Data Sheet

ADuM6000

Rev. D | Page 13 of 16

the output can turn on, so the peak current is proportional to

the maximum input voltage.

minimum voltage. The current surge is approximately 300 mA

behavior during startup is similar to when the device load is a

short circuit; these values are consistent with the short-circuit

current shown in Figure 7.

The ADuM6000 device may not be able to drive the output to

voltage during startup. As a result, the ADuM6000 device can

draw large amounts of current at low voltage for extended

periods of time.

overshoot during startup. If this overshoot could potentially

such as a Zener diode can be used to clamp the voltage. Typical

behavior is shown in Figure 12 and Figure 13.

EMI CONSIDERATIONS

The dc-to-dc converter section of the ADuM6000 must operate

at 180 MHz to allow efficient power transfer through the small

transformers. This creates high frequency currents that can

propagate in circuit board ground and power planes, causing

edge emissions and dipole radiation between the primary and

secondary ground planes. Grounded enclosures are recommended

for applications that use these devices. If grounded enclosures

are not possible, follow good RF design practices in the layout

of the PCB. See the AN-0971 Application Note for board layout

recommendations.

THERMAL ANALYSIS

The ADuM6000 consists of four internal silicon die attached to

a split lead frame with two die attach paddles. For the purposes of

thermal analysis, it is treated as a thermal unit with the highest

mounted on a JEDEC standard 4-layer board with fine width

traces and still air. Under normal operating conditions, the

ADuM6000 operates at full load across the full temperature

range without derating the output current. However, following

the recommendations in the PCB Layout section decreases the

thermal resistance to the PCB, allowing increased thermal

margin at high ambient temperatures.

CURRENT LIMIT AND THERMAL OVERLOAD

PROTECTION

The ADuM6000 is protected against damage due to excessive

power dissipation by thermal overload protection circuits.

Thermal overload protection limits the junction temperature to

a maximum of 150°C (typical). Under extreme conditions (that

is, high ambient temperature and power dissipation), when the

junction temperature starts to rise above 150°C, the PWM is

turned off, turning off the output current. When the junction

temperature drops below 130°C (typical), the PWM turns on

again, restoring the output current to its nominal value.

At first, the ADuM6000 reaches its maximum current, which is

the primary side of the converter (see Figure 7). If self-heating

of the junction becomes great enough to cause its temperature

to rise above 150°C, thermal shutdown is activated, turning off

the PWM and turning off the output current. As the junction

temperature cools and drops below 130°C, the PWM turns on

and power dissipates again on the primary side of the converter,

causing the junction temperature to rise to 150°C again. This

thermal oscillation between 130°C and 150°C causes the part

to cycle on and off as long as the short remains at the output.

Thermal limit protections are intended to protect the device

against accidental overload conditions. For reliable operation,

externally limit device power dissipation to prevent junction

temperatures from exceeding 130°C.

POWER CONSIDERATIONS

The ADuM6000 converter primary side is protected from pre-

mature operation by undervoltage lockout (UVLO) circuitry.

Below the minimum operating voltage, the power converter

holds its oscillator inactive.

When the primary side oscillator begins to operate, it transfers

starts below its UVLO limit, making it inactive and unable to

generate a regulation control signal. The primary side power

oscillator is allowed to free run under this condition, supplying

the maximum amount of power to the secondary side.

As the secondary side voltage rises to its regulation setpoint, a

tion point is reached, the regulation control circuit produces the

regulation control signal that modulates the oscillator on the

tional to the load current. The inrush current is less than the

short-circuit current shown in Figure 7. The duration of the