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XC9511

Series

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Application Information

1. The XC9511 series is designed for use with a ceramic output capacitor. If, however, the potential difference

between dropout voltage or output current is too large, 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.

is the possibility that some cycles may be skipped completely.

and there is the possibility that some cycles may be skipped completely: in this case, the Lx pin may not go low at all.

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NOTES ON USE

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DC/DC Waveform (3.3V, 1.2MHz)

5. The IC's DC/DC converter operates in synchronous mode when the coil current is in a continuous state and

non-synchronous mode when the coil current is in a discontinuous state. In order to maintain the load current

value when synchronous switches to non-synchronous and vise versa, a ripple voltage may increase because of

the repetition of switching between synchronous and non-synchronous. When this state continues, the increase

in the ripple voltage stops. To reduce the ripple voltage, please increase the load capacitance value or use a

schottky diode externally. When the current used becomes close to the value of the load current when

synchronous switches to non- synchronous and vise versa, the switching current value can be changed by

changing the coil inductance value.

In case changes to coil inductance are to values other than the

recommended coil inductance values, verification with actual components should be done.

Ics =

Ics: Switching current from synchronous rectification to non-synchronous rectification

OnDuty: OnDuty ratio of P-ch driver transistor (

L: Coil inductance value

Fosc: Oscillation Frequency

current

< External Components>

L:4.7μH(CDRH4D28C,SUMIDA)

CIN:4.7μF(ceramic)

CL:10μF(ceramic)

< External Components>

L:4.7μH(CDRH4D28C,SUMIDA)

CIN:4.7μF(ceramic)

CL:10μF(ceramic)