® RT7277 3A, 18V, 700kHz ACOTTM Synchronous Step-Down Converter General Description Features The RT7277 is a synchronous step-down DC/DC converter with Advanced Constant On-Time (ACOTTM) mode control. z It achieves high power density to deliver up to 3A output current from a 4.5V to 18V input supply. The proprietary ACOTTM mode offers an optimal transient response over a wide range of loads and all kinds of ceramic capacitors, which allows the device to adopt very low ESR output capacitors for ensuring performance stabilization. In addition, RT7277 keeps an excellent constant switching frequency under line and load variation and the integrated synchronous power switches with the ACOTTM mode operation provides high efficiency in whole output current load range. Cycle-by-cycle current limit provides an accurate protection by a valley detection of low side MOSFET and external soft-start setting eliminates input current surge during startup. Protection functions also include output under voltage protection, output over voltage protection, and thermal shutdown. z z z z z z z z z z z z z 4.5V to 18V Input Voltage Range 3A Output Current 60mΩ Ω Internal Low Site N-MOSFET Advanced Constant On-Time Control Support All Ceramic Capacitors Up to 95% Efficiency 700kHz Switching Frequency Adjustable Output Voltage from 0.765V to 8V Adjustable Soft-Start Cycle-by-Cycle Current Limit Input Under Voltage Lockout Thermal Shutdown RoHS Compliant and Halogen Free Applications z z z Marking Information z z RT7277GSP : Product Number RT7277 GSPYMDNN ACOTTM Mode Enables Fast Transient Response YMDNN : Date Code Industrial and Commercial Low Power Systems Computer Peripherals LCD Monitors and TVs Green Electronics/Appliances Point of Load Regulation for High-Performance DSPs, FPGAs, and ASICs Simplified Application Circuit RT7277 VIN SW VIN C1 C2 L1 VOUT C7 C6 BOOT C3 R1 VPVCC R2 Chip Enable EN FB SS PVCC C5 C4 GND Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS7277-00 October 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT7277 Pin Configurations Ordering Information (TOP VIEW) RT7277 Package Type SP : SOP-8 (Exposed Pad-Option 2) Lead Plating System G : Green (Halogen Free and Pb Free) Note : 8 EN FB 2 PVCC SS 3 GND BOOT 6 SW 5 GND 9 4 VIN 7 SOP-8 (Exposed Pad) 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 1 EN Enable Input. A logic-high enables the converter; a logic-low forces the IC into shutdown mode reducing the supply current to less than 10μA. 2 FB Feedback Input. It is used to regulate the output of the converter to a set value via an external resistive voltage divider. The feedback threshold voltage is 0.765V typically. 3 PVCC Internal Regulator Output. Connect a 1μF capacitor to GND to stabilize output voltage. 4 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 3.9nF capacitor sets the soft-start period of VOUT to 2.6ms. GND Ground. The Exposed pad should be soldered to a large PCB and connected to GND for maximum thermal dissipation. 6 SW Switch Node. Connect this pin to an external L-C filter. 7 BOOT Bootstrap Supply for High Side Gate Driver. Connect a 0.1μF or greater ceramic capacitor from BOOT to SW pins. 8 VIN Power Input. The input voltage range is from 4.5V to 18V. Must bypass with a suitably large ( ≥10μF x 2) ceramic capacitor. 5, 9 (Exposed Pad) Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS7277-00 October 2012 RT7277 Function Block Diagram BOOT PVCC Internal Regulator VIN PVCC VIBIAS Over Current PVCC Protection VREF UGATE Switch Controller PVCC SW Driver Ripple Gen. LGATE GND SW 2µA + - - SS FB FB Comparator On-Time EN EN Operation In normal operation, the high side N-MOSFET is turned on when the FB Comparator sets the Switch Controller, and it is turned off when On-Time Controller resets the Switch Controller. While the high side N-MOSFET is turned off, the low side N-MOSFET is turned on and waits for the FB Comparator to set the beginning of next cycle. Enable The FB Comparator sets the Switch Controller by comparing the feedback signal (FB) from output voltage with the internal 0.765V reference. When load transient induces VOUT drop, the FB voltage will be less than its threshold voltage. This means that the high side N-MOSFET will turn on again immediately after minimum off-time expired. The switching frequency will vary during the transient period thus can provide a very fast transient response. After the load transient finished, the RT7277 will be back to steady state with a constant switching frequency. Provide internal power for logic control and switch gate drivers. Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS7277-00 October 2012 Activate internal regulator once EN input level is higher than the target level. Force IC to enter shutdown mode when the EN input level is lower than 0.4V Internal Regulator PGOOD Comparator When the feedback signal is higher than 90% of reference voltage, the PGOOD open drain output will be high impedance. On-Time Controller Control on-time according to VIN and SW to obtain constant switching frequency. is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT7277 Absolute Maximum Ratings z z z z z z z z z z (Note 1) Supply Voltage, VIN ----------------------------------------------------------------------------------------------Switch Voltage, SW ----------------------------------------------------------------------------------------------<10ns ----------------------------------------------------------------------------------------------------------------BOOT to SW, PVCC ---------------------------------------------------------------------------------------------Other Pins Voltage ------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C SOP-8 (Exposed Pad) -------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) SOP-8 (Exposed Pad), θJA --------------------------------------------------------------------------------------SOP-8 (Exposed Pad), θJC -------------------------------------------------------------------------------------Junction Temperature Range ------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------Storage Temperature Range ------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Model) --------------------------------------------------------------------------------------- Recommended Operating Conditions z z z −0.3V to 21V −0.8V to (VIN + 0.3V) −5V to 25V −0.3V to 6V −0.3V to 21V 2.041W 49°C/W 15°C/W 150°C 260°C −65°C to 150°C 2kV (Note 4) Supply Voltage, VIN ----------------------------------------------------------------------------------------------- 4.5V to 18V 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 Supply Current Shutdown Current ISHDN VEN = 0V -- 1.5 10 μA Quiescent Current IQ VEN = 3V, VFB = 1V -- 0.7 -- mA Logic-High 2 -- 18 Logic-Low -- -- 0.4 Logic Threshold EN Voltage V VFB Voltage and Discharge Resistance Feedback Threshold Voltage VFB 4.5V ≤ VIN ≤ 18V 0.757 0.765 0.773 V Feedback Input Current IFB VFB = 0.8V −0.1 0 0.1 μA VPVCC 6V ≤ VIN ≤ 18V, 0 < IPVCC < 5mA 4.7 5.1 5.5 V VPVCC Output VPVCC Output Voltage Line Regulation 6V ≤ VIN ≤ 18V, IPVCC = 5mA -- -- 20 mV Load Regulation 0 < IPVCC < 5mA -- -- 100 mV VIN = 6V, VPVCC = 4V -- 110 -- mA Output Current IPVCC Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS7277-00 October 2012 RT7277 Parameter Symbol Test Conditions Min Typ Max Unit R DS(ON) Switch On Resistance High Side RDS(ON)_H -- 90 -- Low Side RDS(ON)_L -- 60 -- ILIM 3.5 4.1 5.7 A TSD -- 150 -- °C -- 20 -- °C -- 145 -- ns mΩ Current Limit Current Limit Thermal Shutdown Thermal Shutdown Threshold Thermal Shutdown Hysteresis ΔTSD On-Time Timer Control On-Time tON VIN = 12V, VOUT = 1.05V Minimum On-Time tON(MIN) -- 60 -- ns Minimum Off-Time tOFF(MIN) -- 230 -- ns Soft-Start SS Charge Current VSS = 0V 1.4 2 2.6 μA SS Discharge Current VSS = 0.5V 0.05 0.1 -- mA VIN Rising to Wake up VPVCC 3.55 3.85 4.15 -- 0.3 -- UVLO UVLO Threshold Hysteresis 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. θJC is measured at the exposed pad of the package. The PCB copper area of exposed pad is 70mm2. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS7277-00 October 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT7277 Typical Application Circuit VIN C1 10µF x 2 C2 0.1µF RT7277 6 8 SW VIN 1 Chip Enable 5, 9 (Exposed Pad) C5 3.9nF EN GND 4 SS BOOT FB PVCC 7 L1 1.4µH C6 0.1µF C3 R1 8.25k C7 22µF x 2 VOUT 1.05V/3A 2 3 VPVCC R2 22.1k C4 1µF Table 1. Suggested Component Values VOUT (V) R1 (kΩ) R2 (kΩ) C3 (pF) L1 (μH) C7 (μF) 1 6.81 22.1 -- 1.4 22 to 68 1.05 8.25 22.1 -- 1.4 22 to 68 1.2 12.7 22.1 -- 1.4 22 to 68 1.8 30.1 22.1 5 to 22 2 22 to 68 2.5 49.9 22.1 5 to 22 2 22 to 68 3.3 73.2 22.1 5 to 22 2 22 to 68 5 124 22.1 5 to 22 3.3 22 to 68 7 180 22.1 5 to 22 3.3 22 to 68 Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS7277-00 October 2012 RT7277 Typical Operating Characteristics Output Voltage vs. Input Voltage Efficiency vs. Output Current 100 1.065 90 1.060 Output Voltage (V) Efficiency (%) 80 70 60 50 VIN = 5V VIN = 12V VIN = 17V 40 30 20 1.055 1.050 1.045 1.040 1.035 1.030 10 VOUT = 1.05V VOUT = 1.05V 0 0.001 1.025 0.01 0.1 1 10 4 6 8 Output Current (A) 12 14 1.060 1.060 1.055 1.055 Output Voltage (V) 1.065 1.050 1.045 1.040 1.035 1.030 1.050 VIN = 17V VIN = 12V VIN = 5V 1.045 1.040 1.035 1.030 VOUT = 1.05V VIN = 12V, VOUT = 1.05V, IOUT = 0A 1.025 1.025 -50 -25 0 25 50 75 100 125 0 0.5 1 Temperature (°C) 1.5 2 2.5 3 Output Current (A) Frequency vs. Input Voltage Reference Voltage vs. Temperature 750 0.785 740 0.780 Reference Voltage (V) 730 Frequency (kHz)1 18 Output Voltage vs. Output Current 1.065 720 710 700 690 680 670 0.775 0.770 0.765 0.760 0.755 0.750 660 650 0.745 4 6 8 10 12 14 16 Input Voltage (V) Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS7277-00 16 Input Voltage (V) Output Voltage vs. Temperature Output Voltage (V) 10 October 2012 18 -50 -25 0 25 50 75 100 125 Temperature (°C) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT7277 Current Limit vs. Input Voltage Current Limit vs. Temperature 6.0 6.0 5.5 Current Limit (A) Current Limit (A) 5.6 5.2 4.8 4.4 5.0 4.5 4.0 3.5 VIN = 12V, VOUT = 1.05V VIN = 12V, VOUT = 1.05V 3.0 4.0 -50 -25 0 25 50 75 100 4 125 8 10 12 Temperature (°C) Input Voltage (V) Load Transient Response Switching 14 16 18 VSW (10V/Div) IOUT (2A/Div) VOUT (10mV/Div) VOUT (20mV/Div) VIN = 12V, VOUT = 1.05V, IOUT = 0A to 3A IL (2A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 3A Time (100μs/Div) Time (1μs/Div) Power On from VIN Power Off from VIN VIN (5V/Div) VOUT (1V/Div) VIN (5V/Div) VOUT (1V/Div) IOUT (2A/Div) IOUT (2A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 3A Time (5ms/Div) Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 6 VIN = 12V, VOUT = 1.05V, IOUT = 3A Time (10ms/Div) is a registered trademark of Richtek Technology Corporation. DS7277-00 October 2012 RT7277 Power On from EN Power Off from EN VEN (2V/Div) VEN (2V/Div) VOUT (1V/Div) VOUT (1V/Div) IOUT (2A/Div) IOUT (2A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 3A Time (1ms/Div) VIN = 12V, VOUT = 1.05V, IOUT = 3A Time (10μs/Div) EN Current vs. EN Voltage 10 9 EN Current (μA) 8 7 6 5 4 3 2 1 VIN = 17V 0 0 2 4 6 8 10 12 14 16 18 EN Voltage (V) Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS7277-00 October 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT7277 Application Information The RT7277 is a synchronous high voltage Buck converter that can support the input voltage range from 4.5V to 18V and the output current up to 3A. It adopts ACOTTM mode control to provide a very fast transient response with few external compensation components. device again. For external timing control, the EN pin can also be externally pulled high by adding a REN resistor and CEN capacitor from the VIN pin (see Figure 1). EN VIN PWM Operation It is suitable for low external component count configuration with appropriate amount of Equivalent Series Resistance (ESR) capacitors at the output. The output ripple valley voltage is monitored at a feedback point voltage. The synchronous high side MOSFET is turned on at the beginning of each cycle. After the internal ontime timer expires, the MOSFET is turned off. The pulse width of this on-time is determined by the converter's input and output voltages to keep the frequency fairly constant over the entire input voltage range. Advanced Constant On-Time Control The RT7277 has a unique circuit which sets the on-time by monitoring the input voltage and SW signal. The circuit ensures the switching frequency operating at 700kHz over input voltage range and loading range. Soft-Start The RT7277 contains an external soft-start clamp that gradually raises the output voltage. The soft-start timing can be programmed by the external capacitor between SS pin and GND. The chip provides a 2μA charge current for the external capacitor. If a 3.9nF capacitor is used, the soft-start will be 2.6ms (typ.). The available capacitance range is from 2.7nF to 220nF. t SS C5 (nF) × 1.365 (ms) = ISS (μ A) Chip Enable Operation The EN pin is the chip enable input. Pulling the EN pin low (<0.4V) will shut down the device. During shutdown mode, the RT7277 quiescent current drops to lower than 10μA. Driving the EN pin high (>2V, <18V) will turn on the Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 REN EN RT7277 CEN GND Figure 1. External Timing Control An external MOSFET can be added to implement digital control on the EN pin when no system voltage above 2V is available, as shown in Figure 2. In this case, a 100kΩ pull-up resistor, REN, is connected between VIN and the EN pin. MOSFET Q1 will be under logic control to pull down the EN pin. VIN REN 100k EN Q1 EN RT7277 GND Figure 2. Digital Enable Control Circuit To prevent enabling circuit when VIN is smaller than the VOUT target value, a resistive voltage divider can be placed between the input voltage and ground and connected to the EN pin to adjust IC lockout threshold, as shown in Figure 3. For example, if an 8V output voltage is regulated from a 12V input voltage, the resistor REN2 can be selected to set input lockout threshold larger than 8V. VIN REN1 REN2 EN RT7277 GND Figure 3. Resistor Divider for Lockout Threshold Setting is a registered trademark of Richtek Technology Corporation. DS7277-00 October 2012 RT7277 Output Voltage Setting The resistive divider allows the FB pin to sense the output voltage as shown in Figure 4. VOUT R1 FB RT7277 R2 GND Figure 4. Output Voltage Setting The output voltage is set by an external resistive divider according to the following equation. It is recommended to use 1% tolerance or better divider resistors. VOUT = 0.765 × (1+ R1 ) R2 inductor to achieve this goal. For the ripple current selection, the value of ΔIL = 0.2(IMAX) will be a reasonable starting point. The largest ripple current occurs at the highest VIN. To guarantee that the ripple current stays below the specified maximum, the inductor value should be chosen according to the following equation : ⎡ VOUT ⎤ ⎡ VOUT ⎤ L =⎢ ⎥ × ⎢1 − VIN(MAX) ⎥ f I × Δ L(MAX) ⎣ ⎦ ⎣ ⎦ Input and Output Capacitors Selection The input capacitance, C IN, is needed to filter the trapezoidal current at the source of the high side MOSFET. A low ESR input capacitor with larger ripple current rating should be used for the maximum RMS current. The RMS current is given by : Under Voltage Lockout Protection V IRMS = IOUT(MAX) OUT VIN The RT7277 has Under Voltage Lockout Protection (UVLO) that monitors the voltage of PVCC pin. When the VPVCC voltage is lower than UVLO threshold voltage, the RT7277 will be turned off in this state. This is non-latch protection. This formula has a maximum at VIN = 2VOUT, where IRMS = IOUT / 2. This simple worst-case condition is commonly used for design because even significant deviations do not offer much relief. Over Temperature Protection The RT7277 equips an Over Temperature Protection (OTP) circuitry to prevent overheating due to excessive power dissipation. The OTP will shut down switching operation when junction temperature exceeds 150°C. Once the junction temperature cools down by approximately 20°C the main converter will resume operation. To keep operating at maximum, the junction temperature should be prevented from rising above 150°C. Inductor Selection The inductor value and operating frequency determine the ripple current according to a specific input and an output voltage. The ripple current ΔIL increases with higher VIN and decreases with higher inductance. V V ΔIL = ⎡⎢ OUT ⎤⎥ × ⎡⎢1− OUT ⎤⎥ f × L VIN ⎦ ⎣ ⎦ ⎣ Having a lower ripple current reduces not only the ESR losses in the output capacitors but also the output voltage ripple. High frequency with small ripple current can achieve highest efficiency operation. However, it requires a large Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS7277-00 October 2012 VIN −1 VOUT Choose a capacitor rated at a higher temperature than required. Several capacitors may also be paralleled to meet size or height requirements in the design. For the input capacitor, two 10μF and 0.1μF low ESR ceramic capacitors are recommended. The selection of COUT is determined by the required ESR to minimize voltage ripple. Moreover, the amount of bulk capacitance is also a key for COUT selection to ensure that the control loop is stable. The output ripple, ΔVOUT, is determined by : 1 ⎤ ΔVOUT ≤ ΔIL ⎡⎢ESR + 8fCOUT ⎦⎥ ⎣ The output ripple will be highest at the maximum input voltage since ΔIL increases with input voltage. Multiple capacitors placed in parallel may need to meet the ESR and RMS current handling requirements. 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. However, care must be taken when these capacitors are used at input and is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT7277 output. When a ceramic capacitor is used at the input and the power is supplied by a wall adapter through long wires, a load step at the output can induce ringing at the input, VIN. A sudden inrush of current through the long wires can potentially cause a voltage spike at VIN large enough to damage the part. External Bootstrap Diode Connect a 0.1μF low ESR ceramic capacitor between the BOOT and SW pins. This capacitor provides the gate driver voltage for the high side MOSFET. It is recommended to add an external bootstrap diode between an external 5V and the BOOT pin for efficiency improvement when input voltage is lower than 5.5V or duty ratio is higher than 65%. The bootstrap diode can be a low cost one such as 1N4148 or BAT54. The external 5V can be a 5V fixed input from system or a 5V output of the RT7277. Note that the external boot voltage must be lower than 5.5V 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, the maximum junction temperature is 125°C. The junction to ambient thermal resistance, θJA, is layout dependent. For SOP-8 (Exposed Pad) package, the thermal resistance, θJA, is 49°C/W on a standard JEDEC 51-7 four-layer PD(MAX) = (125°C − 25°C) / (49°C/W) = 2.041W for SOP-8 (Exposed Pad) package 0.1µF SW Figure 5. External Bootstrap Diode PVCC Capacitor Selection Decouple with a 1μF ceramic capacitor. X7R or X5R grade dielectric ceramic capacitors are recommended for their stable temperature characteristics. Over Current Protection When the output shorts to ground, the inductor current decays very slowly during a single switching cycle. An over current detector is used to monitor inductor current to prevent current runaway. The over current detector monitors the voltage between SW and GND during the low side MOS turn-on state. This is cycle-by-cycle protection. The over current detector also supports temperature compensated. Copyright © 2012 Richtek Technology Corporation. All rights reserved. The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curve in Figure 6 allow the designer to see the effect of rising ambient temperature on the maximum power dissipation. 2.5 Maximum Power Dissipation (W)1 BOOT www.richtek.com 12 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 : thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formulas : 5V RT7277 Thermal Considerations Four-Layer PCB 2.0 1.5 1.0 0.5 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 6. Derating Curve of Maximum Power Dissipation is a registered trademark of Richtek Technology Corporation. DS7277-00 October 2012 RT7277 Layout Consideration Follow the PCB layout guidelines for optimal performance of the RT7277 ` Keep 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). The resistor divider must be connected as close to the device as possible. R2 GND C4 C5 SW node is with high frequency voltage swing and should be kept at small area. Keep sensitive components away from the SW node to prevent stray capacitive noise pickup. ` Connect feedback network behind the output capacitors. Keep the loop area small. Place the feedback components near the RT7277 feedback pin. ` The GND and Exposed Pad should be connected to a strong ground plane for heat sinking and noise protection. Input capacitor must be placed C1 as close to the IC as possible. VOUT R1 ` C2 EN 8 FB 2 PVCC SS 3 GND 4 9 SW should be connected to inductor by wide and short trace. Keep sensitive components away from this trace. VIN 7 BOOT 6 SW 5 GND C6 C7 L1 VOUT Figure 7. PCB Layout Guide Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS7277-00 October 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 13 RT7277 Outline Dimension H A M EXPOSED THERMAL PAD (Bottom of Package) Y J X B F C I D Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 4.801 5.004 0.189 0.197 B 3.810 4.000 0.150 0.157 C 1.346 1.753 0.053 0.069 D 0.330 0.510 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.170 0.254 0.007 0.010 I 0.000 0.152 0.000 0.006 J 5.791 6.200 0.228 0.244 M 0.406 1.270 0.016 0.050 X 2.000 2.300 0.079 0.091 Y 2.000 2.300 0.079 0.091 X 2.100 2.500 0.083 0.098 Y 3.000 3.500 0.118 0.138 Option 1 Option 2 8-Lead SOP (Exposed Pad) Plastic Package 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 DS7277-00 October 2012