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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
GENERAL DESCRIPTION
The XC9508 series consists of a step-down DC/DC converter and a high-speed LDO regulator connected in series with the DC/DC converter's output. 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, diode and two capacitors, the XC9508 can deliver output currents up to 600mA at efficiencies over 90%. small ceramic capacitors. A choice of three switching frequencies are available, 300 kHz, 600 kHz, and 1.2 MHz. Output voltage settings for the DC/DC is set-up internally in 100mV steps within the range of 1.6V to 4.0V( 2.0%) and for the VR are set-up internally within the range of 0.9V to 4.0V ( 2.0%). 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 U.V.L.O. (Under Voltage Lock Out) function, the internal P-channel driver transistor is forced OFF when input voltage becomes 1.4 V or lower. 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. For the VD, the The XC9508 is designed for use with
FEATURES
Input Voltage Range Low ESR Capacitor VD Function Output Voltage Range Output Current Controls : 2.4V ~ 6.0V : Ceramic capacitor compatible : N-channel open drain output : 1.6V ~ 4.0V (Accuracy 2%) : 600mA (for MSOP-10 package) 400mA (for USP-10 package) : PWM Control PWM, PWM/PFM Automatic Switching External Oscillation Frequency Output Voltage Range Current Limit Dropout Voltage High Ripple Rejection : 0.9V ~ 4.0V (Accuracy 2%) : 300mA : 80mV @ IOUT=100mA (VOUT=2.8V) : 60dB @1kHz (VOUT=2.8V) : 300kHz, 600kHz, 1.2MHz

TYPICAL APPLICATION CIRCUIT
TYPICAL PERFORMANCE CHARACTERISTICS
XC9508Cxxxx
VIN=3.6V, Topr=25OC L=4.7H (CDRH4D28C) CIN:4.7F `(ceramic), CL1:10F (ceramic), CL2: 4.7F (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 CE 2 VDD 3 VDOUT 4 VDIN 5 10 LX 9 DCOUT 8 VROUT 7 MODE 6 AGND
PIN ASSIGNMENT
PIN NUMBER 1 2 3 4 5 6 7 8 9 10 PIN NAME PGND CE VDD VDOUT VDIN AGND MODE VROUT DCOUT LX FUNCTION Power Ground Chip Enable Power Supply VD Output VD Input Analog Ground Mode Switch VR Output DC/DC Output Sense 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
XC9508
DESIGNATOR
The input for the voltage regulator block comes from the DC/DC.
DESCRIPTION Control Methods and the VD Sense Pin Setting Voltage & Specifications SYMBOL As chart below Internal standard 3 6 C A D R L :: Setting voltage and specifications of each DC/DC, VR, and VD (Based on the internal standard) : 300kHz : 600kHz : 1.2MHz : MSOP-10, Current limiter: 1.1A (TYP.) : USP-10, Current limiter: 0.7A (TYP.) : Embossed Tape, standard feed : Embossed Tape, reverse feed DESCRIPTION

DC/DC Oscillation Frequency Package & DC/DC Current limit Device Orientation
Control Methods and MODE Pin
SERIES XC9508 A C DC/DC CONTROL METHODS PWM Control PWM, PFM/PWM Manual Switch MODE PINS (H LEVEL) VR: OFF PFM / PWM Switch MODE PINS (L LEVEL) VR: ON 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.)
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Data Sheet ud200541
XC9508
Series
PACKAGING INFORMATION
MSOP-10
1 0.15+0.08
USP-10
1 0.53+0.13 3.00+0.10 1 4.90+0.20
3.00+0.10 1 0~6
O
* Soldering fillet surface is not formed because the sides of the pins are not plated.
1 0.86+0.15
1 0.20 -0.05
+0.1
(0.5)
MARKING RULE
MSOP-10, USP-10
Represents product series
MARK 7 PRODUCT SERIES XC9508xxxxxx
USP-10 (TOP VIEW) MSOP-10 (TOP VIEW)
Represents 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
Represents detect voltage DC/DC,VR and VD.
ex) MARK 1 5 DC/DC 2.0V VR 1.5V VD 1.9V PRODUCT SERIES XC9508x15xxx
Represents oscillation frequency
MARK 3 6 C
OSCILLATION FREQUENCY
1 0~0.15
300kHz 600kHz 1.2MHz
PRODUCT SERIES XC9508xxx3xx XC9508xxx6xx XC9508XXXCXX
Represents 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
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XC9508 Series
BLOCK DIAGRAM
* Diodes shown in the above circuit are protective diodes
ABSOLUTE MAXIMUM RATINGS
PARAMETER VDD Pin Voltage DCOUT Pin Voltage VROUT Pin Voltage VROUT Pin Current VDOUT Pin Voltage VDOUT Pin Current VDIN Pin Voltage Lx Pin Voltage Lx Pin Current MSOP-10 USP-10 SYMBOL VDD DCOUT VROUT IROUT VDOUT IVD VDIN Lx Ilx CE MODE Pd Topr Tstg RATINGS
Ta = 25
UNIT V V V mA V mA V V mA V V mW
- 0.3 ~ 6.5 - 0.3 ~ VDD + 0.3 - 0.3 ~ VDD + 0.3 800 - 0.3 ~ VDD + 0.3 50 - 0.3 ~ VDD + 0.3 - 0.3 ~ VDD + 0.3 1300 900 - 0.3 ~ VDD + 0.3 - 0.3 ~ VDD + 0.3 350 (*) 150 - 40 ~ + 85 - 55 ~ + 125
CE Pin Voltage MODE Pin Voltage Power Dissipation MSOP-10 USP-10
Operating Temperature Range Storage Temperature Range
(*) When PC board mounted.
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Data Sheet ud200541
XC9508
Series
ELECTRICAL CHARACTERISTICS
XC9508xxxCAx
Common Characteristics
PARAMETER Supply Current 1 Supply Current 2 Stand-by Current (*1) Input Voltage Range CE `H' Level Voltage CE `L' Level Voltage CE `H' Level Current CE `L' Level Current MODE 'H' Level Voltage*XC9508A MODE 'H' Level Voltage*XC9508C MODE 'L' Level Voltage*XC9508A MODE 'L' Level Voltage*XC9508C MODE 'H' Level Current MODE 'L' Level Current SYMBOL IDD1 IDD2 ISTB VIN VCEH VCEL ICEH ICEL VMH VMH VML VML IMH IML CONDITIONS VIN=CE=DCOUT=5.0V VIN=CE=5.0V, DCOUT=0V VIN=6.5V, CE=0V MIN. 2.4 0.6 VSS - 0.1 - 0.1 0.6 0.6 VSS VSS - 0.1 - 0.1 TYP. 250 300 0.5 MAX. 310 360 2.5 6.0 VDD 0.25 0.1 0.1 VDD VDD 0.25 0.25 0.1 0.1 UNITS A A A V V V A A V V V V A A Topr=25
CIRCUIT
1 1 1 3 3 1 1 2 3 2 3 1 1 Topr=25
DC/DC Converter (2.2V product)
PARAMETER Supply Current 1 *XC9508A Supply Current 2 *XC9508A PFM Supply Current 1 * 9508C PFM Supply Current 2 * 9508C Output Voltage Oscillation Frequency Maximum Duty Ratio Minimum Duty Ratio PFM Duty Ratio U.V.L.O. Voltage (*2) LX SW `High' ON Resistance (*3) LX SW `Low' ON Resistance LX SW `High' Leak Current (*12) LX SW `Low' Leak Current (*12) Maximum Output Current Current Limit (*9) Efficiency (*4) Output Voltage Temperature Characteristics Soft-Start Time Latch Time (*5, 10) SYMBOL IDD_DC1 IDD_DC2 IDD_PFM1 IDD_PFM2 DCOUT(E) FOSC MAXDUTY MINDUTY PFMDUTY VUVLO RLXH RLXL IleakH IleakL Imax1 Ilim1 EFFI DCOUT ( ToprDCOUT) TSS Tlat Connected to the external components, IDOUT=100mA IDOUT=30mA -40Topr85 Connected to the external components, CE=0V VIN, IDOUT=1mA Connected to the external components, VIN=CE=5.0V, Short DCOUT by 1 resistor CONDITIONS VIN=CE=DCOUT=5.0V VIN=CE=5.0V, DCOUT=0V VIN=CE=DCOUT=5.0V VIN=CE=5.0V, DCOUT=0V Connected to the external components, IDOUT=30mA Connected to the external components, IDOUT=10mA DCOUT=0V DCOUT=VIN Connected to the external components, No load Connected to the external components DCOUT=0V, LX=VIN-0.05V Connected to the external components, VIN=5.0V VIN=LX=6.0V, CE=0V VIN=6.0V, LX=CE=0V Connected to the external components 2.156 1.02 100 21 1.00 600 1.0 2 MIN. TYP. 200 250 250 300 2.200 1.20 30 1.40 0.5 0.5 0.05 0.05 1.1 90 100 5 8 MAX. 280 330 310 360 2.244 1.38 0 38 1.78 0.9 0.9 1.00 1.00 10 25 UNITS A A A A V MHz % % % V A A mA A % ppm/ mS mS
CIRCUIT
1 1 1 1 3 3 4 4 3 3 5 3 11 11 3 6 3 3 3 10
Data Sheet ud200541
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XC9508 Series
ELECTRICAL CHARACTERISTICS (Continued)
XC9508xxxCAx (Continued)
Regulator (1.8V product)
PARAMETER Output Voltage Maximum Output Current Load Regulation Dropout Voltage 1 (*6) Dropout Voltage 2 Line Regulation Current Limit Short-Circuit Current Ripple Rejection Rate Output Voltage Temperature Characteristics SYMBOL VROUT(E) Imax2 VROUT Vdif 1 Vdif 2 VROUT VINVROUT Ilim2 Ishort PSRR VROUT ToprVROUT 1mAIROUT100mA IROUT=30mA IROUT=100mA IROUT=30mA VROUT(T)+1VVIN6V VROUT=VROUT(E) x 0.9 VROUT=VSS VIN={VOUT(T)+1.0} VDC+0.5Vp-pAC, IROUT=30mA, f=1kHz IROUT=30mA -40Topr85 CONDITIONS IROUT=30mA MIN. 1.764 200 240 TYP. 1.800 15 30 100 0.05 300 30 60 100 MAX. 1.836 50 200 200 0.25 UNITS V mA mV mV mV %/V mA mA dB ppm/ Topr=25 CIRCUIT 2 2 2 2 2 2 7 7 12 2
Detector (2.7V product)
PARAMETER Detect Voltage Hysteresis Range VD Output Current Output Voltage Temperature Characteristics SYMBOL VDF(E) VHYS IVD VDF ToprVDF CE=0V VHYS=[VDR(E)
(*11)
CONDITIONS - VDF(E)] / VDF(E) x 100
MIN. 2.646 2 1 -
TYP. 2.700 5 100
MAX. 2.754 8 -
UNITS V % mA ppm/
CIRCUIT 8 8 9 8
VDOUT=0.5V, CE=0V -40Topr85
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 ()= 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 1 of resistance from a state of operation and is set to DCOUT=0V from current limit pulse generating. *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 5.0A (maximum) may leak.
( 7) ( 8)
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Data Sheet ud200541
XC9508
Series
TEST CIRCUITS
Circuit 1 Supply Current, Stand-by Current, CE Current, MODE current Circuit 2 Output Voltage (VR), Load Regulation, Dropout Voltage, Maximum Output Current, (MODE Voltage)
Circuit 3
Output Voltage (DC/DC) Oscillation Frequency, UVLO Voltage, Soft-start Time, CE Voltage, Maximum Output Current, Efficiency, (PFM Duty Cycle), (MODE Voltage)
Circuit 4
Minimum Duty Cycle, Maximum Duty Cycle
Circuit 5
Lx ON Resistance
Circuit 6
Current Limit 1 (DC/DC)
Data Sheet ud200541
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XC9508 Series
TEST CIRCUITS (Continued)
Circuit 7 Current Limit 2 (VR), Short Circuit Current (VR) Circuit 8 Detect Voltage, Release Voltage (Hysteresis Range)
Circuit 9
VD Output Current
Circuit 10
Latch Time
Circuit 11
Off-Leak
Circuit 12
Ripple Rejection Rate
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Data Sheet ud200541
XC9508
Series
TYPICAL APPLICATION CIRCUIT
FOSC 1.2MHz 600KHz 300kHz
L 4.7H (CDRH4D28C, SUMIDA) 10H (CDRH5D28, SUMIDA) 22H (CDRH6D28, SUMIDA)
MSOP-10 (TOP VIEW)
CIN 4.7F (ceramic, TAIYO YUDEN)
CL1 10F (ceramic, TAIYO YUDEN) VROUT2.0V VROUT2.0V Vdif1.0V Vdif1.0V
CL2 (*2) 4.7F (ceramic, TAIYO YUDEN) 1.0F (ceramic, TAIYO YUDEN) 4.7F (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 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. The Schottky
However, in cases where high efficiency is required when using the DC/DC converter during in
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. The reference voltage source provides the reference voltage to ensure stable output voltage of the DC/DC converter. 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. 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
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XC9508 Series
OPERATIONAL EXPLANATION (Continued)
DC/DC Converter (Continued) 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. 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
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Data Sheet ud200541
XC9508
Series
OPERATIONAL EXPLANATION (Continued)
DC/DC Converter (Continued) 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. 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. When the driver transistor is turned off, the limiter circuit is then released from the current limit detection state. 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. 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 through . 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
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. The reference voltage source provides the reference voltage to ensure stable output voltage of the regulator. The error amplifier compares the reference voltage with the signal from VROUT, and the amplifier controls the output of the Pch driver transistor. 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
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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) 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 0.6A (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 0A (TYP.). 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:4.7H(CDRH4D28C,SUMIDA) CIN:4.7F(ceramic) CL:10F(ceramic)
< External Components> L:4.7H(CDRH4D28C,SUMIDA) CIN:4.7F(ceramic) CL:10F(ceramic)
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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 DutyStep down ratio = DCOUT / VINx100 (%) 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:10H(CDRH5D28C,SUMIDA) CIN:4.7F(ceramic) CL:10F(ceramic) Step down ratio:1.8V / 6.0V=30%
Data Sheet ud200541
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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)xOnDuty / (2xLxFosc) + 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 = IDOUT2xRON VR power dissipation: PdVR=(DCOUT - VROUT)xIROUT RON: ON resistance of the built-in driver transistor to the DC/DC (= 0.5 ) RON=RponxP-chOnDuty / 100 + Rnonx(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)x85%* * 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.
CL1
CE
LX
+
MODE
+
DCOUT VROUT CL2
IC
VDOUT VDIN VIN ( Through Hole to SD )
+
AGND CIN
PGND
SD
L
Data Sheet ud200541
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
(9) U.V.L.O. Voltage vs. Ambient Temperature
Data Sheet ud200541
21
XC9508 Series
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
(A) DC/DC CONVERTER (Continued) (10-1) DC/DC LOAD TRANSIENT RESPONSE (DCOUT:1.8V, Fosc:1.2MHz) (10-1) DC/DC 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
(3) Shutdown Current VS. Ambient Temperature
Data Sheet ud200541
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

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