® RT7271A 6A, 17V, 500kHz CSP Synchronous Step-Down Converter General Description Features The RT7271A is a high efficiency, synchronous step-down DC/DC converter for applications operating from 4.5V to 17V and requiring up to 6A maximum load. The current mode architecture of RT7271A allows the transient response to be optimized. Cycle-by-cycle current limit provides protection against shorted output and soft-start eliminates input current surge during start-up. Fault conditions also include output under voltage protection, output over voltage protection, and thermal shutdown. The low current shutdown mode provides output disconnect, enabling easy power management in battery powered systems. z 4.5V to 17V Input Voltage Range z 6A Output Current Current Mode Control 0.6V ± 1% Voltage Reference Over Temperature Latch Off when Short Circuit Monotonic Start-Up in Pre-biased Output 500kHz Switching Frequency Low On-Resistance 45mΩ Ω of High Side MOSFET 25mΩ Ω of Low Side MOSFET Cycle-by-Cycle Current Limit Power Good Monitor for UVP & OVP Input Under Voltage Lockout Thermal Shutdown RoHS Compliant and Halogen Free z z z z z z z z z z Pin Configurations z (TOP VIEW) Applications A1 A2 A3 LX LX LX B1 B2 B3 VIN GND GND C1 C2 C3 z z z COMP D1 D2 FB EN z BOOT PGOOD D3 AGND z Industrial and Commercial Low Power Systems Computer Peripherals LCD Monitors and TVs Point of Load Regulation for High Performance DSPs, FPGAs and ASICs Green Electronics/Appliances WL-CSP-12B 1.65x1.95 (BSC) Simplified Application Circuit BOOT VIN VIN CIN CBOOT RT7271A L VOUT LX RPGOOD PGOOD R1 PGOOD 3.3V VIN COUT FB R3 EN COMP GND AGND R2 RC CP CC Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS7271A-00 February 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT7271A Ordering Information Marking Information 17 : Product Code RT7271A Package Type WSC : WL-CSP-12B 1.65x1.95 (BSC) 17W W : Date Code Note : Richtek products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. Functional Pin Description Pin No. Pin Name Pin Function A1, A2, A3 LX Switch Node. Connect this pin to the external inductor. B1 VIN Power Input. Connect two 10μF or larger ceramic capacitors to this pin. B2, B3 GND Power Ground. C1 COMP Compensation Node. Connect external compensation elements to this pin to stabilize the control loop. C2 PGOOD Power Good Indicator Output. Asserts low if output voltage is low due to OTP, UVP, UVLO, OVP, EN shutdown or during soft-start. C3 BOOT Bootstrap Supply for the High Side MOSFET. Connect a capacitor between this pin and LX pin. D1 FB Feedback Voltage Input. This pin receives the feedback voltage from a resistive divider connected across the output. D2 EN Enable Control Input. Connecting this pin to ground forces the device into shutdown mode. Pulling this pin over 1.4V enables the device. D3 AGND Analog Ground. Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS7271A-00 February 2013 RT7271A Function Block Diagram PGOOD VIN UVLO EN 1.4V 0.72V 0.3V + Shutdown Comparator BOOT UVLO + - OV Comparator Protection Control + AGND 0.6V Driver Control HS Switch Current Comparator + EA + Oscillator Soft-Start Current Sense BOOT - UV Comparator FB Internal Regulator LS Switch Current Comparator LX Current Sense GND Slope Compensation COMP Operation The RT7271A is a constant frequency, current mode synchronous step-down converter. In normal operation, the high side N-MOSFET is turned on when the driver control is set by the oscillator and is turned off when the current comparator resets the driver control. While the high side N-MOSFET is turned off, the low side N-MOSFET is turned on to conduct the inductor current until next cycle begins. Error Amplifier The error amplifier adjusts its output voltage by comparing the feedback signal (VFB) with the internal 0.6V reference. When the load current increases, it causes a drop in the feedback voltage relative to the reference, the error amplifier's output voltage then rises to allow higher inductor current to match the load current. Enable The converter is turned on when the EN pin is higher than 1.4V. When the EN pin is lower than 1.15V, the converter will enter shutdown mode. Soft-Start (SS) An internal current source charges an internal capacitor to build a soft-start ramp voltage. The FB voltage will track the internal ramp voltage during soft-start interval. The typical soft-start time is 1.5ms. UV Comparator If the feedback voltage (VFB) is lower than 0.3V, the UV Comparator will go high to turn off the high side MOSFET. The output under voltage protection is designed to operate in latch mode. When the UV condition is removed, the controller can be reset by EN pin or VIN pin. Oscillator The internal oscillator runs at fixed frequency 500kHz. Internal Regulator The regulator provides low voltage power to supply the internal control circuits and the bootstrap power for high side gate driver. Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS7271A-00 February 2013 Thermal Shutdown The over temperature protection function will shut down the switching operation when the junction temperature exceeds 160°C. Once the junction temperature cools down by the hysteresis, the converter will automatically resume switching. is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT7271A Absolute Maximum Ratings z z z z z z z z z z z (Note 1) Supply Input Voltage, VIN ---------------------------------------------------------------------------------LX Pin Switch Voltage, VLX --------------------------------------------------------------------------------Boot Voltage, VBOOT ----------------------------------------------------------------------------------------EN Voltage, VEN ---------------------------------------------------------------------------------------------Other Pins -----------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C −0.3V to 20V −0.3V to (VIN + 0.3V) (VLX − 0.3V) to (VLX + 6V) −0.3V to 3.6V −0.3V to 6V WL-CSP-12B 1.65x1.95 (BSC) --------------------------------------------------------------------------Package Thermal Resistance (Note 2) WL-CSP-12B 1.65x1.95 (BSC), θJA --------------------------------------------------------------------Junction Temperature ---------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------Storage Temperature Range ------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Model) --------------------------------------------------------------------------------- 1.88W Recommended Operating Conditions z z z 53°C/W 150°C 260°C −65°C to 150°C 2kV (Note 4) Supply Input Voltage, VIN ---------------------------------------------------------------------------------- 4.5V to 17V Junction Temperature Range ------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range ------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 12V, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Shutdown Current ISHDN VEN = 0V -- 4 15 μA VIN UVLO Threshold VIN_TH VIN Rising -- 4 4.5 V VIN UVLO Hysteresis VIN_HYS -- 250 -- mV Enable Threshold VENR Rising -- 1.4 1.5 V Enable Threshold VENF Falling 1.15 1.25 -- V Quiescent Current IQ VFB = 0.61V -- 0.9 1.2 mA Feedback Reference Voltage VREF 0.594 0.6 0.606 V High-Side RDS(ON)_H -- 45 -- mΩ Low-Side RDS(ON)_L -- 25 -- mΩ −2μ < ICOMP < 2μ,VCOMP = 1V -- 1600 -- μA/V VCOMP = 1V, 100mV Input Overdrive -- 110 -- μA COMP to Current Sense transconductance -- 16 -- A/V High side Switch Peak Current ILIM_H Limit 8 12 -- A Minimum On-Time -- 100 -- ns Switch On-Resistance Error Amplifier transconductance gm Error Amp Source/Sink TON(MIN) Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS7271A-00 February 2013 RT7271A Parameter Symbol Test Conditions Min Typ Max Unit Thermal Shutdown TSD -- 160 -- °C Thermal Shutdown Hysteresis TSD_HYS -- 10 -- °C Switching Frequency fSW 425 500 575 kHz -- 120 -- % -- 50 -- % Soft-Start Time -- 1.5 -- ms Power Good Threshold Rising -- 90 -- % Power Good Threshold Falling -- 85 -- % OVP Threshold Under Voltage Threshold VUVP Power Good Output High Leakage Current VFB = VREF, VPGOOD = 5.5V -- 30 -- nA Power Good Output Low IPGOOD = 2mA -- -- 0.3 V Note 1. Stresses beyond those listed “Absolute Maximum Ratings” 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 operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect device reliability. Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS7271A-00 February 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT7271A Typical Application Circuit VIN B1 BOOT VIN CIN C3 RT7271A LX A1, A2, A3 3.3V PGOOD RPGOOD C2 VIN R3 D2 FB COMP AGND D3 VOUT R1 PGOOD EN CBOOT L D1 COUT C1 GND B2, B3 R2 RC CP CC Table 1. Recommended Component Selection VOUT (V) R1 (kΩ) R2 (kΩ) RC (kΩ) CC (nF) CP (pF) L (μH) COUT (μF) 5 73.2 10 8.2 6.8 150 3.3 66 3.3 45.3 10 6.8 3.9 150 3.3 66 2.5 31.6 10 7.5 4.7 150 1.5 66 1.8 20 10 6.2 3.9 150 1.5 66 1.5 15 10 5.6 3.9 150 1.5 66 1.05 7.5 10 3 3.3 150 1.0 66 Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS7271A-00 February 2013 RT7271A Typical Operating Characteristics Efficiency vs. Load Current Efficiency vs. Load Current 100% 1000 90% 900 100% 1000 90% 900 80% 800 Efficiency (%) Efficiency (%) VIN = 7.4V VIN = 12V VIN = 17V 70% 700 60% 600 50% 500 40% 400 30% 300 80% 800 70% 700 VIN = 7.4V VIN = 12V VIN = 17V 60% 600 50% 500 40% 400 30% 300 20% 200 20% 200 10% 100 10% 100 VOUT = 3.3V VOUT = 1.8V 0% 00 0% 00 0 1 2 3 4 5 0 6 1 2 Load Current (A) Efficiency vs. Load Current 1.82 90% 900 1.82 Output Voltage (V) Efficiency (%) 80% 800 VIN = 7.4V VIN = 12V VIN = 17V 60% 600 50% 500 400 40% 300 30% 200 20% 5 6 1.81 1.81 1.80 VIN = 17V VIN = 12V VIN = 7.4V 1.80 1.79 1.79 100 10% VOUT = 1.05V 00 0% VOUT = 1.8V 1.78 0 1 2 3 4 5 6 0 1 2 Load Current (A) 3 4 5 6 Load Current (A) Current Limit vs. Input Voltage Current Limit vs. Temperature 11.0 11.0 10.5 10.5 10.0 10.0 Current Limit (A) Current Limit (A) 4 Output Voltage vs. Load Current 100% 1000 70% 700 3 Load Current (A) 9.5 9.0 8.5 8.0 9.5 VIN = 17V VIN = 12V VIN = 7.4V 9.0 8.5 8.0 7.5 7.5 VOUT = 1.05V 7.0 VOUT = 1.05V 7.0 4 6 8 10 12 14 16 18 Input Voltage (V) Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS7271A-00 February 2013 20 -50 -25 0 25 50 75 100 125 Temperature (°C) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT7271A Load Transient Response VOUT (50mV/Div) IL (2A/Div) Load Transient Response VOUT (50mV/Div) VIN = 12V, VOUT = 1.8V, IOUT = 1A to 4A IL (2A/Div) Time (200μs/Div) Time (200μs/Div) Output Voltage Ripple Output Voltage Ripple VOUT (10mV/Div) VOUT (10mV/Div) VLX (10V/Div) VLX (10V/Div) IL (2A/Div) IL (2A/Div) VIN = 12V, VOUT = 1.8V, IOUT = 3A Time (2μs/Div) Over Voltage Protection Under Voltage Protection VOUT (1V/Div) VIN = 12V, VOUT = 1.8V, IOUT = 1A Time (1ms/Div) Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 VIN = 12V, VOUT = 1.8V, IOUT = 6A Time (2μs/Div) VOUT (1V/Div) VLX (5V/Div) VIN = 12V, VOUT = 1.8V, IOUT = 3A to 6A VLX (5V/Div) VIN = 12V, VOUT = 1.8V Time (5μs/Div) is a registered trademark of Richtek Technology Corporation. DS7271A-00 February 2013 RT7271A Over Current Protection VOUT (2V/Div) Power On from VIN VIN (10V/Div) VOUT (1V/Div) IL (5A/Div) VLX (10V/Div) VIN = 12V, VOUT = 1.8V IL (3A/Div) VIN = 12V, VOUT = 1.8V, IOUT = 6A Time (50μs/Div) Time (2ms/Div) Power Off from VIN Power On from EN VIN (10V/Div) VEN (3V/Div) VOUT (1V/Div) VOUT (1V/Div) IL (3A/Div) IL (3A/Div) VIN = 12V, VOUT = 1.8V, IOUT = 6A Time (2ms/Div) VIN = 12V, VOUT = 1.8V, IOUT = 6A Time (1ms/Div) Power Off from EN VEN (3V/Div) VOUT (1V/Div) IL (3A/Div) VIN = 12V, VOUT = 1.8V, IOUT = 6A Time (20μs/Div) Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS7271A-00 February 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT7271A Application Information The RT7271A is a single-phase Buck converter. It provides single feedback loop, current mode control with fast transient response. An internal 0.6V reference allows the output voltage to be precisely regulated for low output voltage applications. A fixed switching frequency (500kHz) oscillator and internal compensation are integrated to minimize external component count. Protection features include over current protection, under voltage protection, over voltage protection and over temperature protection. Output Voltage Setting Connect a resistive voltage divider at the FB between VOUT and GND to adjust the output voltage. The output voltage is set according to the following equation : R VOUT = VREF × ⎛⎜ 1 + FB1 ⎞⎟ R FB2 ⎠ ⎝ where VREF is 0.6V (typ.). VOUT RFB1 FB RFB2 GND Figure 1. Setting VOUT with a Voltage Divider Chip Enable and Disable The EN pin allows for power sequencing between the controller bias voltage and another voltage rail. The RT7271A remains in shutdown if the EN pin is lower than 1.25V. When the EN pin rises above the VEN threshold, the RT7271A begins a new initialization and soft-start cycle. Internal Soft-Start The RT7271A provides an internal soft-start function to prevent large inrush current and output voltage overshoot when the converter starts up. The soft-start (SS) automatically begins once the chip is enabled. During softstart, the internal soft-start capacitor becomes charged and generates a linear ramping up voltage across the capacitor. This voltage clamps the voltage at the FB pin, causing PWM pulse width to increase slowly and in turn Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 reduce the output surge current. The internal 0.6V reference takes over the loop control once the internal ramping up voltage becomes higher than 0.6V. UVLO Protection The RT7271A provides input Under Voltage Lockout Protection (UVLO). If the input voltage exceeds the UVLO rising threshold voltage (4V typ.), the converter resets and prepares the PWM for operation. If the input voltage falls below the UVLO falling threshold voltage during normal operation, the device will stop switching. The UVLO rising and falling threshold voltage has a hysteresis to prevent noise-caused reset. Inductor Selection The switching frequency (on-time) and operating point (% ripple or LIR) determine the inductor value as shown below: L= VOUT × ( VIN − VOUT ) fSW × LIR × ILOAD(MAX) × VIN where LIR is the ratio of the peak-to-peak ripple current to the average inductor current. Find a low loss inductor having the lowest possible DC resistance that fits in the allotted dimensions. Ferrite cores are often the best choice, although powdered iron is inexpensive and can work well at 200kHz. The core must be large enough and will not saturate at the peak inductor current (IPEAK) : IPEAK = ILOAD(MAX) + ⎛⎜ LIR × ILOAD(MAX) ⎞⎟ ⎝ 2 ⎠ The calculation above serves as a general reference. To further improve transient response, the output inductor can be further reduced. This relation should be considered along with the selection of the output capacitor. Input Capacitor Selection High quality ceramic input decoupling capacitor, such as X5R or X7R, with values greater than 20μF are recommended for the input capacitor. The X5R and X7R ceramic capacitors are usually selected for power regulator capacitors because the dielectric material has less capacitance variation and more temperature stability. is a registered trademark of Richtek Technology Corporation. DS7271A-00 February 2013 RT7271A Voltage rating and current rating are the key parameters when selecting an input capacitor. Generally, selecting an input capacitor with voltage rating 1.5 times greater than the maximum input voltage is a conservatively safe design. The input capacitor is used to supply the input RMS current, which can be approximately calculated using the following equation : IIN_RMS = ILOAD × VOUT ⎛ VOUT ⎞ × 1− VIN ⎜⎝ VIN ⎟⎠ The next step is selecting a proper capacitor for RMS current rating. A good design uses more than one capacitor with low equivalent series resistance (ESR) in parallel to form a capacitor bank. The input capacitance value determines the input ripple voltage of the regulator. The input voltage ripple can be approximately calculated using the following equation : ΔVIN = IOUT(MAX) × VOUT CIN × fSW × VIN For example, if IOUT_MAX = 6A, CIN = 22μF, fSW = 500kHz, VIN = 12V and VOUT = 1.05V, the input voltage ripple will be 47.7mV. Output Capacitor Selection The output capacitor and the inductor form a low pass filter in the Buck topology. In steady state condition, the ripple current flowing into/out of the capacitor results in ripple voltage. The output voltage ripple (VP-P) can be calculated by the following equation : 1 ⎞ VP_P = LIR × ILOAD(MAX) × ⎛⎜ ESR + 8 × COUT × fSW ⎟⎠ ⎝ When load transient occurs, the output capacitor supplies the load current before the controller can respond. Therefore, the ESR will dominate the output voltage sag during load transient. The output voltage undershoot (VSAG) can be calculated by the following equation : VSAG = ΔILOAD × ESR For a given output voltage sag specification, the ESR value can be determined. Another parameter that has influence on the output voltage sag is the equivalent series inductance (ESL). The rapid change in load current results in di/dt during transient. Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS7271A-00 February 2013 Therefore, the ESL contributes to part of the voltage sag. Using a capacitor with low ESL can obtain better transient performance. Generally, using several capacitors connected in parallel can have better transient performance than using a single capacitor for the same total ESR. Unlike the electrolytic capacitor, the ceramic capacitor has relatively low ESR and can reduce the voltage deviation during load transient. However, the ceramic capacitor can only provide low capacitance value. Therefore, use a mixed combination of electrolytic capacitor and ceramic capacitor to obtain better transient performance. Power Good Output (PGOOD) PGOOD is an open-drain output and requires a pull-up resistor. PGOOD is actively held low in soft-start, standby, and shutdown. It is released when the output voltage rises above 90% of nominal regulation point. The PGOOD signal goes low if the output is turned off or VOUT under 85% of setting. Under Voltage Protection (UVP) The output voltage can be continuously monitored for under voltage protection. Both high side and low side gate drivers will be forced to low if the output is less than 50% of its set voltage threshold. The UVP will be ignored for at least 1.5ms (typ.) after start up or a rising edge on the EN threshold. Remove the UVP fault latch by reseting the EN pin and VIN to restart the controller. Over Voltage Protection (OVP) The RT7271A is latched once OVP is triggered and can only be released by toggling EN threshold or cycling VIN. There is a 20μs delay built into the over voltage protection circuit to prevent false transition. Over Current Protection (OCP) The RT7271A provides over current protection by detecting high side MOSFET peak inductor current. If the sensed peak inductor current is over the current limit threshold (12A typ.), the OCP will be triggered. When OCP is tripped, the RT7271A will keep the over current threshold level until the over current condition is removed. is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT7271A Thermal Shutdown (OTP) Thermal Considerations For continuous operation, do not exceed absolute maximum junction temperature. The maximum power dissipation depends on the thermal resistance of the IC package, PCB layout, rate of surrounding airflow, and difference between junction and ambient temperature. The maximum power dissipation can be calculated by the following formula : PD(MAX) = (TJ(MAX) − TA) / θJA where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and θJA is the junction to ambient thermal resistance. For recommended operating condition specifications of the RT7271A, the maximum junction temperature is 125°C and TA is the ambient temperature. The junction to ambient thermal resistance, θ JA , is layout dependent. For WL-CSP-12B 1.65x1.95 (BSC), the thermal resistance, θJA, is 53°C/W on a standard JEDEC 51-7 four-layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formulas : P D(MAX) = (125°C − 25°C) / (53°C/W) = 1.88W for WL-CSP-12B 1.65x1.95 (BSC) package The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curve in Figure 2 allow the designer to see the effect of rising ambient temperature on the maximum power dissipation. Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 2.0 Maximum Power Dissipation (W)1 The device implements an internal thermal shutdown function when the junction temperature exceeds 160°C. The thermal shutdown forces the device to stop switching when the junction temperature exceeds the thermal shutdown threshold. Once the die temperature decreases below the hysteresis of 10°C, the device reinstates the power up sequence. Four-Layer PCB 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 2. Derating Curve of Maximum Power Dissipation Layout Considerations Layout is very important in high frequency switching converter design. The PCB can radiate excessive noise and contribute to converter instability with improper layout. Certain points must be considered before starting a layout using the RT7271A. Make the traces of the main current paths as short and wide as possible. Put the input capacitor as close as possible to the device pins (VIN and GND). LX node encounters high frequency voltage swings so it should be kept in a small area. Keep sensitive components away from the LX node to prevent stray capacitive noise pick-up. Ensure all feedback network connections are short and direct. Place the feedback network as close to the chip as possible. The GND pin should be connected to a strong ground plane for heat sinking and noise protection. An example of PCB layout guide is shown in Figure 3 for reference. is a registered trademark of Richtek Technology Corporation. DS7271A-00 February 2013 RT7271A The output capacitor must be placed near the IC. GND COUT VOUT Input capacitors must be placed as close to the IC as passable. L CIN VIN RC B1 B2 B3 VIN GND GND C1 C2 D1 D2 FB EN R2 CF R1 RPG CB C3 BOOT D3 AGND REN VIN 3V3 CC A3 LX COMP PGOOD GND The voltage divider and compensation components must be placed as close to the IC as passable. A2 LX VOUT CP A1 LX LX should be connected to inductor by wide and short trace. Keep sensitive components away form this trace. GND Figure 3. PCB Layout Guide Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS7271A-00 February 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 13 RT7271A Outline Dimension Symbol Dimensions In Millimeters Dimensions In Inches Min. Max. Min. Max. A 0.700 0.800 0.028 0.031 A1 0.200 0.260 0.008 0.010 b 0.290 0.350 0.011 0.014 D 1.900 2.000 0.075 0.079 D1 E 1.500 1.600 0.059 1.700 0.063 0.067 E1 1.200 0.047 e 0.700 0.028 e1 0.500 0.020 12B WL-CSP 1.65x1.95 Package (BSC) Richtek Technology Corporation 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries. www.richtek.com 14 DS7271A-00 February 2013