XC9510A1333 TOREX [Torex Semiconductor], XC9510A1333 Datasheet - Page 12

• Manufacturer Part Number: XC9510A1333
• Description: Synchronous Step-Down DC/DC Converter With Built-In LDO Regulator Plus Voltage Detector
• Manufacturer: TOREX [Torex Semiconductor]

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■NOTES ON USE (Continued)
●Application Information (Continued)
XC9510
5. The IC's DC/DC converter operates in synchronous mode when the coil current is in a continuous state and
6. When the XC9510H to L series operates in PWM/PFM automatic switching control mode, the reverse current may
become quite high around the load current value when synchronous switches to non-synchronous and vise versa
(also refer to no. 5 above).
rectification may be repeated because of the reverse current, and the ripple voltage may be increased to 100mV or
more. The reverse current is the current that flows in the PGND direction through the N-ch driver transistor from the
coil. The conditions which cause this operation are as follows.
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.
●DC/DC Waveform (1.8V, 600kHz) @ VIN=6.0V
Ics =
PFM Duty < Step down ratio = DC
Please switch to PWM control via the MODE function in cases where the load current value of the DC/DC converter
is close to synchronous
PFM Duty: 30% (TYP.)
(the sum of the DC/DC's and the regulator's load if the regulator has load.)
(V
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
ID
Series
IN
OUT
- DC
: The DC/DC load
OUT
.
) x OnDuty / (L x Fosc)
< External Components>
L:10μH(CDRH5D28C,SUMIDA)
CIN:4.7μF(ceramic)
CL:10μF(ceramic)
Step down ratio : 1.8V / 6.0V = 30%<PFM Duty 31%>
Under this condition, switching synchronous rectification and non-synchronous
OUT
current
/ V
IN
x 100 (%)
.
=.step down ratio : DC
OUT
/ V
IN
)