Data Sheet ADP198
Rev. G | Page 15 of 16
DIODE OR’ing APPLICATIONS
+
LOAD
6V
AC
V2
V
OUT
=
V2 – (I
LOAD
× R
ON
)
VOUTVIN
EN
ADP198
09484-031
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)
CURRENT (A)
SCHOTTKY
FORWARD
VOLTAGE
SLOPE =
1
R
ON
75mV (V
HYS
)
300mV
1A
09484-032
Figure 32. Forward Voltage vs. Forward Current of a Schottky
Diode and ADP198
