XC9116
Series
■TYPICAL
APPLICATION CIRCUITS
●XC9116B02A
●XC9116D02A
■EXTERNAL
COMPONENTS
SYMBOL
L
SBD (*1)
C
IN
CL (*3)
ZD (*4)
R1
NOTE :
VALUE
22µH
-
4.7µF
0.22µF
18V
100
Ω
PART NUMBER
VLF3010A-220MR
XB0ASB03A1BR (*2)
MA2Z720
JMK107BJ475MA-B
TMK107BJ224KA-B
MAZ8180
-
MANUFACTURER
TDK
TOREX
PANASONIC
TAIYO YUDEN
TAIYO YUDEN
PANASONIC
-
*1: Please use a Schottky
barrier diode (SBD) with a low junction capacitance, Cj.
*2: For using the XB0ASB03A1BR with four white LEDs in series, please be noted with a direct reverse voltage (V
R
=20V) and a
repetitive peak reverse voltage (V
RM
=30V).
*3: Use ceramic capacitors processing a low temperature coefficient.
*4: Please refer to the LED Open-circuit Protection at Application Information for setting the Zener diode.
■OPERATIONAL
EXPLANATION
The series consists of a reference voltage source, ramp wave circuit, error amplifier, PWM comparator, phase
compensation circuit, Lx overvoltage limit circuit, N-channel MOS driver transistor, current limiter 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 FB pin. Phase compensation is performed on the resulting error amplifier output, to input a signal to the
PWM comparator to determine the turn-on time during switching. 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 N-channel MOS driver transistor 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 detects the N-channel MOS driver transistor's
current for each switching operation, and modulates the error amplifier output signal. 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 IC.
<Ramp Wave Circuit>
The ramp wave circuit determines switching frequency. The 1MHz (TYP.) of frequency is fixed internally.
Clock pulses generated in this circuit are used to produce ramp waveforms needed for PWM operation.
<Error Amplifier>
The error amplifier is designed to monitor output voltage. The amplifier compares the reference voltage with the FB pin
voltage. When a voltage lower than the reference voltage is fed back, the output voltage of the error amplifier
increases. Gain and frequency characteristics of the error amplifier output are fixed internally as an optimize signal.
5/22
TOREX [ TOREX SEMICONDUCTOR ]
