® RT8010/A 1.5MHz, 1A, High Efficiency PWM Step-Down DC/DC Converter General Description Features The RT8010/A is a high efficiency Pulse-Width-Modulated (PWM) step-down DC/DC converter. Capable of delivering 1A output current over a wide input voltage range from 2.5V to 5.5V, the RT8010/A is ideally suited for portable electronic devices that are powered from 1-cell Li-ion battery or from other power sources such as cellular phones, PDAs and hand-held devices. 2.5V to 5.5V Input Range Output Voltage (Adjustable Output From 0.6V to VIN) RT8010 : 1V, 1.2V, 1.5V, 1.6V, 1.8V, 2.5V and 3.3V Fixed/Adjustable Output Voltage RT8010A Adjustable Output Voltage Only 1A Output Current 95% Efficiency No Schottky Diode Required 1.5MHz Fixed-Frequency PWM Operation Small 6-Lead WDFN and 16-Lead WQFN Package RoHS Compliant and 100% Lead (Pb)-Free Two operating modes are available including : PWM/LowDropout autoswitch and shutdown modes. The Internal synchronous rectifier with low RDS(ON) dramatically reduces conduction loss at PWM mode. No external Schottky diode is required in practical application. The RT8010/A enters Low Dropout mode when normal PWM cannot provide regulated output voltage by continuously turning on the upper P-MOSFET. RT8010/A enter shut-down mode and consumes less than 0.1μA when EN pin is pulled low. The switching ripple is easily smoothed-out by small package filtering elements due to a fixed operating frequency of 1.5MHz. This along with small WDFN-6L 2x2 and WQFN-16L 3x3 package provides small PCB area application. Other features include soft start, lower internal reference voltage with 2% accuracy, over temperature protection, and over current protection. Applications Mobile Phones Personal Information Appliances Wireless and DSL Modems MP3 Players Portable Instruments Marking Information For marking information, contact our sales representative directly or through a Richtek distributor located in your area. Pin Configurations IC LX LX LX (TOP VIEW) 16 15 14 13 IC EN VIN 1 6 2 5 3 7 4 FB/VOUT GND LX GND GND GND FB/VOUT 1 12 2 11 3 10 VIN VIN 9 VIN 17 4 6 7 8 GND IC EN IC 5 VIN WDFN-6L 2x2 (RT8010) WQFN-16L 3x3 (RT8010A) Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS8010/A-10 February 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 ® RT8010/A Ordering Information RT8010/A(- ) Pin 1 Orientation*** (3) : Quadrant 3, Follow EIA-481-D (For RT8010AGQW Only) Package Type QW : WDFN/WQFN (W-Type) Lead Plating System P : Pb Free G : Green (Halogen Free and Pb Free) Output Voltage Default : Adjustable (RT8010/A) Fixed (RT8010) 10 : 1.0V 12 : 1.2V 15 : 1.5V 16 : 1.6V 18 : 1.8V 25 : 2.5V 33 : 3.3V WQFN-16L 3x3 WDFN-6L 2x2 Note : ***Empty means Pin1 orientation is Quadrant 1 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. Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS8010/A-10 February 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 2 RT8010/A Typical Application Circuit VIN 2.5V to 5.5V 3 CIN 4.7µF VIN LX L 2.2µH 4 VOUT RT8010/A 2 1 EN VOUT IC GND 6 COUT 10µF 5 Figure 1. Fixed Voltage Regulator VIN 2.5V to 5.5V 3 LX 4 VOUT CIN C1 RT8010/A 4.7µF 2 1 VOUT VREF VIN L 2.2µH EN FB IC GND R1 COUT 6 10µF 5 IR2 x 1 R1 R2 R2 with R2 = 300kΩ to 60kΩ so the IR2 = 2μA to 10μA, and (R1 x C1) should be in the range between 3x10-6 and 6x10-6 for component selection. Figure 2. Adjustable Voltage Regulator Layout Guide RT8010/A_ADJ RT8010/A_FIX IC 1 6 VOUT EN 2 5 GND Output capacitor must be near RT8010 3 1 6 FB EN 2 5 GND VIN 3 4 LX 4 LX COUT COUT CIN CIN must be placed to the VIN as close as possible. Output capacitor must be near RT8010/A L1 L1 VIN IC CIN LX should be connected to Inductor by wide and short trace, keep sensitive components away from this trace. CIN must be placed to the VIN as close as possible. LX should be connected to Inductor by wide and short trace, keep sensitive components away from this trace. R1 R2 Figure 3 Layout note : 1. The distance that CIN connects to VIN is as close as possible (Under 2mm). 2. COUT should be placed near RT8010/A. Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS8010/A-10 February 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8010/A Functional Pin Description Pin No. Pin Name Pin Function RT8010 RT8010A 1 6, 8, 16 IC Internal Connection. Leave floating and do not make connection to this pin. 2 7 EN Chip Enable (Active High). 3 9, 10, 11, 12 VIN Power Input. (Pin 9 and Pin 10 must be connected with Pin 11). 4 13, 14, 15 LX Pin for Switching. (Pin 13 must be connected with Pin 14). 5 1, 2, 3, 5 GND Ground. 6 4 FB/VOUT Feedback/Output Voltage. Ground. The exposed pad must be soldered to a large PCB and 7 (Exposed Pad) 17 (Exposed Pad) GND connected to GND for maximum thermal dissipation. Function Block Diagram EN VIN RS1 OSC & Shutdown Control Slope Compensation FB/VOUT Error Amplifier Current Limit Detector Current Sense Control Logic PWM Comparator Driver LX RC COMP UVLO & Power Good Detector RS2 VREF GND Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS8010/A-10 February 2015 RT8010/A Absolute Maximum Ratings (Note 1) Supply Input Voltage ------------------------------------------------------------------------------------------------EN, FB Pin Voltage -------------------------------------------------------------------------------------------------LX Pin Switch Voltage ----------------------------------------------------------------------------------------------<20ns ------------------------------------------------------------------------------------------------------------------LX Pin Switch Current ----------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C WDFN-6L 2x2 --------------------------------------------------------------------------------------------------------WQFN-16L 3x3 ------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) WDFN-6L 2x2, θJA ---------------------------------------------------------------------------------------------------WDFN-6L 2x2, θJC --------------------------------------------------------------------------------------------------WQFN-16L 3x3, θJA -------------------------------------------------------------------------------------------------WQFN-16L 3x3, θJC ------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------Storage Temperature Range --------------------------------------------------------------------------------------Junction Temperature -----------------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Model) ----------------------------------------------------------------------------------------- Recommended Operating Conditions 6.5V −0.3V to VIN −0.3V to (VIN + 0.3V) −4.5V to 7.5V 2A 0.833W 1.47W 120°C/W 20°C/W 68°C/W 7.5°C/W 260°C −65°C to 150°C 150°C 2kV (Note 4) Supply Input Voltage ------------------------------------------------------------------------------------------------- 2.5V to 5.5V Junction Temperature Range --------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range --------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 3.6V, VOUT = 2.5V, L = 2.2μH, CIN = 4.7μF, COUT = 10μF, TA = 25°C, IMAX = 1A unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit 2.5 -- 5.5 V Input Voltage Range VIN Quiescent Current IQ IOUT = 0mA, VFB = VREF + 5% -- 50 70 A Shutdown Current I SHDN EN = GND -- 0.1 1 A Reference Voltage VREF For Adjustable Output Voltage 0.588 0.6 0.612 V Adjustable Output Range VOUT (Note 5) VREF -- VIN 0.2V V VOUT VIN = 2.5V to 5.5V, VOUT = 1V 0A < IOUT < 1A VIN = 2.5V to 5.5V, VOUT = 1.2V 0A < IOUT < 1A VIN = 2.5V to 5.5V, VOUT = 1.5V 0A < IOUT < 1A VIN = 2.5V to 5.5V, VOUT = 1.6V 0A < IOUT < 1A VIN = 2.5V to 5.5V, VOUT = 1.8V 0A < IOUT < 1A 3 -- 3 3 -- 3 3 -- 3 3 -- 3 3 -- 3 VOUT Output Voltage Accuracy Fix VOUT VOUT VOUT Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS8010/A-10 February 2015 % is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT8010/A Parameter Test Conditions Min Typ Max VOUT VIN = VOUT + V to 5.5V (Note 6) VOUT = 2.5V, 0A < IOUT < 1A 3 -- 3 VOUT VIN = VOUT + V to 5.5V (Note 6) VOUT = 3.3V, 0A < IOUT < 1A 3 -- 3 VOUT VIN = VOUT + V to 5.5V 0A < IOUT < 1A 3 -- 3 % FB Input Current IFB VFB = VIN 50 -- 50 nA 0.28 -- RDS(ON)_P IOUT = 200mA VIN = 3.6V -- P-MOSFET RON VIN = 2.5V -- 0.38 -- 0.25 -- RDS(ON)_N IOUT = 200mA VIN = 3.6V -- N-MOSFET RON VIN = 2.5V -- 0.35 -- P-Channel Current Limit ILIM_P VIN = 2.5V to 5.5 V 1.4 1.5 -- EN High-Level Input Voltage VEN_H VIN = 2.5V to 5.5V 1.5 -- -- EN Low-Level Input Voltage VEN_L VIN = 2.5V to 5.5V -- -- 0.4 Under Voltage Lock Out threshold UVLO -- 1.8 -- V Hysteresis -- 0.1 -- V 1.2 1.5 1.8 MHz -- 160 -- C 100 -- -- % 1 -- 1 A Output Voltage Accuracy Symbol Fix Adjustable Oscillator Frequency fOSC Thermal Shutdown Temperature TSD (Note 6) VIN = 3.6V, IOUT = 100mA Max. Duty Cycle LX Leakage Current VIN = 3.6V, VLX = 0V or VLX = 3.6V Unit % A 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. Note 3. Devices are ESD sensitive. Handling precaution recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Note 5. Guarantee by design. Note 6. ΔV = IOUT x PRDS(ON) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS8010/A-10 February 2015 RT8010/A Typical Operating Characteristics Efficiency vs. Output Current Efficiency vs. Output Current 100 100 90 80 80 70 Efficiency (%) Efficiency (%) 90 VIN = 3.6V VIN = 4.2V VIN = 5V 60 50 40 30 70 VIN = 5V VIN = 3.3V VIN = 2.5V 60 50 40 30 20 20 10 10 VOUT = 3.3V, COUT = 4.7μF, L = 4.7μH VOUT = 1.2V, COUT = 4.7μF, L = 4.7μH 0 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 1 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Output Current (A) Output Current (A) Efficiency vs. Output Current UVLO Voltage vs. Temperature 100 2.0 90 1.9 Rising 70 Input Voltage (V) Efficiency (%) 80 VIN = 5V VIN = 3.3V VIN = 2.5V 60 50 40 30 1.8 1.7 1.6 Falling 1.5 1.4 20 1.3 10 VOUT = 1.2V, IOUT = 0A VOUT = 1.2V, COUT = 10μF, L = 2.2μH 0 1.2 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 -40 -25 -10 5 1.15 1.5 1.10 1.4 1.05 Rising 0.95 0.90 0.85 35 50 65 80 95 110 125 EN Pin Threshold vs. Temperature 1.6 EN Pin Threshold (V) EN Pin Threshold (V) EN Pin Threshold vs. Input Voltage 1.20 1.00 20 Temperature (°C) Output Current (A) Falling 0.80 0.75 0.70 1.3 1.2 1.1 1.0 Rising 0.9 0.8 Falling 0.7 0.6 0.65 VOUT = 1.2V, IOUT = 0A 0.60 0.5 VIN = 3.6V, VOUT = 1.2V, IOUT = 0A 0.4 2.5 2.8 3.1 3.4 3.7 4 4.3 4.6 4.9 5.2 Input Voltage (V) Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS8010/A-10 February 2015 5.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature (°C) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT8010/A Output Voltage vs. Temperature 1.25 1.225 1.24 1.220 1.23 1.215 Output Voltage (V) Output Voltage (V) Output Voltage vs. Load Current 1.230 VIN = 5V 1.210 1.205 VIN = 3.6V 1.200 1.195 1.22 1.21 1.20 1.19 1.18 1.190 1.17 1.185 1.16 1.180 1.15 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 VIN = 3.6V, IOUT = 0A -40 -25 -10 5 35 50 65 80 95 110 125 Frequency vs. Temperature 1.60 1.60 1.55 1.55 1.50 1.50 Frequency (kHz)1 Frequency (kHz) Frequency vs. Input Voltage 1.45 1.40 1.35 1.30 1.45 1.40 1.35 1.30 1.25 1.25 VIN = 3.6V, VOUT = 1.2V, IOUT = 300mA VIN = 3.6V, VOUT = 1.2V, IOUT = 300mA 1.20 1.20 2.5 2.8 3.1 3.4 3.7 4 4.3 4.6 4.9 5.2 -40 -25 -10 5.5 5 Output Current Limit vs. Input Voltage 35 50 65 80 95 110 125 Output Current Limit vs. Temperature 2.6 2.5 2.5 2.4 2.4 Output Current Limit (A) 2.6 2.3 2.2 2.1 2.0 1.9 1.8 1.7 1.6 20 Temperature (°C) Input Voltage (V) Output Current Limit (A) 20 Temperature (°C) Load Current (A) VOUT = 1.2V @ TA = 20°C 1.5 2.3 VIN = 5V VIN = 3.6V 2.2 2.1 VIN = 3.3V 2.0 1.9 1.8 1.7 1.6 VOUT = 1.2V 1.5 2.5 2.8 3.1 3.4 3.7 4 4.3 4.6 4.9 5.2 Input Voltage (V) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 5.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature (°C) is a registered trademark of Richtek Technology Corporation. DS8010/A-10 February 2015 RT8010/A Power On from EN Power On from EN VIN = 3.6V, VOUT = 1.2V, IOUT = 10mA VIN = 3.6V, VOUT = 1.2V, IOUT = 1A VEN (2V/Div) VEN (2V/Div) VOUT (1V/Div) VOUT (1V/Div) I IN (500mA/Div) I IN (500mA/Div) Time (100μs/Div) Time (100μs/Div) Power On from VIN Power Off from EN VIN = 3.6V, VOUT = 1.2V, ILX = 1A VEN = 3V, VOUT = 1.2V, ILX = 1A VIN (2V/Div) VEN (2V/Div) VOUT (1V/Div) VOUT (1V/Div) ILX (1A/Div) ILX (1A/Div) Time (250μs/Div) Time (100μs/Div) Load Transient Response Load Transient Response VIN = 3.6V, VOUT = 1.2V IOUT = 50mA to 0.5A VIN = 3.6V, VOUT = 1.2V IOUT = 50mA to 1A VOUT ac (50mV/Div) VOUT ac (50mV/Div) IOUT (500mA/Div) IOUT (500mA/Div) Time (50μs/Div) Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS8010/A-10 February 2015 Time (50μs/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT8010/A Load Transient Response Load Transient Response VIN = 5V, VOUT = 1.2V IOUT = 50mA to 0.5A VIN = 5V, VOUT = 1.2V IOUT = 50mA to 1A VOUT ac (50mV/Div) VOUT ac (50mV/Div) IOUT (500mA/Div) IOUT (500mA/Div) Time (50μs/Div) Time (50μs/Div) Output Ripple Voltage Output Ripple Voltage VIN = 3.6V, VOUT = 1.2V IOUT = 1A VIN = 5V, VOUT = 1.2V IOUT = 1A VOUT (10mV/Div) VOUT (10mV/Div) VLX (2V/Div) VLX (2V/Div) Time (500ns/Div) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 Time (500ns/Div) is a registered trademark of Richtek Technology Corporation. DS8010/A-10 February 2015 RT8010/A Applications Information The basic RT8010/A application circuit is shown in Typical Application Circuit. External component selection is determined by the maximum load current and begins with the selection of the inductor value and operating frequency followed by CIN and COUT. current is exceeded. This results in an abrupt increase in inductor ripple current and consequent output voltage ripple. Do not allow the core to saturate! Inductor Selection Toroid or shielded pot cores in ferrite or permalloy materials are small and don't radiate energy but generally cost more than powdered iron core inductors with similar characteristics. The choice of which style inductor to use mainly depends on the price vs size requirements and any radiated field/EMI requirements. For a given input and output voltage, the inductor value and operating frequency determine the ripple current. 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 the ESR losses in the output capacitors and the output voltage ripple. Highest efficiency operation is achieved at low frequency with small ripple current. This, however, requires a large inductor. A reasonable starting point for selecting the ripple current is ΔIL = 0.4(IMAX). The largest ripple current occurs at the highest VIN. To guarantee that the ripple current stays below a specified maximum, the inductor value should be chosen according to the following equation : VOUT VOUT L= 1 VIN(MAX) f I L(MAX) Inductor Core Selection Once the value for L is known, the type of inductor must be selected. High efficiency converters generally cannot afford the core loss found in low cost powdered iron cores, forcing the use of more expensive ferrite or mollypermalloy cores. Actual core loss is independent of core size for a fixed inductor value but it is very dependent on the inductance selected. As the inductance increases, core losses decrease. Unfortunately, increased inductance requires more turns of wire and therefore copper losses will increase. Ferrite designs have very low core losses and are preferred at high switching frequencies, so design goals can concentrate on copper loss and preventing saturation. Ferrite core material saturates “hard”, which means that Different core materials and shapes will change the size/ current and price/current relationship of an inductor. CIN and COUT Selection The input capacitance, C IN, is needed to filter the trapezoidal current at the source of the top MOSFET. To prevent large ripple voltage, a low ESR input capacitor sized for the maximum RMS current should be used. RMS current is given by : V IRMS = IOUT(MAX) OUT VIN VIN 1 VOUT This formula has a maximum at VIN = 2VOUT, where I RMS = I OUT/2. This simple worst-case condition is commonly used for design because even significant deviations do not offer much relief. Note that ripple current ratings from capacitor manufacturers are often based on only 2000 hours of life which makes it advisable to further derate the capacitor, or 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. The selection of COUT is determined by the Effective Series Resistance (ESR) that is required to minimize voltage ripple and load step transients, as well as the amount of bulk capacitance that is necessary 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 inductance collapses abruptly when the peak design Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS8010/A-10 February 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT8010/A The output ripple is highest at maximum input voltage since ΔIL increases with input voltage. Multiple capacitors placed in parallel may be needed to meet the ESR and RMS current handling requirements. Dry tantalum, special polymer, aluminum electrolytic and ceramic capacitors are all available in surface mount packages. Special polymer capacitors offer very low ESR but have lower capacitance density than other types. Tantalum capacitors have the highest capacitance density but it is important to only use types that have been surge tested for use in switching power supplies. Aluminum electrolytic capacitors have significantly higher ESR but can be used in cost-sensitive applications provided that consideration is given to ripple current ratings and long term reliability. Ceramic capacitors have excellent low ESR characteristics but can have a high voltage coefficient and audible piezoelectric effects. The high Q of ceramic capacitors with trace inductance can also lead to significant ringing. For adjustable voltage mode, the output voltage is set by an external resistive divider according to the following equation : VOUT VREF 1+ R1 R2 where VREF is the internal reference voltage (0.6V typ.) Using Ceramic Input and Output Capacitors The VIN quiescent current loss dominates the efficiency loss at very low load currents whereas the I2R loss dominates the efficiency loss at medium to high load currents. In a typical efficiency plot, the efficiency curve at very low load currents can be misleading since the actual power lost is of no consequence. 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 the 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. Output Voltage Programming The resistive divider allows the FB pin to sense a fraction of the output voltage as shown in Figure 4. VOUT R1 FB RT8010/A R2 Efficiency Considerations The efficiency of a switching regulator is equal to the output power divided by the input power times 100%. It is often useful to analyze individual losses to determine what is limiting the efficiency and which change would produce the most improvement. Efficiency can be expressed as : Efficiency = 100% − (L1+ L2+ L3+ ...) where L1, L2, etc. are the individual losses as a percentage of input power. Although all dissipative elements in the circuit produce losses, two main sources usually account for most of the losses : VIN quiescent current and I2R losses. 1. The VIN quiescent current appears due to two factors including : the DC bias current as given in the electrical characteristics and the internal main switch and synchronous switch gate charge currents. The gate charge current results from switching the gate capacitance of the internal power MOSFET switches. Each time the gate is switched from high to low to high again, a packet of charge ΔQ moves from VIN to ground. The resulting ΔQ/Δt is the current out of VIN that is typically larger than the DC bias current. In continuous mode, IGATECHG = f (QT + QB) where QT and QB are the gate charges of the internal top and bottom switches. Both the DC bias and gate charge losses are proportional to VIN and thus their effects will be more pronounced at higher supply voltages. GND Figure 4. Setting the Output Voltage Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 is a registered trademark of Richtek Technology Corporation. DS8010/A-10 February 2015 RT8010/A The Figure 5 of derating curves allows the designer to see the effect of rising ambient temperature on the maximum power allowed. 1.6 Maximum Power Dissipation (W)1 2. I2R losses are calculated from the resistances of the internal switches, R SW and external inductor RL. In continuous mode, the average output current flowing through inductor L is “chopped” between the main switch and the synchronous switch. Thus, the series resistance looking into the LX pin is a function of both top and bottom MOSFET RDS(ON) and the Duty Cycle (DC) as follows : RSW = RDS(ON)TOP x DC + RDS(ON)BOT x (1 − DC) The RDS(ON) for both the top and bottom MOSFETs can be obtained from the Typical Performance Characteristics curves. Thus, to obtain I2R losses, simply add RSW to RL and multiply the result by the square of the average output current. Four Layers PCB 1.4 1.2 WQFN-16L 3x3 1.0 0.8 WDFN-6L 2x2 0.6 0.4 0.2 0.0 Other losses including CIN and COUT ESR dissipative losses and inductor core losses generally account for less than 2% of the total loss. 0 25 50 75 100 125 Ambient Temperature (°C) Figure 5. Derating Curve of Maximum Power Dissipation Thermal Considerations 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, where TJ(MAX) is the maximum junction temperature of the die and TA is the maximum ambient temperature. The junction to ambient thermal resistance θJA is layout dependent. For WDFN-6L 2x2 packages, the thermal resistance θJA is 120°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 : PD(MAX) = (125°C − 25°C) / 120°C/W = 0.833W for WDFN-6L 2x2 packages The maximum power dissipation depends on operating ambient temperature for fixed T J(MAX) and thermal resistance θJA. Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS8010/A-10 February 2015 Checking Transient Response The regulator loop response can be checked by looking at the load transient response. Switching regulators take several cycles to respond to a step in load current. When a load step occurs, VOUT immediately shifts by an amount equal to ΔILOAD (ESR), where ESR is the effective series resistance of COUT. ΔILOAD also begins to charge or discharge COUT generating a feedback error signal used by the regulator to return VOUT to its steady-state value. During this recovery time, VOUT can be monitored for overshoot or ringing that would indicate a stability problem. Layout Considerations Follow the PCB layout guidelines for optimal performance of RT8010/A. For the main current paths as indicated in bold lines in Figure 6, keep their traces short and wide. Put the input capacitor as close as possible to the device pins (VIN and GND). LX node is with high frequency voltage swing and should be kept small area. Keep analog components away from LX node to prevent stray capacitive noise pick-up. is a registered trademark of Richtek Technology Corporation. www.richtek.com 13 RT8010/A Connect feedback network behind the output capacitors. Keep the loop area small. Place the feedback components near the RT8010/A. An example of 2-layer PCB layout is shown in Figure 7 to Figure 8 for reference. VIN RT8010/A 3 4 VIN LX 1 2 Figure 7. Top Layer C2 IC FB/VOUT C1 VOUT L1 EN GND 6 R1 C3 5 R2 VIN R3 Figure 8. Bottom Layer Figure 6. EVB Schematic Table 1. Recommended Inductors Supplier Inductance Current Rating (mA) (H) DCR (m) Dimensions (mm) Series TAIYO YUDEN 2.2 1480 60 3.00 x 3.00 x 1.50 NR 3015 GOTREND 2.2 1500 58 3.85 x 3.85 x 1.80 GTSD32 Sumida 2.2 1500 75 4.50 x 3.20 x 1.55 CDRH2D14 Sumida 4.7 1000 135 4.50 x 3.20 x 1.55 CDRH2D14 TAIYO YUDEN 4.7 1020 120 3.00 x 3.00 x 1.50 NR 3015 GOTREND 4.7 1100 146 3.85 x 3.85 x 1.80 GTSD32 Table 2. Recommended Capacitors for CIN and COUT Supplier Capacitance (F) Package Part Number TDK 4.7 0603 C1608JB0J475M MURATA 4.7 0603 GRM188R60J475KE19 TAIYO YUDEN 4.7 0603 JMK107BJ475RA TAIYO YUDEN 10 0603 JMK107BJ106MA TDK 10 0805 C2012JB0J106M MURATA 10 0805 GRM219R60J106ME19 MURATA 10 0805 GRM219R60J106KE19 TAIYO YUDEN 10 0805 JMK212BJ106RD Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 14 is a registered trademark of Richtek Technology Corporation. DS8010/A-10 February 2015 RT8010/A Outline Dimension D2 D L E E2 1 e b A A1 SEE DETAIL A 2 1 2 1 A3 DETAIL A Pin #1 ID and Tie Bar Mark Options Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.700 0.800 0.028 0.031 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.200 0.350 0.008 0.014 D 1.950 2.050 0.077 0.081 D2 1.000 1.450 0.039 0.057 E 1.950 2.050 0.077 0.081 E2 0.500 0.850 0.020 0.033 e L 0.650 0.300 0.026 0.400 0.012 0.016 W-Type 6L DFN 2x2 Package Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS8010/A-10 February 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 15 RT8010/A D SEE DETAIL A D2 L 1 E E2 e b A A1 1 1 2 2 DETAIL A Pin #1 ID and Tie Bar Mark Options A3 Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.700 0.800 0.028 0.031 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 D 2.950 3.050 0.116 0.120 D2 1.300 1.750 0.051 0.069 E 2.950 3.050 0.116 0.120 E2 1.300 1.750 0.051 0.069 e L 0.500 0.350 0.020 0.450 0.014 0.018 W-Type 16L QFN 3x3 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. www.richtek.com 16 DS8010/A-10 February 2015