SB6284 SB6284SB6284 is available in a small SB6284 includes under The SB6284 features The SB6284 is a constant frequency, 628The SDB
High Efficiency 1.2MHz
2A Step Up Converter
FEATURES
• Integrated 80m Ω Power MOSFET • 2V to 24V Input Voltage
• 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太平小学
APPLICATIONS
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• Battery-Powered Equipment • Set-Top Boxed • LCD Bais Supply
张学友的祝福• DSL and Cable Modems and Routers • Networking cards powered from PCI or PCI express slots
TYPICAL APPLICATION
Figure 1. Basic Application Circuit
The SB6284 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.
The SB6284features
automatic shifting to pul frequency modulation mode at light loads. The
SB6284includes under
-voltage lockout, current limiting, and thermal overload protection to prevent damage in the event of an output overload. The
SB6284is available in a small
6-pin SOT-23
package.
Efficiency
Iout (mA)
Figure 2. Efficiency Curve
E f f i c
i e n c y (%)
GENERAL DESCRIPTION
SB6284SB6284 u Shouding
SB6284五大战役
IN, EN voltages ………..….…… -0.3V to 26V
Operating Temperature….... -40°C to +85°C FB Voltages ................................-0.3V to 6V Junction Temperature ………………...160°C
茄子饭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
6SOT23-5IN
GND
FB
SW
EN
(MT3540)5
NC
网络智能
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 ()
Shouding SB6284SB6284
(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.
SB6284 has internal soft start to limit the amount of SB6284 can be understood by referring to the block SB6284 us a fixed frequency, peak current The SB6284 us a fixed frequency, peak current
mode boost regulator architecture to regulate voltage at the feedback pin. The operation of the SB6284 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
SB6284 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
TYPICAL OPERATING CHARACTERISTICS
Efficiency Curve
Iout (mA)
line Regulation
Vin (V)
Freq VS Vin
关于勇气的名言
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 )
Diode is a good choice for SB6284 SB6284 ud
diode is a good choice for SB6284
山茶花提取物
For best performance of the SB6284 For best performance of the SB6284
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 SB6284 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
Input and output ceramic capacitors of 22μF are SB6284 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
diode is a good choice for SB6284 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 :
PEAK
OUT D I I RMS I ×≈)(
The diode ’ s rever breakdown voltage should be
larger than the output voltage.
For best performance of the SB6284 , the following guidelines must be strictly followed.
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
