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YB1685
2A 380KHz 32V PWM Buck DC/DC Converter
Description
The YB1685 is a 380 KHz fixed frequency monolithic step down switch mode regulator with a built in internal Power MOSFET. It achieves 2A continuous output current over a wide input supply range with excellent load and line regulation. The device includes a voltage reference, oscillation circuit, error amplifier, internal PMOS and etc. The PWM control circuit is able to adjust the duty ratio linearly from 0 to 100%. An enable function, an over current protection function and a short circuit protection function are built inside. An internal compensation block is built in to minimize external component count. The YB1685 serves as ideal power supply units for portable devices.
Features
2A Constant Output Current 140m RDSON Internal Power PMOSFET Switch Up to 92% Efficiency Fixed 380KHz Frequency Wide 3.6V to 32V Input Voltage Range Output Adjustable from 1.235V to 30V Output Current Protection Built in Frequency Compensation Built in Thermal Shutdown Function Built in Current Limit Function SOP8 Package is Available The Minimum Dropout up to 0.3V Pb-free Package
Applications
Portable DVD LCD Monitor / TV Battery Charger ADSL Modem Telecom / Networking Equipment
Typical Application Circuit
Figure 1: Typical Application Circuit
YB1685 Rev.1.0
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YB1685
2A 380KHz 32V PWM Buck DC/DC Converter
Pin Configuration
NC VIN SW GND
1 2 3 4
SOP-8
8 7 6 5
NC EN NC FB
Figure 2: Pin Configuration
Pin Description
Table 1
Pin 1,6,8
Name NC Not Connect.
Description
2
VIN
Supply Voltage Input Pin. YB1685 operates from a 3.6V to 32VDC voltage. Bypass VIN to GND with a suitably large capacitor to eliminate noise on the input. Power Switch Output Pin. SW is the switch node that supplies power to the output. Ground Pin. Care must be taken in layout. This pin should be placed outside of the Schottky Diode to output capacitor ground path to prevent switching current spikes from inducing voltage noise into YB1685. Feedback Pin. Through an external resistor divider network, FB senses the output voltage and regulates it. The feedback threshold voltage is 1.235V. Enable Pin. EN is a digital input that turns the regulator on or off. Drive EN pin high to turn on the regulator, drive it low to turn it off.
3
SW
4
GND
5
FB
7
EN
Ordering Information
Order Number YB1685SPX8P Package Type SOP-8 Supplied As 2500 units Tape & Reel Package Marking Please contact sales representative
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YB1685 Rev.1.0
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YB1685
2A 380KHz 32V PWM Buck DC/DC Converter
Absolute Maximum Ratings
Input Voltage............................. -0.3V to 32V Feedback Pin Voltage .................-0.3V to VIN Enable Pin Voltage.................... -0.3V to 12V Switch Pin Voltage ......................-0.3V to VIN Power Dissipation .............. Internally Limited Operating Junction Temperature......... 150C Storage Temperature ............ -65C to 150C
Recommended Operating Conditions
Input Voltage............................ 3.6V to 32V Operating Junction Temperature ... -40C to 125C Operating Ambient Temperature.......-40C to 85C
Lead Temperature (Soldering, 10 sec)... 260C ESD (HBM).......................................2000V
Note: Stresses greater than those listed under Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.
Electrical Characteristics
Table 2 (VCC = 12V, TA=25C, unless otherwise specified.) Description Input Voltage Shutdown Supply Current Supply Current Feedback Voltage Feedback Bias Current Switch Current Limit Oscillator Frequency EN Pin Threshold EN Pin Input Leakage Current Internal PMOS RDSON Max. Duty Cycle Efficiency Thermal Shutdown Symbol VIN ISTBY ICC VFB IFB ILIM FOSC VEN IH IL RDSON DMAX TOTSD VEN = 2.5V VEN = 0.5V VIN O 12V, VFB =0V VEN = 12V, IOUT = 2A VFB = 0V, ISW = 0.1A VIN = 12V, VOUT = 5V, IOUT = 2A 320 0.7 VEN = 0V VEN = 2V, VFB = 1.3V VIN = 3.6V to 23V VFB = 1.3V 1.21 Test Conditions MIN 3.6 30 3.6 1.235 0.1 3 380 1.2 -0.1 -3 140 100 92 165 TYP MAX 32 90 4 1.26 0.5 4 440 1.7 -1 -10 Units V A mA V A A KHz V A A m % % C
YB1685 Rev.1.0
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YB1685
2A 380KHz 32V PWM Buck DC/DC Converter
Typical Performance Characteristics
Efficiency V.S Load (Vin=12V)
System Efficiency(%)
Output Load Current(A)
YB1685 Rev.1.0
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YB1685
2A 380KHz 32V PWM Buck DC/DC Converter
Function Block
Figure 3: Function Block
Functional Description
VIN This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be present at this pin to minimize voltage transients and to supply the switching currents needed by the regulator. Gnd Circuit ground. SW Internal switch. The voltage at this pin and switches between (VIN - VGS) approximately - 0.5V, with a duty cycle of approximately VOUT / VIN. To minimize coupling to sensitive circuitry, the PC board copper area connected to this pin should be kept a minimum.
YB1685 Rev.1.0
FB Senses the regulated output voltage to complete the feedback loop. EN Allows the switching regulator circuit to be shutdown using logic level signals thus dropping the total input supply current to approximately 30A. Pulling this pin below a threshold voltage of approximately 0.7V turns the regulator down, and pulling this pin above 1.3V (up to a maximum of 12V) shuts the regulator on. For automatic star up condition, can be implemented by the addition of a resistive voltage divider from VIN to GND.
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YB1685
2A 380KHz 32V PWM Buck DC/DC Converter
Thermal Considerations The SOP8 package needs a heat sink under most conditions. The size of the heat sink depends on the input voltage, the output voltage, the load current and the ambient temperature. The YB1685 junction temperature rises above ambient temperature for a 2A load and different input and output voltages. The data for these curves was taken with the YB1685 (SOP8 package) operating as a buck-switching regulator in an ambient temperature of 25 C (still air). These temperature rise numbers are all approximate and there are many factors that can affect these temperatures. Higher ambient temperatures require more heat sinking. For the best thermal performance, wide copper traces and generous amounts of printed circuit board copper should be used in the board layout. (Once exception to this is the output (switch) pin, which should not have large areas of copper.) Large areas of copper provide the best transfer of heat (lower thermal resistance) to the surrounding air, and moving air lowers the thermal resistance even further. Package thermal resistance and junction temperature rise numbers are all approximate, and there are many factors that will affect these numbers. Some of these factors include board size, shape, thickness, position, location, and even board temperature. Other factors are, trace width, total printed circuit copper area, copper Thick ness, single or double-sided, multi-layer board and the amount of solder on the board. The effectiveness of the PC board to dissipate heat also depends on the size, quantity and spacing of other components on the board, as well as whether the surrounding air is still or moving. Furthermore, some of these components such as the catch diode will add heat to the PC board and the heat can vary as the input voltage changes. For the inductor, depending on the physical size, type of core material and the DC resistance, it could either act as a heat sink taking heat away from the board, or it could add heat to the board.
YB1685 Rev.1.0
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YB1685
2A 380KHz 32V PWM Buck DC/DC Converter
Typical Application Circuit
YB1685 Rev.1.0
www.yobon.com.tw
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YB1685
2A 380KHz 32V PWM Buck DC/DC Converter
Schottky Rectifier Selection Guide
YB1685 Lists some rectifier manufacturers.
VIN (Max)
2A Load Current Part Number B220 Diodes, Inc. Pan Jit International Pan Jit International International Rectifier Diodes, Inc. Pan Jit International General Semiconductor, Pan Jit International General Semiconductor SK23 SR22 20QB030 B230 Vendor
20V
30V
SK23 SR23 SS23
Output Voltage vs. R1, R2 Resistor Selection Guide ( VOUT = ( 1 + R1 / R2 ) * 1.235V )
YB1685 VOUT vs. R1, R2 Select Table
VOUT 1.8V 2.5V 3.3V 5V 9V 12V
R1 5.1K 5.1K 2.7K 11K 43K 13K
R2 11K 5K 1.6K 3.6K 6.8K 1.5K
YB1685 Rev.1.0
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YB1685
2A 380KHz 32V PWM Buck DC/DC Converter
Package Information (SOP-8)
NOTICE: The information described herein is subject to change without notice. Yobon does not assume any responsibility for use of any circuitry or applications described herein, nor does it convey any patent license.
YB1685 Rev.1.0
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