RT6200

RT6200 RICHTEK | Alldatasheet

Document overview

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Technical content

Features

 Wide Operating Input Voltage Range : 4.5V to 36V  Adjustable Output Voltage Range : 0.8V to 15V  0.6A Output Current  0.35ΩΩΩΩΩ Internal Power MOSFET Switch  High Efficiency up to 95%  1.2MHz Fixed Switching Frequency (Duty <90%)  Support duty up to 95%  Stable with Low ESR Output Ceramic Capacitors  Cycle-By-Cycle Over-Current Protection

Applications

 Distributed Power Systems  Battery Chargers  Pre-Regulator for Linear Regulators  WLED Drivers Simplified Application Circuit Marking Information RT6200 Package Type E : SOT-23-6 Lead Plating System G : Green (Halogen Free and Pb Free) 0Q=DNN 0Q= : Product Code DNN : Date Code Pin Configurations (TOP VIEW) SOT-23-6 BOOT GND FB PHASE VIN EN VIN EN GND BOOT FB PHASE L1CB VOUT Enable VIN RT6200 Open = Automatic Startup

DS6200-04 August 2015www.richtek.com ©Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Functional Pin Description Pin No. Pin Name Pin Function

1 BOOT

Bootstrap Supply for High-Side Gate Driver. A capacitor is connected between the PHASE and BOOT pins to form a floating supply across the power switch driver. This capacitor is needed to drive the power switch’s gate above the supply voltage.

2 GND

Ground. This pin is the voltage reference for the regulated output voltage. For this reason, care must be taken in its layout. This node should be placed outside of the D1 to C1 ground path to prevent switching current spikes from inducing voltage noise into the part. 3 FB Feedback Voltage Input. An external resistor divider from the output to GND tapped to the FB pin sets the output voltage. The value of the divider resistors also set loop bandwidth. 4 EN Enable Control Input (Active High). If the EN pin is open, it will be pulled to high by internal circuit. If using pull high resistor connected to VIN, the recommended value is larger than 250k. 5 VIN Supply Voltage Input. Bypass VIN to GND with a suitable large capacitor to prevent large voltage spikes from appearing at the input. 6 PHASE Switch Node.

DS6200-04 August 2015 www.richtek.com ©Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Function Block Diagram Driver R Q S Bootstrap Control Ramp Generator Oscillator 1.2MHz - PWM Comparator EA Reference Regulator -1.1V 1µA + 400k 30pF 2pF Shutdown Comparator OC Limit Clamp Current Sense Amp X20 BOOT GND FB EN VIN PHASE 10k 45mΩ Operation The RT6200 is a constant frequency, current mode asynchronous 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 N-MOSFET is turned off, the inductor current conducts through the external diode. Error Amplifier The error amplifier adjusts its output voltage by comparing the feedback signal (V FB) with the internal 0.8V reference. When the load current increases, it causes a drop in the feedback voltage relative to the reference, the error amplifier's output voltage then rises to allow higher inductor current to match the load current. Oscillator The internal oscillator runs at fixed frequency 1.2MHz. The RT6200 can support duty up to 95% by decreasing switching frequency to 600kHz. In short circuit condition, the frequency is reduced for low power consumption. Internal Regulator The regulator provides low voltage power to supply the internal control circuits and the bootstrap power for high- side gate driver. Enable The converter is turned on when the EN pin is higher than 1.2V and turned off when the EN pin is lower than 0.94V. When the EN pin is open, it will be pulled up to logic-high by 1μA current internally. 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 700μs. 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.

DS6200-04 August 2015www.richtek.com ©Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.

Electrical Characteristics

Parameter Symbol Test Conditions Min Typ Max Unit Feedback Reference Voltage V FB 4.5V  VIN  36V 0.784 0.8 0.816 V Feedback Current I FB V FB = 0.8V -- 0.1 0.3 A Switch On Resistance R DS(ON) V BOOT  VPHASE = 4.8V -- 0.35 --  Switch Leakage V EN = 0V, VPHASE = 0V -- -- 10 A Current Limit I LIM V BOOT  VPHASE = 4.8V, duty = 90% -- 1.2 -- A Oscillator Frequency f SW Duty < 90% 1 1.2 1.4 MHz Maximum Duty Cycle -- 95 -- % Minimum On-Time t ON -- 80 -- ns Under-Voltage Lockout Threshold Rising 3.9 4.2 4.5 V Under-Voltage Lockout Threshold Hysteresis -- 200 -- mV EN Input Voltage Logic-High V IH 0.98 1.08 1.2 V Logic-Low V IL 0.94 1 1.06 (VIN = 12V, TA = 25°C unless otherwise specified) Absolute Maximum Ratings (Note 1)  Power Dissipation, PD @ TA = 25°C  Package Thermal Resistance (Note 2)  ESD Susceptibility (Note 3) Recommended Operating Conditions (Note 4)

DS6200-04 August 2015 www.richtek.com ©Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Parameter Symbol Test Conditions Min Typ Max Unit EN Pull-Up Current V EN = 0V -- 1 -- A Shutdown Current I SHDN V EN = 0V -- 20 -- A Quiescent Current I Q V EN = 2V, VFB = 1V (Not Switching) -- 0.55 0.8 mA Thermal Shutdown T SD -- 150 -- °C 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. θ JA is measured at T A = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions.

DS6200-04 August 2015www.richtek.com ©Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Typical Application Circuit VIN EN GND BOOT FB PHASE 15µH CB 10nF 10µF 91k 17.4k VOUT 5VC1 4.7µF Enable VIN RT6200 Open = Automatic Startup B250A

DS6200-04 August 2015 www.richtek.com ©Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Frequency vs. Temperature 800 900 1000 1100 1200 1300 1400 1500 1600 -50 -25 0 25 50 75 100 125 Temperature (°C) Frequency (kHz) a VIN = 12V, VOUT = 3.3V Typical Operating Characteristics Output Voltage vs. Output Current 4.60 4.65 4.70 4.75 4.80 4.85 4.90 4.95 5.00 5.05 5.10 5.15 5.20 Output Current (A) Output Voltage (V) VIN = 7V VIN = 12V VIN = 17V VOUT = 5V Efficiency vs. Output Current 100 Output Current (A) Efficiency (%) VOUT = 5V VIN = 7V VIN = 12V VIN = 17V Output Voltage vs. Input Voltage 4.80 4.85 4.90 4.95 5.00 5.05 5.10 6 1 11 62 12 63 13 6 Input Voltage (V) Output Voltage (V) VOUT = 5V IOUT = 0.6A IOUT = 0.1A IOUT = 0A Frequency vs. Input Voltage 800 900 1000 1100 1200 1300 1400 1500 1600 4 8 12 16 20 24 28 32 36 Input Voltage (V) Frequency (kHz) A VOUT = 3.3V, IOUT = 0A Reference Voltage vs. Temperature 0.76 0.77 0.78 0.79 0.80 0.81 0.82 0.83 0.84 -50 -25 0 25 50 75 100 125 Temperature (°C) Reference Voltage (V) VIN = 12V, IOUT = 0.1A

DS6200-04 August 2015www.richtek.com ©Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Load Transient Response Time (50 μs/Div) VOUT (50mV/Div) IOUT (200mA/Div) VIN = 12V, VOUT = 5V, IOUT = 50mA to 0.6A, L = 15μH Load Transient Response Time (50 μs/Div) VOUT (50mV/Div) IOUT (200mA/Div) VIN = 12V, VOUT = 5V, IOUT = 0.25A to 0.6A, L = 15μH IPHASE (200mA/Div) Output Ripple Voltage Time (1 μs/Div) VOUT (10mV/Div) VPHASE (10V/Div) VIN = 12V, VOUT = 5V, IOUT = 0.6A, L = 15 μH Output Ripple Voltage Time (1 μs/Div) IPHASE (200mA/Div) VOUT (10mV/Div) VPHASE (10V/Div) VIN = 12V, VOUT = 5V, IOUT = 0.1A, L = 15 μH Power On from EN Time (200 μs/Div) VEN (2V/Div) IPHASE (500mA/Div) VOUT (5V/Div) VPHASE (10V/Div) VIN = 12V, VOUT = 5V, IOUT = 0.6A Power Off from EN Time (200 μs/Div) VEN (2V/Div) IPHASE (500mA/Div) VOUT (5V/Div) VPHASE (10V/Div) VIN = 12V, VOUT = 5V, IOUT = 0.6A

DS6200-04 August 2015www.richtek.com ©Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. OUT INRMS OUT(MAX) IN OUT V VI = I 1 VV  This formula has a maximum at V IN = 2V OUT, where IRMS = I OUT/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. The selection of C OUT is determined by the required Effective Series Resistance (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, ΔV OUT , is determined by : OUT L OUT 1VI E S R 8fC The output ripple will be highest at the 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 requirement. Dry tantalum, special polymer, aluminum electrolytic and ceramic capacitors are all available in surface mount packages. Special polymer capacitors offer very low ESR value. However, it provides lower capacitance density than other types. Although Tantalum capacitors have the highest capacitance density, it is important to only use types that pass the surge test for use in switching power supplies. Aluminum electrolytic capacitors have significantly higher ESR. However, it can be used in cost-sensitive applications for ripple current rating and long term reliability considerations. 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. 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, V IN. 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 V IN large enough to damage the part. 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, V OUT immediately shifts by an amount equal to ΔILOAD (ESR) also begins to charge or discharge COUT generating a feedback error signal for 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. Different core materials and shapes will change the size/ current and price/current relationship of an inductor. Toroid or shielded pot cores in ferrite or permalloy materials are small and do not radiate energy. However, they are usually more expensive than the similar powdered iron inductors. The rule for inductor choice mainly depends on the price vs. size requirement and any radiated field/ EMI requirements. Diode Selection When the power switch turns off, the path for the current is through the diode connected between the switch output and ground. This forward biased diode must have a minimum voltage drop and recovery times. Schottky diode is recommended and it should be able to handle those current. The reverse voltage rating of the diode should be greater than the maximum input voltage, and current rating should be greater than the maximum load current. 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 current, a low ESR input capacitor sized for the maximum RMS current should be used. The RMS current is given by :

DS6200-04 August 2015www.richtek.com 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 furnish ed 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 infringeme nts 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 R ichtek or its subsidiaries. Outline Dimension A e b B D C H L SOT-23-6 Surface Mount Package Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.889 1.295 0.031 0.051 A1 0.000 0.152 0.000 0.006 B 1.397 1.803 0.055 0.071 b 0.250 0.560 0.010 0.022 C 2.591 2.997 0.102 0.118 D 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 H 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024