ADM2582E/ADM2587E
Rev. C | Page 17 of 20
In the case of unipolar ac or dc voltage, the stress on the insulation
is significantly lower. This allows operation at higher working
voltages while still achieving a 50-year service life. The working
voltages listed in
Table 9 can be applied while maintaining the
50-year minimum lifetime, provided the voltage conforms to either
the unipolar ac or dc voltage cases. Any crossinsulation voltage
be treated as a bipolar ac waveform, and its peak voltage should
be limited to the 50-year lifetime voltage value listed in
Table 9.
0V
RATED PEAK VOLTAGE
08
11
1-
02
1
Figure 36. Bipolar AC Waveform
0V
RATED PEAK VOLTAGE
08
111
-02
3
Figure 37. DC Waveform
0V
RATED PEAK VOLTAGE
NOTES
1. THE VOLTAGE IS SHOWN AS SINUSODIAL FOR ILLUSTRATION
PURPOSES ONLY. IT IS MEANT TO REPRESENT ANY VOLTAGE
WAVEFORM VARYING BETWEEN 0 AND SOME LIMITING VALUE.
THE LIMITING VALUE CAN BE POSITIVE OR NEGATIVE, BUT THE
VOLTAGE CANNOT CROSS 0V.
08
11
1-
0
22
Figure 38. Unipolar AC Waveform
ISOLATED POWER SUPPLY CONSIDERATIONS
The typical output voltage of the integrated isoPower dc-to-dc
isolated supply is 3.3 V. The isolated supply in the ADM2587E
is capable of supplying a current of 55 mA when the junction
temperature of the device is kept below 120°C. It is important
to note that the current available on the VISOOUT pin is the total
current available and includes the current required to supply the
internal RS-485 circuitry.
The ADM2587E can typically supply 15 mA externally on
VISOOUT when the driver is switching at 500 kbps loaded with 54 Ω,
while the junction temperature of the part is less than 120°C.
Table 14. Typical Maximum External Current Available
on VISOOUT
External Load Current (mA)
RT
System Configuration
15
54 Ω
Double terminated
bus with RT = 110 Ω
29
120 Ω
Single terminated bus
46
Unloaded
Unterminated bus
The ADM2582E typically has no current available externally
on VISOOUT.
When external current is drawn from the VISOOUT pin, there is
an increased risk of generating radiated emissions due to the
high frequency switching elements used in the isoPower dc to-
dc converter. Special care must be taken during PCB layout to
meet emissions standards. See Application Note AN-0971,
Control of Radiated Emissions with isoPower Devices, for details
on board layout considerations.
ADM2582E/ADM2587E
TxD
A
B
Y
Z
DE
VCC
RxD
RE
ISOLATION
BARRIER
TRANSCEIVER
GND1
GND2
GND1
RT
ENCODE
DECODE
D
R
DECODE
ENCODE
OSCILLATOR
RECTIFIER
REGULATOR
EXTERNAL
LOAD
VISOOUT
DIGITAL ISOLATION iCoupler
isoPower DC-TO-DC CONVERTER
VISOIN
081
11-
0
38
500kbps
GND
Figure 39. ADM2587E Typical Maximum External Current Measurements