XC9235/XC9236/XC9237Series
ETR0514-005
600mA Driver Tr. Built-In, Synchronous Step-Down DC/DC Converters
☆GreenOperation Compatible
■GENERAL DESCRIPTION
The XC9235/XC9236/XC9237 series is a group of synchronous-rectification type DC/DC converters with a built-in 0.42Ω
P-channel driver transistor and 0.52ΩN-channel switching transistor, designed to allow the use of ceramic capacitors. The ICs
enable a high efficiency, stable power supply with an output current of 600mA to be configured using only a coil and two
capacitors connected externally. Operating voltage range is from 2.0V to 6.0V. Output voltage is internally set in a range from
0.8V to 4.0V in increments of 50mV (accuracy: ±2.0%). With the built-in oscillator, ether 1.2MHz or 3.0MHz can be selected
for suiting to your particular application. As for operation mode, the XC9235 series is PWM control, the XC9236 series is
automatic PWM/PFM switching control and the XC9237 series can be manually switched between the PWM control mode and
the automatic PWM/PFM switching control mode, allowing fast response, low ripple and high efficiency over the full range of
loads (from light load to heavy load).
The soft start and current control functions are internally optimized. During stand-by, all circuits are shutdown to reduce
current consumption to as low as 1.0μA or less. With the built-in UVLO (Under Voltage Lock Out) function, the internal
P-channel driver transistor is forced OFF when input voltage becomes 1.4V or lower.
The XC9235B/XC9236B/XC9237B series provide short-time turn-on by the soft start function internally set in 0.2 ms (TYP). The
XC9235B(C)/XC9236B(C)/XC9237B(C) integrate CL auto discharge function which enables the electric charge at the output
capacitor CL to be discharged via the internal auto-discharge switch located between the LX and VSS pins. When the devices
enter stand-by mode, output voltage quickly returns to the VSS level as a result of this function.
Two types of package SOT-25 and USP-6C are available.
■FEATURES
■APPLICATIONS
●Mobile phones
●Bluetooth equipment
P-ch Driver Transistor Built-In : ON resistance 0.42Ω
N-ch Driver Transistor Built-In : ON resistance 0.52Ω
Input Voltage
: 2.0V ~ 6.0V
●PDAs, portable communication modem
●Portable games
Output Voltage
: 0.8V ~ 4.0V
High Efficiency
: 92% (TYP.)
●Digital cameras, video cameras
●Cordless phones
Output Current
: 600mA
Oscillation Frequency
Maximum Duty Cycle
Control Methods
: 1.2MHz, 3.0MHz (+15%)
: 100%
●Notebook computers
: PWM (XC9235)
PWM/PFM Auto (XC9236)
PWM/PFM Manual (XC9237)
Soft-Start Circuit Built-In
Current Limiter Circuit Built-In (Constant Current & Latching)
Low ESR Ceramic Capacitor Compatible
Packages
: SOT-25, USP-6C
CL High Speed Discharge
(XC9235B(C)/XC9236B(C)/XC9237B(C) Series)
High Speed Soft Start
(XC9235B/XC9236B/XC9237B Series)
* Performance depends on external components and wiring on the PCB.
■TYPICAL APPLICATION CIRCUIT
■TYPICAL PERFORMANCE
CHARACTERISTICS
●Efficiency vs. Output Current(FOSC=1.2NHz, VOUT=1.8V)
PWM/PFM Automatic Sw itching Control
100
90
80
VIN= 4.2V
70
PWM Control
VIN= 4.2V
3.6V
2.4V
60
50
40
30
20
10
0
3.6V
2.4V
0.1
1
10
100
1000
Output Current:IOUT(mA)
1/29