XC9511A1434 TOREX [Torex Semiconductor], XC9511A1434 Datasheet - Page 12

• Manufacturer Part Number: XC9511A1434
• Description: Synchronous Step-Down DC/DC Converter with built-in LDO Regulator in parallel plus Voltage Detector
• Manufacturer: TOREX [Torex Semiconductor]

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■NOTES ON USE (Continued)
●Application Information (Continued)
XC9511
10. In the integral latch circuit, latch time may become longer and latch operation may not work when V
11. Use of the IC at voltages below the recommended voltage range may lead to instability.
12. This IC and the external components should be used within the stated absolute maximum ratings in order to prevent
13. When using IC with a regulator output at almost no load, a capacitor should be placed as close as possible between
6. When the XC9511D to F series operate in PWM/PFM automatic switching control mode, the reverse current may
7. With the DC/DC converter of the IC, the peak current of the coil is controlled by the current limit circuit. Since the
8. When the peak current, which exceeds limit current flows within the specified time, the built-in driver transistor is
9. When V
become quite high around the load current value when synchronous switches to non-synchronous and vise versa
(also refer to no. 5).
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 P
conditions which cause this operation are as follows.
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:
turned off (the 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 or the Schottky diode.
resistance of the coil.
A
reference. Should it not be possible to place the input capacitor nearby, the regulated output level may increase up
to the V
more.
damage to the device.
PFM Duty < Step down ratio = DC
PFM Duty: 30% (TYP.)
Please use XC9511A to C types (PWM control) in cases where the load current value of the DC/DC converter is
close to synchronous.
●DC/DC Waveform (1.8V, 600kHz) @ VIN=6.0V
Peak current : Ipk = (V
VDD
and A
DD
IN
is low, limit current may not be reached because of voltage falls caused by ON resistance or serial
level while the load of the DC/DC converter increases and the regulator output is at almost no load.
GND
Series
(C
IN
2), connected with low impedance. Please also see the recommended pattern layout for your
IN
Under this condition, switching synchronous rectification and non-synchronous rectification
- D
COUT
< External Components>
L:10μH(CDRH5D28,SUMIDA)
CIN:4.7μF(ceramic)
CL:10μF(ceramic)
Step-down ratio: 1.8V / 6.0V = 30% <PFM Duty 31%>
) x OnDuty / (2 x L x Fosc) + I
OUT
/ V
IN
x 100 (%)
GND
direction through the N-ch driver transistor from the coil. The
DOUT
IN
is 3.0V or