XC9206/XC9207/XC9208
Series
■
NOTES ON USE
●
Application Information
1. The XC9206/9207/9208 series are designed for use with an output ceramic capacitor. If, however, the potential
difference between input and output is too large, a ceramic capacitor may fail to absorb the resulting high switching
energy and oscillation could occur on the output. If the input-output potential difference is large, connect an
electrolytic capacitor in parallel to compensate for insufficient capacitance.
2. Spike noise and ripple voltage arise in a switching regulator as with a DC/DC converter. These are greatly influenced
by external component selection, such as the coil inductance, capacitance values, and board layout of external
components. Once the design has been completed, verification with actual components should be done.
3. When the difference between V
IN
and V
OUT
is large and the load current is light, very narrow pulses will be outputted,
and there is the possibility that some cycles may be skipped completely.
●Oscillation
Wave Form (FOSC=1.2MHz)
①
V
IN
= 5.5V, V
OUT
=1.8V, I
OUT
=10mA
CH1 : Lx
L
SD
C
IN
C
L
: 4.7μH
: CRS02
: 4.7μF
: 10μF
CH2 : V
OUT
AC-COUPLED
(CDRH3D16,
SUMIDA)
(TOSHIBA)
(Ceramic)
(Ceramic)
4.
When the difference between V
IN
and V
OUT
is small, and the load current is heavy, very wide pulses will be outputted
and there is the possibility that some cycles may be skipped completely: in this case, the Lx pin may not go low at all.
●Oscillation
Wave Form (FOSC=1.2MHz)
②
V
IN
= 2.0V, V
OUT
=1.8V, I
OUT
=60mA
CH1 : Lx
L
SD
C
IN
C
L
: 4.7μH
: CRS02
: 4.7μF
: 10μF
CH2 : V
OUT
AC-COUPLED
(CDRH3D16,
SUMIDA)
(TOSHIBA)
(Ceramic)
(Ceramic)
5. With the IC, the peak current of the coil is controlled by the current limit circuit. Since the 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:
Ipk = (V
IN
- V
OUT
) x On Duty / (2 x L x FOSC) + I
OUT
OnDuty: OnDuty ratio of Pch Driver Transistor
L
: Coil Inductance Value
FOSC : Oscillation Frequency
6. When the peak current which exceeds limit current flows within the specified time, the built-in P-ch driver transistor is
turned off. 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.
7. When V
IN
is less than 2.4V, limit current may not be reached because voltage falls caused by ON resistance.
9/16
TOREX [ TOREX SEMICONDUCTOR ]
