® RT6202A/B 5A, 18V, 650kHz, ACOTTM Synchronous Step-Down Converter General Description Features The RT6202A/B is a synchronous step-down DC/DC converter with Advanced Constant On-Time (ACOTTM) mode control. It achieves high power density to deliver up to 5A 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 capacitor for ensuring performance stabilization. In addition, RT6202A/B 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 include thermal shutdown for RT6202A/B. The RT6202A/B are available in the SOP-8 (Exposed Pad) package. Pin Configurations (TOP VIEW) FB 2 VREG5 3 SS 4 GND 8 VIN 7 BOOT 6 SW 5 GND 9 4.5V to 18V Input Voltage Range 5A Output Current 35mΩ Ω Internal Low Side N-MOSFET Advanced Constant On-Time Control Support All Ceramic Capacitors Up to 95% Efficiency 650kHz Switching Frequency at all Load Current (RT6202B) Discontinuous Operating Mode at Light Load (RT6202A) 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 EN ACOTTM Mode Enables Fast Transient Response 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 SOP-8 (Exposed Pad) Simplified Application Circuit RT6202A/B VIN VIN Enable EN SW VOUT BOOT VREG5 SS Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS6202A/B-00 December 2013 FB GND is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT6202A/B Ordering Information Marking Information RT6202A/B RT6202AHGSP Package Type SP : SOP-8 (Exposed Pad-Option 2) Lead Plating System G : Green (Halogen Free and Pb Free) UVP Trim Operation H : Hiccup PSM/PWM Mode A : PSM Mode B : PWM Mode RT6202AHGSP : Product Number RT6202AH GSPYMDNN YMDNN : Date Code RT6202BHGSP RT6202BHGSP : Product Number RT6202BH GSPYMDNN YMDNN : 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 1 EN Enable Control Input. A logic-high enables the converter; a logic-low forces the IC into shutdown mode reducing the supply current to less than 10A. 2 FB Feedback Voltage 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 VREG5 Internal Regulator Output. Connect a 1F capacitor to GND to stabilize output voltage. 4 SS Soft-Start Time Setting. Connect an external capacitor between this pin and GND to set the soft- start time. GND Power Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power 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 0.1F capacitor between the BOOT and SW pin. 8 VIN Power Input. The input voltage range is from 4.5V to 18V. Must bypass with a suitably large (10F x 2) ceramic capacitor. 5, 9 (Exposed Pad) Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS6202A/B-00 December 2013 RT6202A/B Function Block Diagram VREG5 EN POR & Reg VBIAS BOOT Min. Off-Time VREG5 VIN VREF OC Control SW Driver UV & OV GND SW VREG5 6µA SS ZC Ripple Gen. FB + Comparator VIN On-Time FB Operation The RT6202A/B is a synchronous step-down converter with advanced constant on-time control mode. Using the ACOTTM control mode can reduce the output capacitance and provide fast transient response. It can minimize the component size without additional external compensation network. UVLO Protection To protect the chip from operating at insufficient supply voltage, the UVLO is needed. When the input voltage of VIN is lower than the UVLO falling threshold voltage, the device will be latch-off. Thermal Shutdown Internal Regulator The regulator provides 5V power to supply the internal control circuit. Connecting a 1μF ceramic capacitor for decoupling and stability is required. Soft-Start When the junction temperature exceeds the OTP threshold value, the IC will shut down the switching operation. Once the junction temperature cools down and is lower than the OTP lower threshold, the converter will automatically resume switching In order to prevent the converter output voltage from overshooting during the startup period, the soft-start function is necessary. The soft-start time is adjustable and can be set by an external capacitor. Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS6202A/B-00 December 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT6202A/B Absolute Maximum Ratings (Note 1) Supply Voltage, VIN ----------------------------------------------------------------------------------------------Switch Voltage, SW ----------------------------------------------------------------------------------------------< 10ns ---------------------------------------------------------------------------------------------------------------BOOT to SW -------------------------------------------------------------------------------------------------------EN ---------------------------------------------------------------------------------------------------------------------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 -------------------------------------------------------------------------------------Junction Temperature Range ------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------Storage Temperature Range ------------------------------------------------------------------------------------- Recommended Operating Conditions −0.3V to 20V −0.8V to (VIN + 0.3V) −5V to 25V −0.3V to 6V −0.3V to 20V −0.3V to 6V 2.041W 49°C/W 15°C/W 150°C 260°C −65°C to 150°C (Note 3) 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 I SHDN VEN = 0V -- 1 10 A Quiescent Current IQ VEN = 5V, VFB = 0.8V -- 1 1.3 mA Logic-High 2 -- 18 Logic-Low -- -- 0.4 Logic Threshold EN Input Voltage V VFB Voltage TA = 25C 0.757 TA = 40C to 85C 0.755 -- 0.775 -- 0.01 0.1 A 6V V IN 18V, 0 < IVREG5 5mA 6V V IN 18V, IVREG5 = 5mA 4.8 5.1 5.4 V -- -- 20 mV 0 I VREG5 5mA VIN = 6V, VREG5 = 4V, TA = 25C -- -- 100 mV -- 70 -- mA Feedback Threshold Voltage V FB Feedback Input Current I FB VFB = 0.8V V REG5 0.765 0.773 V VREG5 Output VREG5 Output Voltage Line Regulation Load Regulation Output Current I VREG5 Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS6202A/B-00 December 2013 RT6202A/B Parameter Symbol Test Conditions Min Typ Max Unit -- 120 -- -- 35 -- 6.1 6.9 8.4 A -- 150 -- -- 20 -- C RDS(ON) Switch On Resistance High-Side RDS(ON)_H Low-Side RDS(ON)_L (VBOOT VSW) = 5.5V m Current Limit Current Limit ILIM Thermal Shutdown Thermal Shutdown Threshold TSD Shutdown Temperature Thermal Shutdown Hysteresis TSD On-Time Timer Control On-Time tON VIN = 12V, VOUT = 1.05V -- 135 -- ns Minimum Off-Time tOFF(MIN) VFB = 0.7V -- 260 310 ns SS Charge Current VSS = 0V -- 6 -- A SS Discharge Current VSS = 0.5V 0.1 0.2 -- mA Wake Up VREG5 3.6 3.85 4.1 0.16 0.35 0.47 115 120 125 % OVP Prop Delay -- 5 -- s UVP Trip Threshold 65 70 75 UVP Hysteresis -- 10 -- UVP Prop Delay -- 250 -- s -- tSS x 1.7 -- ms Soft-Start UVLO UVLO Threshold Hysteresis V Output Under Voltage and Over Voltage Protection OVP Trip Threshold UVP Enable Delay OVP Detect tUVPEN Relative to Soft-Start Time % 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. 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. DS6202A/B-00 December 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT6202A/B Typical Application Circuit VIN C1 10µF x 2 C2 0.1µF BOOT 1 Input Signal C4 1µF C5 3.9nF L1 1.4µH RT6202A/B 6 8 VIN SW EN 3 VREG5 4 SS FB 7 C6 0.1µF VOUT 1.05V/4A C3 C7 22µF x 2 R1 8.25k 2 R2 22k GND 5, 9 (Exposed Pad) Table 1. Suggested Component Values (VIN = 12V) VOUT (V) R1 (k) R2 (k) C3 (pF) L1 (H) C7 (F) 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 © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS6202A/B-00 December 2013 RT6202A/B Typical Operating Characteristics Efficiency vs. Output Current Efficiency vs. Output Current 100 100 RT6202B 90 80 80 70 70 60 Efficiency (%) Efficiency (%) RT6202A 90 VIN = 5V VIN = 12V VIN = 18V 50 40 30 60 50 VIN = 5V VIN = 12V VIN = 18V 40 30 20 20 10 10 VOUT = 1.05V 0 0.001 0.01 0.1 1 VOUT = 1.05V 0 0.001 10 0.01 10 Feedback Threshold Voltage vs. Temperature Output Voltage vs. Input Voltage 0.780 Feedback Threshold Voltage (V) 1.060 1.058 1.056 Output Voltage (V) 1 Output Current (A) Output Current (A) 1.054 1.052 1.050 1.048 1.046 1.044 1.042 VIN = 4.5V to 18V, VOUT = 1.05V 0.775 0.770 0.765 0.760 0.755 VIN = 12V, VOUT = 1.05V, IOUT = 0A 0.750 1.040 4 6 8 10 12 14 16 -50 18 -25 0 Input Voltage (V) RT6202A 1.08 1.08 Output Voltage (V) 1.09 1.07 1.06 1.05 VIN = 18V VIN = 12V VIN = 5V 1.03 50 75 100 125 Output Voltage vs. Output Current 1.10 1.09 1.04 25 Temperature (°C) Output Voltage vs. Output Current 1.10 Output Voltage (V) 0.1 1.02 RT6202B 1.07 1.06 1.05 VIN = 18V VIN = 12V VIN = 5V 1.04 1.03 1.02 1.01 1.01 VOUT = 1.05V 1.00 VOUT = 1.05V 1.00 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Output Current (A) Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS6202A/B-00 December 2013 5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Output Current (A) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT6202A/B Switching Frequency vs. Temperature 700 690 690 Switching Frequency (kHz)1 Switching Frequency (kHz)1 Switching Frequency vs. Input Voltage 700 680 670 660 650 640 630 620 610 600 680 670 660 650 640 630 620 610 600 4 6 8 10 12 14 16 18 -50 -25 0 Input Voltage (V) 50 75 100 125 Temperature (°C) Current Limit vs. Temperature Current Limit vs. Input Voltage 8.0 9.0 8.5 Current Limit (A) 7.5 Current Limit (A) 25 7.0 6.5 6.0 8.0 7.5 7.0 6.5 6.0 5.5 5.5 VIN = 12V, VOUT = 1.05V 5.0 5.0 -50 -25 0 25 50 75 100 125 4 10 12 14 16 Load Transient Response Load Transient Response 18 RT6202B VOUT (20mV/Div) VOUT (20mV/Div) VIN = 12V, VOUT = 1.05V, IOUT = 1A to 5A Time (100μs/Div) Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 8 Input Voltage (V) RT6202A IOUT (2A/Div) 6 Temperature (°C) IOUT (2A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 0A to 5A Time (100μs/Div) is a registered trademark of Richtek Technology Corporation. DS6202A/B-00 December 2013 RT6202A/B Switching Switching VSW (10V/Div) VSW (10V/Div) VOUT (5mV/Div) VOUT (5mV/Div) IL (1A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 1A IL (5A/Div) Time (1μs/Div) Time (1μs/Div) Power On from VIN Power Off from VIN VIN (10V/Div) VIN (10V/Div) VOUT (1V/Div) VOUT (1V/Div) IOUT (2A/Div) IOUT (2A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 5A VIN = 12V, VOUT = 1.05V, IOUT = 5A Time (2.5ms/Div) Time (10ms/Div) Power On from EN Power Off from EN VEN (2V/Div) VEN (2V/Div) VOUT (1V/Div) VOUT (1V/Div) IOUT (5A/Div) IOUT (5A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 5A Time (500μs/Div) Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS6202A/B-00 VIN = 12V, VOUT = 1.05V, IOUT = 5A December 2013 VIN = 12V, VOUT = 1.05V, IOUT = 5A Time (500μs/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT6202A/B UVLO vs. Temperature EN Threshold Voltage vs. Temperature 4.0 1.4 3.9 1.3 1.2 Rising UVLO (V) EN Threshold Voltage (V) 1.5 1.1 Falling 1.0 Rising 3.8 3.7 3.6 Falling 0.9 3.5 0.8 VIN = 12V, VOUT = 1.05V 0.7 3.4 -50 -25 0 25 50 75 100 125 Temperature (°C) -50 -25 0 25 50 75 100 125 Temperature (°C) UVP VOUT (500mV/Div) IOUT (2A/Div) VIN = 12V, VOUT = 1.05V, IOUT shot to GND Time (10ms/Div) Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 is a registered trademark of Richtek Technology Corporation. DS6202A/B-00 December 2013 RT6202A/B Application Information The RT6202A/B 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 2A. It adopts ACOTTM mode control to provide a very fast transient response with few external compensation components. 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 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 on-time 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. RT6202A/B 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 the VIN and EN pins. MOSFET Q1 will be under logic control to pull down the EN pin. VIN REN 100k EN RT6202A/B Q1 EN GND Figure 2. Digital Enable Control Circuit Soft-Start The RT6202A/B contains an external soft-start clamp that gradually raises the output voltage. The soft-start timing can be programmed by the external capacitor between the SS and GND pins. The chip provides a 6μA charge current for the external capacitor. If a 3.9nF capacitor is used, the soft-start will be 0.87ms (typ.). The available capacitance range is from 2.7nF to 220nF. t SS (ms) = EN CEN Advanced Constant On-Time Control The RT6202A/B has a unique circuit which sets the ontime by monitoring the input voltage and SW signal. The circuit ensures the switching frequency operating at 700kHz over input voltage range and loading range. REN C5 (nF) 1.365 ISS ( 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 RT6202A/B's quiescent current drops to lower than 10μA. Driving the EN pin high (>1.6V, <18V) will turn Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS6202A/B-00 December 2013 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 EN REN2 RT6202A/B GND Figure 3. Resistor Divider for Lockout Threshold Setting is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT6202A/B Output Voltage Setting Inductor Selection The resistive divider allows the FB pin to sense the output voltage as shown in Figure 4. 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 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 highest efficiency operation. However, it requires a large 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 f I V L(MAX) IN(MAX) VOUT R1 FB RT6202A/B 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. R1 VOUT = 0.765 (1 ) R2 Under Voltage Lockout Protection The RT6202A/B has Under Voltage Lockout Protection (UVLO) that monitors the voltage of VIN pin. When the VIN voltage is lower than UVLO threshold voltage, the RT6202A/B will be turned off in this state. This is nonlatch protection. Over Temperature Protection The RT6202A/B 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. Hiccup Mode UVP A Hiccup Mode Under-Voltage Protection (UVP) function is provided for the RT6202A/B. When the FB voltage drops below half of the feedback reference voltage, VFB, the UVP function will be triggered and the RT6202A/B will shut down for a period of time before recovering automatically. The Hiccup Mode UVP can reduce input current in short-circuit conditions. Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 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 : V VIN IRMS = IOUT(MAX) OUT 1 VIN 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 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 VOUT IL ESR 8fCOUT is a registered trademark of Richtek Technology Corporation. DS6202A/B-00 December 2013 RT6202A/B 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. 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 RT6202A/B. Note that the external boot voltage must be lower than 5.5V 5V BOOT RT6202A/B 0.1µF SW Figure 5. External Bootstrap Diode 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. Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS6202A/B-00 December 2013 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, 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 thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formulas : PD(MAX) = (125°C − 25°C) / (49°C/W) = 2.041W for SOP-8 (Exposed Pad) package The maximum power dissipation depends on operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curves in Figure 6 allow the designer to see the effect of rising ambient temperature on the maximum power dissipation. Maximum Power Dissipation (W)1 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. 2.5 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. www.richtek.com 13 RT6202A/B Layout Consideration 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 RT6202A/B FB pin. The GND and Exposed Pad should be connected to a strong ground plane for heat sinking and noise protection. Follow the PCB layout guidelines for optimal performance of the RT6202A/B 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. VOUT R1 R2 GND C4 C5 C1 C2 8 EN FB 2 VREG5 3 SS 4 GND 7 6 9 5 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 VIN components away from this trace. BOOT C6 SW L1 GND C7 VOUT Figure 7. PCB Layout Guide Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 14 is a registered trademark of Richtek Technology Corporation. DS6202A/B-00 December 2013 RT6202A/B 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 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. DS6202A/B-00 December 2013 www.richtek.com 15