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1.2MHZ MICROPOWER SYNCHRONOUS STEP-UP CONVERTER
FSP3603
FEATURES
High Efficiency: Up to 92% 1.2MHz Constant Switching Frequency 3.3V Output Voltage at IOUT=100mA from a Single AA Cell; 3.3V Output Voltage at IOUT=400mA from two AA cells Low Start-up Voltage: 0.85V Integrated main switch and synchronous rectifier. No Schottky Diode Required 2.5V to 5V Output Voltage Range Automatic Pulse Skipping Mode Operation Tiny External Components <1 A Shutdown Current Antiringing Control Reduces EMI Space Saving 6-Pin Thin SOT23 Package
GENERAL DESCRIPTION
The FSP3603 is a 1.2MHz constant frequency, current mode PWM step-up converter. It can supply 3.3V output voltage at 100mA from a single AA Cell. The device integrates a main switch and a synchronous rectifier for high efficiency without an external Schottky diode. A switching frequency of 1.2MHz allows the use of tiny, low profile inductors and ceramic capacitors. The current mode PWM operation with internal compensation provides excellent line and load transient characteristics. The FSP3603 features Pulse Skipping Mode operation at light loads to avoid unacceptable ripple voltage. The FSP3603 is offered in a low profile (1mm) small 6-Pin SOT23 Package
APPLICATIONS
Cellular and Smart Phones Microprocessors and DSP Core Supplies Wireless and DSL Modems MP3 Player Digital Still and Video Cameras Portable Instruments
PIN CONFIGURATION
(Top View)
VIN
VOUT SHDN
6
5
4
1
SW
2
GND
3
FB
Pin Number 1 2 3 4 5 6
Pin Name SW GND FB SHDN VOUT VIN
Pin Function Power Switch Pin. It is the switch node connection to Inductor. Ground Pin Feedback Input Pin. Connect FB to the center point of the external resistor divider. The feedback threshold voltage is 1.23V. Chip Shutdown Signal Input. Logic high is normal operation mode, Logic Low is Shutdown. Typically, this pin is connected to VIN through a 1 M resistor. Power Output Pin. VOUT is held 0.6V below than VIN in shutdown. Power Supply Input. Must be closely decoupled to GND, Pin 2, with a 4.7F or greater ceramic capacitor.
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1.2MHZ MICROPOWER SYNCHRONOUS STEP-UP CONVERTER ABSOLUTE MAXIMUM RATINGS(NOTE 1)
Parameter VIN Rating
FSP3603
Unit
V - 0.3 ~ +6 VOUT - 0.3 ~ +6 V VSW - 0.3 ~ +6 A FB SHDN Voltages - 0.3 ~ +6 - 40 ~ +85 Operating Temperature RangeNote 2 Lead Temperature (Soldering 10 sec.) + 300 250(JA) Thermal Resistance(Note 3) /W 110(JC) Storage Temperature Range - 65 ~ +150 Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: TJ = TA + (PD) x (250C/W Note 3: Thermal Resistance is specified with approximately 1 square of 1 oz copper.
ELECTRICAL CHARACTERISTICS (NOTE 4)
(VIN= 1.2V, VOUT= 3.3V, TA=25, Unless otherwise noted) Parameter Condition Output Voltage Range Minimum Start-Up Voltage Minimum Operating Voltage Switching Frequency Max Duty Cycle Current Limit Delay to Output Feedback Voltage NMOS Switch Leakage PMOS Switch Leakage NMOS Switch On Resistance ILOAD = 1mA VSHDN= VIN 0.95 - 40 ~ +85 VFB = 1.15V - 40 ~ +85 Guaranteed by design - 40 ~ +85 VSW = 5V VSW = 0V VOUT = 3.3V VOUT = 5V VOUT = 3.3V PMOS Switch On Resistance NMOS Current Limit Quiescent Current (Active) Measured on VOUT VOUT = 5V 600 1.192 0.85 80 Min. 2.5 0.85 0.5 1.2 1.2 85 40 1.230 0.1 0.1 0.40 0.35 0.70 0.60 850 300 500 1.268 5 5 Typ. Max. 5 1.0 0.65 1.5 1.5 MHz % ns V A A Unit V V V
mA A
Shutdown Current VSHDN=0V Line Regulation VIN = 0.8V to 3.0V, IOUT = 10mA Load Regulation IOUT = 1 mA to 100mA SHDN Input Threshold 0.35 SHDN Input Current VSHDN = 5.5V Note 4: 100% production test at +25C. Specifications over the temperature range are and characterization.
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0.01 1 A 1 %/V 0.02 %/mA 0.60 1.50 V 0.01 1 A guaranteed by design
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1.2MHZ MICROPOWER SYNCHRONOUS STEP-UP CONVERTER
FUNCTIONAL BLOCK DIAGRAM
FSP3603
FUNCTION DESCROPTION
Operation The FSP3603 is a synchronous step-up DC-DC converter. It utilizes internal MOSFETs to achieve high efficiency over the full load current range. It operates at a fixed switching frequency of 1.2MHz, and uses the slope compensated current mode architecture. The device can operate with input voltage even below 1 V and the typical start-up voltage is 0.85V. Synchronous Rectification The FSP3603 integrates a synchronous rectifier to improve efficiency as well as to eliminate the external Schottky diode. The synchronous rectifier is used to reduce the conduction loss contributed by the forward voltage of Schottky diode. The synchronous rectifier is realized by a P-CH MOSFET with gate control circuitry that incorporates relatively complicated timing concerns. Low Voltage Start-Up The FSP3603 can start up at supply voltage down to 0.85V. During start-up, the internal low voltage start-up circuitry controls the NMOS switch to maximum peak inductor current. The device leaves the start-up mode once the VOUT exceeds 2.3V. A Comparator (VOUT GOOG Comp) monitors the output voltage and allows the chip into normal operation once the VOUT exceeds 2.3V. The device is biased by VIN during start-up while biased by VOUT once VOUT exceeds VIN then the operation will be independent of VIN. Current Mode PWM Control The FSP3603 is based on a slope compensated current mode control topology. It operates at a fixed frequency of 1.2MHz. At the beginning of each clock cycle, the main switch (NMOS) is turned on and the inductor current starts to ramp. After the maximum duty cycle or the sense current signal equals to the error amplifier(EA) output, the main switch is turned off and the synchronous switch (PMOS) is turn on. This control topology features cycle by cycle current limiting which can prevent the main switch from overstress and prevent external inductor from saturation. Pulse Skipping Mode At very light load, the FSP3603 automatically switches into Pulse Skipping Mode to improve efficiency. During this mode, the PWM control will skip some pulses to maintain regulation. If the load increases and the output voltage drops, the device will automatically switch back to normal PWM mode and maintain regulation. Antiringing Control An antiringing circuitry is included to remove the high frequency ringing that appears on the SW pin when the inductor current goes to zero. In this case, a ringing on the SW pin is induced due to remaining energy stored in parasitic components of switch and inductor. The antiringing circuitry clamps the voltage internally to battery voltage
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1.2MHZ MICROPOWER SYNCHRONOUS STEP-UP CONVERTER
and therefore dampens this ringing. Device Shutdown When SHDN is set logic high, the FSP3603 is put into operation. If SHDN is set logic low, the device is put into shutdown mode and consumes lower than 1 A current. After start-up timing, the internal circuitry is supplied by VOUT, however, if shutdown mode is enabled, the internal circuitry will be supplied by battery again.
FSP3603
TYPICAL CHARACTERISCITS
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1.2MHZ MICROPOWER SYNCHRONOUS STEP-UP CONVERTER
TYPICAL CHARACTERISCITS (CONTINUED)
FSP3603
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FSP3603
TYPICAL CHARACTERISCITS (CONTINUED)
TYPICAL APPLICATION CIRCUIT
APPLICATION INFORMATION
Setting the Output Voltage An external resistor divider is used to set the output voltage. The output voltage of the switching regulator (VOUT) is determined by the following equation:
Table 1 list the resistor selection for output voltage setting. R1() R2() VOUT 3.3V 1.02M 604k 5.0V 1.02M 332k Inductor Selection The high switching frequency of 1.2MHz allows for small surface mount inductors. For most designs, the FSP3603 operates with inductors of 4.7H to 10H.The equation below can help to select the inductor, the
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maximum output current can be get by this equation; where is the efficiency, IPEAK is the peak current limit, f is the switching frequency, L is the inductance value and D is the duty cycle.
FSP3603
Larger inductors mean less inductor current ripple and usually less output voltage ripple. Larger inductors also mean more load power can be delivered. But large inductors are also with large profile and costly. The inductor ripple current is typically set for 20% to 40% of the maximum inductor current. When selecting an inductor, the DC current rating must be high enough to avoid saturation at peak current. For optimum load transient and efficiency, the low DCR should be selected. Table 2 lists some typical surface mount inductors that meet target applications for the FSP3603: Max DCR (m) 108.7 182 72 101 109 128 45 68 90 Rated D.C. Current (A) Size WxLxH (mm)
Part Number Sumida CR43 Sumida CDRH4D 28 Toko D53LC
L (H) 4.7 10 4.7 5.6 6.8 10 4.7 6.8 10
1.15 4.3x4.8x3. 5 1.04 1.32 1.17 5.0x5.0x3. 0 1.12 1.00 1.87 5.0x5.0x3. 1.51 0 1.33
Output Capacitor Selection The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. A 2.2F to 10F output capacitor is sufficient for most applications. If output capacitor is larger than 10F, a phase lead capacitor must be included to maintain enough phase margin. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current ratings. Input Capacitor Selection The input capacitor reduces the surge current drawn from the input and switching noise from the device. A minimum 4.7F input capacitor is needed for most applications. The input capacitor impedance at the switching frequency should be less than input source impedance to prevent high frequency switching current passing to the input. A low ESR input capacitor sized for maximum RMS current must be used. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. Output Diode Selection An Shottky diode should be included when the output voltage is above 4.5V. The Schottky diode is optional for the output voltage not more than 4.5V, but can improve efficiency by about 2% to 3%.
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ORDERING INFORMATION
FSP3603XXX Package: TC: TSOT23-6L Packing: A: Tape & Reel Temperature Grade: D: -40~85
FSP3603
MARKING INFORMATION
UBYMX
Internal Code Date Code: Y: Year (1=2001) M: Month (1~9, O, N, D) Part Number: FSP3603
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FSP3603
PACKAGE INFORMATION
D
e1
6
5
4
E1 E
A2 A
e
b
C L
Symbol A A1 A2 b C D E E1 L e e1
Dimensions In Millimeters Min. Max. 0.900 1.100 0.000 0.100 0.900 1.000 0.300 0.500 0.100 0.200 2.800 3.100 2.50 3.100 1.500 1.700 0.200 0.550 0.95 Bsc. 1.90 Bsc. 0 10
A1
1
2
3
Dimensions In Inches Min. Max. 0.036 0.044 0.000 0.004 0.036 0.040 0.012 0.020 0.004 0.008 0.112 0.124 0.100 0.124 0.060 0.068 0.002 0.022 0.038 Bsc. 0.076 Bsc. 0 10
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