® RT2652 2A, 1.2MHz Synchronous Step-Down Converter General Description Features The RT2652 is a high efficiency synchronous, step-down DC/DC converter. The available input voltage range is from 2.7V to 5.5V the regulated output voltage is adjustable from 0.6V to VIN while delivering up to 2A of output current. The internal synchronous low on-resistance power switches increase efficiency and eliminate the need for an external Schottky diode. The switching frequency is fixed internally at 1.2MHz. The 100% duty cycle provides low dropout operation extending battery life in portable systems. Current mode operation with internal compensation allows the transient response to be optimized. The RT2652 is available in the WDFN-10L 3x3 package. High Efficiency : Up to 95% Fixed Frequency : 1.2MHz No Schottky Diode Required Internal Compensation 0.6V Reference Allows Low Output Voltage 100% Duty Cycle for Low Dropout Operation OCP, UVP, OTP RoHS Compliant and Halogen Free Applications Ordering Information Enterprise Servers Ethernet Switches & Routers Global Storage Telecom & Industrial Cell Phones & DSC's Pin Configurations RT2652 EN VIN VIN AGND FB Lead Plating System G : Green (Halogen Free and Pb Free) 1 2 3 4 5 PGND (TOP VIEW) Package Type QW : WDFN-10L 3x3 (W-Type) 10 9 11 8 7 6 PGND PGND LX LX AGND Note : WDFN-10L 3x3 Richtek products are : RoHS compliant and compatible with the current require- Marking Information ments of IPC/JEDEC J-STD-020. 0K= : Product Code Suitable for use in SnPb or Pb-free soldering processes. 0K=YM DNN YMDNN : Date Code Simplified Application Circuit RT2652 VIN VIN LX EN FB VOUT AGND PGND Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS2652-02 October 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT2652 Functional Pin Description Pin No. Pin Name Pin Function 1 EN Enable Control Input. Pull high to turn on. Do not float. 2, 3 VIN Power Input. Decouple this pin to GND with a 22F ceramic capacitor at least. 4, 6 AGND Analog Ground. FB Feedback Voltage Input. This pin receives the feedback voltage from an external resistive divider connected across the output. 5 7, 8 LX 9, 10, PGND 11 (Exposed Pad) Power MOSFET Switch Node. Connect this pin to the inductor. Power Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. Function Block Diagram EN EN POR OSC 0.6V FB EA VIN ISEN Slope Comp. Output Clamp OC Limit SS Driver 0.2V UV LX Control Logic NISEN AGND PGND OTP N-MOSFET Limit Operation The RT2652 is a monolithic, constant-frequency, current mode step-down DC/DC converter. During normal operation, the internal high side MOSFET is turned on at the beginning of each cycle. Current in the inductor increases until the peak inductor current reaches the value defined by the internal error amplifier. The error amplifier adjusts the voltage of its output by comparing the feedback signal from a resistor divider on the FB pin with an internal 0.6V reference. When the load current increases, it causes a reduction in the feedback voltage relative to the reference. The error amplifier raises its output voltage until the average inductor current matches the new load current. When the Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 high side MOSFET turns off, the synchronous power switch (N-MOSFET) turns on until either the bottom current limit is reached or the beginning of the next cycle. The operating frequency is set by the internal oscillator at 1.2MHz. In VIN larger than 6V condition, the high side MOSFET is turned off and the low side MOSFET is switched on until either the VIN over voltage condition is cleared or the low side MOSFET's current limit is reached. is a registered trademark of Richtek Technology Corporation. DS2652-02 October 2015 RT2652 Absolute Maximum Ratings (Note 1) Supply Voltage, VIN ----------------------------------------------------------------------------------------------Switch Node Voltage, LX -----------------------------------------------------------------------------------------Other Pins -----------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C WDFN-10L 3x3 -----------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) WDFN-10L 3x3, θJA -----------------------------------------------------------------------------------------------WDFN-10L 3x3, θJC -----------------------------------------------------------------------------------------------Junction Temperature ---------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------Storage Temperature Range ------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Model) --------------------------------------------------------------------------------------- Recommended Operating Conditions −0.3V to 6.5V −0.3V to (VIN + 0.3V) −0.3V to 6.5V 1.429W 70°C/W 8.2°C/W 150°C 260°C −65°C to 150°C 2kV (Note 4) Supply Voltage, VIN ----------------------------------------------------------------------------------------------- 2.7V to 5.5V Junction Temperature Range ------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range ------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 3.3V, TA = 25°C unless otherwise specified) Parameter Symbol Min Typ Max Unit 0.594 0.6 0.606 V -- 0.1 0.4 A Active, VFB =0.7V, not switching -- 110 220 A Shutdown -- -- 1 A Output Voltage Line Regulation VIN = 2.7V to 5.5V -- 0.04 -- %/V Output Voltage Load Regulation IOUT = 10mA to 2000mA -- 0.2 -- %/A Switch Leakage Current EN = 0V -- -- 1 A 0.96 1.2 1.44 MHz Feedback Reference Voltage VREF Feedback Leakage Current IFB DC Bias Current Test Conditions Switching Frequency Switch On-Resistance High-Side RDS(ON)_H -- 110 130 Low-Side RDS(ON)_L -- 70 90 2.5 3.5 -- A VDD Rising -- 2.4 -- V VDD Falling -- 2.2 -- V P-MOSFET Current Limit ILIM Under Voltage Lockout Threshold EN Input Voltage Logic-High VIH 1.5 -- -- Logic-Low VIL -- -- 0.3 -- 500 -- EN Pull Low Resistance Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS2652-02 October 2015 m V k is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT2652 Parameter Symbol Test Conditions Min Typ Max Unit -- 150 -- °C 1.3 -- -- ms VOUT Discharge Resistance -- 100 150 VOUT UVP (latch-off) -- 33 -- % Over Temperature Protection (latch-off) 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 © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS2652-02 October 2015 RT2652 Typical Application Circuit RT2652 2, 3 VIN CIN 22µF VIN LX 7, 8 L VOUT R1 1 EN FB CF COUT 5 R2 4, 6 9, 10, AGND PGND 11 (Exposed Pad) Table 1. Recommended Component Selection VOUT (V) R1 (k) R2 (k) CF (pF) L (H) COUT (F) 3.3 37 8.2 200 2 22 2.5 26 8.2 200 2 22 1.8 16.5 8.2 200 1.5 22 1.5 12.3 8.2 200 1.5 22 1.2 8.2 8.2 200 1.5 22 1 5.6 8.2 200 1.5 22 Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS2652-02 October 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT2652 Typical Operating Characteristics Efficiency vs. Output Current 100 90 90 80 80 VIN = 5V, VOUT = 3.3V VIN = 5V, VOUT = 1.2V VIN = 3.3V, VOUT = 1.2V 70 60 Efficiency (%) Efficiency (%) Efficiency vs. Output Current 100 50 40 30 VIN = 5V, VOUT = 3.3V VIN = 3.3V, VOUT = 1.2V VIN = 5V, VOUT = 1.2V 70 60 50 40 30 20 20 10 10 IOUT = 0 to 2A IOUT = 0 to 2A 0 0 0.001 0.01 0.1 1 0 10 0.25 0.5 Output Current (A) Output Voltage vs. Output Current 1.25 1.5 1.75 2 Output Voltage vs. Output Current 3.38 1.215 3.37 Output Voltage (V) Output Voltage (V) 1 Output Current (A) 1.220 1.210 1.205 1.200 VIN = 5V VIN = 3.3V 1.195 1.190 3.36 3.35 3.34 3.33 1.185 VOUT = 1.2V, IOUT = 0 to 2A VIN = 5V, VOUT = 3.3V, IOUT = 0 to 2A 3.32 1.180 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 0 2 0.2 0.4 0.6 Output Current (A) 1.5 1.5 Switching Frequency (MHz)1 1.6 1.4 1.3 1.2 1.1 VIN = 3.3V VIN = 5V 0.9 0.8 0.7 1 1.2 1.4 1.6 1.8 2 Switching Frequency vs. Temperature 1.6 1.0 0.8 Output Current (A) Switching Frequency vs. Temperature Switching Frequency (MHz)1 0.75 VOUT = 1.2V, IOUT = 0.6A 0.6 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 VIN = 5V, VOUT = 3.3V, IOUT = 0.6A 0.6 -50 -25 0 25 50 75 100 Temperature (°C) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 125 -50 -25 0 25 50 75 100 125 Temperature (°C) is a registered trademark of Richtek Technology Corporation. DS2652-02 October 2015 RT2652 Enable Voltage vs. Temperature 1.5 2.7 1.4 2.6 1.3 Enable Voltage (V) VIN UVLO (V) VIN UVLO vs. Temperature 2.8 2.5 Rising 2.4 2.3 2.2 Falling 2.1 1.2 1.1 1.0 Falling 0.9 2.0 0.8 1.9 0.7 0.6 1.8 -50 -25 0 25 50 75 100 IOUT (1A/Div) -50 125 -25 0 25 50 75 100 Temperature (°C) Temperature (°C) Load Transient Response Load Transient Response VOUT (100mV/Div) 125 VOUT (100mV/Div) VIN = 5V, VOUT = 1.2V, IOUT = 1A to 2A IOUT (1A/Div) VIN = 5V, VOUT = 3.3V, IOUT = 1A to 2A Time (100μs/Div) Time (100μs/Div) Output Ripple Voltage Output Ripple Voltage VLX (5V/Div) VLX (5V/Div) VOUT (5mV/Div) VOUT (5mV/Div) VIN = 5V, VOUT = 1.2V, IOUT = 2A Time (500ns/Div) Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS2652-02 Rising October 2015 VIN = 5V, VOUT = 3.3V, IOUT = 2A Time (500ns/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT2652 Power On from VIN Power On from VIN VIN (5V/Div) VIN (5V/Div) VLX (5V/Div) VLX (5V/Div) VOUT (5V/Div) IOUT (5A/Div) VOUT (5V/Div) IOUT (5A/Div) VIN = 5V, VOUT = 1.2V, IOUT = 2A Time (2.5ms/Div) Time (2.5ms/Div) Power Off from VIN Power Off from VIN VIN (5V/Div) VIN (5V/Div) VLX (5V/Div) VLX (5V/Div) VOUT (5V/Div) IOUT (5A/Div) VOUT (5V/Div) IOUT (5A/Div) VIN = 5V, VOUT = 1.2V, IOUT = 2A Time (5ms/Div) Power On from EN VEN (5V/Div) VEN (5V/Div) VLX (5V/Div) VLX (5V/Div) VOUT (5V/Div) IOUT (5A/Div) VOUT (5V/Div) IOUT (5A/Div) VIN = 5V, VOUT = 1.2V, IOUT = 2A Time (500μs/Div) Copyright © 2015 Richtek Technology Corporation. All rights reserved. VIN = 5V, VOUT = 3.3V, IOUT = 2A Time (5ms/Div) Power On from EN www.richtek.com 8 VIN = 5V, VOUT = 3.3V, IOUT = 2A VIN = 5V, VOUT = 3.3V, IOUT = 2A Time (500μs/Div) is a registered trademark of Richtek Technology Corporation. DS2652-02 October 2015 RT2652 Power Off from EN Power Off from EN VEN (5V/Div) VEN (5V/Div) VLX (5V/Div) VLX (5V/Div) VOUT (5V/Div) IOUT (5A/Div) VOUT (5V/Div) IOUT (5A/Div) VIN = 5V, VOUT = 1.2V, IOUT = 2A Time (500μs/Div) VIN = 5V, VOUT = 3.3V, IOUT = 2A Time (500μs/Div) Reference Voltage vs. Temperature 0.620 Reference Voltage (V) 0.615 0.610 0.605 0.600 0.595 0.590 0.585 IOUT = 0.6A 0.580 -50 -25 0 25 50 75 100 125 Temperature (°C) Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS2652-02 October 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT2652 Application Information The RT2652 is a single-phase buck PWM converter. It provides single feedback loop, current mode control with fast transient response. An internal 0.6V reference allows the output voltage to be precisely regulated for low output voltage applications. A fixed switching frequency (1.2MHz) oscillator and internal compensation are integrated to minimize external component count. Output Voltage Setting The output voltage is set by an external resistive voltage divider according to the following equation : VOUT = VREF 1 R1 R2 Where VREF is equals 0.6V (typ.). The resistive voltage divider allows the FB pin to sense a fraction of the output voltage as shown in Figure 1. VOUT R1 FB RT2652 R2 GND Figure 1. Setting the Output Voltage Inductor Selection 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 f L VIN Having a lower ripple current reduces not only the ESR losses in the output capacitors but also the output voltage ripple. Highest efficiency operation is achieved by reducing ripple current at low frequency, but a large inductor is required to attain this goal. For ripple current selection, the value of ΔIL = 0.4(IMAX) is a reasonable starting point. The largest ripple current occurs at the highest VIN. To guarantee that the ripple current stays below a specified maximum value, the inductor should be chosen according to the following equation : Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 VOUT VOUT L = 1 f IL(MAX) VIN(MAX) Slope Compensation and Inductor Peak Current Slope compensation provides stability in constant frequency architectures by preventing sub-harmonic oscillations at duty cycles greater than 50%. It is accomplished internally by adding a compensating ramp to the inductor current signal. Normally, the maximum inductor peak current is reduced when slope compensation is added. In this IC, however, separated inductor current signal is used to monitor over current condition and this keeps the maximum output current relatively constant regardless of duty cycle. Low Dropout Operation The RT2652 is designed to operate down to an input supply voltage of 2.7V. One important consideration at low input supply voltage is that the RDS(ON) of the P-Channel and NChannel power switches increases. The user should calculate the power dissipation when the RT2652 is used at 100% duty cycle with low input voltages to ensure that thermal limits are not exceeded. Slope compensation and inductor peak current slope compensation provides stability in constant frequency architectures by preventing sub-harmonic oscillations at duty cycles greater than 50%.It is accomplished internally by adding a compensating ramp to the inductor current signal. Normally, the maximum inductor peak current is reduced when slope compensation is added. In the RT2652, however, separated inductor current signals are used to monitor over current condition. This keeps the maximum output current relatively constant regardless of duty cycle. Short Circuit Protection When the output is shorted to ground, the inductor current decays very slowly during a single switching cycle. A current runaway detector is used to monitor inductor current. As current increases beyond the control of current loop, switching cycles will be skipped to prevent current runaway from occurring. is a registered trademark of Richtek Technology Corporation. DS2652-02 October 2015 RT2652 The IC includes an input Under Voltage Lockout Protection (UVLO). If the input voltage exceeds the UVLO rising threshold voltage, the converter resets and prepares the PWM for operation. If the input voltage falls below the UVLO falling threshold voltage during normal operation, the device stops switching. The UVLO rising and falling threshold voltage includes a hysteresis to prevent noise caused reset. Thermal Shutdown The device implements an internal thermal shutdown function when the junction temperature exceeds 150°C. The thermal shutdown disables the device until the junction temperature drops below the hysteresis (20°C typ.). Then, the device is re-enabled and automatically reinstates the power up sequence. The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curves in Figure 2 allow the designer to see the effect of rising ambient temperature on the maximum power dissipation. Maximum Power Dissipation (W)1 Under Voltage Lockout Threshold 1.6 Four-Layer PCB 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) Thermal Considerations Figure 2. Derating Curve of Maximum Power Dissipation 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 WDFN-10L 3x3 packages, the thermal resistance, θJA, is 70°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) / (70°C/W) = 1.429W for WDFN-10L 3x3 package Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS2652-02 October 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT2652 Outline Dimension D2 D L E E2 1 e SEE DETAIL A b 2 1 2 1 A A1 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. Symbol Dimensions In Millimeters Dimensions In Inches 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 2.300 2.650 0.091 0.104 E 2.950 3.050 0.116 0.120 E2 1.500 1.750 0.059 0.069 e L 0.500 0.350 0.020 0.450 0.014 0.018 W-Type 10L DFN 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 12 DS2652-02 October 2015