TS3420 2A, 1.25MHz Synchronous Buck Converter SOT-26 Pin Definition: 1. EN 2. Ground 3. Switching Output 4. Input 5. Ground 6. Feedback General Description TS3420 is a high efficiency monolithic synchronous buck regulator using a constant frequency, current mode architecture. The device is available in an adjustable version. Supply current with no load is 200uA and drops to <1uA in shutdown. The 2.8V to 5.5V input voltage range makes TS3420 ideally suited for single Li-Ion, two to three AA battery-powered applications. 100% duty cycle provides low dropout operation, extending battery life in portable systems. Switching frequency is internally set at 1.25MHz, allowing the use of small surface mount inductors and capacitors. The internal synchronous switch increases efficiency and decreases need of an external schottky diode. Low output voltages are easily supported with the 0.6V feedback reference voltage. Features Application ● High Efficiency: Up to 96% ● 2.8V to 5.5V Input Voltage Range ● Output Voltage from 0.6V to VIN ● Short Circuit Protection (SCP) ● ● ● ● ● Build in Soft-Start Function ● 1.25MHz Constant Frequency Operation ● Up to 2A Output Current ● No Schottky Diode Required in Application Cellular Phones Digital Still Cameras Portable Electronics USB Devices Pin Description ● ≤1uA Shutdown Current ● Current Mode Operation for Excellent Line and Name EN GND Load Transient Response SW Ordering Information Part No. Package Packing TS3420CX6 RFG SOT-26 3Kpcs/ 7” Reel VCC FB Description Power-off pin H：normal operation L：Step-down operation stopped Ground pin Switch output pin. Connect external inductor here. Minimize trace area at this pin to reduce EMI. IC power supply pin Output Feedback pin Note: “G” denote for Halogen Free Product Application Circuit 1/9 Version: A12 TS3420 2A, 1.25MHz Synchronous Buck Converter Absolute Maximum Rating Characteristics Symbol Rating Unit VIN Pin Voltage VIN VSS - 0.3 to VSS + 6.5 V Feedback Pin Voltage VFB VSS - 0.3 to VIN + 0.3 V EN Pin Voltage VEN VSS - 0.3 to VIN + 0.3 V Switch Pin Voltage VSW VSS - 0.3 to VIN + 0.3 V Power Dissipation PD ( TJ-TA ) / θJA mW Storage Temperature Range TST -40 to +150 °C Operating Temperature Range TOP -40 to +85 °C TJ +125 Junction Temperature θJC Thermal Resistance from Junction to case θJA Thermal Resistance from Junction to ambient °C 50 o 100 o C/W C/W 2 Note: θJA is measured with the PCB copper area of approximately 1 in (Multi-layer). Electrical Specifications (Ta = 25oC, VIN=VRUN=3.6V unless otherwise noted) Characteristics Symbol Conditions Min Typ Max Units Input Voltage Range VIN 2.8 -- 5.5 V VIN UVLO Threshold VIN -- 2.2 -- V VIN UVLO Hysteresis VIN(hys) -- 0.35 -- V 0.588 0.6 0.612 V Feedback Voltage VFB TA =25℃ Feedback Bias Current IFB VFB=0.65V -- -- ±30 nA Quiescent Current ICCQ VFB=1V -- 200 350 uA Shutdown Supply Current ISD VEN =0V -- 0.1 1 uA 2.2 3 -- A Switching Current Limit ILIMIT Line Regulation △VOUT/VOUT VIN=2.5V to 5.5V -- 0.4 -- %/V Load Regulation △VOUT/VOUT IOUT=0.01 to 2A -- 1 -- % 1.0 1.25 1.5 MHz VIN=5V -- 120 - mΩ VFB=0.65V -- -- ±30 nA VIN = 5V (Note) -- 100 - mΩ Oscillation Frequency R DS(ON) of P-CH MOSFET Feedback Bias Current R DS(ON) of N-CH MOSFET FOSC RDSON IFB RDSON IOUT=300mA EN pin logic Input Threshold VENL -- -- 0.4 Voltage VENH 1.5 -- --. EN Pin Input Current IEN -- ±0.1 ±1 uA Thermal shutdown TDS -- 150 -- °C Thermal shutdown Hysteresis TSH -- 30 -- °C V Note: Guaranteed by Design 2/9 Version: A12 TS3420 2A, 1.25MHz Synchronous Buck Converter Block Diagram VIN SLOPE COMP OSC + REF Isense AMP - 0.6V SET Soft-Star FB + - RESET Icomp + PWM LOGIC NON-OVERLAP CONTROL SW + Izero COMP - Over-Temperature and Short-Circuit Protection GND Enable Logic EN Function Description Operation TS3420 is a monolithic switching mode step-down DC-DC converter. It utilizes internal MOSFETs to achieve high efficiency and can generate very low output voltage by using internal reference at 0.6V. It operates at a fixed switching frequency, and uses the slope compensated current mode architecture. This step-down DC-DC Converter supplies minimum 2A output current at input voltage range from 2.8V to 5.5V. Current Mode PWM Control Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for excellent load and line transient responses and protection of the internal main switch (P-Ch MOSFET) and synchronous rectifier (N-CH MOSFET). During normal operation, the internal P-Ch MOSFET is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. The current comparator, ICOMP, limits the peak inductor current. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current starts to reverse, as indicated by the current reversal comparator, IZERO, or the beginning of the next clock cycle. 3/9 Version: A12 TS3420 2A, 1.25MHz Synchronous Buck Converter Application Information Setting the Output Voltage Application circuit item shows the basic application circuit with TS3410 adjustable output version. The external resistor sets the output voltage according to the following formula: Table 1: Resistor Select for Output Voltage Setting VOUT R2 R1 1.2V 1.5V 1.8V 2.5V 3.3V 300K 300K 300K 150K 120K 300K 450K 600K 470K 540K Inductor Selection For most designs, the TS3410 operates with inductors of 2.2µH to 3.3µH. Low inductance values are physically smaller but require faster switching, which results in some efficiency loss. The inductor value can be derived from the following formula: Table 2: Inductor Select for Output Voltage Setting (VIN=3.6V) VOUT 1.2V 1.5V 1.8V 2.5V Inductor 2.7uH 2.7uH Part Number 7440430027 7440430027 WE-TPC Note: Part Type MH or M (www.we-online.com) 2.7uH 2.2uH 7440430027 7440430022 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 20% of the maximum load current 2A, ∆IL=400mA. For output voltages above 2.0V, when light-load efficiency is important, the minimum recommended inductor is 2.7µH. For optimum voltage-positioning load transients, choose an inductor with DC series resistance in the 50mΩ to 150mΩ range. For higher efficiency at heavy loads (above 200mA), or minimal load regulation (but some transient overshoot), the resistance should be kept below 100mΩ. 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 (2000mA+200mA) Input Capacitor Selection The input capacitor reduces the surge current drawn from the input and switching noise from the device. The input capacitor impedance at the switching frequency shall 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. A 10µF ceramic capacitor for most applications is sufficient. Output Capacitor Selection The output capacitor is required to be 10uF×2 to keep the output voltage ripple small and to ensure regulation loop stability. 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 Compensation Capacitor Selection The compensation capacitors for increasing phase margin provide additional stability. It is required and more than 27pF. Please refer to demo board schematic for design. 4/9 Version: A12 TS3420 2A, 1.25MHz Synchronous Buck Converter Electrical Characteristics Curve Figure 1. Output Voltage vs. Input Voltage Figure 2. Load Regulation (VOUT=3.3V) Figure 3. Quiescent Current vs. Input Voltage Figure 4. Switching Frequency vs. Input Voltage Figure 5. Output Voltage vs. Temperature Figure 6. Quiescent Current vs. Temperature 5/9 Version: A12 TS3420 2A, 1.25MHz Synchronous Buck Converter Electrical Characteristics Curve Figure 7. Frequency vs. Temperature Figure 8. Efficiency vs. Output Current Figure 9. VIN = 5V, VOUT = 1.2V, No Load Figure 10. VIN = 5V, VOUT = 1.2V, RLOAD=0.5ohm Figure 11. VIN = 3.3V, VOUT = 1.2V, No Load Figure 12. VIN = 5V, VOUT = 1.2V, RLOAD=0.5ohm 6/9 Version: A12 TS3420 2A, 1.25MHz Synchronous Buck Converter Electrical Characteristics Curve Figure 13. VIN = 3.3V, VOUT = 1.2V, IOUT=0~2A Figure 14. VIN = 5V, VOUT = 1.2V, IOUT=0~2A 7/9 Version: A12 TS3420 2A, 1.25MHz Synchronous Buck Converter SOT-26 Mechanical Drawing DIM SOT-26 DIMENSION MILLIMETERS INCHES MIN MIN TYP MAX TYP A A1 0.95 BSC 1.9 BSC MAX B C 2.60 1.40 2.80 1.50 3.00 1.70 0.0374 BSC 0.0748 BSC 0.1024 0.1102 0.1181 0.0551 0.0591 0.0669 D E 2.80 1.00 2.90 1.10 3.10 1.20 0.1101 0.0394 0.1142 0.0433 0.1220 0.0472 F G 0.00 0.35 -0.40 0.10 0.50 0.00 0.0138 0.0157 0.0039 0.0197 H I 0.10 0.30 0.15 -- 0.20 0.60 0.0039 0.0118 0.0059 -- 0.0079 0.0236 J 5º -- 10º 5º -- 10º arking Diagram GGYWX GG = Device Code Y = Year Code 2 = 2012 3 = 2013 W = Week Code 01 ~ 26 (A~Z) 27 ~ 52 (a~z) X = Internal ID Code 8/9 Version: A12 TS3420 2A, 1.25MHz Synchronous 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. 9/9 Version: A12