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■NOTE ON USE (Continued)

5.

When the input-output voltage differential is small in the DC/DC converter and heavy load condition, a duty cycle is getting

large and keeps the 100% duty cycle in a several period cycles. At the time of duty cycle transition to 100% or from 100%,

noise may appear on the voltage regulator output. Please evaluate this on the actual design board when the condition is

in small input-output voltage differential and heavy load.

6.

When the load is changed at the DC/DC converter, ringing may happen in some load conditions of DC/DC and VR at the

7.

In order to turn off the input voltage, the EN2 pin should be turned off first. If the input voltage is turned off with keeping VR

operation, the VROUT voltage goes up instantaneously as a result of the VR bias voltage transient.

8.

happen which result in starting the DC/DC short-circuit protection.

9.

It is recommended to test this in the actual product design board.

<DC/DC BLOCK>

1. The XCM519 series is designed for use with ceramic output capacitors. If, however, the potential difference is too large

between the input voltage and the output voltage, a ceramic capacitor may fail to absorb the resulting high switching

energy and oscillation could occur on the output. If the input-output potential difference is large, connect an electrolytic

capacitor in parallel 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.

As a result of input-output voltage and load conditions, oscillation frequency goes to 1/2, 1/3, and continues, then a ripple

may increase.

4.

When input-output voltage differential is large and light load conditions, a small duty cycle comes out. After that, 0%duty

cycle may continue in several periods.

5.

When input-output voltage differential is small and heavy load conditions, a large duty cycle comes out and may

continues100% duty cycle in several periods.

6. 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 operation, 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

200us/div

VIN(5V/div)

DCOUT(500mV/div)

VROUT(500mV/div)