628 The SDB High Efficiency 1.2MHz 2A Step Up Converter
FEATURES
• Integrated 80mΩ Power MOSFET
• 2V to 24V Input Voltage金字部首
• 1.2MHz Fixed Switching Frequency
• Internal 4A Switch Current Limit
• Adjustable Output Voltage
• Internal Compensation
• Up to 28V Output Voltage
• Automatic Pul Frequency Modulation
Mode at Light Loads
• up to 97% Efficiency
• Available in a 6-Pin SOT23-6 Package APPLICATIONS
我的英雄英语作文• Battery-Powered Equipment
• Set-Top Boxed
• LCD Bais Supply
• DSL and Cable Modems and Routers
• Networking cards powered from PCI
or PCI express slots
TYPICAL APPLICATION Figure 1. Basic Application Circuit
The FSB6 is a constant frequency, 6-pin SOT23 current mode step-up converter intended for small, low power applications. The switches at 1.2MHz and allows the u of tiny, low cost capacitors and inductors 2mm or less in height. Internal soft-start results in small inrush current and extends battery life.
features automatic shifting to pul frequency modulation mode at light loads. The includes under-voltage lockout, current limiting, and thermal overload protection to prevent damage in the event of an output overload. The is available in a small 6-pin SOT-23 package.2个字的网名
Efficiency
Iout (mA)
Figure 2. Efficiency Curve
E
f
f
i
c
i
e
n
c
y
(
%
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GENERAL DESCRIPTION 28
FSB628
The FSB628
FSB628
FSB628
FSB628
IN, EN voltages ………..….…… -0.3V to 26V
Operating Temperature….... -40°C to +85°C FB Voltages ................................-0.3V to 6V Junction Temperature ………………...160°C
SW Voltage ……………………..-0.3V to 30V Storage Temperature Range -65°C to 150°C Peak SW Sink and Source Current ………4A Lead Temperature (Soldering, 10s) ...+300°C
PACKAGE/ORDER INFORMATION
3
124
6SOT23-5
IN
GND
FB
SW
EN
(MT3540)5
NC
PIN DESCRIPTION
PIN NAME FUNCTION
1 SW Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the power inductor and output rectifier to SW. SW can swing between GND and 28V.
2 GND Ground Pin
3 FB Feedback Input. The FB voltage is 0.6V. Connect a resistor divider to FB.
4 EN Regulator On/Off Control Input. A high input at EN turns on the converter, and a low input turns it off. When not ud, connect EN to the input supply for automatic startup.
5 IN Input Supply Pin. Must be locally bypasd. 6
NC
NC
ABSOLUTE MAXIMUM RATINGS SOT23-6 ()
FSB628 FSB628
ELECTRICAL CHARACTERISTICS
(V IN=V EN=5V, T A = 25°C, unless otherwi noted.)
Parameter Conditions MIN TYP MAX unit Operating Input Voltage 2 24 V Under Voltage Lockout 1.98 V Under Voltage Lockout Hysteresis 100 mV Current (Shutdown) V EN= 0V 0.1 1 µA Quiescent Current (PFM) V FB=0.7V，No switch 100 200 µA Quiescent Current (PWM) V FB=0.5V，switch 1.6 2.2 mA Switching Frequency 1.2 MHz Maximum Duty Cycle V FB = 0V 90 % EN Input High Voltage 1.5 V EN Input Low Voltage 0.4 V FB Voltage 0.588 0.6 0.612 V FB Input Bias Current V FB = 0.6V -50 -10 nA SW On Resistance (1) 80 150 mΩSW Current Limit (1) V IN= 5V, Duty cycle=50% 4 A SW Leakage V SW = 20V 1 μA Thermal Shutdown 155 ℃
Note:
1) Guaranteed by design, not tested.
The us a fixed frequency, peak current
mode boost regulator architecture to regulate voltage at the feedback pin. The operation of the can be understood by referring to the block diagram of Figure 3. At the start of each oscillator cycle the MOSFET is turned on through the control circuitry. To prevent sub-harmonic oscillations at duty cycles greater than 50 percent, a stabilizing ramp is added to the output of the current n amplifier and the result is fed into the negative input of the PWM comparator. When this voltage equals
The output voltage of the error amplifier the power MOSFET is turned off. The voltage at the output of the error amplifier is an amplified version of the difference between the 0.6V bandgap reference voltage and the feedback voltage. In this way the peak current level keeps the output in regulation. If the feedback voltage starts to drop, the output of the error amplifier increas. The results in more current to flow through the power MOSFET, thus
increasing the power delivered to the output. The has internal soft start to limit the amount of input current at startup and to also limit the amount of overshoot on the output.
Figure 3. Functional Block Diagram
OPERATION
FSB628FSB628FSB628
TYPICAL OPERATING CHARACTERISTICS
Efficiency Curve
柳亚子故居
Iout (mA)
line Regulation
Vin (V)
Freq VS Vin
Efficiency Curve
Iout(mA)
Load regualation
Iout (mA)
Efficiency VS Vin
E f f i c i e n c y
V o u t (V )
C u r r e n t l i m i t (A )
V o u t (V )
Setting the Output Voltage
The internal reference VREF is 0.6V (Typical).The
output voltage is divided by a resistor divider,R1 and R2 to the FB pin. The output voltage is given by
)1(2
1
R R V V REF OUT +
×= Inductor Selection
The recommended values of inductor are 4.7 to 22μH. Smal l size and better efficiency are the major concerns for portable device, such as ud for mobile phone. The inductor should have low core loss at 1.2MHz and low DCR for better efficiency. To avoid inductor saturation current rating should be considered.
Capacitor Selection
形象推广Input and output ceramic capacitors of 22μF are recommended for applications. For better voltage filtering, ceramic capacitors with low ESR are recommended. X5R and X7R types are suitable becau of their wider voltage and temperature ranges.
Diode Selection疫情班会
Schottky diode is a good choice for
becau of its low forward voltage drop and fast revers recovery. Using Schottky diode can get better efficiency. The high speed rectification is also a good characteristic of Schottky diode for high switching frequency. Current rating of the diode must meet the root mean square of the peak current and output average current multiplication as following :
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OUT D I I RMS I ×≈)(
The diode ’ s rever breakdown voltage should be
larger than the output voltage.
Layout Consideration
For best performance of the , the following guidelines must be strictly followed.
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Input and Output capacitors should be placed
clo to the IC and connected to ground plane to reduce noi coupling.
The GND should be connected to a strong
ground plane for heat sinking and noi protection.
Keep the main current traces as possible as
short and wide.
SW node of DC-DC converter is with high
frequency voltage swing. It should be kept at a small area.
Place the feedback components as clo as
possible to the IC and keep away from the noisy devices.
APPLICATION INFORMATION FSB628FSB628FSB628FSB628
