VEE

Ω

HCPL-316J

100 pF

RC 8 Ω

10 nF

-5 V

15 V

allowing sensing of the IGBT’s

saturated collector-to-emitter

voltage, VCESAT, (when the IGBT

is “on”) and to block high

voltages (when the IGBT is “off”).

During the short period of time

when the IGBT is switching, there

is commonly a very high dVCE/dt

voltage ramp rate across the

IGBT’s collector-to-emitter. This

results in ICHARGE (= CD-DESAT x

dVCE/dt) charging current which

will charge the blanking

capacitor, CBLANK. In order to

minimize this charging current

and avoid false DESAT triggering,

it is best to use fast response

diodes. Listed in the below table

are fast-recovery diodes that are

suitable for use as a DESAT diode

(DDESAT). In the recommended

application circuit shown in

Figure 62, the voltage on pin 14

(DESAT) is VDESAT = VF + VCE,

(where VF is the forward ON

voltage of DDESAT and VCE is the

IGBT collector-to-emitter

voltage). The value of VCE which

triggers DESAT to signal a

FAULT condition, is nominally 7V

– VF. If desired, this DESAT

threshold voltage can be

decreased by using multiple

DESAT diodes in series. If n is

the number of DESAT diodes

then the nominal threshold value

becomes VCE,FAULT(TH) = 7 V – n

x VF. In the case of using two

diodes instead of one, diodes with

half of the total required

maximum reverse-voltage rating

may be chosen.

Max. Reverse Voltage

Part Number

Manufacturer

trr (ns)

Rating, VRRM (Volts)

Package Type

MUR1100E

Motorola

1000

59-04 (axial leaded)

MURS160T3

Motorola

600

Case 403A (surface mount)

UF4007

General Semi.

1000

DO-204AL (axial leaded)

BYM26E

Philips

1000

SOD64 (axial leaded)

BYV26E

Philips

1000

SOD57 (axial leaded)

BYV99

Philips

600

SOD87 (surface mount)

VLED2+

DESAT

VCC2

VOUT

VEE

Ω

HCPL-316J

100 pF

10 nF

MJD44H11 or

D44VH10

4.5

Ω

2.5

Ω

MJD45H11 or

D45VH10

15 V

-5 V

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