A7230 AITSEMI | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 17
Technical content
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 1 - DESCRIPTION FEATURES The A7230 is a monolithic synchronous buck regulator. The device integrates 100mΩ MOSFETS that provide 3A continuous load current over a wide operating input voltage of 4.75V to 18V. Current mode control provides fast transient response and cycle-by- cycle current limit. An adjustable soft -start prevents inrush current at turn-on. In shutdown mode, the supply current drops below 1μA. This device, available in an SOP8 package, provides a very compact system solution with minimal reliance on external components. The A7230 is available in PSOP8 package. 3A Output Current Wide 4.75V to 18V Operating Input Range Integrated 100mΩ Power MOSFET Switches Output Adjustable from 0.925V to 15V Up to 95% Efficiency Programmable Soft-Start Stable with Low ESR Ceramic Output Capacitors Fixed 370kHz Frequency Cycle-by-Cycle Over Current Protection Input Under Voltage Lockout Available in PSOP8 package APPLICATION Distributed Power Systems Networking Systems FPGA, DSP, ASIC Power Supplies Green Electronics/ Appliances Notebook Computers
ORDERING INFORMATION
SPQ : 4,000pcs/Reel MP8 A7230MP8R A7230MP8VR Note R: Tape & Reel V: Halogen free Package AiT provides all RoHS products TYPICAL APPLICATION
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 2 - PIN DESCRIPTION Top View Pin # Name Description 1 BS High-Side Gate Drive Boost Input. BS supplies the drive for the high - side N -Channel MOSFET switch. Connect a 0.01 μ F or greater capacitor from SW to BS to power the high side switch. 2 IN Power Input. IN supplies the power to the IC, as well as the step-down converter switches. Drive IN with a 4.75V to 18V power source. Bypass IN to GND with a suitably large capacitor to eliminate noise on the input to the IC. See Input Capacitor. 3 SW Power Switching Output. SW is the switching node that supplies power to the output. Connect the output LC filter from SW to the output load. Note that a capacitor is required from SW to BS to power the high-side switch. 4 GND Ground (Connect Exposed Pad to Pin 4). 5 FB Feedback Input. FB senses the output voltage to regulate that voltage. Drive FB with a resistive voltage divider from the output voltage. The feedback threshold is 0.925V. See Setting the Output Voltage.
6 COMP
Compensation Node. COMP is used to compensate the regulation control loop. Connect a series RC network from COMP to GND to compensate the regulation control loop. In some cases, an additional capacitor from COMP to GND is required. See Compensation Components. 7 EN Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the regulator, drive it low to turn it off. Pull up with 100kΩ resistor for automatic startup. 8 SS Soft-Start Control Input. SS controls the soft -start period. Connect a capacitor from SS to GND to set the soft-start period. A 0.1μF capacitor sets the soft -start period to 15ms. To disable the soft -start feature, leave SS unconnected.
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 3 - ABSOLUTE MAXIMUM RATINGS VIN, Supply Voltage -0.3V ~ 20V VSW, Switch Voltage -1V ~ VIN +0.3V VBS, Bootstrap Voltage VSW-0.3V ~ VSW +6V VEN, Enable/UVLO Voltage -0.3V ~ +6V VCOMP, Comp Voltage -0.3V ~ +6V VFB, Feedback Voltage -0.3V ~ +6V Junction Temperature +150℃ Lead Temperature (Soldering, 10s) +260℃ Storage Temperature -65°C ~ +150℃ Stresses above may cause permanent damage to the device. These 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. RECOMMENDED OPERATING CONDITIONS Parameter Value Unit VIN, Input Voltage 4.75 to 18 V VOUT, Output Voltage 0.925 to 15 V Operating Temperature -40 to +85 ℃ NOTE: The device is not guaranteed to function outside of its operating conditions. THERMAL RESISTANCE Package θJA θJC PSOP8 50℃/W 10℃/W NOTE: Measured on approximately 1” square of 1 oz copper.
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 4 -
ELECTRICAL CHARACTERISTICS
VIN = 12V, TA = +25℃, unless otherwise noted. Parameter Conditions Min Typ Max Unit Shutdown Supply Current VEN ≤ 0.3V - 0.3 3 μA Supply Current VEN = 2.0V, VFB = 1.0V - 1.3 1.5 mA Feedback Voltage 4.75V≤VIN≤18V 900 925 946 mV Feedback Overvoltage Threshold - 1.1 - V Error Amplifier Voltage - 480 - V/V Error Amplifier Transconductance ΔIC = ±10μA - 800 - μA/V High-Side Switch-On Resistance - 100 - mΩ Low-Side Switch-On Resistance - 100 - mΩ High-Side Switch Leakage VEN = 0V, VSW = 0V - 0 10 μA Upper Switch Current Limit 4 6 - A Lower Switch Current Limit - 0.9 - A COMP to Current Sense Transconductance - 5.2 - А/V Oscillator Frequency 310 370 390 kHz Short Circuit Frequency VFB = 0V - 150 - kHz Maximum Duty Cycle VFB = 1.0V - 90 - % Minimum On Time - 220 - nS EN Shutdown Threshold Voltage VEN Rising 1.1 1.3 1.5 V EN Shutdown Threshold Voltage Hysterisis - 40 - mV EN Lockout Threshold Voltage 2.2 2.5 2.7 V EN Lockout Hysterisis - 210 - mV Input UVLO Threshold Rising VIN Rising 3.8 4.05 4.4 V Input UVLO Threshold Hysteresis - 210 - mV Soft-start Current VSS = 0V - 6 - μA Soft-start Period CSS = 0.1μF - 15 - ms Thermal Shutdown - 160 - °C
Figure 1. Typical Application Circuit Figure 2. Typical Efficiency Curve
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 6 - TYPICAL PERFORMENCE CHARACTERISTICS 1. Short circuit test (Channel3:ISW, Channel2:VO) 2. Soft-start (Channel1:EN, Channel2:VO) 3. Transient response (Channel3:ISW, Channel2:VO) 4. Ripple
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 7 - BLOCK DIAGRAM
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 8 - DETAILED INMFORMATION The A7230 is a synchronous rectified, current -mode, step -down regulator. It regulates input voltages from 4.75V to 18V down to an output voltage as low as 0.925V, and supplies up to 3A of load current. The A7230 uses current -mode control to regulate the output voltage. The output voltage is measured at FB through a resistive voltage divider and amplified through the internal transconductance error amplifier. The voltage at the COMP pin is compared to the switch current measured internally to control the output voltage. The converter uses internal N -Channel MOSFET switches to step -down the input voltage to the regulated output voltage. Since the high side MOSFET requires a gate voltage greater than the input voltage, a boost capacitor connected between SW and BS is needed to drive the high side gate. The boost capacitor is charged from the internal 5V rail when SW is low. When the A7230 FB pin exceeds 20% of the nominal regulation voltage of 0.925V, the over voltage comparator is tripped and the COMP pin and the SS pin are discharged to GND, forcing the high -side switch off. Component Selection Setting the Output Voltage The output voltage is set using a resistive voltage divider from the output voltage to FB (see Typical Application circuit on page 1). The voltage divider divides the output voltage down by the ratio: VFB = VOUT R2 R1+R2 Where VFB is the feedback voltage and VOUT is the output voltage. Thus the output voltage is: VOUT = 0.925 x R1+R2 R2 can be as high as 100kΩ, but a typical value is 10kΩ. Using the typical value for R2, R1 is determined by: R1 = 10.81 x (VOUT – 0.925) (kΩ)
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 9 - For example, for a 3.3V output voltage, R2 is 10kΩ, and R1 is 26.1kΩ. Table 1 lists recommended resistance values of R1 and R2 for standard output voltages. Table.1 Recommended Resistance Values VOUT R1 R2 1.8V 9.53kΩ 10kΩ 2.5V 16.9kΩ 10kΩ 3.3V 26.1kΩ 10kΩ 5V 44.2kΩ 10kΩ 12V 121kΩ 10kΩ Inductor The inductor is required to supply constant current to the output load while being driven by the switched input voltage. A larger value inductor will result in less ripple current that will result in lower output ripple voltage. However, the larger value inductor will have a larger physical size, higher series resistance, and/or lower saturation current. A good rule for determining the inductance to use is to allow the peak-to-peak ripple current in the inductor to be approximately 30% of the maximum switc h current limit. Also, make sure that the peak inductor current is below the maximum switch current limit. The inductance value can be calculated by: L= VOUT fs x ΔIL x (1- VOUT VIN Where VOUT is the output voltage, V IN is the input voltage, f S is the switching frequency, and ΔIL is the peak- to- peak inductor ripple current. Choose an inductor that will not saturate under the maximum inductor peak current. The peak inductor current can be calculated by: ILP = ILOAD + VOUT 2 x fs x L x (1 - VOUT VIN Where ILOAD is the load current. The choice of which style inductor to use mainly depends on the price vs. size requirements and any EMI requirements.
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 10 - Optional Schottky Diode During the transition between high -side switch and low -side switch, the body diode of the low-side powe r MOSFET conducts the inductor current. The forward voltage of this body diode is high. An optional Schottky diode may be paralleled between the SW pin and GND pin to improve overall efficiency. Table 2 lists example Schottky diodes. Table.2 Diode Selection Guide Part Number Voltage/Current Rating Vendor SM140A 40V, 1A AiT Semi MBR130 30V, 1A AiT Semi Input Capacitor The input current to the step -down converter is discontinuous, therefore a capacitor is required to supply the AC current to the step-down converter while maintaining the DC input voltage. Use low ESR capacitors for the best performance. Ceramic capacitors are preferred, but tantalum or low-ESR electrolytic capacitors may also suffice. Choose X5R or X7R dielectrics when using ceramic capacitors. Since the input capacitor absorbs the input switching current it requires an adequate ripple current rating. The RMS current in the input capacitor can be estimated by: IC1 = ILOAD x√VOUT VIN x (1- VOUT VIN The worst-case condition occurs at V IN = 2VOUT, where ICIN = ILOAD/2. For simplification, choose the input capacitor whose RMS current rating greater than half of the maximum load current. The input capacitor can be electrolytic, tantalum or ceramic. When usin g electrolytic or tantalum capacitors, a small, high quality ceramic capacitor, i.e. 0.1μF, should be placed as close to the IC as possible. When using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. The input voltage ripple for low ESR capacitors can be estimated by: ΔVIN = ILOAD C1 x fs x VOUT VIN x (1 - VOUT VIN Where C1 is the input capacitance value.
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 11 - Output Capacitor The output capacitor is required to maintain the DC output voltage. Ceramic, tantalum, or low ESR electrolytic capacitors are recommended. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by: ΔVOUT = VOUT fs x L x (1 - VOUT VIN ) x (RESR x 1 8 x fs x C2) Where C2 is the output capacitance value and RESR is the equivalent series resistance (ESR) value of the output capacitor. In the case of ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance. The output voltage ripple is mainly caused by the capacitance. For simplification, the output voltage ripple can be estimated by: ΔVOUT = VOUT 8 x fs 2 x L x C2 x (1 - VOUT VIN In the case of tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to: ΔVOUT = VOUT fs x L x (1 - VOUT VIN ) x RESR The characteristics of the output capacitor also affect the stability of the regulation system. The A7230 can be optimized for a wide range of capacitance and ESR values. For A7230 normal operation, the output can be an electrolytic capacitor in parallel. Compensation Components A7230 employs current mode control for easy compensation and fast transient response. The system stability and transient response are controlled through the COMP pin. COMP pin is the output of the internal transconductance error amplifier. A series capacitor -resistor combination sets a pole -zero combination to control the characteristics of the control system. The DC gain of the voltage feedback loop is given by: AVDC = RLOAD x GCS x AEA x VFB VOUT
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 12 - Where VFB is the feedback voltage, 0.925V; AVEA is the error amplifier voltage gain; GCS is the current sense transconductance and RLOAD is the load resistor value. The system has two poles of importance. One is due to the compensation capacitor (C3) and the output resistor of the error amplifier, and the other is due to the output capacitor and the load resistor. These poles are located at: fP1 = GEA 2π x C3 x AVEA fP2 = 1 2π x C2 x RLOAD Where GEA is the error amplifier transconductance. The system has one zero of importance, due to the compensation capacitor (C3) and the compensation resistor (R3). This zero is located at: fZ1 = 1 2π x C3 x R3 The system may have another zero of importance, if the output capacitor has a large capacitance and/or a high ESR value. The zero, due to the ESR and capacitance of the output capacitor, is located at: fESR = 1 2π x C2 x RESR In this case, a third pole set by the compensation capacitor (C6, an additional capacitor from COMP to GND) and the compensation resistor (R3) is used to compensate the effect of the ESR zero on the loop gain. This pole is located at: fP3 = 1 2π x C6 x R3 The goal of compensation design is to shape the converter transfer function to get a desired loop gain. The system crossover frequency where the feedback loop has the unity gain is important. Lower crossover frequencies result in slower line and load transient responses, while higher crossover frequencies could cause system instability. A good rul e of thumb is to set the cross over frequency bel ow one-tenth of the switching frequency.
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 13 - To optimize the compensation components, the following procedure can be used. 1. Choose the compensation resistor (R3) to set the desired crossover frequency. Determine the R3 value by the following equation: R3 = 2π x C2 x fC GEA x GCS x VOUT VFB < 2π x C2 x 0.1 x fS GEA x GCS x VOUT VFB Where fc is the desired crossover frequency which is typically below one tenth of the switching frequency. 2. Choose the compensation capacitor (C3) to achieve the desired phase margin. For applications with typical inductor values, setting the compensation zero, fZ1, below one -forth of the crossover frequency provides sufficient phase margin. Determine the C3 value by the following equation: C3 > 4 2π x R3 x fC Where R3 is the compensation resistor. 3. Determine if the second compensation capacitor (C6) is required. It is required if the ESR zero of the output capacitor is located at less than half of the switching frequency, or the following relationship is valid: 2π x C2 x RESR < fS If this is the case, then add the second compensation capacitor (C6) to set the pole fP3 at the location of the ESR zero. Determine the C6 value by the equation: C6 = C2 x RESR External Bootstrap Diode An external bootstrap diode may enhance the efficiency of the regulator, the applicable conditions of external BS diode are:
- VOUT is 5V or 3.3V
- Duty cycle is high: D=VOUT/VIN > 65%
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 14 - In these cases, an external BS diode is recommended from the output of the voltage regulator to BS pin, see below: Add Optional External Bootstrap Diode to Enhance Efficiency The recommended external BS diode is 1N4148, and the BS cap is 0.1~1μF. The EN pin peripheral components If it is the just requirement to automatically turn on or off A7230, add 100 k resistor between V IN and EN as shown in Figure 3. The internal 5.8V Zener diode on the EN PIN clamps EN pin voltage to 5.8V. Figure 3 Switch on/off automatically To enable A7230 by MCU I/O 5V or 3.3V Logic signal, 1 k resistor connected between MCU I/O port and the A7230 EN pin is suggested, as shown in figure 4.
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 16 -
PACKAGE INFORMATION
Dimension in PSOP8 Package (Unit: mm) Symbol Millimeters Inches Min Max Min Max A 1.350 1.750 0.053 0.069 A1 0.050 0.150 0.004 0.010 A2 1.350 1.550 0.053 0.061 b 0.330 0.510 0.013 0.020 c 0.170 0.250 0.006 0.010 D 4.700 5.100 0.185 0.200 D1 3.202 3.402 0.126 0.134 E 3.800 4.000 0.150 0.157 E1 5.800 6.200 0.228 0.244 E2 2.313 2.513 0.091 0.099 e 1.270 BSC 0.050 BSC L 0.400 1.270 0.016 0.050 θ 0° 8° 0° 8°
AiT Semiconductor Inc. www.ait-ic.com A7230 DC-DC CONVERTER BUCK (STEP-DOWN) 3A, 18V SYNCHRONOUS RECTIFIED REV1.1 - MAR 2011 RELEASED, JUL 2020 UPDATED - - 17 - 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 plac ing 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 critica l 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 servere 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.