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AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 1 - DESCRIPTION FEATURES The A7525 is synchronous, fixed frequency, step-up DC/DC converters delivering high efficiency in a 6- lead SOT package. Capable of supplying 3.3V at 100mA from a single AA cell input, the device contain an internal NMOS switch and PMO S synchronous rectifier. A switching frequency of 1.2MHz minimizes solution footprint by allowing the use of tiny, low profile inductors and ceramic capacitors. The current mode PWM design is internally compensated, reducing external parts count. The A7525 features continuous switching at light loads. Anti -ringing control circuitry reduces EMI concerns by damping the inductor in discontinuous mode, and the device features low shutdown current of under 1uA. The A7525 is available in SOT-26 package. High Efficiency: Up to 92% 1.2MHz Constant Switching Frequency 3.3V Output Voltage at I OUT=100mA from a Single AA Cell; 5.0V Output Voltage at I OUT=500mA from one Li battery. Low Start-up Voltage: 1.0V Integrated main switch and synchronous rectifier. No Schottky Diode Required 2.5V to 5V Output Voltage Range Automatic Pulse Skipping Mode Operation Tiny External Components <1μA Shutdown Current Anti-ringing Control Reduces EMI Available in SOT-26 Package APPLICATION Cellular and Smart Phones Microprocessors and DSP Core Supplies Wireless and DSL Modems MP3 Player Digital Still and Video Cameras Portable Instruments TYPICAL APPLICATION CIRCUIT Figure 1 Basic Application Circuit with A7525 Adjustable Version
ORDERING INFORMATION
SPQ: 3,000pcs/Reel A7525E6R-ADJ A7525E6VR-ADJ Note V: Halogen free Package R : Tape & Reel AiT provides all RoHS products
AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 2 - PIN DESCRIPTION Top V iew Pin # Symbol Function 1 CE Chip Shutdown Signal Input. Logic high is normal operation mode, Logic Low is Shutdown 2,3 GND Ground Pin. 4 LX Power Switch Pin. It is the switch node connection to Inductor.
5 VDD Power Output Pin
Feedback Input Pin. Connect FB to the center point of the external resistor divider. The feedback threshold voltage is 1.23V
AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 3 - ABSOLUTE MAXIMUM RATINGS LX Voltage -0.3V～+6V FB, CE Voltages -0.3V～+6V VDD Voltage -0.3V～+6V θJA 220℃/W θJC 110℃/W Operating Temperature Range -40℃～+85℃ Storage Temperature Range -65℃～+150℃ Lead Temperature (Soldering, 10s) ＋260℃ Stresses above may caus e permanent damage to the device. T hese are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated in the Electrical Characteristics are not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. NOTE1: Thermal Resistance is specified with approximately 1 square of 1oz copper.
AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 4 - ELECTRICAL CHARACTERISTICSNOTE2 VIN =1.2V, VOUT=3.3V, TA=25°C, Test Circuit of Figure 1, unless otherwise noted. Parameter Condition Min. Typ. Max. Unit Minimum Start-Up Voltage IOUT =1mA - 1.0 - V IOUT =40mA - 1.8 - Minimum Operating Voltage VCE = VIN - 0.8 - V Output Voltage Range 2.5 - 5 V Feedback Voltage -40℃≤TA≤ 85℃ 1.192 1.230 1.268 V Quiescent Current(Shutdown) VCE = 0V - 0.01 1 μA Quiescent Current(Active) Measured on VOUT - 300 500 μA NMOS Switch Leakage VLX = 5V - 0.1 5 μA PMOS Switch Leakage VLX = 0V - 0.1 5 μA NMOS Switch ON Resistance VOUT = 3.3V - 0.40 - Ω VOUT = 5V - 0.35 - Ω PMOS Switch ON Resistance VOUT = 3.3V - 0.70 - Ω VOUT = 5V - 0.60 - Ω Output Voltage VOUT = 3.3V, IOUT = 1mA 3.201 3.300 3.399 V VOUT = 5V , IOUT = 1mA, VIN = 2.4V 4.850 5.000 5.150 V Line Regulation VIN = 0.8V to 3.0V, IOUT = 10mA - 1 - %/V Load Regulation IOUT = 1mA to 100mA - 0.02 - %/mA NMOS Current Limit Peak Drain Current 600 850 - mA Current Limit Delay to Output NOTE 3 - 40 - ns Max Duty Cycle VFB = 1.15V, -40℃≤TA≤ 85℃ 80 85 - % Switching Frequency 0.95 1.2 1.5 MHz CE Input Threshold 0.35 0.60 1.50 V CE Input Current VCE = 5.5V - 0.01 1 μA NOTE2:100% production test at +25°C. Specifications over the temperature range are guaranteed by design and characterization. NOTE3: Guaranteed by design.
AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 5 - TYPICAL PERFORMANCE CHARACTERISTICS 1. Efficiency vs. Output Current VOUT=3.3V, TA = 25°C(have schottky) 2. Efficiency vs. Output Current VOUT=5.0V, TA = 25°C (have schottky) 5. Output Voltage vs. Output Current 6. Output Voltage vs. Output Current
AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 6 - 7. Maximum Output Current vs. Input Voltage 8. Load Transient Response 9. No Load Input Current vs. Input Voltage 10. VOUT vs. Temperature 11. Pulse Skipping Mode operation 12. Antiringing Operation at SW
AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 7 - BLOCK DIAGRAM
AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 8 - DETAILED INFORMATION Operation The A7525 is 1.2MHz, synchronous boost converter housed in a 6-lead SOT package. Able to operate from an input voltage 1V, the device features fixed frequency, current mode PWM control for exceptional line and load regulation. With its low R DS(ON) and gate charge internal MOSFET switches, the device maintains high efficiency over a wide range of load current. Detailed descriptions of the operating modes follow. Operation can be best understood by referring to the Block Diagram. Synchronous Rectification The A7525 integrates a synchronous rectifier to improve efficiency as well as to eliminate the external Schottky diode. The synchronous rectifier is used to reduce the conduction loss contributed by the forward voltage of Schottky diode. The synchronous rectifier is realized by a P channel MOSFET with gate control circuitry that incorporates relatively complicated timing concerns. Low Noise Fixed Frequency Operation Oscillator: The frequency of operation is internally set to 1.2MHz. Error Amp: The error amplifier is an inter nally compensated trans -conductance type (current output) with a trans-conductance (gm) = 33 micro-siemens. The internal 1.23V reference voltage is compared to the voltage at the FB pin to generate an error signal at the output of the error amplifier. A vo ltage divider from VOUT to ground programs the output voltage via FB from 2.5V to 5V using the equation: VOUT = 1.23V x [1 + (R1/R2)] Current Sensing: A signal representing NMOS switch current is summed with the slope compensator. The summed signal is comp ared to the error amplifier output to provide a peak current control command for the PWM. Peak switch current is limited to approximately 850mA independent of input or output voltage. The current signal is blanked for 40ns to enhance noise rejection. Zero Current Comparator: The zero current comparator monitors the inductor current to the output and shuts off the synchronous rectifier once this current reduces to approximately 20mA. This prevents the inductor current from reversing in polarity improving efficiency at light loads. Antiringing Control : The antiringing control circuitry pre-vents high frequency ringing of the LX pin as the inductor current goes to zero by damping the resonant circuit formed by L and CLX (capacitance on LX pin).
AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 9 - Pulse Skipping Mode At very light load, the A7525 automatically switches into Pulse Skipping Mode to improve efficiency. During this mode, the PWM control will skip some pulses to maintain regulation. If the load increases and the output voltage drops, the device will automatically switch back to normal PWM mode and maintain regulation. Device Shutdown When CE is set logic high, the A7525 is put into operation. If CE is set logic low, the device is put into shutdown mode and consumes lower than 1μA current. Application Setting the Output Voltage: An external resistor divider is used to set the output voltage. The output voltage of the switching regulator (VOUT) is determined by the following equation: VOUT = 1.23V x [1 + (R1/R2)] Table 1 list the resistor selection for output voltage setting. Table 1 Resistor selection for output voltage setting VOUT R1(Ω) R2(Ω) 3.3V 1.02M 604k 5.0V 1.02M 332k Inductor Selection: The high switching frequency of 1.2MHz allows for small surface mount inductors. For most designs, the A7525 operates with inductors of 4.7μH to 10μH.The equation below can help to select the inductor, the maximum output current can be get by this equation; where η is the efficiency, I PEAK is the peak current limit, f is the switching frequency, L is the inductance value and D is the duty cycle. IOUT= η x [ IPEAK - VIN x D ] x (1-D) 2 x f x L Larger inductors mean less inductor current ripple and usually less output voltage ripple. Larger inductors also mean more load power can be delivered. But large inductors are also with large profile and costly. The inductor ripple current is ty pically set for 20% to 40% of the maximum inductor current. When selecting an inductor, the DC current rating must be high enough to avoid saturation at peak current. For optimum load transient and efficiency, the low DCR should be selected. Table 2 lists some typical surface mount inductors that meet target applications for the A7525:
AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 10 - Table2. Typical Surface Mount Inductors Part Number L(μH) Max DCR (mΩ) Rated D.C. Current (A) Size WxLxH (mm) Sumida CR43 4.7 108.7 182 1.15 1.04 4.3x4.8x3.5 Sumida CDRH4D28 4.7 5.6 6.8 101 109 128 1.32 1.17 1.12 1.00 5.0x5.0x3.0 Toko D53LC 4.7 6.8 1.87 1.51 1.33 5.0x5.0x3.0 Output Capacitor Selection : The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. A 2.2μF to 10μF output capacitor is sufficient for most applications. If output capacitor is larger than 10μF, a phase lead capacitor must be included to maintain enough phase margin. The output capacitor must have low impedance at the swi tching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current ratings Input Capacitor Selection: The input capacitor reduces the surge current drawn from the input and switching noise from the device. A minimum 4.7μF input capacitor is needed for most applications. The input capacitor impedance at the switching frequency should 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. Output Diode Selection : An Shottky diode should be included when the output voltage is above 4.5V. The Schottky diode is optional for the output voltage not more than 4.5V, but can improve efficiency by about 2% to 3%. PCB Layout Guidance The A7525 operates at 1.2MHz typically. This is a considerably high frequency for DC-DC converters. In such case PCB layout is important to guarantee satisfactory performance. It is recommended to make traces of the power loop, especially where switching node is involved as short and wide as possible. First of all, the inductor, input and output capacitor should be close to the device. Feedback and shut down circuit should avoid the proximity of large AC signals, e.g. the power inductor and switching nodes. The optional rectifier diode (D1) can improve efficiency and alleviate the stress on the integrated MOSFET. The diode should also
AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 11 - be close to the inductor and the chip to form the shortest possible switching loop. Large and integral multi layer ground planes are ideal for high power applications. Large area of copper has lower resistance and helps to dissipate heat on the device. The converter’s ground should join the system ground to which it supplies power at one point only.
AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 12 -
PACKAGE INFORMATION
Dimension in SOT-26 (Unit: mm) Symbol Millimeters Inches Min Max Min Max A 1.050 1.250 0.041 0.049 A1 0.000 0.100 0.000 0.004 A2 1.050 1.150 0.041 0.045 b 0.300 0.500 0.012 0.020 c 0.100 0.200 0.004 0.008 D 2.820 3.020 0.111 0.119 E 1.500 1.700 0.059 0.067 E1 2.650 2.950 0.104 0.116 e 0.950(BSC) 0.037(BSC) e1 1.800 2.000 0.071 0.079 L 0.300 0.600 0.012 0.024 θ 0° 8° 0° 8°
AiT Semiconductor Inc. www.ait-ic.com A7525 DC-DC CONVERTER BOOST(STEP-UP) 1.2MHz, MICROPOWER SYNCHRONOUS REV1.3 - JAN 2012 RELEASED, DEC 2019 UPDATED - - 13 - IMPORTANT NOTICE AiT Semiconductor Inc. (AiT) reserves the right to make changes to any its product, specifications, to discontinue any integrated circuit product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current. AiT Semiconductor Inc.'s integrated circuit products are not designed, intended, authorized, or warranted to be suitable for use in life support applications, devices or systems or other critical applications. Use of AiT products in such applications is understood to be fully at the risk of the customer. As used herein may involve potential risks of death, personal injury, or server property, or environmental damage. In order to minimize risks associated with the customer's applications, the customer should provide adequate design and operating safeguards. AiT Semiconductor Inc . assumes to no liability to customer product design or application support. AiT warrants the performance of its products of the specifications applicable at the time of sale.