RT6296C RICHTEK | Alldatasheet
Document overview
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Technical content
Features
4.5V to 17V Input Voltage Range 2A Output Current Internal N-Channel MOSFETs Current Mode Control Fixed Switching Frequency : 1.4MHz Synchronous to External Clock : 300kHz to 3MHz Cycle-by-Cycle Current Limit External Soft-Start Function Input Under-Voltage Lockout Output Under-Voltage Protection Thermal Shutdown
Applications
Industrial and Commercial Low Power Systems Computer Peripherals LCD Monitors and TVs Set-top Boxes Marking Information 0E=DNN 0E= : Product Code DNN : Date Code Simplified Application Circuit Enable VIN EN/SYNC GND BOOT FB SW VOUT VIN RT6296C R5 R1 PVCC SS C4C2
Copyright © 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS6296C-00 May 2015 Pin Configurations SS SW GND FB EN/SYNC BOOT VIN PVCC 3 4 (TOP VIEW) TSOT-23-8 (FC) Functional Pin Description Pin No. Pin Name Pin Function 1 SS Soft-Start Control Input. SS control the soft -start period. Connect a capacitor from SS to GND to set the soft-start period. 2 VIN Power Input. Support 4.5 V to17V Input Voltage. Must bypass with a suitable large ceramic capacitor at this pin. 3 SW Switch Node. Connect to external L-C filter. 4 GND System Ground. 5 BOOT Bootstrap Supply for High -Side Gate Driver. Connect a 0.1 F ceramic capacitor between the BOOT and SW pins.
6 EN/SYNC
Enable Control Input. High = Enable. Apply an external clock to adjust the switching frequency . If using pull high resistor connected to VIN, the recommended value range is 60k to 300k. 7 PVCC 5V Bias Supply Output. Connect a 0.1F capacitor to ground. 8 FB Feedback Voltage Input. The pin is used to set the output voltage of the converter to regulate to the desired voltage via a resistive divider. Feedback reference = 0.8V.
Copyright © 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS6296C-00 May 2015 www.richtek.com Function Block Diagram - UV Comparator Oscillator 0.4V Internal Regulator Shutdown Comparator BOOT GND SW FB EN/SYNC HS Switch Current Comparator+ - EA0.807V Power Stage & Deadtime Control 1.4V Slope Compensation LS Switch Current Comparator UVLO Logic & Protection Control BOOT UVLO Current Sense Current Sense PVCC SS 50pF 1pF 400k 11µA VIN Operation Under Voltage Lockout Threshold The IC includes an input Under Voltage Lockout Protection (UVLO). If the input voltage exceeds the UVLO rising threshold v oltage ( 3.9V), the converter resets and prepares the PWM for operation. If the input voltage falls below the UVLO falling threshold voltage (3.25V) during normal operation, the device stops switching. The UVLO rising and falling threshold voltage includes a hysteresis to prevent noise caused reset. Chip Enable The EN pin is the chip enable input. Pulling the EN pin low (<1.1V) will shutdown the device. During shutdown mode, the RT6296C’s quiescent current drops to lower than 1A. Driving the EN pin high (> 1.6V) will turn on the device. Operating Frequency and Synchronization The internal oscillator runs at 1400kHz (typ.) when the EN/SYNC pin is at logic -high level (> 1.6V). If the EN pin is pulled to low -level over 8μs, the IC will shut down. The RT 6296C can be synchronized with an external clock ranging from 300kHz to 3MHz applied to the EN/SYNC pin. The external clock duty cycle must be from 20% to 80% with logic -high level = 2V and logic-low level = 0.8V. Internal Regulator The internal regulator gener ates 5V power and drive internal circuit. When VIN is below 5V, PVCC will drop with VIN. A capacitor (>0.1F) between PVCC and GND is required. Soft-Start Function The RT6296C provides external soft-start function. The soft-start function is used to preven t large inrush current while converter is being powered -up. The soft-start timing can be programmed by the external
Copyright © 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS6296C-00 May 2015 capacitor between SS pin and GND. The Chip provides a 11A charge current for the external capacitor. Over Current Protection RT6296C provides cycle -by-cycle over current limit protection. When the inductor current peak value reaches current limit, IC will turn off High Side MOS to avoid over current. Under Voltage Protection (Hiccup Mode) RT6296C provides Hiccup Mode of Under Voltage Protection (UVP). When the FB voltage drops below half of the feedback reference voltage, V FB, the UVP function will be triggered and the IC will shut down for a period of time and then recover automatically. The Hiccup Mode of UVP can reduce input current in short-circuit conditions. Thermal Shutdown Thermal shutdown is implemented to prevent the chip from operating at excessively high temperatures. When the junction temperature is higher than 150C, the chip will shutdown th e switching operation. The chip is automatically re -enabled when the junction temperature cools down by approximately 20C.
Copyright © 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS6296C-00 May 2015 www.richtek.com Absolute Maximum Ratings (Note 1) Power Dissipation, PD @ TA = 25C Package Thermal Resistance (Note 2) ESD Susceptibility (Note 3) Recommended Operating Conditions (Note 4)
Electrical Characteristics
(VIN = 12V, TA = 25C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Shutdown Supply Current VEN = 0V -- -- 1 A Quiescent Current with no Load at DCDC Output VEN = 2V, VFB = 1V -- 0.8 1 mA Feedback Voltage VFB 0.799 0.807 0.815 V Feedback Current IFB VFB = 820mV -- 10 50 nA Switch On-Resistance High-Side RDS(ON)H -- 100 -- Low-Side RDS(ON)L -- 40 -- Switch Leakage VEN = 0V, VSW = 0V -- -- 1 A Current Limit ILIM Under 40% duty-cycle 3.4 -- -- A Low-Side Switch Current Limit From Drain to Source -- 2 -- A Oscillation Frequency fOSC VFB = 0.75V 1100 1400 1700 kHz SYNC Frequency Range fSYNC 300 -- 3000 kHz Fold-Back Frequency VFB < 400mV -- 125 -- kHz Maximum Duty-Cycle DMAX VFB = 0.7V -- 85 -- % Minimum On-Time tON -- 60 -- ns
Copyright © 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS6296C-00 May 2015 Parameter Symbol Test Conditions Min Typ Max Unit EN Input Voltage Logic-High VIH 1.2 1.4 1.6 V Logic-Low VIL 1.1 1.25 1.4 EN Input Current IEN VEN = 2V -- 2 -- VEN = 0V -- 0 -- EN Turn-off Delay ENtd-off -- 8 -- s Input Under-Voltage Lockout Threshold VIN Rising VUVLO VIN Rising 3.7 3.9 4.1 V Hysteresis VUVLO -- 650 -- mV VCC Regulator VCC -- 5 -- V VCC Load Regulation VLOAD IVCC = 5mA -- 3 -- % Soft-Start Charge Current ISS -- 11 -- A Thermal Shutdown Temperature TSD -- 150 -- oC Thermal Shutdown Hysteresis TSD -- 20 -- oC 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. JA is measured at T A = 25C on a high effective thermal conductivity four -layer test board per JEDEC 51 -7. JC 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.
Copyright © 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. Table 1. Suggested Component Values
Copyright © 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS6296C-00 May 2015 Typical Operating Characteristics Efficiency vs. Output Current 100 0 0.5 1 1.5 2 Output Current (A) Efficiency (%) VOUT = 3.3V VIN = 4.5V VIN = 12V VIN = 17V Output Voltage vs. Input Voltage 3.14 3.18 3.22 3.26 3.30 3.34 3.38 3.42 3.46 5 6 7 8 9 10 11 12 13 14 15 16 17 Input Voltage (V) Output Voltage (V) VOUT = 3.3V, IOUT = 2A 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) IOUT = 1A Output Voltage vs. Output Current 3.14 3.18 3.22 3.26 3.30 3.34 3.38 3.42 3.46 0 0.5 1 1.5 2 Output Current (A) Output Voltage (V) VIN = 12V, VOUT = 3.3V UVLO Voltage vs. Temperature 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 -50 -25 0 25 50 75 100 125 Temperature (°C) UVLO Voltage (V) Rising Falling VOUT = 3.3V, IOUT = 0A EN Threshold vs. Temperature 1.15 1.20 1.25 1.30 1.35 1.40 1.45 1.50 -50 -25 0 25 50 75 100 125 Temperature (°C) EN Threshold (V) Rising Falling VOUT = 3.3V, IOUT = 0A
Copyright © 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS6296C-00 May 2015 www.richtek.com VIN = 12V, VOUT = 3.3V, IOUT = 1A to 2A to 1A, L = 2.2H VOUT (50mV/Div) IOUT (1A/Div) Time (200s/Div) Load Transient Response VOUT (20mV/Div) VLX (5V/Div) Time (1s/Div) Output Ripple Voltage VIN = 12V, VOUT = 3.3V, IOUT = 2A, L = 2.2H VOUT (2V/Div) VEN (2V/Div) VLX (10V/Div) ILX (2A/Div) Time (2ms/Div) Power On from EN VIN = 12V, VOUT = 3.3V, IOUT = 2A VOUT (2V/Div) VEN (2V/Div) VLX (10V/Div) ILX (2A/Div) Time (2ms/Div) Power Off from EN VIN = 12V, VOUT = 3.3V, IOUT = 2A VIN = 12V, VOUT = 3.3V, IOUT = 2A VOUT (2V/Div) VIN (10V/Div) VLX (10V/Div) ILX (2A/Div) Time (5ms/Div) Power On from VIN VOUT (2V/Div) VIN (10V/Div) VLX (10V/Div) ILX (2A/Div) Time (5ms/Div) Power Off from VIN VIN = 12V, VOUT = 3.3V, IOUT = 2A
Copyright © 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS6296C-00 May 2015 www.richtek.com 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. 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 : OUT INRMS OUT(MAX) IN OUT VVI 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 d esign. 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, VOUT, is determined by : OUT L OUT 1V I ESR 8fC The output ripple will be highest at the maximum input voltage since IL 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. 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 calculat ed by the following formula : PD(MAX) = (TJ(MAX) TA) / JA where T J(MAX) is the maximum junction temperature, TA is the ambient temperature, and JA is the junction to ambient thermal resistance. For recommended operating condition specifications, the ma ximum junction temperature is 125 C. The junction to ambient thermal resistance, JA, is layout dependent. For TSOT-23-8 (FC) package, the thermal resistance, JA, is 70C/W on a standard JEDEC 51 -7 four-layer thermal test board. The maximum power dissipation at T A = 25 C can be calculated by the following formula : PD(MAX) = (125 C 25C) / (70 C/W) = 1.428W for TSOT-23-8 (FC) package The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, JA. The derating curve in Figure 3 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation.
Copyright © 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS6296C-00 May 2015 www.richtek.com Outline Dimension Symbol Dimensions In Millimeters Dimensions In Inches Min. Max. Min. Max. A 0.700 1.000 0.028 0.039 A1 0.000 0.100 0.000 0.004 B 1.397 1.803 0.055 0.071 b 0.220 0.380 0.009 0.015 C 2.591 3.000 0.102 0.118 D 2.692 3.099 0.106 0.122 e 0.585 0.715 0.023 0.028 H 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024 TSOT-23-8 (FC) Surface Mount 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 witho ut 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 fur nished 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 pate nts 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.