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1.

The XC9223/XC9224 series is designed for use with ceramic output capacitors. If, however, the potential difference

between dropout voltage, a ceramic capacitor may fail to absorb the resulting high switching energy and oscillation could

occur on the output. In this case, use a larger capacitor etc. to compensate for insufficient capacitance.

2.

Spike noise and ripple voltage arise in a switching regulator as with a DC/DC converter.

These are greatly influenced by

external component selection, such as the coil inductance, capacitance values, and board layout of external components.

Once the design has been completed, verification with actual components should be done.

3.

In PWM control, very narrow pulses will be outputted, and there is the possibility that some cycles may be skipped

completely.

This may happens while synchronizing with an external clock.

4.

there is the possibility that some cycles may be skipped completely.

5.

With the IC, the peak current of the coil is controlled by the current limit circuit.

Since the peak current increases when

dropout voltage or load current is high, current limit starts operating, and this can lead to instability. When peak current

becomes high, please adjust the coil inductance value and fully check the circuit operation. In addition, please calculate

the peak current according to the following formula:

L: Coil Inductance Value

FOSC: Oscillation Frequency

6.

When the peak current, which exceeds limit current, flows within the specified time, the built-in P-ch driver transistor is

turned off (an integral latch circuit). During the time until it detects limit current and before the built-in transistor can be

turned off, the current for limit current flows; therefore, care must be taken when selecting the rating for the coil.

7.

The voltage drops because of ON resistance of a driver transistor or in-series resistance of a coil.

For this, the current

limit may not be attained to the limit current value, when input voltage is low.

8.

Malfunction may occur in the U.V.L.O. circuit because of the noise when pulling current at the minimum operation voltage.

9.

This IC and the external components should be used within the stated absolute maximum ratings in order to prevent

damage to the device.

10.

Depending on the state of the PC Board, latch time may become longer and latch operation may not work.

The board

should be laid out so that capacitors are placed as close to the chip as possible.

11.

In heavy load, the noise of DC/DC may influence and the delay time of the voltage detector may be prolonged.

12.

Output voltage may become unstable when synchronizing high internal frequency with the external clock.

In such a case, please use a larger output capacitor etc. to compensate for insufficient capacitance.

13.

When a voltage lower than minimum operating voltage is applied, the output voltage may fall before reaching the over

current limit.

14.

When the IC is used in high temperature, output voltage may increase up to input voltage level at light load (less than 100

μA) because of the leak current of the driver transistor.

15.

The current limit is set to LIM=H: 2000mA (MAX.).

However, the current of 2000mA or more may flow.

In case that the

for input voltage will occur at both ends of a coil.

For this, the time rate of coil current becomes large.

By contrast,

the GND pin.

Consequently, the time rate of coil current becomes quite small.

According to the repetition of this

operation, and the delay time of the circuit, coil current will be converged on a certain current value, exceeding the

amount of current, which is supposed to be limited originally.

The short protection does not operate during the soft-start

time.

The short protection starts to operate and the circuit will be disabled after the soft-start time.

Current larger than

over current limit may flow because of a delay time of the IC when step-down ratio is large.

A coil should be used within

the stated absolute maximum rating in order to prevent damage to the device.

the current limit to OFF of P-ch MOSFET.

③Because of no potential difference at both ends of the coil, the time rate of coil current becomes quite small.

④Lx oscillates very narrow pulses by the current limit for several msec.

⑤The short protection operates, stopping its operation.

VLX

ILX

（Coil Current）

Overcurrent

Limit Value

①

②

③

④ #ms

⑤

Delay

■NOTES ON USE