[AP1152]

014011330-E-02

- 21 -

2017/03

11.5 On/Off Control

It is recommended to turn the regulator off when the circuit following the regulator is non-operating. A

design with little electric power loss can be implemented. We recommend the use of the on/off control of

the regulator without using a high side switch to provide an output from the regulator. A highly accurate

output voltage with low voltage drop is obtained. Because the control current is small, it is possible to

control it directly by CMOS logic. The pull-

down resister (500kΩ) is built-in.

Table 4. Control terminal voltage and operating state

Status

ON

OFF

The Figure 4 is multiple regulators being controlled by a single On/Off control signal. There is fear of

overheating, because the power loss of the low voltage side IC (AP1152ADU20) is large. The series

resistor (R) is put in the input line of the low output voltage regulator in order to prevent over-dissipation.

The voltage dropped across the resistor reduces the large input-to-output voltage across the regulator,

reducing the power dissipation in the device. When the thermal sensor works, a decrease of the output

voltage, oscillation, etc.

may be observed.

R

On/Off cont.

AP1152ADU50

5.0V

AP1152ADU33

3.3V

AP1152ADU20

2.0V

Figure 4. Parallel-Connected On/Off Control

11.6 Noise Pass Terminal

The noise and the ripple rejection characteristics depend on the capacitance on the Np terminal. The

ripple rejection characteristic of the low frequency region improves by increasing the capacitance of

=0.1μF. Increase CNP in a design with important output noise and ripple

rejection requirements. The IC will not be damaged if the capacitor value is increased. The On/Off

switching speed changes depending on the NP terminal capacitance. The switching speed slows when

the capacitance is large.

11.7 Notes on output terminal (VOUT) to GND short-circuit evaluation

The resonance phenomenon due to stick to the output terminal CL (C component) and the short-circuit

line (L component), the output terminal will become a negative potential. Output terminal parasitic

transistor operates in the IC enters the minus side, leads to the worst case burning for packages that

latch-up phenomenon occurs in the IC (white smoke) or damage.

The resonance phenomenon appears remarkably In the ESR value is small ceramic capacitors and the

like of the capacitor. As a measure of this phenomenon, we can to reduce the resonance phenomenon to

be short-circuited by connecting the short-circuit line and

the series in more than 2Ω resistance. This

allows you to prevent latch-up phenomenon in the IC.

In large tantalum and electrolytic capacitor of ESR, it generally influence of there resonance

phenomenon ESR value is greater than or equal to 2Ω is reduced. Also, if a constraint or the like on your

set can not be performed the measures as described above, please insert a schottky diode between