XC9253R Series
ETR0528_002
Synchronous Step-Down DC/DC Converter
■GENERAL DESCRIPTIO N
The XC9253R series is a group of synchronous-rectification type DC/DC converters wit h a built-in 0.6ΩP-channel driver
transistor and 0.7ΩN-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 500mA to be configured using only a coil and two capacitors
connected externally. Minimum operating voltage is 2.0V~6.0V. Output voltage is 3.3V(accuracy: ±2.0%). With the built-in
oscillator, oscillation frequency is set to 600kHz. As for operation mode, the XC9253R series is automatic PWM/PFM
switching control allowing fast response, low ripple and high efficiency over the full range of load (from light load to high
output current conditions).
The soft start and current control functions are internally optimized. During standby, 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. Two types of package, SOT-25 and
USP-6B, are available.
■APPLICATIONS
●Mobile phones
●Bluetooth equipment
●PDAs, Portable communication modem
●Portable games
●Cameras, Digital cameras
●Cordless phones
●Notebook computers
■TYPICAL APPLICATION CIRCUIT
VIN
L
1
VIN
5
Lx
V
500mA
OUT
■FEATURES
P-Ch Driver Tr. Built-In
N-Ch DriverTr. built-in
Input Voltage Range
Output Voltage Range
Low Power Consumption
Control Method
High Efficiency
Output Current
Oscillation Frequency
Low Output Ripple
Maximum Duty Ratio
Operating Ambient Temperature
Packages
Soft-Start Circuit Built-In
Current Limiter Circuit Built-In
Low ESR Ceramic Capacitor Compatible
* Performance depends on external components and wiring on the PCB
☆GreenOperation Compatible
: ON resistance 0.6Ω
: ON resistance 0.7Ω
: 2.0V~6.0V
: 3.3V
: 15μA (TYP.) (VIN=3.6V)
: PWM/PFM Automatic
: 92% (TYP.)
(VIN=4.5V, V
: 500mA
: 600kHz (±15%)
: 10mV
: 100%
: -40℃ ～ +85℃
: SOT-25, USP-6B
(Constant Current & Latching)
OUT
=3.3V, I
OUT
=100mA)
IN
C
(ceramic)
CE
2
VSS
CE
34
VOUT
L
C
(ceramic)
1/13
XC9253R
■PIN CONFIGURATION
■PIN ASSIGNMENT
Lx VOUT
5 4
132
SOT-25
(TOP VIEW)
VSS CEVIN
Series
VIN 6
VSS 5
CE 4
USP-6B
(BOTTOM VIEW)
* Please short the VSS (No. 2 and 5) pin.
* The dissipation pad for the USP-6B package should be
solder-plated in recommended mount pattern and metal
masking so as to enhance mounting strength and heat
release. If the pad needs to be connected to other pins,
it should be connected to the V
1 Lx
2 VSS
3 VOUT
SS (No. 5) pin.
PIN NUMBER
SOT-25 USP-6B
PIN NAME FUNCTION
1 6 VIN Power Input
2 2, 5 VSS Ground
3 4 CE Chip Enable
4 3 VOUT Output Voltage Sense
5 1 Lx Switching Output
■FUNCTIONS
CE OPERATION
VOLTAGE LEVEL
H Level
Synchronous PWM/PFM Automatic
XC9253Ｒ SERIES
Switching Control
L Level Stand-by
■PRODUCT CLASSIFICATION
●Ordering Information
PWM / PFM automatic switching control
PRODUCT NAME PACKAGE (ORDER UNIT)
XC9253R001MR-G
XC9253R001DR-G
(*1)
The “-G” suffix indicates that the products are Halogen and Antimony free as well as being fully RoHS compliant.
(*1)
SOT-25 (3,000/Reel)
(*1)
USP-6B (3,000/Reel)
2/13
■BLOCK DIAGRAM
■ABSOLUTE MAXIMUM RATINGS
VOUT
R2
R1
VIN
VSS
NOTE: The signal from CE Control Logic to PWM/PFM Selector is being fixed to "H" level inside,
R3R4U.V.L.O.
and XC9253R series chooses only PWM/PFM automatic switching control.
Phase
Compensation
Error Amp.
Vref with
Soft Start,
CE
PWM/PFM
Selector
U.V.L.O. Cmp
Current Feedback
Current Limit
PWM
Comparator
Logic
Synch.
Buffer
Drive
Ramp Wave
Generator
OSC
CE
Control Logic
Lx
CE
PARAMETER SYMBOL RATINGS UNITS
VIN Pin Voltage VIN - 0.3 ~ 6.5 V
Lx Pin Voltage VLx - 0.3 ~ VIN + 0.3 V
VOUT Pin Voltage VOUT - 0.3 ~ 6.5 V
CE Pin Voltage VCE - 0.3 ~ VIN + 0.3 V
Lx Pin Current ILx ±1000 mA
Power Dissipation
SOT-25 250
USP-6B
Pd
100
Operating Ambient Temperature Topr - 40 ~ + 85 ℃
Storage Temperature Tstg - 55 ~ +125 ℃
XC9253R
Series
Ta=25℃
mW
3/13
)
XC9253R
■ELECTRICAL CHARACTERISTICS (Continued
XC9253R001xx
Series
V
OUT
=3.3V, f
=600kHz, Ta=25℃
OSC
PARAMETER SYMBOL CONDITIONS MIN. TYP. MAX. UNIT
Output Voltage V
OUT
When connected to external
components, VCE=VIN, I
OUT
=30mA
3.234 3.300 3.366 V ①
Operating Volt age Range VIN 2.0 - 6.0 V ①
Maximum Output Current I
U.V.L.O. Voltage V
OUTMAX
UVLO
VIN=V
external components (A series) (*7)
VCE=VIN, V
voltage holding "L" level (*1), (*9)
Supply Current IDD VIN=VCE=5.0V, V
Stand-by Current I
STB
Oscillation Frequency fosc
PFM Switch Current I
PFM
VIN=5.0V, VCE=0V,
V
OUT
When connected to external
components, I
When connected to external
components, VCE =VIN, I
Maximum IPFM Current MAXIPFM VIN=V
Maximum Duty Ratio MAXDTY VCE=VIN, V
Minimum Duty Ratio MINDTY VCE=V
+1.2V,
OUT
when connected to
=0V, Voltage which Lx pin
OUT
=set voltage×1.1V - 12 30 μA ③
OUT
=set voltage×1.1V
=100mA
OUT
+1.0V, VCE=VIN, I
OUT
=0V 100 - - % ④
OUT
- - 0 % ④
OUT=VIN
500 - - mA ①
1.00 1.40 1.78 V ②
- 0 1.0 μA ③
510 600 690 kHz ①
=1mA
OUT
=0.1mA 35 44 50 % ①
OUT
120 160 200 mA ①
When connected to external
Efficiency (*2) EFFI
Lx SW “H” ON Resistance R
Lx SW “L” ON Resistance R
Lx SW “H” Leak Current I
Lx SW “L” Leak Current I
Current Limit (*8) I
Output Voltage
Temperature Characteristics
V
OUT
CE “H” Voltage V
CE “L” Voltage V
CE “H” Current I
CE “L” Current I
Soft-Start Time tSS
△
LxH
LxL
LeakH
LeakL
LIM
V
・△
CEH
CEL
CEH
CEL
components, VCE=VIN=4.5V,
I
=100mA
OUT
VCE=0.5VIN, V
OUT
=0V, ILx=100mA (*3) - 0.5 1.0 Ω ⑤
- 92 - % ①
VCE=0.5VIN, ILx=100mA (*4) - 0.6 1.2 Ω ⑤
VIN=V
VIN=V
VIN=VCE=5.0V, V
I
OUT
OUT
Topr
-40℃≦Topr≦85℃
V
OUT
Lx determine "H" (*9)
V
OUT
Lx determine "L" (*9)
VIN=VCE=5.5V, V
VIN=5.5V, VCE=0V, V
When connected to external
components, VCE=0V→VIN, I
=5.0V, VCE=0V, Lx=0V (*5) - 0.01 1.0 μA ⑥
OUT
=5.0V, VCE =0V, Lx=5.0V - 0.01 1.0 μA ⑥
OUT
=0V 600 700 mA ⑦
OUT
=30mA
=0V, When CE voltage is applied
=0V, When CE voltage is applied
=0V - 0.1 - 0.1 μA ⑧
OUT
=0V - 0.1 - 0.1 μA ⑧
OUT
=1mA
OUT
- ±100 - ppm/ ℃ ①
0.65 - VIN V ⑧
VSS - 0.25 V ⑧
0.5 1.0 3.0 ms ①
When connected to external
Latch Time tlat
Test conditions: Unless otherwise stated, VIN=5.0V
External components L: 10μH, CIN: 4.7μF (ceramic) CL: 10μF (ceramic)
NOTE:
*1:Including hysteresis operating voltage range.
*2:EFFI = { ( output voltage×output current ) / ( input voltage×input current) }×100
*3:On resistance (Ω)= Lx pin measurement voltage / 100mA
*4:Design value
*5:When temperature is high, a current of approximately 20μA (maximum) may leak.
*6: Time until it short-circuits VOUT with GND through 1Ωof resistance from a state of operation and is set to VOUT=0V from current limit
pulse generating.
*7:When the difference between the input and the output is small, some cycles may be skipped completely before current maximizes.
If current is further pulled from this state, output voltage will decrease because of P-ch driver ON resistance.
*8: Current limit denotes the level of detection at peak of coil current..
*9: “H”=V
1.2V, “L”=+0.1V~-0.1V
IN~VIN-
components, VIN=VCE=5.0V,
Short V
by 1Ω resistance (*6)
OUT
1 - 20 ms ⑨
CIRCUIT
4/13
XC9253R
Series
■TYPICAL APPLICATION CIRCUIT
OUT
VIN
(ceramic)
CE
1
VIN
IN
C
2
VSS
CE
34
VOUT
5
Lx
L
■OPERATIONAL EXPLANATION
The XC9253R series consists of a reference voltage source, ramp wave circuit, error amplifier, PWM comparator, phase
compensation circuit, output voltage adjustment resistors, P-channel MOSFET driver transistor, N-chann el MOSFET switching
transistor for the synchronous switch, current limiter circuit, U.V.L.O. circuit and others. (See the block diagram above.) The
series ICs compare, using the error amplifier, the voltage of the internal voltage reference source with the feedback voltage
from the V
to input a signal to the PWM comparator to determine the turn-on time during PWM operation. 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 buffer driver circuit 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 monitors the P-channel 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 a low ESR capacitor, such as a ceramic capacitor, is used, ensurin g
stable output voltage.
<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 intern ally as 600kHz. 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 divided by the internal split resistors, R1 and R2. 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.
<Current Limit>
The current limiter circuit of the XC9253R series monitors the current flowing through the P-channel MOS driver transistor
connected to the Lx pin, and features a combination of the constant-current type current limit mode and the operatio n
suspension mode.
① When the driver current is greater than a specific level, the constant-current type current limit function operates to turn off
the pulses from the Lx pin at any given timing.
② When the driver transistor is turned off, the limiter circuit is then released from the current limit detection state.
③ At the next pulse, the driver transistor is turned on. However, the transistor is immediately turned off in the case of an over
current state.
④ When the over current state is eliminated, the IC resumes its normal operation.
The IC waits for the over current state to end by repeating the steps ① through ③ . If an over current state continues for a
few msec and the above three steps are repeatedly performed, the IC performs the function of latching the OF F state of the
driver transistor, and goes into operation suspension mode. Once the IC is in suspension mode, operations can be resumed by
either turning the IC off via the CE pin, or by restoring power to the VIN pin. The suspension mode does not mean a complete
shutdown, but a state in which pulse output is suspended; therefore, the internal circuitry remains in ope r ation. The
constant-current type current limit of the XC9253R series can be set at 700mA at typical. Besides, care must be taken when
laying out the PC Board, in order to prevent misoperation of the current limit mode. Depen ding on the state of the PC Board,
latch time may become longer and latch operation may not work. In order to avoid the effect of noise, the board should be laid
out so that capacitors are placed as close to the chip as possible.
OUT pin through split resistors, R1 and R2. Phase compensation is performed on the resulting error amplifier output,
Limit < #mS Limi t > #mS
Iout
VOUT
LX
CE/MODE
VIN
V
500mA
(ceramic)
●fosc=600kHz
L : 10μH (NR4018, TAIYO YUDEN)
: 10μH (VLF4012A, TDK)
L
C
: 10μH (CDRH4, SUMIDA)
CIN : 4.7μF (Ceramic)
CL : 10μF (Ceramic)
Cur rent Limit LEVEL
0mA
VSS
Restart
5/13
)
XC9253R
■OPERATIONAL EXPLANATION (Continued
<U.V.L.O. Circuit>
When the V
output caused by unstable operation of the internal circuitry. W hen the V
operation takes place. By releasing the U.V.L.O. function, the IC performs the soft start function to initiate output startup
operation. The soft start function operates even when the V
voltage. The U.V.L.O. circuit does not cause a complete shutdown of the IC, but causes pulse output to be suspended;
therefore, the internal circuitry remains in operation.
<PFM Switch Current>
In PFM control operation, until coil current reaches to a specified level (I
case, time that the P-ch MOSFET is kept on (t
t
= L×I
ON
<Maximum I
In PFM control operation, the maximum duty ratio (MAXPFM) is set to 44% (TYP.). Therefore, under the condition that the
duty increases (e.g. the condition that the step-down ratio is small), it’s possible for P-ch MOSFET to be turned off even
when coil current doesn’t reach to I
<CE Pin Function>
The operation of the XC9253R series will enter into the shut down mode when a low level signal is input to the CE pin. During the
shut down mode, the current consumption of the IC becomes 0μA (TYP.), with a state of high impedance at the Lx pin and V
pin. The IC starts its operation by inputting a high level signal to the CE pin. The input to the CE pin is a CMOS input and the sink
current is 0μA (TYP.).
●XC9253R series - Examples of how to use CE pin
(A)
SW＿CE
ON Stand-by
OFF Operation
(B)
SW＿CE
ON Operation
OFF Stand-by
pin voltage becomes 1.4V or lower, the P-channel output driver transistor is forced OFF to prevent false pulse
IN
/ (V
PFM
PFM
－
V
IN
Limit>
IPFM
Lx
I Lx
STATUS
STATUS
Series
) →I
OUT
①
t
ON
PFM
①
PFM
. →I
pin voltage becomes 1.8V or higher, switching
IN
pin voltage falls momentarily below the U.V.L.O. operating
IN
), the IC keeps the P-ch MOSFET on. In this
) can be given by the following formula.
ON
②
PFM
IPFM
Lx
IPFM
0mA
I Lx
PFM
②
fosc
Maxumum IPFM Current
(A)
IPFM
0mA
(B)
OUT
6/13
XC9253R
Series
■NOTES ON USE
●Application Information
1 . The XC9253R series is designed for use with ceramic output capacitors. If, however, the potential difference between
dropout voltage or output current 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 . Depending on the input-output voltage differential, or load current, some pulses may be skipped, an d the ripple voltage
may increase.
4 . When the difference between V
possibility that some cycles may be skipped completely.
5 . When the difference between V
there is the possibility that some cycles may be skipped completely: in this case, the Lx pin may not go low at all.
6 . 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 calc ulate the
peak current according to the following formula:
Ipk = (V
L: Coil Inductance Value
fosc: Oscillation Frequency
7 . 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.
8 . When VIN is less than 2.4V, limit current may not be reached because voltage falls caused by ON resistance.
9 . Care must be taken when laying out the PC Board, in order to prevent misoperation of the current limit mode. Depending
on the state of the PC Board, latch time may become longer and latch operation may not work. In order to avoid the effect of
noise, the board should be laid out so that capacitors are placed as close to the chip as possible.
10. Use of the IC at voltages below the recommended voltage range may lead to instability.
11. This IC should be used within the stated absolute maximum ratings in order to prevent damage to the device.
12. When the IC is used in high temperature, output voltage may increase up to input voltage level at no load because of the
leak current of the driver transistor.
13. The current limit is set to 700mA at typical. However, the current of 700mA or more may flow. In case that the current
limit functions while the V
voltage will occur at both ends of a coil. For this, the time rate of coil current becomes large. By cont rast, when N-ch
MOSFET is ON, there is almost no potential difference at both ends of the coil since the V
pin. Consequently, the time rate of coil current becomes quite small. According to the repetition of this operation, and
the delay time of the circuit, coil current will be converged on a certain current value, exceeding the amount of current,
which is supposed to be limited originally. Even in this case, however, after the overcurrent state continues for several
msec, the circuit will be latched. A coil should be used within the stated absolute maximum rating in order to prevent
damage to the device.
①Current flows into P-ch MOSFET to reach the current limit (I
②The current of I
OFF of P-ch MOSFET.
③Because of no potential difference at both ends of the coil, the time rate of coil current becomes quite small.
④Lx oscillates very narrow pulses by the current limit for several msec.
⑤The circuit is latched, stopping its operation.
- V
IN
) * OnDuty / (2 x L x fosc) + I
OUT
or more flows since the delay time of the circuit occurs during from the detection of the current limit to
LIM
LX
ILIM
ILX
and V
IN
and V
IN
pin is shorted to the GND pin, when P-ch MOSFET is ON, the potential difference for input
OUT
①
Delay
is large in PWM control, very narrow pulses will be outputted, and there is the
OUT
is small, and the load current is heavy, very wide pulses will be outputted and
OUT
OUT
pin is shorted to the GND
OUT
).
LIM
②
③
④
Limit > # mS
⑤
7/13
XC9253R
■NOTES ON USE (Continued)
●Application Information (Continued)
14. In order to stabilize VIN’s voltage level and oscillation frequency, we recommend that a by-pass capacitor (CIN) be
connected as close as possible to the V
15. High step-down ratio and very light load may lead an intermittent oscillation.
16. When the inductance value of the coil is large and under the condition of large dropout voltage in continuous mode,
operation may become unstable.
17. Maximum output current is 500mA. Limit current of this IC denotes a peak current, which flows to coils. When using a
coil with a small L value, output current (I
function operates before the output current reaches maximum output current. Accordingly, in the heavy load, the coils’
value should be 10μH or more for 600kHz.
●Instructions of pattern layouts
1. In order to stabilize V
the V
& VSS pins.
2. Please mount each external component as close to the IC as possible.
3. Wire external components as close to the IC as possible and use thick, short connecting traces to reduce the circuit
4. Make sure that the PCB GND traces are as thick as possible, as variations in ground potential caused by high ground
5. This series’ internal driver transistors bring on heat because of the output current and On resistance of driver transistors.
IN
impedance.
currents at the time of switching may result in instability of the IC.
Please be careful of the heat ability of the PCB when using the XC9253R series.
Series
& VSS pins.
IN
) may not flow because the peak current increase and the limit current
OUT
’s voltage level, we recommend that a by-pass capacitor (CIN) be connected as close as possible to
IN
8/13
■NOTES ON USE (Continued)
●Reference Pattern Layout
SOT-25
USP-6B
L
VIN
CIN
VSS
IC
CE
* Please use an electric wire for VIN, VOUT, VSS and CE.
CL
IC
VOUT
CE
VSS
* Please use an electric wire for VIN, VOUT, VSS and CE.
VSS
CIN
VOUT
CL
VSS
L
VIN
XC9253R
Series
Ceramic_Cap
Inductor
Ceramic_Cap
Inductor
9/13
XC9253R
■TEST CIRCUITS
Series
10/13
CE
■PACKAGING INFORMATION
●SOT-25
●USP-6B Reference Pattern Layout
XC9253R
Series
●USP-6B
●USP-6B Reference Metal Mask Design
11/13
●
●
XC9253R
■MARKING RULE
SOT-25
Series
① represents product series
② represents integer of output voltage
SOT-25 (TOP VIEW)
USP-6B
③ represents decimal point of output voltage and oscillation frequency
USP-6B (TOP VIEW)
12/13
MARK PRODUCT SERIES
U
OUTPUT VOLTAGE (V) MARK
3.x
XC9253R
3
PRODUCT SERIES
XC9253R001xx
OUTPUT VOLTAGE (V) MARK
x.3 3
④ represents production lot number
0 to 9, A to Z, reversed character of 0 to 9 and A to Z repeated (G, I, J, O, Q, W excepted)
① represents product series
MARK PRODUCT SERIES
P XC9253R
② represents the type of DC/DC converters
MARK PRODUCT SERIES
A XC9253R001xx
③ represents integer of output voltage
MARK OUTPUT VOLTAGE (V)
3 3.xx
④ represents decimal point of output voltage
MARK OUTPUT VOLTAGE (V)
3 x.30
⑤ represents oscillation frequency
MARK OSCILLATION FREQUENCY PRODUCT SERIES
6 600kHz XC9253R001xx
⑥ represents production lot number
0 to 9 and A to Z repeated (G, I, J, O, Q, W excepted)
XC9253R
Series
1. The products and product specifications contained he rein are subject to change without
notice to improve performance characteristics. Consult us, or our representatives
before use, to confirm that the information in this datasheet is up to date.
2. We assume no responsibility for any infringement of patents, patent rights, or other
rights arising from the use of any information and circuitry in this datasheet.
3. Please ensure suitable shipping controls (including fail-safe designs and aging
protection) are in force for equipment employing products listed in this datasheet.
4. The products in this datasheet are not developed, designed, or approved for use with
such equipment whose failure of malfunction can be reasonably expected to directly
endanger the life of, or cause significant injury to, the user.
(e.g. Atomic energy; aerospace; transport; combustion and associated safety
equipment thereof.)
5. Please use the products listed in this datasheet within the specified ranges.
Should you wish to use the products under conditions exceeding the specifications,
please consult us or our representatives.
6. We assume no responsibility for damage or loss due to abnormal use.
7. All rights reserved. No part of this datasheet may be copied or reproduced without the
prior permission of TOREX SEMICONDUCTOR LTD.
13/13
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