xc9509c03cdr TOREX SEMICONDUCTOR LTD., xc9509c03cdr Datasheet - Page 8

• Manufacturer Part Number: xc9509c03cdr
• Description: Xc9509 Synchronous Step-down Dc/dc Converter With Built-in Ldo Regulator In Parallel Plus Voltage Detector
• Manufacturer: TOREX SEMICONDUCTOR LTD.

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■TYPICAL APPLICATION CIRCUIT
■OPERATIONAL EXPLANATION
The XC9509 series consists of a synchronous step-down DC/DC converter, a high speed LDO voltage regulator, and a
voltage detector.
●DC/DC Converter
SD *1 : XB0ASB03A1BR (TOREX)
*1 The DC/DC converter of the XC9508 series automatically switches between synchronous / non-synchronous. The Schottky diode is
*2 Please be noted that the recommend value above of the CL2 may be changed depending on the input voltage value and setting voltage
XC9509
(ceramic, TAIYO YUDEN)
not normally needed. However, in cases where high efficiency is required when using the DC/DC converter during in the light load
while in non-synchronous operation, please connect a Schottky diode externally.
value.
The series consists of a reference voltage source, ramp wave circuit, error amplifier, PWM comparator, phase
compensation circuit, output voltage adjustment resistors, driver transistor, synchronous switch, current limiter circuit,
U.V.L.O. circuit and others. The series ICs compare, using the error amplifier, the voltage of the internal voltage
reference source with the feedback voltage from the V
performed on the resulting error amplifier output, to input a signal to the PWM comparator to determine the turn-on time
during PWM operation. The PWM comparator compares, in terms of voltage level, the signal from the error amplifier
with the ramp wave from the ramp wave circuit, and delivers the resulting output to the buffer driver circuit to cause the
Lx pin to output a switching duty cycle. This process is continuously performed to ensure stable output voltage. The
current feedback circuit monitors the P-channel MOS driver transistor current for each switching operation, and
modulates the error amplifier output signal to provide multiple feedback signals. This enables a stable feedback loop
even when a low ESR capacitor, such as a ceramic capacitor, is used, ensuring stable output voltage.
<Reference Voltage Source>
The reference voltage source provides the reference voltage to ensure stable output voltage of the DC/DC converter.
<Ramp Wave Circuit>
The ramp wave circuit determines switching frequency. The frequency is fixed internally and can be selected from
300kHz, 600 kHz and 1.2 MHz. Clock pulses generated in this circuit are used to produce ramp waveforms needed for
PWM operation, and to synchronize all the internal circuits.
<Error Amplifier>
The error amplifier is designed to monitor output voltage. The amplifier compares the reference voltage with the
feedback voltage divided by the internal split resistors. When a voltage lower than the reference voltage is fed back,
the output voltage of the error amplifier increases. The gain and frequency characteristics of the error amplifier output
are fixed internally to deliver an optimized signal to the mixer.
4.7μF
C
IN
Series
MSOP-10 (TOP VIEW)
(ceramic, TAIYO YUDEN)
10μF
C
L1
V
V
ROUT
ROUT
OUT
<2.0V
>2.0V
pin through split resistors.
Vdif>1.0V
Vdif<1.0V
1.2MHz
600kHz
300kHz
FOSC
4.7μF (ceramic, TAIYO YUDEN)
C
L2
1.0μF (ceramic, TAIYO YUDEN)
4.7μF (ceramic, TAIYO YUDEN)
(*2)
(CDRH4D28C, SUMIDA)
(CDRH6D28, SUMIDA)
(CDRH5D28, SUMIDA)
Phase compensation is
4.7μH
10μH
22μH
L