AN836 APPLICATION NOTE

2/5

Table 1. Main Characteristics of Schottky

Note: 1. Main characteristics of the 25V low VF Schottky

OR-ING SCHOTTKY

To increase system reliability, power supplies are sometimes connected in parallel (Fig.1).

Figure 1. OR-ing Schottky in redundant power supply

The Schottky diodes are connected in series with the output of each power supply. In the steady state a

When a power supply fails, the corresponding ORING diodes ceases to carry current and the system out-

In this application the most critical parameter is the forward voltage drop in order to maintain the best ef-

ficiency of the system. A breakdown voltage of 10V is sufficient for output voltage of 5V and 3.3.V.

The trade-off has been chosen to obtain a low forward voltage. In this application we can accept a high

leakage current because when the diode is blocked the reapplied voltage is low (3.3V or 5V), the junction

temperature is also low because there are only reverse losses. So it’s easy to keep reverse losses under

control.

PART NUMBER

PACKAGE

Io

(Io,125°C)

(125°C, 25V)

typ

Max

Max

AmV

mV

mA

STPS125U

SOD6

1

STPS5L25B

DPAK

5

310

350

175

STPS10L25D

TO220AC

10

300

350

400

STPS15L25D/G

D2PAK/TO220AC

15

300

350

640

STPS20L25CT

TO220AB

2x10

300

350

400

STPS20L25CG

D2PAK

2x10

300

350

400

POWER

SUPPLY

1

POWER

SUPPLY

2

OUT/n

I

OUT/n

I

OUT/n

I

OUT

I

V

OUT

3.3V, 5V or 12V

POWER

SUPPLY

n