LNBH24L

Introduction

Doc ID 16857 Rev 2

7/25

failure detected), set to LOW. The diagnostic bits are dedicated to the over-temperature and

over-load protections status (OTF and OLF).

2.9

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 by the PCL

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

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

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.

2.10

Thermal protection and diagnostic

The LNBH24L 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.)

2.11

Output current limit selection

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

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

Equation 1

k

Ω. The above equation defines the typical threshold value for each output. However, it is

suggestible to not exceed for a long period a total amount of current of 1 A from both

Note:

External components are needed to comply to bidirectional DiSEqC™ bus hardware

requirements. Full compliance of the whole application with DiSEqC™ specifications is not

implied by the bare use of this IC. NOTICE: DiSEqC™ is a trademark of EUTELSAT.

R

SEL

[A]

I

MAX

10000

=

R

SEL

[A]

I

MAX

10000

=