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Copyrights 2000-2021, Analog Technologies, Inc. All Rights Reserved. Updated on 4/9/2021 3 Analog Technologies ATI2305 DC-DC Converter Thermal Information Table 2. Parameter Package Symbol Maximum Unit Thermal Resistance (Junction to Case) SOT23-5Note θJC 130 /W℃ DFN 2×2-6 25 QFN 3×3-16 14 Thermal Resistance (Junction to Ambient) SOT23-5 θJA 250 DFN 2×2-6 68 QFN 3×3-16 35 Internal Power Dissipation SOT23-5 PD 400 mW DFN 2×2-6 980 QFN 3×3-16 1470 NOTE: The maximum output current for SOT23-5 package is limited by internal power dissipation capacity as described in Application Information hereinafter. CHARACTERISTICS TA = 25℃，VIN = 3.6V , VO = 1.8V , CIN = 10uF , L = 4.7uH , unless otherwise noted. Table 3. PARAMETER SYMBOL Test Conditions MIN TYP MAX UNITS Input Voltage Range V IN 2.5 5.5 V Regulated Feedback Voltage VFB 0.588 0.6 0.612 V Reference Voltage Line Regulation ΔVFB 0.3 %/V Regulated Output Voltage Accuracy VO I O=100mA -3 +3 % Peak Inductor Current I PK VIN=3V, VFB=0.5V or VO=90% 1.5 A Output Voltage Line Regulation LNR V IN=2.5V to 5V, IO=10mA 0.2 0.5 %/V Output Voltage Load Regulation LDR I O=1mA to 800mA 0.5 1.5 % Quiescent Current I Q No load 40 70 uA Shutdown Current I SD V EN=0V 0.1 1 uA Oscillator Frequency F OSC VO=100% 1.2 1.5 1.8 MHz VFB=0V or VO=0V 500 KHz Drain-Source On-State Resistance RDS(ON) I DS=100mA P MOSFET 0.3 0.45 Ω N MOSFET 0.35 0.5 Ω SW Leakage Current I LSW ±0.01 1 uA EN Threshold High V EH 1.5 V EN Threshold Low V EL 0.3 V EN Leakage Current I EN ±0.01 uA High Efficiency η 96 % Over Temperature Protection OTP 150 °C OTP Hysteresis OTH 30 °C
Copyrights 2000-2021, Analog Technologies, Inc. All Rights Reserved. Updated on 4/9/2021 4 Analog Technologies ATI2305 DC-DC Converter
APPLICATION INFORMATION
For most application, the inductor value is from 1 μH to 4.7μH. Its value is chosen based on the desired ripple current. Large value inductors lower ripple current and small value inductors result in higher ripple current. Higher V IN or VOUT also increases the ripple current as shown in the following equation. A reasonable starting point for setting ripple current is ΔI L = 400mA (40% of 1A). ΔIL = ))(( Lf VOUT IN OUT V 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. Thus, a 1.4A rated inductor should be enough for most applications (1A + 400mA). For better efficiency, choose a low DC-resistance inductor. Vo CIN and COUT Selection In continuous mode, the source current of the top MOSFET is a square wave o f duty cycle V OUT/VIN. To prevent large voltage transients, a low ESR input capacitor sized for the maximum RMS current must be used. The maximum RMS capacitor current is given by: CIN required IRMS IOMAX IN OUTINOUT V )]V-(V[V This formula has a maximum at V IN = 2VOUT, where I RMS =IOUT /2. This simple worst-case condition is commonly used for design because even significant deviations do not offer much relief. Note that the capacitor manufacturer’s ripple current ratings are often based on 2000 hours of life. This makes it advisable to further derate the capacitor, or choose a capacitor rated at a higher temperature than required. Consult the manufacturer if there is any question. The selection of C OUT is on the basis of required effective series resistance (ESR). Typically, once the ESR requirement for C OUT has been met, the RMS current rating generally far exceeds the I RIPPLE (P-P) requirement. The △output ripple V OUT is determined by: VVOUT VIL OUTfC8 1ESR Where f = operating frequency, C OUT = output capacitance and ΔIL = ripple current in the inductor. For a fixed output voltage, the output ripple is highest at maximum input voltage since ΔIL increases with input voltage. Using Ceramic Input and Output Capacitors Higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. Their high ripple current, high voltage rating and low ESR make them ideal for switching regulator applications. Using ceramic capacitors can achieve very low output ripple and small circuit size. When choosing the input and output ceramic capacitors, choose the X5R or X7R dielectric formulations. These dielectrics have the best temperature and voltage characteristics of all the ceramics for a given value and size. Thermal Consideration Thermal protection limits power dissipation in the ATI2305. When the junction temperature exceeds 150 ℃, the OPT (Over Temperature Protection) starts the thermal shutdown and turns the pass transistor off. The pass transistor resumes operation after the junction temperature drops below 120℃. For continuous operation, the junction temperature should be maintained below 125℃. The power dissipation is defined as: P D=IO2 INQOSSW IN DSONLOINDSONH VIIFTV RVVR )()(VO IQ is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down converter switching losses. For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: P D = IO 2 RDSONH +IQ VIN Since R DS (ON) , quiescent current and switching losses all vary with input voltage, the total losses should be investigated over the complete input voltage range. The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surrounding airflow and temperature difference between junction and ambient. The maximum power dissipation can be calculated by the following formula: P JA AMAXJ T )(T Where T J(MAX) is the maximum allowable junction temperature 125℃. TA is the ambient temperature and JA is the thermal resistance from the junction to the ambient. Based on the standard JEDEC for a two layers thermal test board, the thermal resistance JA of SOT23-5 package is 250℃/W, DFN2×2 102 ℃/W, and QFN3×3 68 ℃/W, respectively. The maximum power dissipation at T A = 25℃ can be calculated by following formula:
The output voltage is given by Table 4. Table 4. Resistor selection for output voltage setting ILOAD=output current, RL=inductor DC resistance. steps to the P-channel current limit (1500mA). 120℃, at which time the circuit can be restarted.
- The power traces, consisting of the GND trace,
- The resistive divider R1/R2 must be connected
- This capacitor provides the AC current to the
- Keep the switching node, SW, away from the
- Keep the (–) plates of C IN and C OUT as close as
Figure 9. ATI2305 Suggested Layout
Figure 36. Start-up from Shutdown
Copyrights 2000-2021, Analog Technologies, Inc. All Rights Reserved. Updated on 4/9/2021 12 Analog Technologies ATI2305 DC-DC Converter PURCHASING INFORMATION Table 6. Part Number Output Voltage Marking Package Type Standard Package ATI2305AAB330 3.3V BEKYW SOT-23-5 3000Units/Tape&Reel ATI2305AAB280 2.8V BEHYW SOT-23-5 3000Units/Tape&Reel ATI2305AAB250 2.5V BEGYW SOT-23-5 3000Units/Tape&Reel ATI2305AAB180 1.8V BEEYW SOT-23-5 3000Units/Tape&Reel ATI2305AAB150 1.5V BECYW SOT-23-5 3000Units/Tape&Reel ATI2305AAB120 1.2V BEBYW SOT-23-5 3000Units/Tape&Reel ATI2305AABADJ ADJ BEAYW SOT-23-5 3000Units/Tape&Reel ATI2305BJE330 3.3V P2305K QFN3×3 3000Units/Tape&Reel ATI2305BJE280 2.8V P2305H QFN3×3 3000Units/Tape&Reel ATI2305BJE250 2.5V P2305G QFN3×3 3000Units/Tape&Reel ATI2305BJE180 1.8V P2305E QFN3×3 3000Units/Tape&Reel ATI2305BJE150 1.5V P2305C QFN3×3 3000Units/Tape&Reel ATI2305BJE120 1.2V P2305B QFN3×3 3000Units/Tape&Reel ATI2305BJEADJ ADJ P2305A QFN3×3 3000Units/Tape&Reel ATI2305CGF330 3.3V BEKYW DFN2×2-6 3000Units/Tape&Reel ATI2305CGF280 2.8V BEHYW DFN2×2-6 3000Units/Tape&Reel ATI2305CGF250 2.5V BEGYW DFN2×2-6 3000Units/Tape&Reel ATI2305CGF180 1.8V BEEYW DFN2×2-6 3000Units/Tape&Reel ATI2305CGF150 1.5V BECYW DFN2×2-6 3000Units/Tape&Reel ATI2305CGF120 1.2V BEBYW DFN2×2-6 3000Units/Tape&Reel ATI2305CGFADJ ADJ BEAYW DFN2×2-6 3000Units/Tape&Reel DIMENSIONS SOT 23-5 REF Millimeter Min Max A 1.10MAX A1 0 0.10 A2 0.70 1 c 0.12REF D 2.70 3.10 E 2.60 3.00 E1 1.40 1.80 L 0.45REF L1 0.60REF θ 0° 10° b 0.30 0.50 e 0.95REF e 1 1.90REF Table 7.
Copyrights 2000-2021, Analog Technologies, Inc. All Rights Reserved. Updated on 4/9/2021 13 Analog Technologies ATI2305 DC-DC Converter DFN 2×2 Figure37. Top View Figure 38. Bottom View Figure 39. Side View Table 8. COMMON DIMENSIONS (MM) PKG W: VERY VERY THIN REF MIN NOM MAX A 0.70 0.75 0.80 A1 0.00 - 0.05 A3 0.2 REF D 1.95 2.00 2.05 E 1.95 2.00 2.05 b 0.25 0.30 0.35 L 0.25 0.35 0.45 D2 1.35 1.50 1.60 E2 0.65 0.80 0.90 e 0.65 BSC PIN #1 IDENTIFICATION CHAMFER
Copyrights 2000-2021, Analog Technologies, Inc. All Rights Reserved. Updated on 4/9/2021 15 Analog Technologies ATI2305 DC-DC Converter NOTICE 1. ATI reserves the right to make changes to its products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. 2. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability. Testing and other quality control techniques are utilized to the extent ATI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. 3. Customers are responsible for their applications using ATI components. In order to minimize risks associated with the customers’ applications, adequate design and operating safeguards must be provided by the customers to minimize inherent or procedural hazards. ATI assumes no liability for applications assistance or customer product design. 4. ATI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of ATI covering or relating to any combination, machine, or process in which such products or services might be or are used. ATI’s publication of information regarding any third party’s products or services does not constitute ATI’s approval, warranty or endorsement thereof. 5. IP (Intellectual Property) Ownership: ATI retains the ownership of full rights for special technologies and/or techniques embedded in its products, the designs for mechanics, optics, plus all modifications, improvements, and inventions made by ATI for its products and/or projects.