June 9, 2005 V7
◆Synchronous Step-Down DC/DC Converter with
Built-In LDO Regulator plus Voltage Detector
◆Step-Down DC/DC Converter's Output Connected in
Series with LDO Regulator
◆High Efficiency, Low Noise Regulated Output
◆Ultra Small Packages: MSOP-10, USP-10
◆Small-Footprint
◆Output Current
DC/DC:600mA, VR: 200mA
◆Ceramic Capacitor Compatible (Low ESR Capacitors)
■APPLICATIONS
●CD-R / RW, DVD
●HDD
●PDAs, portable communication modem
●Cellular phones
●Palmtop computers
●Cameras, video recorders
■FEATURES
■GENERAL DESCRIPTION
Input Voltage Range
: 2.4V ~ 6.0V
high-speed LDO regulator connected in series with the DC/DC
Low ESR Capacitor
: Ceramic capacitor compatible
converter's output.
VD Function
: N-channel open drain output
The XC9508 series consists of a step-down DC/DC converter and a
A voltage detector is also built-in.
A highly
efficient, low noise output is possible since the regulator is stepped-down
further from the DC/DC output.
The DC/DC converter block incorporates a P-channel driver transistor
and a synchronous N-channel switching transistor. With an external coil,
<DC/DC Converter Block>
Output Voltage Range
: 1.6V ~ 4.0V (Accuracy ± 2%)
Output Current
: 600mA (for MSOP-10 package)
diode and two capacitors, the XC9508 can deliver output currents up to
600mA at efficiencies over 90%.
The XC9508 is designed for use with
small ceramic capacitors.
400mA (for USP-10 package)
Controls
: PWM Control
PWM, PWM/PFM Automatic
A choice of three switching frequencies are available, 300 kHz, 600 kHz,
Switching External
and 1.2 MHz.
Output voltage settings for the DC/DC is set-up internally in 100mV steps
Oscillation Frequency
within the range of 1.6V to 4.0V(± 2.0%) and for the VR are set-up
<Regulator Block>
internally within the range of 0.9V to 4.0V (± 2.0%).
For the VD, the
: 300kHz, 600kHz, 1.2MHz
Output Voltage Range
: 0.9V ~ 4.0V (Accuracy ± 2%)
Current Limit
: 300mA
U.V.L.O. (Under Voltage Lock Out) function, the internal P-channel driver
Dropout Voltage
: 80mV @ IOUT=100mA (VOUT=2.8V)
transistor is forced OFF when input voltage becomes 1.4 V or lower.
High Ripple Rejection
: 60dB @1kHz (VOUT=2.8V)
range is of 0.9V to 5.0V (± 2.0%).
The soft start time of the series is internally set to 5ms.
With the built-in
The functions of the MODE pin can be selected via the external control
pin to switch the DC/DC control mode and the disable pin to shut down
the regulator block.
■TYPICAL APPLICATION CIRCUIT
■TYPICAL PERFORMANCE
CHARACTERISTICS
XC9508Cxxxx
VIN=3.6V, Topr=25OC
L=4.7μH (CDRH4D28C)
CIN:4.7μF ‘(ceramic), CL1:10μF (ceramic), CL2: 4.7μF (ceramic)
MSOP-10 (TOP VIEW)
* Please refer to the typical application circuit when external
components are selected.
Data Sheet
ud200541
1
XC9508 Series
■PIN CONFIGURATION
PGND 1
■PIN ASSIGNMENT
PIN NUMBER
PIN NAME
FUNCTION
1
PGND
Power Ground
2
CE
Chip Enable
VDD
Power Supply
VD Output
10 LX
CE 2
9 DCOUT
VDD 3
8 VROUT
VDOUT 4
7 MODE
3
VDIN 5
6 AGND
4
VDOUT
5
VDIN
VD Input
6
AGND
Analog Ground
7
MODE
Mode Switch
8
VROUT
VR Output
9
DCOUT
DC/DC Output Sense
10
LX
Switch
MSOP-10 (TOP VIEW)
USP-10 (BOTTOM VIEW)
*Please use the circuit without connecting the
heat dissipation pad.
If the pad needs to be
connected to other pins, it should be
connected to the AGND pin.
■PRODUCT CLASSIFICATION
●Ordering Information
XC9508①②③④⑤⑥
The input for the voltage regulator block comes from the DC/DC.
DESIGNATOR
DESCRIPTION
Control Methods and
①
the VD Sense Pin
②③
④
SYMBOL
As chart below
Setting Voltage &
Internal
Specifications
standard
DC/DC Oscillation Frequency
⑤
⑥
DESCRIPTION
:: Setting voltage and specifications of each DC/DC, VR, and VD
(Based on the internal standard)
3
: 300kHz
6
: 600kHz
C
: 1.2MHz
Package &
A
: MSOP-10, Current limiter: 1.1A (TYP.)
DC/DC Current limit
D
: USP-10, Current limiter: 0.7A (TYP.)
Device Orientation
R
: Embossed Tape, standard feed
L
: Embossed Tape, reverse feed
●Control Methods and MODE Pin
SERIES
XC9508
①
DC/DC CONTROL METHODS
MODE PINS (H LEVEL)
MODE PINS (L LEVEL)
A
PWM Control
VR: OFF
VR: ON
C
PWM, PFM/PWM Manual Switch
PFM / PWM Switch
PWM Control
* The XC9508A series' MODE pin switches the regulator to the stand-by mode.
When the CE mode is off, every function except for the VD function enters into the stand-by mode.
(The MODE pin does not operate independently.)
2
Data Sheet
ud200541
XC9508
Series
■PACKAGING INFORMATION
●USP-10
●MSOP-10
1 4.90+0.20
3.00+0.10
1 0.53+0.13
1 0.15+0.08
1
0~6
3.00+0.10
O
+0.1
1 0.20 -0.05
(0.5)
1 0~0.15
1 0.86+0.15
* Soldering fillet surface is not
formed because the sides of
the pins are not plated.
■MARKING RULE
●MSOP-10, USP-10
①Represents product series
MARK
7
PRODUCT SERIES
XC9508xxxxxx
USP-10
MSOP-10
(TOP VIEW)
(TOP VIEW)
②Represents DC/DC control methods and MODE pin
MARK
A
C
S
DC/DC CONTROL
MODE PIN (H level)
MODE PIN (L level) PRODUCT SERIES
PWM Control
VR:OFF
VR:ON
XC9508Axxxxx
PWM, PFM/PWM Manual Switching PFM/PWM Auto Switching
PWM Control
XC9508Cxxxxx
Custom
XC9508Cxxxxx
③④Represents detect voltage DC/DC,VR and VD.
ex)
MARK
③
1
④
5
DC/DC
VR
VD
PRODUCT SERIES
2.0V
1.5V
1.9V
XC9508x15xxx
⑤Represents oscillation frequency
MARK
3
6
C
OSCILLATION FREQUENCY
300kHz
600kHz
1.2MHz
PRODUCT SERIES
XC9508xxx3xx
XC9508xxx6xx
XC9508xxxCxx
⑥Represents production lot number
0 to 9, A to Z reverse character 0 to 9, A to Z repeated (G, I, J, O, Q, W excepted)
Note: No character inversion used.
Data Sheet
ud200541
3
XC9508 Series
■BLOCK DIAGRAM
* Diodes shown in the above circuit are protective diodes
■ABSOLUTE MAXIMUM RATINGS
Ta = 25℃
PARAMETER
SYMBOL
RATINGS
UNIT
VDD Pin Voltage
VDD
- 0.3 ~ 6.5
V
DCOUT Pin Voltage
DCOUT
- 0.3 ~ VDD + 0.3
V
VROUT Pin Voltage
VROUT
- 0.3 ~ VDD + 0.3
V
VROUT Pin Current
IROUT
800
mA
VDOUT Pin Voltage
VDOUT
- 0.3 ~ VDD + 0.3
V
VDOUT Pin Current
IVD
50
mA
VDIN Pin Voltage
VDIN
- 0.3 ~ VDD + 0.3
V
Lx Pin Voltage
Lx
- 0.3 ~ VDD + 0.3
V
Lx Pin Current
MSOP-10
USP-10
Ilx
1300
900
mA
CE Pin Voltage
CE
- 0.3 ~ VDD + 0.3
V
MODE Pin Voltage
MODE
- 0.3 ~ VDD + 0.3
V
Power Dissipation
MSOP-10
USP-10
Pd
350 (*)
150
mW
Operating Temperature Range
Topr
- 40 ~ + 85
℃
Storage Temperature Range
Tstg
- 55 ~ + 125
℃
(*) When PC board mounted.
4
Data Sheet
ud200541
XC9508
Series
■ELECTRICAL CHARACTERISTICS
XC9508xxxCAx
●Common Characteristics
Topr=25℃
PARAMETER
SYMBOL
CONDITIONS
MIN.
TYP.
MAX.
UNITS
Supply Current 1
IDD1
VIN=CE=DCOUT=5.0V
-
250
310
μA
1
Supply Current 2
IDD2
VIN=CE=5.0V, DCOUT=0V
-
300
360
μA
1
Stand-by Current (*1)
ISTB
VIN=6.5V, CE=0V
Input Voltage Range
VIN
CE ‘H’ Level Voltage
CE ‘L’ Level Voltage
CIRCUIT
-
0.5
2.5
μA
1
2.4
-
6.0
V
-
VCEH
0.6
-
VDD
V
3
VCEL
VSS
-
0.25
V
3
CE ‘H’ Level Current
ICEH
- 0.1
-
0.1
μA
1
CE ‘L’ Level Current
ICEL
- 0.1
-
0.1
μA
1
MODE 'H' Level Voltage*XC9508A
VMH
0.6
-
VDD
V
2
MODE 'H' Level Voltage*XC9508C
VMH
0.6
-
VDD
V
3
MODE 'L' Level Voltage*XC9508A
VML
VSS
-
0.25
V
2
MODE 'L' Level Voltage*XC9508C
VML
VSS
-
0.25
V
3
MODE 'H' Level Current
IMH
- 0.1
-
0.1
μA
1
MODE 'L' Level Current
IML
- 0.1
-
0.1
μA
1
●DC/DC Converter (2.2V product)
Topr=25℃
PARAMETER
SYMBOL
CONDITIONS
Supply Current 1 *XC9508A
IDD_DC1
VIN=CE=DCOUT=5.0V
Supply Current 2 *XC9508A
IDD_DC2
VIN=CE=5.0V, DCOUT=0V
PFM Supply Current 1 * 9508C
IDD_PFM1
VIN=CE=DCOUT=5.0V
PFM Supply Current 2 * 9508C
IDD_PFM2
VIN=CE=5.0V, DCOUT=0V
2.156
Connected to the external components,
MIN.
MAX.
UNITS
CIRCUIT
200
280
μA
1
250
330
μA
1
250
310
μA
1
300
360
μA
1
2.200
2.244
V
3
1.02
1.20
1.38
MHz
3
-
TYP.
Output Voltage
DCOUT(E)
Oscillation Frequency
FOSC
Maximum Duty Ratio
MAXDUTY
DCOUT=0V
100
-
-
%
4
Minimum Duty Ratio
MINDUTY
DCOUT=VIN
-
-
0
%
4
21
30
38
%
3
1.00
1.40
1.78
V
3
-
0.5
0.9
Ω
5
-
0.5
0.9
Ω
3
PFM Duty Ratio
PFMDUTY
U.V.L.O. Voltage (*2)
VUVLO
LX SW ‘High’ ON Resistance (*3)
RLXH
IDOUT=30mA
Connected to the external components,
IDOUT=10mA
Connected to the external components,
No load
Connected to the external components
DCOUT=0V, LX=VIN-0.05V
Connected to the external components,
LX SW ‘Low’ ON Resistance
RLXL
LX SW ‘High’ Leak Current (*12)
IleakH
VIN=LX=6.0V, CE=0V
-
0.05
1.00
μA
11
LX SW ‘Low’ Leak Current (*12)
IleakL
VIN=6.0V, LX=CE=0V
-
0.05
1.00
μA
11
Maximum Output Current
Imax1
Connected to the external components
600
-
-
mA
3
Current Limit (*9)
Ilim1
1.0
1.1
-
A
6
-
90
-
%
3
-
±100
-
2
5
10
mS
3
-
8
25
mS
10
Efficiency (*4)
EFFI
Output Voltage
Temperature Characteristics
U DCOUT
(UTopr・DCOUT)
Soft-Start Time
TSS
Latch Time (*5, 10)
Tlat
Data Sheet
ud200541
VIN=5.0V
Connected to the external components,
IDOUT=100mA
IDOUT=30mA
-40℃≦Topr≦85℃
Connected to the external components,
CE=0VtVIN, IDOUT=1mA
Connected to the external components,
VIN=CE=5.0V, Short DCOUT by 1Ω resistor
ppm/
℃
3
5
XC9508 Series
■ELECTRICAL CHARACTERISTICS (Continued)
XC9508xxxCAx (Continued)
●Regulator (1.8V product)
Topr=25℃
PARAMETER
SYMBOL
CONDITIONS
TYP.
MAX.
UNITS
CIRCUIT
1.764
1.800
1.836
V
2
200
-
-
mA
2
Output Voltage
VROUT(E)
Maximum Output Current
Imax2
Load Regulation
U VROUT
1mA≦IROUT≦100mA
-
15
50
mV
2
Dropout Voltage 1 (*6)
Vdif 1
IROUT=30mA
-
30
200
mV
2
Vdif 2
IROUT=100mA
-
100
200
mV
2
U VROUT
IROUT=30mA
-
0.05
0.25
%/V
2
240
300
-
mA
7
-
30
-
mA
7
-
60
-
dB
12
-
±100
-
Dropout Voltage 2
Line Regulation
IROUT=30mA
MIN.
UVIN・VROUT
VROUT(T)+1V≦VIN≦6V
Current Limit
Ilim2
VROUT=VROUT(E) x 0.9
Short-Circuit Current
Ishort
VROUT=VSS
Ripple Rejection Rate
PSRR
Output Voltage
U VROUT
Temperature Characteristics
UTopr・VROUT
VIN={VOUT(T)+1.0} VDC+0.5Vp-pAC,
IROUT=30mA, f=1kHz
IROUT=30mA
-40℃≦Topr≦85℃
ppm/
2
℃
●Detector (2.7V product)
PARAMETER
SYMBOL
Detect Voltage
VDF(E)
Hysteresis Range
VHYS
VD Output Current
IVD
Output Voltage
U VDF
Temperature Characteristics
UTopr・VDF
CONDITIONS
CE=0V
VHYS=[VDR(E)
(*11)
MIN.
TYP.
MAX.
UNITS
CIRCUIT
2.646
2.700
2.754
V
8
2
5
8
%
8
VDOUT=0.5V, CE=0V
- VDF(E)] / VDF(E) x 100
1
-
-
mA
9
-40℃≦Topr≦85℃
-
±100
-
ppm/
8
℃
Test conditions: Unless otherwise stated:
DC/DC : VIN=3.6V [@ DCOUT:2.2V]
VR: VIN = 2.8V (VIN=VROUT(T) + 1.0V)
VD: VIN=5.0V
Common conditions for all test items: CE=VIN, MODE=0V
* VROUT(T) : Setting output voltage
NOTE:
*1 : Including VD supply current (VD operates when in stand-by mode.)
*2 : Including hysteresis operating voltage range.
*3 : ON resistance (Ω)= 0.05 (V) / ILX (A)
*4 : EFFI = { ( Output Voltage x Output Current ) / ( Input Voltage x Input Current) } x 100
*5 : Time until it short-circuits DCOUT with GND through 1Ω of resistance from a state of operation and is set to DCOUT=0V from
current limit pulse generating.
( 7)
( 8)
*6 : Vdif = (VIN1 * - VROUT1 * )
*7 : VIN 1 = The input voltage when VROUT1 appears as input voltage is gradually decreased.
*8 : VROUT1 = A voltage equal to 98% of the output voltage whenever an amply stabilized IOUT {VROUT(T) + 1.0V} is input.
*9 : Current limit = When VIN is low, limit current may not be reached because of voltage falls caused by ON resistance or serial
resistance of coils.
*10: Integral latch circuit=latch time may become longer and latch operation may not work when VIN is 3.0V or more.
*11: VDR(E) = VD release voltage
*12: When temperature is high, a current of approximately 5.0μA (maximum) may leak.
6
Data Sheet
ud200541
XC9508
Series
■TEST CIRCUITS
Circuit 1
Circuit 3
Circuit 5
Data Sheet
ud200541
Supply Current, Stand-by Current, CE Current,
MODE current
Circuit 2
Output Voltage (DC/DC) Oscillation Frequency, UVLO
Voltage, Soft-start Time, CE Voltage, Maximum Output
Current, Efficiency, (PFM Duty Cycle), (MODE Voltage)
Circuit 4
Lx ON Resistance
Output Voltage (VR), Load Regulation, Dropout Voltage,
Maximum Output Current, (MODE Voltage)
Circuit 6
Minimum Duty Cycle, Maximum Duty Cycle
Current Limit 1 (DC/DC)
7
XC9508 Series
■TEST CIRCUITS (Continued)
Circuit 7
Current Limit 2 (VR), Short Circuit Current (VR)
Circuit 8
Circuit 9
VD Output Current
Circuit 10
Circuit 11
8
Off-Leak
Circuit 12
Detect Voltage, Release Voltage (Hysteresis Range)
Latch Time
Ripple Rejection Rate
Data Sheet
ud200541
XC9508
Series
■TYPICAL APPLICATION CIRCUIT
FOSC
L
1.2MHz
4.7μH (CDRH4D28C, SUMIDA)
600KHz
10μH (CDRH5D28, SUMIDA)
300kHz
22μH (CDRH6D28, SUMIDA)
MSOP-10 (TOP VIEW)
CIN
CL1
4.7μF
10μF
(ceramic, TAIYO YUDEN)
(ceramic, TAIYO YUDEN)
CL2 (*2)
VROUT≦2.0V
VROUT＞2.0V
4.7μF (ceramic, TAIYO YUDEN)
Vdif＞1.0V
1.0μF (ceramic, TAIYO YUDEN)
Vdif≦1.0V
4.7μF (ceramic, TAIYO YUDEN)
SD *1 : XB0ASB03A1BR (TOREX)
*1 The DC/DC converter of the XC9508 series automatically switches between synchronous / non-synchronous.
diode is not normally needed.
The Schottky
However, in cases where high efficiency is required when using the DC/DC converter during in
the light load while in non-synchronous operation, please connect a Schottky diode externally.
*2 Please be noted that the recommend value above of the CL2 may be changed depending on the input voltage value and
setting voltage value.
■OPERATIONAL EXPLANATION
The XC9508 series consists of a synchronous step-down DC/DC converter, a high speed LDO voltage regulator, and a
voltage detector. Since the LDO voltage regulator is stepped-down from the DC/DC's output, high efficiency and low noise
is possible even at lower output voltages.
●DC/DC Converter
The series consists of a reference voltage source, ramp wave circuit, error amplifier, PWM comparator, phase
compensation circuit, output voltage adjustment resistors, driver transistor, synchronous switch, current limiter circuit,
U.V.L.O. circuit and others. The series ICs compare, using the error amplifier, the voltage of the internal voltage
reference source with the feedback voltage from the VOUT pin through split resistors. Phase compensation is
performed on the resulting error amplifier output, 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, ensuring 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 internally and can be selected from
300kHz, 600 kHz and 1.2 MHz. 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. 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.
Data Sheet
ud200541
9
XC9508 Series
■OPERATIONAL EXPLANATION (Continued)
●DC/DC Converter (Continued)
<PWM/PFM>
The XC9508A series is PWM control, while the XC9508C series can be automatically switched between PWM control
and PWM/PFM control. The PWM of the XC9508A series is controlled on a specified frequency from light loads through
the heavy loads. Since the frequency is specified, the composition of a noise filter etc. becomes easy. However, the
efficiency at the time of the light load may become low.
The XC9508C series can switch in any timing between PWM control and PWM/PFM automatic switching control. The
series cannot control only PFM mode. If needed, the operation can be set on a specified frequency; therefore, the
control of the noise etc. is possible and the high efficiency at the time of the light load during PFM control mode is
possible. With the automatic PWM/PFM switching control function, the series ICs are automatically switched from
PWM control to PFM control mode under light load conditions. If during light load conditions the coil current becomes
discontinuous and on-time rate falls lower than 30%, the PFM circuit operates to output a pulse with 30% of a fixed
on-time rate from the Lx pin. During PFM operation with this fixed on-time rate, pulses are generated at different
frequencies according to conditions of the moment. This causes a reduction in the number of switching operations per
unit of time, resulting in efficiency improvement under light load conditions. However, since pulse output frequency is
not constant, consideration should be given if a noise filter or the like is needed. Necessary conditions for switching to
PFM operation depend on input voltage, load current, coil value and other factors.
<Synchronous / Non-synchronous>
The XC9508 series automatically switches between synchronous / non-synchronous according to the state of the DC/DC
converter. Highly efficient operations are achievable using the synchronous mode while the coil current is in a
continuous state. The series enters non-synchronous operation when the built-in N-ch switching transistor for
synchronous operation is shutdown, which happens when the load current becomes low and the operation changes to a
discontinuous state. The IC can operate without an external schottky diode because the parasitic diode in the N-ch
switching transistor provides the circuit's step-down operation. However, since Vf of the parasitic diode is a high 0.6V,
the efficiency level during non-synchronous operation shows a slight decrease. Please use an external schottky diode
if high efficiency is required during light load current.
●Continuous Mode: Synchronous
●Discontinuous Mode: Non-Synchronous
10
Data Sheet
ud200541
XC9508
Series
■OPERATIONAL EXPLANATION (Continued)
●DC/DC Converter (Continued)
<Current Limit>
The current limiter circuit of the XC9508 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 operation
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 8msec* and the above three steps are repeatedly performed, the IC performs the function of latching
the OFF 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/MODE 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 operation. The constant-current type current limit of the XC9508 series
can be set at 1.1A for MSOP-10 package and 0.7A for USP-10 package
<U.V.L.O. Circuit>
When the VIN pin voltage becomes 1.4 V or lower, the P-channel output driver transistor is forced OFF to prevent false
pulse output caused by unstable operation of the internal circuitry. When the VIN pin voltage becomes 1.8 V or higher,
switching 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 VIN pin voltage falls momentarily below the
U.V.L.O. operating 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.
●High Speed LDO Voltage Regulator
The voltage regulator block of the XC9508 series consists of a reference voltage source, error amplifier, and current
limiter circuit. The voltage divided by split resistors is compared with the internal reference voltage by the error
amplifier. The P-channel MOSFET, which is connected to the VROUT pin, is then driven by the subsequent output
signal. The output voltage at the VROUT pin is controlled and stabilized by a system of negative feedback. A stable
output voltage is achievable even if used with low ESR capacitors as a phase compensation circuit is built-in.
<Reference Voltage Source>
The reference voltage source provides the reference voltage to ensure stable output voltage of the regulator.
<Error Amplifier>
The error amplifier compares the reference voltage with the signal from VROUT, and the amplifier controls the output of
the Pch driver transistor.
<Current Limit Circuit>
The voltage regulator block includes a combination of a constant current limiter circuit and a foldback circuit. When the
load current reaches the current limit level, the current limiter circuit operates and the output voltage of the voltage
regulator block drops. As a result of this drop in output voltage, the foldback circuit operates, output voltage drops
further and the load current decreases. When the VROUT and GND pin are shorted, the load current of about 30mA flows.
Data Sheet
ud200541
11
XC9508 Series
■OPERATIONAL EXPLANATION (Continued)
●Voltage Detector
The detector block of the XC9508 series detects output voltage from the VDOUT pin to the signal, which enters from VDIN.
(N-channel Open Drain Type)
<CE Pin Function>
The operation of the XC9508 series' DC/DC converter block and voltage regulator block 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 occurs only in
the detector and is 0.6μA (TYP.), with a state of high impedance at the Lx pin and DCOUT 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.).
<MODE Pin Function>
The operation of the XC9508A series' voltage detector block will enter into stand-by mode when a high level signal is input
to the MODE pin. When a low level signal is input, the voltage regulator block will enter into stand-by mode. However,
if the IC enters into stand-by mode via the CE pin, the voltage regulator block also shuts down. With the XC9508C
series control can be PWM control when the MODE pin is 'H' level and PWM/PFM automatic switching control when the
MODE pin is 'L' level.
■NOTES ON USE
●Application Information
1. The XC9508 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. When the difference between VIN and VOUT is large in PWM control, very narrow pulses will be outputted, and there
is the possibility that some cycles may be skipped completely.
4. When the difference between VIN and VOUT 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.
●DC/DC Waveform (3.3V, 1.2MHz)
< External Components>
L:4.7μH(CDRH4D28C,SUMIDA)
CIN:4.7μF(ceramic)
CL:10μF(ceramic)
12
< External Components>
L:4.7μH(CDRH4D28C,SUMIDA)
CIN:4.7μF(ceramic)
CL:10μF(ceramic)
Data Sheet
ud200541
XC9508
Series
■NOTES ON USE (Continued)
●Application Information (Continued)
5. The IC's DC/DC converter operates in synchronous mode when the coil current is in a continuous state and
non-synchronous mode when the coil current is in a discontinuous state. In order to maintain the load current
value when synchronous switches to non-synchronous and vise versa, a ripple voltage may increase because of the
repetition of switching between synchronous and non-synchronous. When this state continues, the increase in the
ripple voltage stops. To reduce the ripple voltage, please increase the load capacitance value or use a Schottky
diode externally. When the current used becomes close to the value of the load current when synchronous
switches to non- synchronous and vise versa, the switching current value can be changed by changing the coil
inductance value. In case changes to coil inductance are to values other than the recommended coil inductance
values, verification with actual components should be done.
Ics =
(VIN - DCOUT) x OnDuty / (L x Fosc)
Ics: Switching current from synchronous rectification to non-synchronous rectification
.
OnDuty: OnDuty ratio of P-ch driver transistor ( =.step down ratio : DCOUT / VIN)
L: Coil inductance value
Fosc: Oscillation frequency
IDOUT: The DC/DC load current (the sum of the DC/DC's and the regulator's load if the regulator has load.)
6. When the XC9508C series operates in PWM/PFM automatic switching control mode, the reverse current may
become quite high around the load current value when synchronous switches to non-synchronous and vise versa
(also refer to no. 5 above). Under this condition, switching synchronous rectification and non-synchronous
rectification may be repeated because of the reverse current, and the ripple voltage may be increased to 100mV or
more. The reverse current is the current that flows in the PGND direction through the N-ch driver transistor from
the coil. The conditions, which cause this operation, are as follows.
PFM Duty＜Step down ratio = DCOUT / VIN×100 (%)
PFM Duty: 30% (TYP.)
Please switch to PWM control via the MODE function in cases where the load current value of the DC/DC converter
is close to synchronous.
●DC/DC Waveform (1.8V, 600kHz) @ VIN=6.0V
< External Components>
L:10μH(CDRH5D28C,SUMIDA)
CIN:4.7μF(ceramic)
CL:10μF(ceramic)
Step down ratio:1.8V / 6.0V=30% <PFM Duty 31%>
Data Sheet
ud200541
13
XC9508 Series
■NOTES ON USE (Continued)
●Application Information (Continued)
7. With the DC/DC converter of 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:
Peak current: Ipk = (VIN - DCOUT)×OnDuty / (2×L×Fosc) + IDOUT
8. When the peak current, which exceeds limit current flows within the specified time, the built-in driver transistor is
turned off (the integral latch circuit). 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.
9. When VIN is low, limit current may not be reached because of voltage falls caused by ON resistance or serial
resistance of the coil.
10. In the integral latch circuit, latch time may become longer and latch operation may not work when VIN is 3.0V or
more.
11. Use of the IC at voltages below the recommended voltage range may lead to instability.
12. This IC and the external components should be used within the stated absolute maximum ratings in order to prevent
damage to the device.
13. Since the DC/DC converter and the regulator of the XC9508 series are connected in series, the sum of the output
current (IDOUT) of the DC/DC and the output current (IROUT) of the VR makes the current flows inside the DC/DC
converter. Please be careful of the power dissipation when in use. Please calculate power dissipation by using
the following formula.
Pd=PdDC/DC + PdVR
DC/DC power dissipation (when in synchronous operation) : PdDC/DC = IDOUT2×RON
VR power dissipation: PdVR=(DCOUT – VROUT)×IROUT
RON: ON resistance of the built-in driver transistor to the DC/DC (= 0.5Ω <TYP.>)
RON=Rpon×P-chOnDuty / 100 + Rnon×(1 – P-chOnDuty / 100)
14. The voltage detector circuit built-in the XC9508 series internally monitor the VDD pin voltage, the DC/DC output pin
voltage and VR output pin voltage. Please determine the detect voltage value (VDF) by the following equation.
VDF≦(Setting voltage on both the DCOUT voltage and the VROUT voltage)×85%*
* An assumed value of tolerance among the DCOUT voltage, the VROUT voltage, and the VD release voltage
(The VD detect voltage and hysteresis range).
14
Data Sheet
ud200541
XC9508
Series
■NOTES ON USE (Continued)
●Instructions on Pattern Layout
1. In order to stabilize VIN's voltage level, we recommend that a by-pass capacitor (CIN) be connected as close as
possible to the VDD & AGND pins. This IC is the composite IC of the DC/DC converter and regulator. Fluctuation
of the VIN's voltage level causes mutual interference.
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
impedance.
4. Make sure that the PCB GND traces are as thick as possible, as variations in ground potential caused by high
ground currents at the time of switching may result in instability of the DC/DC converter and have adverse influence
on the regulator output.
5. If using a Schottky diode, please connect the anode side to the AGND pin through CIN. Characteristic degradation
caused by the noise may occur depending on the arrangement of the Schottky diode.
<MSOP-10 Recommended pattern layout>
CL1
CE
LX
PGND
L
SD
+
+
IC
VDOUT
VDIN
+
VIN
( Through Hole to SD )
Data Sheet
ud200541
DCOUT
MODE
VROUT
AGND
CL2
CIN
15
XC9508 Series
■TYPICAL PERFORMANCE CHARACTERISTICS
(A) DC/DC CONVERTER
(1) Efficiency vs. Output Current
16
Data Sheet
ud200541
XC9508
Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(A) DC/DC CONVERTER (Continued)
(2) Output Voltage VS. Output Current
Data Sheet
ud200541
17
XC9508 Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(A) DC/DC CONVERTER (Continued)
(3) Output Voltage vs. Ripple Voltage
18
Data Sheet
ud200541
XC9508
Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(A) DC/DC CONVERTER (Continued)
(4) Output Voltage vs. Ambient Temperature
(5) Soft Start Time vs. Ambient Temperature
Data Sheet
ud200541
19
XC9508 Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(A) DC/DC CONVERTER (Continued)
(6) DC/DC Supply Current vs. Ambient Temperature (VR: Shutdown)*
20
Data Sheet
ud200541
XC9508
Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(A) DC/DC CONVERTER (Continued)
(7) LX Pch/Nch on Resistance vs. Input Voltage
(8) Oscillation Frequency vs. Ambient Temperature
Data Sheet
ud200541
(9) U.V.L.O. Voltage vs. Ambient Temperature
21
XC9508 Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(A) DC/DC CONVERTER (Continued)
(10-1) DC/DC
DC/DC LOAD
TRANSIENT
RESPONSE
(DCOUT:1.8V,
Fosc:1.2MHz)
(10-1)
Load
Transient
Response
(DCOUT:
1.8V, FOSC: 1.2MHz)
(a)PWM
control
(a) PWM
Control
(b) PWM/PFM Automatic Switching Control* (*XC9508C Series Only)
22
Data Sheet
ud200541
XC9508
Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(A) DC/DC CONVERTER (Continued)
(10-2) DC/DC Load Transient Response (*DCOUT: 3.3V, FOSC: 1.2MHz)
(a) PWM Control
(b) PWM/PFM Automatic Switching Control* (*XC9508C Series Only)
Data Sheet
ud200541
23
XC9508 Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(A) DC/DC CONVERTER (Continued)
(10-3) DC/DC Load Transient Response (*DCOUT: 1.8V, FOSC: 600kHz)
(a) PWM Control
(b) PWM/PFM Automatic Switching Control* (*XC9508C Series Only)
24
Data Sheet
ud200541
XC9508
Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(A) DC/DC CONVERTER (Continued)
(10-4) DC/DC Load Transient Response (*DCOUT: 3.3V, FOSC: 600kHz)
(a) PWM Control
(b)PWM/PFM Automatic Switching Control* (*XC9508C Series Only)
Data Sheet
ud200541
25
XC9508 Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(B) VOLTAGRE REGULATOR
(1) Output Voltage VS. Input Voltage
26
Data Sheet
ud200541
XC9508
Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(B) VOLTAGRE REGULATOR (Continued)
(2) Output Voltage VS. Output Current (Current Limit)
Data Sheet
ud200541
27
XC9508 Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(B) VOLTAGRE REGULATOR (Continued)
(3) Dropout Voltage VS. Output Current
28
Data Sheet
ud200541
XC9508
Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(B) VOLTAGRE REGULATOR (Continued)
(4) Output Voltage VS. Output Current
Data Sheet
ud200541
29
XC9508 Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(B) VOLTAGRE REGULATOR (Continued)
(5) Output Voltage VS. Ambient Temperature
30
Data Sheet
ud200541
XC9508
Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(B) VOLTAGRE REGULATOR (Continued)
(6) Ripple Rejection Ratio VS. Ripple Frequency
Data Sheet
ud200541
31
XC9508 Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(B) VOLTAGRE REGULATOR (Continued)
(7) VR Load Transient Response
32
Data Sheet
ud200541
XC9508
Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(C) VOLTAGE DETECTOR
(1) Output Current VS. Input Voltage
(2) Detect Voltage VS. Input Voltage
Data Sheet
ud200541
33
XC9508 Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(C) VOLTAGE DETECTOR (Continued)
(3) Detect Voltage, Release Voltage VS. Ambient Temperature
34
Data Sheet
ud200541
XC9508
Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(D) COMMON
(1) Supply Current VS. Ambient Temperature (DC/DC & VR & VD)
(2) Shutdown Current VS. Input Voltage
Data Sheet
ud200541
(3) Shutdown Current VS. Ambient Temperature
35
XC9508 Series
■TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(D) COMMON (Continued)
(4) CE Pin Threshold Voltage VS. Ambient Temperature
Ambient Temperature : Ta (℃)
(5) MODE Pin Threshold Voltage VS. Ambient Temperature
Ambient Temperature : Ta (℃)
36
Data Sheet
ud200541