6

Application information

6.1

The bias input is the supply of the internal driving and control circuitry. In order to assure a proper biasing of the

N-channel power element, the bias pin must have a minimum voltage of 3.0 V and be 1.6 V (typically) higher than

6.2

Output discharge function

EN pin goes to low logic level and has the function to quickly discharge the output capacitor when the device is

disabled by the user.

6.3

Short-circuit and current limitation

The LD57100 is protected against short-circuit on the output. The load current is limited to the maximum value of

6.4

In the LD57100 adjustable version, the desired output voltage is set according to the formula below:

VOUT=VREF× 1+R1R2

(1)

6.5

Thermal protection

Thermal protection works when the junction temperature reaches 160 °C typical. At this point, the output of the

IC shuts down. As soon as the junction temperature falls below the thermal hysteresis value, the device starts

working again.

In order to calculate the maximum power that the device can dissipate, keeping the junction temperature below

the maximum operating value, the following formula is used:

PDMAX= 85−TAMB/RtℎJA

(2)

6.6

Input and output capacitors

The LD57100 requires external capacitors to assure the regulator control loop stability.

Any good quality ceramic capacitor can be used, however the X5R and the X7R are suggested since they

guarantee a very stable combination of capacitance and ESR all over the temperature range.

It is recommended to place the input/output capacitors as close as possible to the relative pins. The LD57100

capacitors must be placed as close as possible to the input pins of the device and returned to a clean analog

ground.

The control loop is designed to be stable with any good quality output ceramic capacitor (such as: X5R/X7R

types) with a minimum value of 1.0 μF and equivalent series resistance in the [3 – 300 mΩ] range. It is important

to highlight that the output capacitor must maintain its capacitance and ESR in the stable region over the

full operating temperature, load and input voltage ranges, to assure stability. Therefore, capacitance and ESR

variations must be taken into account in the design phase to be sure that the device works in the expected

stability region.

LD57100

Application information

DS13123 - Rev 5

page 8/21