TS2508A

TS2508A 3A / 330KHz PWM Buck Converter SOP-8 Pin Definition: 1. FB 5. Vss 2. Enable 6. Vss 3. Ocset 7. SW 4. Vcc 5. SW General Description TS2508A consists of step-down switching regulator with PWM control. These devise include a reference voltage source, oscillation circuit, error amplifier, internal PMOS and etc. TS2508A provides low-ripple power, high efficiency, and excellent transient characteristics. The PWM control circuit is able to very the duty ratio linearly form 0 up to 100%. This converter also contains an error amplifier circuit as well as a soft-start circuit that prevents overshoot at startup. An enable function, an over current protect function and short circuit protect function are built inside, and when OCP or SCP happens, the operation frequency will be reduced. Also, an internal compensation block is built in to minimum external component count. With the addition of an internal P-channel Power MOS, a coil, capacitors, and a diode connected externally, these ICs can function as step-down switching regulators. They serve as ideal power supply units for portable devices when coupled with the SOP-8 package, providing such outstanding features as low current consumption. Since this converter can accommodate an input voltage up to 20V, it is also suitable for the operation via an AC adapter. Features ● ● ● ● ● ● ● ● Input Voltage: 3.6V~23V Output Voltage: 0.8V~Vcc Duty Ratio: 0%~100% PWM Control Oscillation Frequency: 330kHz typ. Soft-Start (SS), Current Limit (CL), Enable Function Thermal Shutdown Function Short Circuit Protect (SCP) Built-in Internal SW P-Channel MOSFET Ordering Information Part No. TS2508ACS RL Package SOP-8 Packing 2.5Kpcs / 13” Reel Application ● ● Simple High-efficiency Step down Regulator On-Card Switching Regulators Absolute Maximum Rating Parameter VCC Pin Voltage Feedback Pin Voltage ON/OFF Pin Voltage Switch Pin Voltage Power Dissipation Storage Temperature Range Operating Temperature Range Operating Supply Voltage Output Current Thermal Resistance from Junction to case Thermal Resistance from Junction to ambient Symbol VCC VFB VEN VSW PD TST TOP VOP IO θJC θJA Rating Gnd -0.3 to Gnd +25 Gnd -0.3 to VCC Gnd -0.3 to VCC +0.3 Gnd -0.3 to VCC +0.3 Internally limited -40 to +150 -20 to +125 +3.6 to +23 3 25 70 Unit V V V V mW ℃ ℃ V A ℃/W ℃/W 1/8 Version: A09 TS2508A 3A / 330KHz PWM Buck Converter Electrical Specifications (VIN=12V, Ta=25oC unless otherwise noted) Characteristics Feedback Voltage Quiescent Current Feedback Bias Current Shutdown Supply Current OCSET pin bias current Switch Current Line Regulation Load Regulation Oscillation Frequency EN Pin Logic input threshold voltage EN Pin Input Current Soft-Start Time Internal P-MOS RDSON Efficiency Symbol VFB Iq IFB ISD IOCSET ISW ∆VOUT/VOUT IOCSET FOSC VSH VSL ISH ISL TSS RDSON EFFI Conditions IOUT =0.1A VFB =1.2V force driver off IOUT =0.1A VEN =0V Min 0.784 ---110 4 --260 2.0 ---0.3 ----- Typ 0.800 3 0.1 2 130 -1 0.3 330 --20 -10 4 90 55 92 91 Max 0.816 5 0.5 10 150 -2 0.5 400 -0.8 --8 140 90 --- Units V mA uA uA uA A % % KHz V uA uA ms mΩ mΩ % VCC = 5V~20V, IOUT =0.2A IOUT = 0.1 to 3A SW pin High (regulator ON) Low (regulator OFF) VEN =2.5V (ON) VEN =0.3V (OFF) VCC = 5V, VFB = 0V VCC = 12V, VFB = 0V IOUT = 2A VCC = 12V, VOUT = 5V IOUT = 3A Block Diagram Pin Assignment Name FB EN OCSET Vcc Description Feedback pin H:Normal operation (Step-down) L:Step-down operation stopped (All circuit deactivated) Add an external resistor to set max switch output current. IC power supply pin Name Vss Vss SW SW GND pin GND pin Description Switch pin. Connect external inductor & diode here Switch pin. Connect external inductor & diode here 2/8 Version: A09 TS2508A 3A / 330KHz PWM Buck Converter Application Circuit Typical Circuit L1 recommend value (VIN=12V, IOUT=3A ) VOUT L1 Value 1.8V 18uH 2.5V 22uH 3.3V 27uH 5V 33uH Function Descriptions PWM Control The TS2508A consists of DC/DC converters that employ a pulse-width modulation (PWM) system. In converters of the TS2508A, the pulse width varies in a range from 0 to 100%, according to the load current. The ripple voltage produced by the switching can easily be removed through a filter because the switching frequency remains constant. Therefore, these converters provide a low-ripple power over broad ranges of input voltage and load current. RDS(ON) Current Limiting The current limit threshold is setting by the external resistor (R3) connecting from VCC supply to OCSET pin. The internal 110uA sink current crossing the resistor sets the voltage at pin of OCSET. When the PWM voltage is less than the voltage at OCSET, an over-current condition is triggered. Please refer to the formula for setting the minimum current limit value: (Normally, The ISW(MAX) setting more than IOUT 1.2A) Example: ISW=(0.11mA * 2k + 0.08) / 70mΩ = 4.3A – (VIN=12V) ISW=(0.11mA * 3.3k + 0.08) / 1000mΩ = 4.4A – (VIN=5V) 3/8 Version: A09 TS2508A 3A / 330KHz PWM Buck Converter Function Descriptions (Continue) Setting the Output Voltage Application circuit item shows the basic application circuit with TS2508A adjustable output version. The external resistor sets the output voltage according to the following equation: Table 1: Resistor select for output voltage setting VOUT R2 R1 1.3K 6.8K 5V 5.6K 30K 1.5K 4.7K 3.3V 5.6K 18K 2.2K 4.7K 2.5V 5.6K 12K 1.8V 1.2K 1.5K 1.5V 2.2K 2K 1.2V 2K 1K 1V 2K 0.5K The R2 setting 5.6k that no load current can be reduce to under 4mA for EL CAP Input Capacitor Selection This capacitor should be located close to the IC using short leads and the voltage rating should be approximately 1.5 times the maximum input voltage. The RMS current rating requirement for the input capacitor of a buck regulator is approximately 1⁄2 the DC load current. A low ESR input capacitor sized for maximum RMS current must be used. A 220µF low ESR capacitor for most applications is sufficient Output Capacitor Selection The output capacitor is required to filter the output and provide regulator loop stability. The important capacitor parameters are; the 100KHz Equivalent Series Resistance (ESR), the RMS ripples current rating, voltage rating, and capacitance value. For the output capacitor, the ESR value is the most important parameter. The ESR can be calculated from the following formula. VRIPPLE = ∆IL x ESR = 0.33A x 130mΩ = 43mV An aluminum electrolytic capacitor's ESR value is related to the capacitance and its voltage rating. In most case, higher voltage electrolytic capacitors have lower ESR values. Most of the time, capacitors with much higher voltage ratings may be needed to provide the low ESR values required for low output ripple voltage. It is recommended to replace this low ESR capacitor by using a 330µF low ESR values < 130mΩ Inductor Selection For most designs, the operate with inductors of 12µH to 33µH. The inductor value can be derived from the following equation: Where is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in high ripple currents. Choose inductor ripple current approximately 15% of the maximum load current 3A, ∆IL=0.4A. The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation (3A+0.2A). 4/8 Version: A09 TS2508A 3A / 330KHz PWM Buck Converter Function Descriptions (Continue) Layout Guidance If you need low Tc & Tj or large PD (Power Dissipation), The dual SW pins (5&6) and Gnd pins (7&8) on the SOP-8 package are internally connected to die pad, The PCB layout should allow for maximum possible copper area at the SW pins. 1. Connect C3 to VCC and Gnd pin as closely as possible to get good power filter effect. 2. Connect R3 to VCC and OCSET pin as closely as possible. 3. Connect ground side of the C2 & D1 as closely as possible. Electrical Characteristics Curve Figure 1. Feedback Voltage vs. Input Voltage Figure 2.Quiescent Current vs. Input Voltage Figure 3. Frequency vs. Input Voltage Figure 4. Frequency vs. Temperature 5/8 Version: A09 TS2508A 3A / 330KHz PWM Buck Converter Electrical Characteristics Curve Figure 7. Feedback Voltage vs. Temperature Figure 8. Quiescent Current vs. Temperature Figure 9. Efficiency vs. Output Current Figure 10. Efficiency vs. Output Current 6/8 Version: A09 TS2508A 3A / 330KHz PWM Buck Converter SOP-8 Mechanical Drawing DIM A B C D F G K M P R SOP-8 DIMENSION MILLIMETERS INCHES MIN MAX MIN MAX. 4.80 5.00 0.189 0.196 3.80 4.00 0.150 0.157 1.35 1.75 0.054 0.068 0.35 0.49 0.014 0.019 0.40 1.25 0.016 0.049 1.27BSC 0.05BSC 0.10 0.25 0.004 0.009 0º 7º 0º 7º 5.80 6.20 0.229 0.244 0.25 0.50 0.010 0.019 Marking Diagram Y = Year Code M = Month Code (A=Jan, B=Feb, C=Mar, D=Apl, E=May, F=Jun, G=Jul, H=Aug, I=Sep, J=Oct, K=Nov, L=Dec) L = Lot Code 7/8 Version: A09 TS2508A 3A / 330KHz PWM Buck Converter Notice Specifications of the products displayed herein are subject to change without notice. TSC or anyone on its behalf, assumes no responsibility or liability for any errors or inaccuracies. Information contained herein is intended to provide a product description only. No license, express or implied, to any intellectual property rights is granted by this document. Except as provided in TSC’s terms and conditions of sale for such products, TSC assumes no liability whatsoever, and disclaims any express or implied warranty, relating to sale and/or use of TSC products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright, or other intellectual property right. The products shown herein are not designed for use in medical, life-saving, or life-sustaining applications. Customers using or selling these products for use in such applications do so at their own risk and agree to fully indemnify TSC for any damages resulting from such improper use or sale. 8/8 Version: A09