Data Sheet

ADP198

Rev. D | Page 15 of 16

DIODE OR’ing APPLICATIONS

+

LOAD

6V

AC

V2

VOUT

VIN

EN

ADP198

Figure 31. ADP198 in a Typical Diode OR’ing Application

Figure 31 shows an application wherein an ac power supply and

battery are OR’ed together to provide a seamless transition from

the primary (ac) supply to the secondary (V2) supply when the

primary supply is disconnected. By connecting the enable input

of the ADP198 to V2, the transition from ac power to battery

power is automatic.

Figure 32 shows the forward voltage vs. the forward current

characteristics of a Schottky diode and the ADP198. The low on

resistance of the ADP198 makes it far superior to a Schottky

diode in diode OR’ing applications.

In addition to low on resistance, the ADP198 reverse leakage

current is much lower than a typical 1 A, 20 V Schottky

rectifier. For example, at 85°C, the reverse current of a Schottky

rectifier can be as high as 30 μA with only 2.5 V of reverse bias.

Figure 32 shows that about 75 mV of hysteresis built into the

circuitry that senses the voltage differential between the input

and output voltage. When the difference between the input

voltage and output voltage exceeds 75 mV, the ADP198 is

switched on.

FORWARD VOLTAGE (V)

SCHOTTKY

FORWARD

VOLTAGE

SLOPE =

1

300mV

1A

Figure 32. Forward Voltage vs. Forward Current of a Schottky

Diode and ADP198