ADM2486 Data Sheet
Rev. E | Page 14 of 20
CIRCUIT DESCRIPTION
ELECTRICAL ISOLATION
In the ADM2486, electrical isolation is implemented on the
logic side of the interface. Therefore, the part has two main
sections: a digital isolation section and a transceiver section
(see Figure 26). Driver input and request-to-send signals,
applied to the TxD and RTS pins, respectively, and referenced to
logic ground (GND
1
), are coupled across an isolation barrier to
appear at the transceiver section referenced to isolated ground
(GND
2
). Similarly, the receiver output, referenced to isolated
ground in the transceiver section, is coupled across the isolation
barrier to appear at the RxD pin referenced to logic ground.
iCoupler Technology
The digital signals are transmitted across the isolation barrier
using iCoupler technology. This technique uses chip-scale
transformer windings to couple the digital signals magnetically
from one side of the barrier to the other. Digital inputs are
encoded into waveforms that are capable of exciting the primary
transformer winding. At the secondary winding, the induced
waveforms are then decoded into the binary value that was
originally transmitted.
04604-022
ISOLATION
BARRIER
V
DD2
V
DD1
A
B
DE
GND
2
GND
1
TxD
RTS
RxD
RE
ENCODE
DECODE
DECODE
DECODE
ENCODE
ENCODE
D
R
TRANSCEIVER
DIGITAL ISOLATION
Figure 26. ADM2486 Digital Isolation and Transceiver Sections
TRUTH TABLES
The truth tables in this section use these abbreviations:
Letter Description
H High level
I Indeterminate
L Low level
X Irrelevant
Z High impedance (off)
Table 9. Transmitting
Supply Status Inputs Outputs
1
V
DD1
V
DD2
RTS TxD A B DE
On On H H H L H
On On H L L H H
On Off X X Z Z L
Off On X X Z Z L
Off Off X X Z Z L
1
The PV pin is tied high.
Table 10. Receiving
Supply Status Inputs Output
1
V
DD1
V
DD2
A − B (V)
RxD
On On >0.2 L or NC H
On On <−0.2 L or NC L
On On −0.2 < A − B < 0.2 L or NC I
On On Inputs open L or NC H
On On X H Z
On Off X L or NC H
Off On X L or NC H
1
The PV pin is tied high.
POWER-UP/POWER-DOWN THRESHOLDS
The power-up/power-down characteristics of the ADM2486 are
in accordance with the supply thresholds shown in Table 11.
Upon power-up, the ADM2486 output signals (A, B, RxD, and
DE) reach their correct state once both supplies have exceeded
their thresholds. Upon power-down, the ADM2486 output
signals retain their correct state until at least one of the supplies
drops below its power-down threshold. When the V
DD1
power-
down threshold is crossed, the ADM2486 output signals reach
their unpowered states within 4 µs.
Table 11. Power-Up/Power-Down Thresholds
Supply Transition Threshold (V)
V
DD1
Power-up 2.0
V
DD1
Power-down 1.0
V
DD2
Power-up 3.3
DD2
