Preliminary Technical Data

ADuM5240/ADuM5241/ADuM5242

Rev. PrN | Page 9 of 10

APPLICATION INFORMATION

DC/DC CONVERTER

The ADuM524x can be operated with the internal DC/DC

enabled or disabled. With the internal DC/DC converter

enabled, the Pin 8 isolated supply provides output power as well

as power to the part’s isolated-side circuitry. Since the power

consumed by the ADuM524x is a function of the input signals’

data rate, the available isolated output power is determined by

the data rate at which the part’s data channels are operating.

The ADuM524x’s internal DC/DC converter state is controlled

internal DC/DC converter is enabled. When/if it is desired to

user and the ADuM524x’s signal channels continue to operate

normally.

GUIDELINES FOR PRE-PRODUCTION SAMPLES

Pre production samples meet all data sheet specifications;

however, a limitation in the internal circuitry of the ADuM524x

prevents proper start-up under all load conditions. This

limitation will be corrected in the final product.

At certain temperature and load conditions the ADuM524x will

converter start-up. The output stabilizes at just under 4V with

no external load or as low as 3V with an external load. If the

converter starts successfully, the output voltage will continue to

regulate properly even as temperature and load conditions

change.

The start-up issue is affected by several circuit and

dependence in most cases. Good results have been obtained

when the system power supply slews at ~0.5V/μS. Faster slew

rates can be tolerated but should be verified over temperature.

Table 14 contains guidelines for the maximum reliable start-up

temperature for two common values of load capacitance.

ADuM542x dissipates between 40 and 63mW under normal

operation, causing the internal temperature of the device to be

higher than ambient during normal operation. A “warm start”

after the device has reached its equilibrium temperature is the

worst case condition and will give the highest probability of

incorrect regulation of output voltage. The guidelines in Table

14 are based on “warm start” at full load. Cold start will be

successful at higher ambient temperatures.

When these guidelines are followed, pre-production samples

may be used for prototype and evaluation. As mentioned above

this issue will be corrected in final silicon and the ADuM524x

will operate at specified load and temperature conditions.

Table 14. Special Usage Conditions for Pre-production

Devices

Max Temperature by Load Capacitance

1

10nF

100nF

ADuM5240

105

Not Recommended

ADuM5241

105

65

ADuM5242

80

80

PC BOARD LAYOUT

The ADuM524x digital isolators require no external interface

circuitry for the logic interfaces. Power supply bypassing is

strongly recommended at the input and output supply pins as

shown in Figure 8. For the ADuM5240 and ADuM5241, a

ensure proper power-up. For all models bypass capacitance is

ADuM5241. The bypass capacitors should be placed as close as

possible to the ADuM524x device.

In cases where EMI is a concern, inductance should be added

between the system supply and ground and the ADuM524x

supply and ground as shown in Figure 8. Inductance can be

added in the form of discrete inductors or ferrite beads, and it’s

recommended the value correspond to an impedance between

50Ω and 100Ω at approximately 300MHz.

where EMI is a concern.