MBR1035 MBR1045

4

Rectifier Device Data

HIGH FREQUENCY OPERATION

Since current flow in a Schottky rectifier is the result of majority

carrier conduction, it is not subject to junction diode forward and

reverse recovery transients due to minority carrier injection and

stored charge. Satisfactory circuit analysis work may be performed

by using a model consisting of an ideal diode in parallel with a

variable capacitance. (See Figure 10.)

Rectification efficiency measurements show that operation will

be satisfactory up to several megahertz. For example, relative

waveform rectification efficiency is approximately 70 percent at

2.0 MHz, e.g., the ratio of dc power to RMS power in the load is

0.28 at this frequency, whereas perfect rectification would yield

0.406 for sine wave inputs. However, in contrast to ordinary

junction diodes, the loss in waveform efficiency is not indicative of

power loss; it is simply a result of reverse current flow through the

diode capacitance, which lowers the dc output voltage.

2.0

µs

1.0 kHz

12 V

100

VCC

12 Vdc

2N2222

CURRENT

AMPLITUDE

ADJUST

0–10 AMPS

100

CARBON

2N6277

1.0 CARBON

1N5817

D.U.T.

2.0 k

Ω

+150 V, 10 mAdc

4.0

µF

+

VR, REVERSE VOLTAGE (VOLTS)

0.5

1500

1000

500

300

150

0.1

0.05

50

700

Figure 10. Capacitance

0.2

2.0

1.0

5.0

200

MAXIMUM

TYPICAL

10

20

UL RATED EPOXY

COPPER

ALUMINUM WIRE

ANODE

SCHOTTKY CHIP (See View A–A)

CATHODE

SOLDER DIPPED

COPPER LEADS

3

1

4

Motorola builds quality and reliability into its Schottky Rectifiers.

First is the chip, which has an interface metal between the

barrier metal and aluminum–contact metal to eliminate any

possible interaction between the two. The indicated guardring

prevents dv/dt problems, so snubbers are not mandatory. The

guardring also operates like a zener to absorb over–voltage

transients.

Second is the package. The Schottky chip is bonded to the

copper heat sink using a specially formulated solder. This gives the

unit the capability of passing 10,000 operating thermal–fatigue

cycles having a

DTJ of 100°C. The epoxy molding compound is

rated per UL 94, V0 @ 1/8

″. Wire bonds are 100% tested in

assembly as they are made.

Third is the electrical testing, which includes 100% dv/dt at 1600

V/

ms and reverse avalanche as part of device characterization.

GUARDRING

PLATINUM BARRIER METAL

OXIDE

PASSIVATION

ALUMINUM CONTACT METAL

SCHOTTKY CHIP — View A–A

Figure 11. Schottky Rectifier

Figure 12. Test Circuit for dv/dt and

Reverse Surge Current