Introduction

LNBH24

8/30

controlled again as per the VSEL/LLC bits status. In order to avoid false triggering, the

IMON function must be used only with the 22 kHz tone transmission deactivated (TEN=0

and DSQIN=LOW), otherwise the IMON bit could be set to 0 even if the output current is

below the minimum current thresholds (6 mA or 12 mA).

2.12

Output current limit selection

The linear regulator current limit threshold can be set through an external resistor connected

to ISEL pin. The resistor value defines the output current limit by the equation:

threshold value for each output. However, it is suggested not to exceed for an extended

triggering the over-temperature protection.

2.13

Over-current and short-circuit protection and diagnostic

In order to reduce the total power dissipation during an overload or a short-circuit condition,

the device is provided with a dynamic short-circuit protection. It is possible to set the short-

circuit current protection either statically (simple current clamp) or dynamically through the

PCL bit of the I²C SR. When the PCL (pulsed current limiting) bit is set to LOW, the over-

current protection circuit works dynamically: as soon as an overload is detected, the output

the system register is set to "1". After this time has elapsed, the output is resumed for a time

overload is detected, normal operation is resumed and the OLF diagnostic bit is reset to

operation can greatly reduce the power dissipation in short-circuit condition, still ensuring

excellent power-on start-up in most conditions. However, there could be some cases in

which a highly capacitive load on the output may cause a difficult start-up when the dynamic

protection is chosen. This can be solved by initiating any power start-up in static mode

(PCL=1) and then switching to the dynamic mode (PCL=0) after a chosen amount of time

depending on the output capacitance. When in static mode, the diagnostic OLF bit goes to

"1" when the current clamp limit is reached and returns LOW when the overload condition is

cleared.

2.14

Thermal protection and diagnostic

The LNBH24 is also protected against overheating. When the junction temperature exceeds

150 °C (typ.), the step-up converter and the liner regulator are shut off, and the diagnostic

OTF SR bit is set to "1". Normal operation is resumed and the OTF bit is reset to LOW when

the junction is cooled down to 135 °C (typ.).

Note: