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ADM2582E/ADM2587E

Rev. 0 | 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

waveform that does not conform to Figure 37 or Figure 38 should

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.

RATED PEAK VOLTAGE

Figure 36. Bipolar AC Waveform

RATED PEAK VOLTAGE

Figure 37. DC Waveform

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.

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)

System Configuration

54 Ω

Double terminated bus with

RT = 110 Ω

120 Ω

Single terminated bus

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

VCC

RxD

ISOLATION

BARRIER

TRANSCEIVER

GND1

GND2

GND1

ENCODE

DECODE

ENCODE

OSCILLATOR

RECTIFIER

REGULATOR

EXTERNAL

LOAD

VISOOUT

DIGITAL ISOLATION iCoupler

isoPower DC-TO-DC CONVERTER

VISOIN

500kbps

GND

Figure 39. ADM2587E Typical Maximum External Current Measurements

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