XC9302 Torex Semiconductor, XC9302 Datasheet - Page 7

• Manufacturer Part Number: XC9302
• Description: PWM, Pwm/pfm Switching Step-up & Down Dc/dc Converter Controller ICs
• Manufacturer: Torex Semiconductor

GProduct Selection (Notes)
XC9301/02 series is a group of PFM controlled (XC9302 series switches from PWM to PFM control during light loads) step-up and down DC/DC
converters. The series is highly efficient with a wide range of input voltage since its stepping-up and down operation is controlled by PWM
movements. In general, there are several methods available for obtaining a stable output voltage at such times when input voltage is changing
from being higher than the established output voltage to being lower than the established output voltage. Each method has its merits and
demerits but is essential that a method which provides the best results in terms of input & output under actual operating conditions. Below, two
methods are highlighted and their respective performances in terms of efficiency are compared.
This is an efficiency comparison of two ways, step-up DC/DC converter + VR and step-up & down DC/DC converter.
[Step-up DC/DC Converter + VR] (XC6361/62)
N Step-up mode (Input voltage < set output voltage + 0.4V)
N Step-down mode (Input voltage > set output voltage + 0.4V)
[Step-up&down DC/DC Converter] (XC9301/02)
N Set ouput voltage obtained as a result of the automatic switching operations of the IC regardless of the difference between input voltage and
The above graph shows that over a wide input voltage range, the efficiency of the XC9301/02 is more or less constant. On the other hand, the
efficiency of the XC6361/62 is clearly shown to decrease as input voltage increases. In step-down mode in particular, the efficiency of the
XC9301/02 is much better than the XC6361/62. In applications that use either a standard dry 3 cell battery or a 2 cell lithium Ion battery to
obtain an output of 3.3V, for example, the efficiency of the XC9301/02 series is again much better. Because the XC9301/02 series does not
have a series regulator output, we recommend a test with samples for use in applications where ripple voltage is a problem.
GExternal Components Selection (Notes)
After input voltage has been stepped-up to set output voltage + 0.4V by the step-up DC/DC converter, the output voltage will be regulated to
the set value by the VR. (0.4V loss via the VR)
After input voltage has been stepped-up to set output voltage + 0.4V by the step-up DC/DC converter, the output voltage will be regulated to
the set value by the VR. (Input/Output voltage difference loss via the VR)
set output voltage.
GThe performance of the DC/DC converter IC circuit is heavily reliant upon the performance of the surrounding circuitry and components. In
GIt is also recommended that a switching MOSFET with a small ON resistance be used. With the XC9301/02, an ON resistance of 500mΩ or
90
85
80
75
70
65
60
55
50
45
40
particular, since the VF voltage of the Schottky Diode used will have a direct effect upon efficiency, the smaller the diode, the better the
efficiency obtainable. (Refer to the graph below)
less is recommended.
85
80
75
70
65
2
0.2
I
V
XC6361(STEP-UP DCDC+VR)
OUT
OUT
Step-Up Mode
=10mA 100mA 200mA
VF Voltage［V］
=3.3V, I
3
OUT
Input Voltage vs. Efficiency
0.4
Input Voltage ［V］
=100mA
4
Step-Down Mode
Set Output Voltage+0.4V
I
XC9301(STEP-UP/DOWN DCDC
5
OUT
=10mA 100mA 200mA
6
V
V
V
IN
IN
IN
=2.4V
=3.0V
=4.5V
7
8
XC9301/9302
Series
603
6