CPC1560

10

PRELIMINARY

R00F

recommended operating conditions given in this

datasheet, are constrained by the 85°C operation of

most industrial applications. For lower operating

temperature ranges, these values can be de-rated

using the information provided in the temperature

graphs in this datasheet.

5.2.1 Effects of Ambient Temperature

One of the most important factors is the temperature

variation of the environment. From the Maximum

(AC and DC) in this datasheet, the user can see how

increases with increasing ambient temperature.

The operating frequency of the device is directly

related to the amount of energy dissipated in it during

rapidly with temperature, as seen in the previously

mentioned graphs. Depending on the operating

temperature range of the application, the user must

derate the maximum allowed energy in the part during

provided) in order to limit the operating switching

frequency.

5.3 Current Limit and Thermal Shutdown

5.3.1 Current Limit

The CPC1560 has a current limit feature in which

current through the output switches is limited to a

value larger than the recommended operating current.

In the AC/DC configuration, the CPC1560 has

bidirectional current limiting, which consists of current

limit circuits in both positive and negative polarities. In

the DC-only configuration, the DC current limit

consists of the parallel of the two AC current limit

circuits in the positive DC polarity.

The current limit function has a negative temperature

coefficient in which increasing temperature lowers the

current limit threshold of the device. Prolonged periods

of current limiting will cause the temperature of the

device to increase, and, if allowed to continue, will

activate the device’s thermal shutdown circuitry,

forcing the output switches to turn off.

5.3.2 Thermal Shutdown

The purpose of the thermal shutdown feature is to

completely shut down the operation of the device

when its junction temperature has gone above 130°C,

whether this is due to high power dissipation in the

device in the form of heat or an increase in the

ambient temperature.

The thermal shutdown feature and the current limit

feature provide great power cross immunity to the

device for improved survivability in harsh

environments.

5.4 dV/dt Fault Tolerance

The CPC1560 device has a finite dV/dt fault tolerance

for both the AC/DC and DC-only configurations, which

must not be exceeded.

The dV/dt tolerance for the device in the AC/DC

configuration is double that of the DC-only

configuration (see “Absolute Maximum Ratings” on

page 3). This is because the dV/dt value of the

CPC1560 is inversely proportional to the size of the

and this capacitance in the DC-only configuration is

double that in the AC/DC configuration.

5.5 Power Derating

Bear in mind the power rating of the CPC1560 when

operating the device at elevated temperatures. The

Absolute Maximum Ratings table shows that the

maximum allowed power dissipation at 25°C is

800mW, which is the maximum power that can be

dissipated before the junction temperature of the

device reaches 125°C.

In order to keep the CPC1560 operating within its

power rating, use the Maximum Allowed Load Current

graphs provided earlier in this document.