® RT2862A 3A, 36V, Synchronous Step-Down Converter General Description Features The RT2862A is a high efficiency, current-mode synchronous step-down DC/DC converter that can deliver up to 3A output current over a wide input voltage range from 4.5V to 36V. The device integrates 105mΩ high-side and 80mΩ low-side MOSFETs to achieve high conversion efficiency. The current-mode control architecture supports fast transient response and simple external compensation. 4.5V to 36V Input Voltage Range 3A Output Current Internal N-MOSFETs Current Mode Control Frequency Operation : 300kHz to 1MHz Adjustable Output Voltage from 0.8V to 30V High Efficiency Up to 95% Stable with Low ESR Ceramic Output Capacitors Cycle-by-Cycle Current Limit Input Under-Voltage Lockout Output Under-Voltage Protection Thermal Shutdown Power Saving at Light Load A cycle-by-cycle current limit function provides protection against shorted output and an internal soft-start eliminates input current surge during start-up. The RT2862A provides complete protection functions such as input under-voltage lockout, output under-voltage protection, over-current protection and thermal shutdown. The RT2862A is available in the thermal enhanced SOP-8 (Exposed Pad) package. Applications Ordering Information RT2862A Package Type SP: SOP-8 (Exposed Pad-Option 2) Lead Plating System G : Green (Halogen Free and Pb Free) Note : Point of Load Regulator in Distributed Power Systems Digital Set Top Boxes Broadband Communications Vehicle Electronics Automotive Audio, Navigation, and Information Systems Enterprise Datacom Platforms Point of Load (POL) Industrial Grade General Purpose Point of Load Marking Information Richtek products are : RT2862AGSP : Product Number RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. RT2862A GSPYMDNN YMDNN : Date Code Suitable for use in SnPb or Pb-free soldering processes. Simplified Application Circuit BOOT VIN VIN CIN RT2862A CB L SW VOUT R1 RT GND Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS2862A-00 May 2015 COUT FB RT CC COMP RC R2 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT2862A Pin Configurations (TOP VIEW) 8 SW BOOT 2 EN 3 GND 4 GND VIN 7 RT 6 COMP 5 FB 9 SOP-8 (Exposed Pad) Functional Pin Description Pin No. Pin Name Pin Function 1 SW Switch Node. Connect to external L-C filter. 2 BOOT Bootstrap Supply for the High-Side MOSFET. Connect a 100nF or greater capacitor between the BOOT and SW pins. 3 EN Enable Control Input. A logic-high enables the converter; a logic-low forces the device into shutdown mode. GND Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum thermal dissipation. 5 FB Feedback Voltage Input. This pin is used to set the output voltage of the converter to regulate to the desired value via an resistive divider. 6 COMP Compensation Node. COMP is used to compensate the regulation control loop. Connect a R-C network from the COMP to GND. In some cases, an additional capacitor from COMP to GND is required. 7 RT Switching Frequency Setting. Connect an external resistor to set the switching frequency from 300kHz to 1MHz. 8 VIN Power Input. The input voltage range is from 4.5V to 36V. Must bypass with a suitable large ceramic capacitor at this pin. 4, 9 (Exposed Pad) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS2862A-00 May 2015 RT2862A Function Block Diagram VIN VCC Internal Regulator Shutdown Comparator 1.2V Oscillator VA VCC - 5k EN Slope Comp Foldback Control + 0.4V Lockout Comparator + 1.7V + + Current Comparator 3.6V 0.8V RT RSENSE VA BOOT UV UV Comparator SS Current Sense Amplifier + - S Q R Q SW GND + + EA - FB COMP Operation The RT2862A is a current-mode synchronous step-down converter. In normal operation, the high-side N-MOSFET is turned on when the S-R latch is set by the oscillator and is turned off when the current comparator resets the S-R latch. 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 0.8V reference. When the load current increases, it causes a drop in the feedback voltage relative to the reference, and then the error amplifier's output voltage rises to allow higher inductor current to match the load current. Oscillator The oscillator frequency can be set by using an external resister RT. Oscillator frequency range is from 300kHz to 1MHz. Internal Regulator The regulator provides low voltage power to supply the internal control circuits and the bootstrap power for highside gate driver. Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS2862A-00 May 2015 Enable The converter is turned on when the EN pin is higher than 2V. When the EN pin is lower than 0.4V, the converter will enter shutdown mode and reduce the supply current to 0.5μA. 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 2ms. UV Comparator If the feedback voltage is lower than 0.4V, the UV Comparator will go high to turn off the high-side MOSFET. The output under voltage protection is designed to operate in hiccup mode. When the UV condition is removed, the converter will resume switching. Thermal Shutdown The over-temperature protection function will shut down the switching operation when the junction temperature exceeds 150°C. Once the junction temperature cools down by approximately 20°C, the converter will automatically resume switching. is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT2862A Absolute Maximum Ratings (Note 1) Supply Voltage, VIN -----------------------------------------------------------------------------------------------Switch Voltage, SW -----------------------------------------------------------------------------------------------BOOT Pin ------------------------------------------------------------------------------------------------------------EN Pin (with REN (150kΩ to 600kΩ) to VIN) ----------------------------------------------------------------SW Voltage (t < 10ns) --------------------------------------------------------------------------------------------EN Pin -----------------------------------------------------------------------------------------------------------------Other Pins ------------------------------------------------------------------------------------------------------------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 --------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Model) ---------------------------------------------------------------------------------------- Recommended Operating Conditions −0.3V to 40V −0.3V to (VIN + 0.3V) −0.3V to 46.3V −0.3V to 40V −5V to 46.3V −0.3V to 3.6V −0.3V to 40V 2.041W 49°C/W 8°C/W 260°C 150°C −65°C to 150°C 2kV (Note 4) Supply Input Voltage, VIN ----------------------------------------------------------------------------------------- 4.5V to 36V Junction Temperature Range -------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 12V, CIN = 20μF, TA = −40°C to 85°C, unless otherwise specified) Parameter Symbol Shutdown Supply Current Test Conditions Min Typ Max Unit VEN = 0V -- -- 10 A -- 1 1.3 mA 0.784 0.8 0.816 V Quiescent Current IQ VEN = 3V, VFB = 0.9V Feedback Reference Voltage VREF 4.5V VIN 36V Switch On-Resistance High-Side RDS(ON)1 -- 105 190 Low-Side RDS(ON)2 -- 80 145 4.25 5 5.75 A -- 1.7 -- A RT = 191k 264 300 336 RT = 113k 440 500 560 RT = 51k 880 1000 1120 High-Side Switch Current Limit Range UOC Low-Side Switch Current Limit Oscillation Frequency From Drain to Source fOSC1 m kHz Short-Circuit Oscillation Frequency fOSC2 VFB = 0V, RT = 113k -- 50 -- kHz Maximum Duty Cycle DMAX VFB = 0.7V -- 95 -- % Minimum On-Time tON -- 100 120 ns Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS2862A-00 May 2015 RT2862A Parameter EN Input Voltage Symbol Test Conditions Min Typ Max Unit Logic-High VIH 2 -- 3.3 Logic-Low VIL -- -- 0.4 3.7 4.2 4.5 V V Input Under-Voltage Lockout Threshold VUVLO Input Under-Voltage Lockout Hysteresis VUVLO -- 250 -- mV Thermal Shutdown Threshold T SD -- 150 -- C Thermal Shutdown Hysteresis TSD -- 25 -- C COMP to Current Sense Trans-conductance GCS -- 4.1 -- A/V -- 950 -- A/V VIN Rising ICOMP = ±10A Error Amplifier Trans-conductance GEA 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 with 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 © 2015 Richtek Technology Corporation. All rights reserved. DS2862A-00 May 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT2862A Typical Application Circuit 8 VIN 4.5V to 36V VIN RT2862A 2 BOOT CIN 10µF x 2 Enable REN SW 1 3 7 RT 113k 4, 9 (Exposed Pad) CB 100nF L VOUT R1 EN FB 5 RT GND COMP 6 COUT CC RC R2 Table 1. Suggested Component Values VOUT (V) R1 (k) R2 (k) RC (k) L (H) CC (nF) COUT (F) 12 47 3.35 47 10 2.7 22 x 2 8 27 3 36 8.2 2.7 22 x 2 5 62 11.8 24 6.8 2.7 22 x 2 3.3 75 24 16 4.7 2.7 22 x 2 2.5 25.5 12 12 3.6 2.7 22 x 2 1.2 30 60 6.8 2.2 2.7 22 x 2 Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS2862A-00 May 2015 RT2862A Typical Operating Characteristics Reference Voltage vs. Input Voltage Efficiency vs. Output Current 100 0.810 90 0.808 VIN = VIN = VIN = VIN = VIN = 70 60 50 Reference Voltage (V) Efficiency (%) 80 5V 12V 24V 30V 36V 40 30 20 0.805 0.803 0.800 0.798 0.795 0.793 10 VOUT = 3.3V, RT = 113k VIN = 4.5V to 36V, IOUT = 0A, RT = 113k 0.790 0 0 0.5 1 1.5 2 2.5 4 3 8 12 16 20 24 28 32 36 Input Voltage (V) Output Current (A) Output Voltage vs. Output Current Reference vs. Temperature 3.50 0.810 0.805 Output Voltage (V) Reference Voltage (V) 3.45 0.800 VIN = VIN = VIN = VIN = 0.795 4.5V 12V 24V 36V VIN = VIN = VIN = VIN = VIN = 3.40 3.35 5V 12V 24V 30V 36V 3.30 3.25 3.20 3.15 VOUT = 3.3V, RT = 113k VOUT = 3.3V, IOUT = 0A, RT = 113k 3.10 0.790 -50 -25 0 25 50 75 100 0 125 0.5 1 Temperature (°C) Switching Frequency vs. Input Voltage 2 2.5 3 Switching Frequency vs. Temperature 600 520 515 Switching Frequency (kHz)1 Switching Frequency (kHz)1 1.5 Output Current (A) 510 505 500 495 490 485 VOUT = 3.3V, IOUT = 0A, RT = 113k 480 580 560 540 520 500 480 VIN = VIN = VIN = VIN = 460 440 420 4.5V 12V 24V 36V VOUT = 3.3V, IOUT = 0A, RT = 113k 400 4 8 12 16 20 24 28 32 Input Voltage (V) Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS2862A-00 May 2015 36 -50 -25 0 25 50 75 100 125 Temperature (°C) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT2862A Current Limit vs. Temperature Frequency vs. RT 8 1200 1100 1000 Frequency (kHz)1 Inductor Current (A) 7 6 5 VIN = VIN = VIN = VIN = 4 3 36V 24V 12V 4.5V 900 800 700 600 500 400 300 2 -50 -25 0 25 50 75 100 125 50 65 80 95 110 125 140 155 170 185 200 RT (kΩ ) Temperature (°C) Load Transient Response Load Transient Response VOUT (500mV/Div) VOUT (200mV/Div) IOUT (2A/Div) VIN = 12V, IOUT = 0A 200 VIN = 12V, VOUT = 3.3V, IOUT = 1.5 to 3A, RT = 113k IOUT (2A/Div) Time (100μs/Div) Time (100μs/Div) Switching Switching VOUT (5mV/Div) VOUT (5mV/Div) VSW (5V/Div) VSW (5V/Div) IL (1A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 1.5A, RT = 113k Time (1μs/Div) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 VIN = 12V, VOUT = 3.3V, IOUT = 0 to 3A, RT = 113k IL (2A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 3A, RT = 113k Time (1μs/Div) is a registered trademark of Richtek Technology Corporation. DS2862A-00 May 2015 RT2862A Power Off from EN Power On from EN VEN (2V/Div) VEN (2V/Div) VOUT (2V/Div) VOUT (2V/Div) IOUT (2A/Div) IOUT (2A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 3A, RT = 113k VIN = 12V, VOUT = 3.3V, IOUT = 3A, RT = 113k Time (2.5ms/Div) Time (2.5ms/Div) Power On from VIN Power Off from VIN VIN (5V/Div) VIN (5V/Div) VOUT (2V/Div) VOUT (2V/Div) IL (2A/Div) IL (2A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 3A, RT = 113k Time (5ms/Div) Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS2862A-00 May 2015 VIN = 12V, VOUT = 3.3V, IOUT = 3A, RT = 113k Time (5ms/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT2862A Application Information Output Voltage Setting Chip Enable Operation The resistive divider allows the FB pin to sense the output voltage as shown in Figure 1. The EN pin is the chip enable input. Pulling the EN pin low (<0.4V) will shutdown the device. During shutdown mode, the RT2862A quiescent current drops to lower than 3μA. Driving the EN pin high (>2.5V, <3.3V) will turn on the 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 3). VOUT R1 FB RT2862A R2 GND REN must be chose between 150kΩ to 600kΩ, which is to avoid huge leak current into chip. Figure 1. Output Voltage Setting EN VIN The output voltage is set by an external resistive voltage divider according to the following equation : VOUT = VREF 1 R1 R2 where VREF is the reference voltage (0.8V typ.). 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 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 IN4148 or BAT54. The external 5V can be a 5V fixed input from system or a 5V output of the RT2862A. Note that the external boot voltage must be lower than 5.5V 5V REN EN RT2862A CEN GND Figure 3. Enable Timing Control An external MOSFET can be added to implement digital control on the EN pin when no system voltage above 2.5V is available, as shown in Figure 4. In this case, a 300kΩ 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 EN REN 300k EN Q1 RT2862A GND Figure 4. Digital Enable Control Circuit Under-Voltage Protection Hiccup Mode BOOT RT2862A 100nF SW Figure 2. External Bootstrap Diode Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 The RT2862A provides Hiccup Mode Under-Voltage Protection (UVP). When the VFB voltage drops below 0.4V, the UVP function will be triggered to shut down switching operation. If the UVP condition remains for a period, the RT2862A will retry automatically. When the UVP condition is removed, the converter will resume operation. The UVP is disabled during soft-start period. is a registered trademark of Richtek Technology Corporation. DS2862A-00 May 2015 RT2862A Hiccup Mode The inductor's current rating (caused a 40°C temperature rising from 25°C ambient) should be greater than the maximum load current and its saturation current should be greater than the short circuit peak current limit. Please see Table 2 for the inductor selection reference. VOUT (2V/Div) Table 2. Suggested Inductors for Typical Application Circuit ILX (2A/Div) IOUT = Short Time (50ms/Div) Figure 5. Hiccup Mode Under-Voltage Protection Component Supplier Series Dimensions (mm) TDK VLF10045 10 x 9.7 x 4.5 TDK TAIYO YUDEN SLF12565 12.5 x 12.5 x 6.5 NR8040 8x8x4 Over-Temperature Protection CIN and COUT Selection The RT2862A features an Over-Temperature Protection (OTP) circuitry to prevent overheat 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 converter will resume operation. To maintain continuous operation, the maximum junction temperature should be lower than 125°C. The input capacitance, C IN, is needed to filter the trapezoidal current at the Source of the high-side MOSFET. To prevent large ripple current, a low ESR input capacitor sized for the maximum RMS current should be used. The approximate RMS current equation is given : Inductor Selection The inductor value and operating frequency determine the ripple current according to a specific input and output voltage. The ripple current ΔIL increases with higher VIN and decreases with higher inductance. V V IL = OUT 1 OUT VIN f L 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 the highest efficiency operation. However, it requires a large inductor to achieve this goal. For the ripple current selection, the value of ΔIL = 0.24(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 L(MAX) Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS2862A-00 May 2015 V IRMS = IOUT(MAX) OUT VIN VIN 1 VOUT 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. 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 low ESR ceramic capacitors are suggested. For the suggested capacitor, please refer to Table 3 for more details. 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. Loop stability can be checked by viewing the load transient response as described in a later section. The output ripple, ΔVOUT, is determined by : 1 VOUT IL ESR 8fCOUT is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT2862A voltage since ΔIL increases with input voltage. Multiple capacitors placed in parallel may be needed to meet the ESR and RMS current handling requirement. 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 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. At best, this ringing can couple to the output and be mistaken as loop instability. At worst, a sudden inrush of current through the long wires can potentially cause a voltage spike at VIN large enough to damage the part. Thermal Considerations For continuous operation, do not exceed the maximum operation junction temperature 125°C. The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surroundings airflow and temperature difference between junction to ambient. The maximum power dissipation can be calculated by following formula : PD(MAX) = (TJ(MAX) − TA ) / θJA Where T J(MAX) is the maximum operation junction temperature , TA is the ambient temperature and the θJA is the junction to ambient thermal resistance. For recommended operating conditions specification of RT2862A, 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 75°C/W on the standard JEDEC 51-7 four-layers thermal test board. The maximum power dissipation at TA = 25°C can be calculated by following formula : The thermal resistance θJA of SOP-8 (Exposed Pad) is determined by the package architecture design and the PCB layout design. However, the package architecture design had been designed. If possible, it's useful to increase thermal performance by the PCB layout copper design. The thermal resistance θJA can be decreased by adding copper area under the exposed pad of SOP-8 (Exposed Pad) package. As shown in Figure 6, the amount of copper area to which the SOP-8 (Exposed Pad) is mounted affects thermal performance. When mounted to the standard SOP-8 (Exposed Pad) pad (Figure 6.a), θJA is 75°C/W. Adding copper area of pad under the SOP-8 (Exposed Pad) (Figure 6.b) reduces the θJA to 64°C/W. Even further, increasing the copper area of pad to 70mm2 (Figure 6.e) reduces the θJA to 49°C/W. The maximum power dissipation depends on operating ambient temperature for fixed T J(MAX) and thermal resistance θJA. The Figure 7 of derating curves allows the designer to see the effect of rising ambient temperature on the maximum power dissipation allowed. 2.2 Four-Layer PCB 2.0 Power Dissipation (W) The output ripple will be the highest at the maximum input 1.8 Copper Area 70mm2 50mm2 30mm2 10mm2 Min.Layout 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 7. Derating Curve of Maximum Power Dissipation P D(MAX) = (125°C − 25°C) / (75°C/W) = 1.333W (min.copper area PCB layout) P D(MAX) = (125°C − 25°C) / (49°C/W) = 2.04W (70mm2copper area PCB layout) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 is a registered trademark of Richtek Technology Corporation. DS2862A-00 May 2015 RT2862A Layout Considerations For best performance of the RT2862A, the following layout guidelines must be strictly followed. (a) Copper Area = (2.3 x 2.3) mm2, θJA = 75°C/W Input capacitor must be placed as close to the IC as possible. SW should be connected to inductor by wide and short trace. Keep sensitive components away from this trace. The RT resistor, compensator and feedback components must be connected as close to the device as possible. (b) Copper Area = 10mm2, θJA = 64°C/W (c) Copper Area = 30mm2 , θJA = 54°C/W (d) Copper Area = 50mm2 , θJA = 51°C/W (e) Copper Area = 70mm2 , θJA = 49°C/W Figure 6. Thermal Resistance vs. Copper Area Layout Design Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS2862A-00 May 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 13 RT2862A Input capacitor must be placed as close to the IC as possible. VOUT VIN COUT SW should be connected to inductor by wide and short trace. Keep sensitive components away from this trace and CBOOT. RS* L CIN The RT resistor must be connected as close to the device as possible. Keep sensitive components away. CS* RT CBOOT VIN 8 SW REN BOOT 2 EN 3 GND 4 GND VIN 7 RT 6 COMP 5 FB 9 CC R1 VOUT RC CP R2 The REN component must be connected. GND The Compensator and feedback components must be connected as close to the device as possible. * : Option Figure 8. PCB Layout Guide Table 3. Suggested Capacitors for CIN and COUT Location Component Supplier Part No. Capacitance (F) Case Size CIN MURATA GRM32ER71H475K 4.7 1206 CIN TAIYO YUDEN UMK325BJ475MM-T 4.7 1206 CIN MURATA GRM31CR61E106K 10 1206 CIN TDK C3225X5R1E106K 10 1206 CIN TAIYO YUDEN TMK316BJ106ML 10 1206 C OUT MURATA GRM31CR60J476M 47 1206 C OUT TDK C3225X5R0J476M 47 1210 C OUT MURATA GRM32ER71C226M 22 1210 C OUT TDK C3225X5R1C22M 22 1210 Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 14 is a registered trademark of Richtek Technology Corporation. DS2862A-00 May 2015 RT2862A Outline Dimension H A M EXPOSED THERMAL PAD (Bottom of Package) Y J X B F C I D Dimensions In Millimeters Symbol Dimensions In Inches 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 14F, No. 8, Tai Yuen 1st 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. DS2862A-00 May 2015 www.richtek.com 15