adm2486 Analog Devices, Inc., adm2486 Datasheet - Page 17

• Manufacturer Part Number: adm2486
• Description: High Speed, Half-duplex Icoupler Isolated Rs-485 Transceiver
• Manufacturer: Analog Devices, Inc.

ISOLATED POWER SUPPLY CIRCUIT
The ADM2486 requires isolated power capable of 5 V at up to
approximately 75 mA (this current is dependant on the data
rate and termination resistors used) to be supplied between the
V
A transformer driver circuit with a center-tapped transformer
and LDO can be used to generate the isolated 5 V supply, as
shown in Figure 32. The center-tapped transformer provides
electrical isolation of the 5 V isolated power supply. The primary
winding of the transformer is excited with a pair of square
waveforms that are 180° out of phase with each other. A pair
of Schottky diodes and a smoothing capacitor are used to create
a rectified signal from the secondary winding. The
linear voltage regulator provides a regulated 5 V power supply
to the ADM2486’s bus-side circuitry (V
DD2
and the GND
2
pins.
TRANSFORMER
DRIVER
V
CC
DD2
).
100nF
ADP667
Figure 32. Isolated Power Supply Circuit
ISOLATION BARRIER
V
GND
V
V
DD1
CC
ADM2486
CC
1
78253
Rev. D | Page 17 of 20
ISO 5V
V
GND
SD103C
SD103C
DD2
2
100nF
22µF
IN
SET
ADP667
GND
SHDN
OUT
5V
10µF
ADM2486