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XC9248B085QR-G

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21
7/21
XC9248
Series
■TYPICAL APPLICATION CIRCUIT
【Typical Examples】
MANUFACTURER PART NUMBER VALUE
TDK CLF10040T100N
10μH
TDK CLF7045T6R8N
6.8μH
TAIYO YUDEN NR6045T4R5M
4.5μH
L
TAIYO YUDEN NR6028T2R2N
2.2μH
C2012X5R1E106K
10μF/25V 2parallel
C
IN
(*1)
TDK
C3216X7R1E106K
10μF/25V 2parallel
C2012X5R1A226M
22μF/10V 2parallel
C3216X5R1E226M
22μF/25V 2parallel
C3225X7R1C226M
22μF/16V 2parallel
C
L
(*1)
TDK
C4532X7R1E226M
22μF/25V 2parallel
C
SS
0.1μF
(*2)
/10V
C
BST
0.1μF/10V
C
VL
0.1μF/10V
(*1)
Select components appropriate to the usage conditions (ambient temperature, input & output voltage).
(*2)
For the coil capacitance value, please refer to P.8 < External soft-start setting >.
<Coil current setting >
For stable operation by current feedback control, the XC9248 series is optimum when the peak-to-peak current (Ipk) in the coil
is set approximately between 0.5A to 1A. The Ipk value can be calculated by using the following equation:
Ipk[A] = (V
IN
−
V
OUT
) × V
OUT
/ V
IN
/ 0.5 / L[
μ
H]
L : Coil Inductance
【Examples】
V
IN
[V] V
OUT
[V]
L[μH]
Ipk[A]
5.0 1.0 2.2 0.73
5.0 2.5 3.3 0.76
12.0 3.3 6.8 0.70
12.0 5.0 6.8 0.86
18.0 5.0 10.0 0.72
18.0 12.0 10.0 0.80
8/21
XC9248 Series
■TYPICAL APPLICATION CIRCUIT (Continued)
<V
OUT
setting>
The output voltage can be set by connecting external dividing resistors. The output voltage is determined by the values of R
FB1
and R
FB2
as given in the equation below. The total of R
FB1
and R
FB2
should be less than 150kΩ. Output voltage range can be
set freely from 1.0V to 12V with a 0.8V reference voltage.
V
OUT
=0.8×(R
FB1
+R
FB2
)/R
FB2
Adjust the value of the phase compensation speed-up capacitor C
FB
so that f
zfp
=1 / (2 ×
π
× C
FB
x R
FB1
) is about 7kHz.
Adjustments are required from 5kHz to 50kHz depending on the application, value of inductance (L), and value of load
capacitance (C
L
).
【Examples】
R
FB1
=47kΩ, R
FB2
=15kΩ, V
OUT
=0.8V×(47kΩ+15kΩ) /15kΩ =3.3V
C
FB
=470pF, fzfb=1/(2×
π
×470pF×47kΩ)=7.2kHz
< Minimum V
OUT
>
The Minimum V
OUT
is set by MINDUTY. The MINDUTY changes by the external inductance(L).
For the L value, please choose the optimal value – see P.7 <Coil current setting>. The Minimum V
OUT
can be calculated by
using the following equation:
V
OUT
= V
IN
× MINDUTY / 100
【L vs. MINDUTY】
L[μH]
MINDUTY[%]
2.2 18
3.3 20
4.7 21
6.8 21
10 22
<External soft-start setting>
A capacitor can be connected to the SS pin to set a time longer than the internal soft-start time voluntarily.
By setting the EN pin to the V
ENH
voltage or higher, a current I
SS
=4μA (TYP.) flows to the SS pin and charges the capacitor.
When the SS pin voltage attains the SS threshold voltage V
SSTH
=1.8V (TYP.), the output voltage reaches about 90% of the set voltage.
External soft-start can be calculated by using the following equation:
External soft-start time=V
SSTH
× C
SS
/ I
SS
【Examples】
C
SS
=0.1
μ
F, External soft-start time=1.8V × 0.1
μ
F / 4
μ
A × 1000=45ms
C
SS
External soft-start time
0.01
μF
0.047
μF
0.1
μF
0.47
μF
1
μF
4.7
μF
4.5ms
20ms
45ms
200ms
450ms
2000ms
9/21
XC9248
Series
■OPERATIONAL EXPLANATION
The XC9248 series consists of a reference voltage source, an internal reference voltage source, ramp wave circuit, error
amplifier, PWM comparator, phase compensation circuit, Nch MOS driver transistor, current limiter circuit, UVLO, short
protection circuit, thermal shutdown circuit, over voltage protection and others. (See the block diagram below.)
By using the error amplifier, the FB pin voltage is compared with the internal reference voltage. The signal is input into the
PWM comparator to determine the on time of switching. The signal from the error amplifier is compared with the ramp wave
from the ramp wave circuit, and the resulting output is delivered to the output buffer circuit to provide on-time of the duty cycle at
the LX pin. This process is continuously performed to ensure stable output voltage.
The current feedback circuit monitors the Nch 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 using a low
ESR capacitor such as ceramic, which results in ensuring stable output voltage.
XC9248 Series
<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 500kHz internally. 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. 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.
The error amplifier output signal optimized in the mixer is modulated with the current feedback signal. This signal is delivered to
the PWM comparator.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21

XC9248B085QR-G

Mfr. #:
Buy XC9248B085QR-G
Manufacturer:
Torex Semiconductor
Description:
Switching Voltage Regulators 2.2A 18V Driver DCDC Converter
Lifecycle:
New from this manufacturer.
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