RT2862GSP

Reference Design Design Tools Sample & Buy ® RT2862 3A, 36V, Synchronous Step-Down Converter General Description Features The RT2862 is a high efficiency, current-mode synchronous step-down DC-DC converter that can deliver up to 3A output current over a wide input voltage range from 4.5V to 36V. The device integrates 105mΩ high-side and 80mΩ low-side MOSFETs to achieve high conversion efficiency. The current-mode control architecture supports fast transient response and simple external compensation.  A cycle-by-cycle current limit function provides protection against shorted output and an internal soft-start eliminates input current surge during start-up. The RT2862 provides complete protection functions such as input under-voltage lockout, output under-voltage protection, over-current protection and thermal shutdown. The RT2862 is available in the thermal enhanced SOP-8 (Exposed Pad) package.            Applications    Ordering Information  RT2862  Package Type SP: SOP-8 (Exposed Pad-Option 2)   Lead Plating System G : Green (Halogen Free and Pb Free) Point of Load Regulator in Distributed Power Systems Digital Set Top Boxes Broadband Communications Vehicle Electronics Automotive Audio, Navigation, and Information Systems Enterprise Datacom Platforms Point of Load (POL) Industrial Grade General Purpose Point of Load Marking Information Note : RT2862GSP : Product Number Richtek products are :  4.5V to 36V Input Voltage Range 3A Output Current Internal N-MOSFETs Current Mode Control Frequency Operation : 300kHz to 1MHz Adjustable Output Voltage from 0.8V to 30V High Efficiency Up to 95% Stable with Low ESR Ceramic Output Capacitors Cycle-by-Cycle Current Limit Input Under-Voltage Lockout Output Under-Voltage Protection Thermal Shutdown RoHS compliant and compatible with the current require- RT2862 GSPYMDNN YMDNN : Date Code ments of IPC/JEDEC J-STD-020.  Suitable for use in SnPb or Pb-free soldering processes. Simplified Application Circuit BOOT VIN VIN CIN RT2862 CB L SW VOUT R1 RT GND Copyright © 2021 Richtek Technology Corporation. All rights reserved. DS2862-03 December 2021 COUT FB RT CC COMP RC R2 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT2862 Pin Configuration (TOP VIEW) 8 SW BOOT 2 EN 3 GND 4 GND VIN 7 RT 6 COMP 5 FB 9 SOP-8 (Exposed Pad) Functional Pin Description Pin No. Pin Name Pin Function 1 SW Switch Node. Connect to external L-C filter. 2 BOOT Bootstrap Supply for the High-Side MOSFET. Connect a 100nF or greater capacitor between the BOOT and SW pins. 3 EN Enable Control Input. A logic-high enables the converter; a logic-low forces the device into shutdown mode. GND Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum thermal dissipation. 5 FB Feedback Voltage Input. This pin is used to set the output voltage of the converter to regulate to the desired value via an resistive divider. 6 COMP Compensation Node. COMP is used to compensate the regulation control loop. Connect a R-C network from the COMP to GND. In some cases, an additional capacitor from COMP to GND is required. 7 RT Switching Frequency Setting. Connect an external resistor to set the switching frequency from 300kHz to 1MHz. 8 VIN Power Input. The input voltage range is from 4.5V to 36V. Must bypass with a suitable large ceramic capacitor at this pin. 4, 9 (Exposed Pad) Copyright © 2021 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS2862-03 December 2021 RT2862 Function Block Diagram VIN VCC Internal Regulator Shutdown Comparator 1.2V Oscillator VA VCC - 5k EN Slope Comp Foldback Control + 0.4V Lockout Comparator + 1.7V + + Current Comparator 3.6V 0.8V RT RSENSE VA BOOT UV UV Comparator SS Current Sense Amplifier + - S Q R Q SW GND + + EA - FB COMP Operation The RT2862 is a constant frequency, current-mode synchronous 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 high-side N-MOSFET is turned off, the low-side N-MOSFET is turned on to conduct the inductor current until next cycle begins. Error Amplifier The error amplifier adjusts its output voltage by comparing the feedback signal (VFB) with the internal 0.8V reference. When the load current increases, it causes a drop in the feedback voltage relative to the reference, and then the error amplifier's output voltage rises to allow higher inductor current to match the load current. Oscillator The oscillator frequency can be set by using an external resister RT. Oscillator frequency range is from 300kHz to 1MHz. Internal Regulator The regulator provides low voltage power to supply the internal control circuits and the bootstrap power for highside gate driver. Copyright © 2021 Richtek Technology Corporation. All rights reserved. DS2862-03 December 2021 Enable The converter is turned on when the EN pin is higher than 2V. When the EN pin is lower than 0.4V, the converter will enter shutdown mode and reduce the supply current to 0.5μA. 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 2ms. UV Comparator If the feedback voltage is lower than 0.4V, the UV Comparator will go high to turn off the high-side MOSFET. The output under voltage protection is designed to operate in hiccup mode. When the UV condition is removed, the converter will resume switching. 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. is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT2862 Absolute Maximum Ratings              (Note 1) Supply Voltage, VIN -----------------------------------------------------------------------------------------------Switch Voltage, SW -----------------------------------------------------------------------------------------------BOOT Pin ------------------------------------------------------------------------------------------------------------EN Pin (with REN (150kΩ to 600kΩ) to VIN) ----------------------------------------------------------------SW Voltage (t < 10ns) --------------------------------------------------------------------------------------------EN Pin -----------------------------------------------------------------------------------------------------------------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 --------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Model) ---------------------------------------------------------------------------------------- Recommended Operating Conditions    −0.3V to 40V −0.3V to (VIN + 0.3V) −0.3V to 46.3V −0.3V to 40V −5V to 46.3V −0.3V to 3.6V −0.3V to 40V 2.041W 49°C/W 8°C/W 260°C 150°C −65°C to 150°C 2kV (Note 4) Supply Input Voltage, VIN ----------------------------------------------------------------------------------------- 4.5V to 36V Junction Temperature Range -------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 12V, CIN = 20μF, TA = −40°C to 85°C, unless otherwise specified) Parameter Symbol Shutdown Supply Current Test Conditions Min Typ Max Unit VEN = 0V -- -- 10 A -- 1 1.3 mA 0.784 0.8 0.816 V Quiescent Current IQ VEN = 3V, VFB = 0.9V Feedback Reference Voltage VREF 4.5V  VIN  36V Switch On-Resistance High-Side RDS(ON)1 -- 105 190 Low-Side RDS(ON)2 -- 80 145 4.25 5 5.75 A -- 1.7 -- A RT = 191k 282 320 358 RT = 113k 467 530 593 RT = 51k 924 1050 1176 High-Side Switch Current Limit Range UOC Low-Side Switch Current Limit Oscillation Frequency From Drain to Source fOSC1 m kHz Short-Circuit Oscillation Frequency fOSC2 VFB = 0V, RT = 113k -- 50 -- kHz Maximum Duty Cycle DMAX VFB = 0.7V -- 95 -- % Minimum On-Time tON -- 100 120 ns Copyright © 2021 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS2862-03 December 2021 RT2862 Parameter EN Input Voltage Symbol Test Conditions Min Typ Max Unit Logic-High VIH 2 -- 3.3 Logic-Low VIL -- -- 0.4 3.7 4.2 4.5 V V Input Under-Voltage Lockout Threshold VUVLO Input Under-Voltage Lockout Hysteresis VUVLO -- 250 -- mV Thermal Shutdown Threshold T SD -- 150 -- C Thermal Shutdown Hysteresis TSD -- 25 -- C COMP to Current Sense Trans-conductance GCS -- 4.1 -- A/V -- 950 -- A/V VIN Rising ICOMP = ±10A Error Amplifier Trans-conductance GEA 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. The PCB copper area with exposed pad is 70mm2. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2021 Richtek Technology Corporation. All rights reserved. DS2862-03 December 2021 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT2862 Typical Application Circuit 8 VIN 4.5V to 36V VIN CIN 10µF x 2 Enable REN SW 1 3 7 RT 113k RT2862 2 BOOT 4, 9 (Exposed Pad) CB 100nF L VOUT R1 EN FB 5 RT GND COMP 6 COUT CC RC R2 Table 1. Suggested Component Values VOUT (V) R1 (k) R2 (k) RC (k) L (H) CC (nF) COUT (F) 12 47 3.35 47 10 2.7 22 x 2 8 27 3 36 8.2 2.7 22 x 2 5 62 11.8 24 6.8 2.7 22 x 2 3.3 75 24 16 4.7 2.7 22 x 2 2.5 25.5 12 12 3.6 2.7 22 x 2 1.2 30 60 6.8 2.2 2.7 22 x 2 Copyright © 2021 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS2862-03 December 2021 RT2862 Typical Operating Characteristics Efficiency vs. Output Current Reference Voltage vs. Input Voltage 100 0.810 90 0.808 VIN = VIN = VIN = VIN = VIN = 70 60 50 Reference Voltage (V) Efficiency (%) 80 5V 12V 24V 30V 36V 40 30 20 0.805 0.803 0.800 0.798 0.795 0.793 10 VOUT = 3.3V, RT = 113k VIN = 4.5V to 36V, IOUT = 0A, RT = 113k 0 0.790 0 0.5 1 1.5 2 2.5 3 4 8 12 16 20 24 28 32 36 Input Voltage (V) Output Current (A) Reference vs. Temperature Output Voltage vs. Output Current 3.300 0.810 3.290 0.805 Output Voltage (V) Reference Voltage (V) 3.295 0.800 VIN = VIN = VIN = VIN = 0.795 4.5V 12V 24V 36V 3.285 3.280 VIN = VIN = VIN = VIN = VIN = 3.275 3.270 3.265 5V 12V 24V 30V 36V 3.260 VOUT = 3.3V, IOUT = 0A, RT = 113k 0.790 3.255 VOUT = 3.3V, RT = 113k 3.250 -50 -25 0 25 50 75 100 0 125 0.5 Temperature (°C) Switching Frequency vs. Input Voltage 2 2.5 3 600 515 Switching Frequency (kHz)1 Switching Frequency (kHz)1 1.5 Switching Frequency vs. Temperature 520 510 505 500 495 490 485 VOUT = 3.3V, IOUT = 0A, RT = 113k 480 580 560 540 520 500 480 VIN = VIN = VIN = VIN = 460 440 420 4.5V 12V 24V 36V VOUT = 3.3V, IOUT = 0A, RT = 113k 400 4 8 12 16 20 24 28 32 Input Voltage (V) Copyright © 2021 Richtek Technology Corporation. All rights reserved. DS2862-03 1 Output Current (A) December 2021 36 -50 -25 0 25 50 75 100 125 Temperature (°C) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT2862 Frequency vs. RT Current Limit vs. Temperature 1200 8 1100 1000 Frequency (kHz)1 Inductor Current (A) 7 6 5 VIN = VIN = VIN = VIN = 4 3 36V 24V 12V 4.5V 900 800 700 600 500 400 300 VIN = 12V, IOUT = 0A 200 2 -50 -25 0 25 50 75 100 50 125 Load Transient Response 95 110 125 140 155 170 185 200 Load Transient Response VOUT (200mV/Div) VOUT (200mV/Div) IOUT (2A/Div) IOUT (2A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 3A to 1.5A, RT = 113k VIN = 12V, VOUT = 3.3V, IOUT = 0A to 3A, RT = 113k Time (100μs/Div) Time (100μs/Div) Switching Switching VOUT (5mV/Div) VOUT (5mV/Div) VSW (5V/Div) VSW (5V/Div) VIN = 12V, VOUT = 3.3V, IOUT = 1.5A, RT = 113k Time (1μs/Div) Copyright © 2021 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 80 RT (kΩ ) Temperature (°C) IL (1A/Div) 65 IL (2A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 3A, RT = 113k Time (1μs/Div) is a registered trademark of Richtek Technology Corporation. DS2862-03 December 2021 RT2862 Power Off from EN Power On from EN VEN (2V/Div) VEN (2V/Div) VOUT (2V/Div) VOUT (2V/Div) IOUT (2A/Div) IOUT (2A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 3A, RT = 113k VIN = 12V, VOUT = 3.3V, IOUT = 3A, RT = 113k Time (2.5ms/Div) Time (2.5ms/Div) Power On from VIN Power Off from VIN VIN (5V/Div) VIN (5V/Div) VOUT (2V/Div) VOUT (2V/Div) IL (2A/Div) IL (2A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 3A, RT = 113k Time (5ms/Div) Copyright © 2021 Richtek Technology Corporation. All rights reserved. DS2862-03 December 2021 VIN = 12V, VOUT = 3.3V, IOUT = 3A, RT = 113k Time (5ms/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT2862 Application Information Output Voltage Setting Chip Enable Operation The resistive divider allows the FB pin to sense the output voltage as shown in Figure 1. The EN pin is the chip enable input. Pulling the EN pin low (2.5V,