AN1280 - APPLICATION NOTE

8/8

Inform ation furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibil ity for the

consequences of use of such inform ation nor for any infring ement of patents or other righ ts of third parties which may result from

its use. No license is granted by implication or oth erwise under any patent or patent rights of STMicroelectronics. Specifications

mentioned in this publica tion are subject to change witho ut notice. This publ ication supersedes and replaces all inform ation

previously supplied. STMicroelectronics products are not authorized for use as critical components in life suppo rt devices or

systems withou t express written approval of STMicroelectronics.

© The ST logo is a registered trademark of STMicroelectronics

© 2000 STMicroelectronics - Printed in Italy - All Rights Reserved

STMicroelectronics GROUP OF COMPANIES

Australia - Brazil - China - Finland - France - Germany - Hong Kong - India - Italy - Japan - Malaysia - Malta - Morocco

Singapore - Spain - Sweden - Switzerland - United Kingdom

© http://www. st.com

Trace A represents the ripple voltage on C

BOOST

(200mV width).

Trace B represents the voltage perturbation due

to the Step-Up converter on the output (source of

the power Mosfet = Board power supply).

Traces 1 and 2 represent the same, but improved

thanks to the Step-Up Noise reduction RC.

5.2. Precision Enhancement

If the system needs accurate current limitation in

an environment subject to very wide temperature

variations, a good way to compensate fluctuations

due to temperature variations is to use a CTN as

described in figure 13.

Figure 13 : Wide Temperature Variations

5.3. Temporisation

In some cases, it can be useful to let short current

peaks pass without reaction of the breaker,

though these are of higher value than the fixed

current limit.

This enables the Electronic Circuit Breaker to be-

have as a thermal disjonctor.

This behaviour can easily be given by adding an

RC constant as shown on figure 14.

Figure 14 : Temporisation

Rs ens e

TD230

CTN

R

R

Rs ens e

TD230

C

R