R1155x

NO.EA-270-150702

8

THEORY OF OPERATION

Power Activation

When starting up the IC using the input voltages of the VDD and CE pins simultaneously with no load, the both

pin voltages have to be 0.06 V/ ms or faster. When starting up the IC using the both pin voltages at 0.06 V/ ms

or slower with no load, the VDD pin has to be started up before the CE pin.

Thermal Shutdown Circuit

The R1155x contains a thermal shutdown circuit, which stops regulator operation if the junction temperature

of the R1155x becomes higher than 145

°C (Typ.). Additionally, if the junction temperature after the regulator

being stopped decreases to a level below 120

°C (Typ.), it restarts regulator operation. As a result the operation

of the thermal shutdown circuit causes the regulator repeatedly to turn off and on until the causes of

overheating are removed. As a consequence a pulse shaped output voltage occurs.

Reverse Current Protection Circuit

The R1155x includes a reverse current protection circuit, which stops the reverse current flowing from the

Usually, the LDO using Pch output transistor contains a parasitic diode between VDD pin and VOUT pin.

from VOUT pin to VDD pin.

by connecting the parasitic diode of Pch output transistor to the backward direction, and connecting the gate

to VOUT pin. As a result, the Pch output transistor is turned off and the all the current pathways from VOUT

Switching to either the normal mode or to the reverse current protection mode is determined by the magnitude

Figure 7 and Figure 8 show the normal operation mode and reverse current protection mode, respectively.

Figure 9 shows the detection/ release timing of reverse current protection function. When giving the VOUT pin

As a result, the reverse current protection starts to function to stop the load current. By increasing the dropout