RT7266ZSP

® RT7266 3A, 18V, 700kHz ACOTTM Synchronous Step-Down Converter General Description Features The RT7266 is an adaptive on-time ACOT TM mode synchronous buck converter. The adaptive on-time ACOTTM mode control provides a very fast transient response with few external components. The low impedance internal MOSFET can support high efficiency operation with wide input voltage range from 4.5V to 18V . The proprietary circuit of the RT7266 enables to support all ceramic capacitors. The output voltage can be adjustable between 0.8V and 8V. The soft-start is adjustable by an external capacitor. z z z z z z z z z z z Ordering Information RT7266 z z z Package Type SP : SOP-8 (Exposed Pad-Option 2) Lead Plating System Z : ECO (Ecological Element with Halogen Free and Pb free) z Applications z Note : z Richtek products are : z RoHS compliant and compatible with the current require- z ments of IPC/JEDEC J-STD-020. z Suitable for use in SnPb or Pb-free soldering processes. Marking Information ACOTTM Mode Enables Fast Transient Response 4.5V to 18V Input Voltage Range 3A Output Current 60mΩ Ω Internal Low Site N-MOSFET Adaptive On-Time Control Fast Transient Response Support All Ceramic Capacitors Up to 95% Efficiency 700kHz Switching Frequency Adjustable Output Voltage from 0.8V to 8V Adjustable Soft-Start Cycle-by-Cycle Current Limit Input Under Voltage Lockout Thermal Shutdown Protection RoHS Compliant and Halogen Free Industrial and Commercial Low Power Systems Computer Peripherals LCD Monitors and TVs Green Electronics/Appliances Point of Load Regulation for High-Performance DSPs, FPGAs, and ASICs Pin Configurations RT7266ZSP : Product Number RT7266 ZSPYMDNN (TOP VIEW) YMDNN : Date Code 8 EN FB 2 PVCC 3 SS 4 GND VIN 7 BOOT 6 SW 5 GND 9 SOP-8 (Exposed Pad) Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS7266-02 September 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT7266 Typical Application Circuit VIN C1 10µF x 2 C2 0.1µF 1 EN 5, 9 (Exposed Pad) GND Chip Enable C5 3.9nF L1 1.4µH RT7266 6 8 SW VIN 4 SS BOOT 7 C6 0.1µF C3 C7 22µF x 2 R1 8.25k VOUT 1.05V/3A FB 2 PVCC 3 VPVCC R2 22.1k C4 1µF Table 1. Suggested Component Values VOUT (V) R1 (kΩ) R2 (kΩ) C3 (pF) L1 (μH) C7 (μF) 1 6.81 22.1 -- 1.4 22 to 68 1.05 8.25 22.1 -- 1.4 22 to 68 1.2 12.7 22.1 -- 1.4 22 to 68 1.8 30.1 22.1 5 to 22 2 22 to 68 2.5 49.9 22.1 5 to 22 2 22 to 68 3.3 73.2 22.1 5 to 22 2 22 to 68 5 124 22.1 5 to 22 3.3 22 to 68 7 180 22.1 5 to 22 3.3 22 to 68 Functional Pin Description Pin No. Pin Name 1 EN 2 FB 3 PVCC 4 SS 5, 9 (Exposed pad) GND Pin Function Enable Input. A logic-high enables the converter; a logic-low forces the RT7266 into shutdown mode reducing the supply current to less than 10μA. Attach this pin to VIN with a 100kΩ pull up resistor for automatic start-up. Feedback Input. It is used to regulate the output of the converter to a set value via an external resistive voltage divider. The feedback reference voltage is 0.765V typically. Internal Regulator Output. Connect a 1μF capacitor to GND to stabilize output voltage. Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor from SS to GND to set the soft-start period. A 3.9nF capacitor sets the soft-start period to 1.5ms. Ground. The Exposed pad should be soldered to a large PCB and connected to GND for maximum thermal dissipation. 6 SW Switch Node. Connect this pin to an external L-C filter. 7 BOOT Bootstrap for High Side Gate Driver. Connect a 0.1μF or greater ceramic capacitor from BOOT to SW pins. 8 VIN Supply Input. The input voltage range is from 4.5V to 18V. Must bypass with a suitable large ( ≥10μF x 2) ceramic capacitor. Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS7266-02 September 2012 RT7266 Function Block Diagram VIN PVCC Reg BOOT UGATE OC Control SW Driver LGATE FB On-Time GND EN + Soft-Start EN - SS Comparator VREF Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS7266-02 September 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT7266 Absolute Maximum Ratings z z z z z z z z z (Note 1) Supply Voltage, VIN ----------------------------------------------------------------------------------------------Switch Voltage, SW ----------------------------------------------------------------------------------------------< 10ns ----------------------------------------------------------------------------------------------------------------BOOT to SW -------------------------------------------------------------------------------------------------------All 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 -------------------------------------------------------------------------------------Junction Temperature Range ------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------Storage Temperature Range ------------------------------------------------------------------------------------- Recommended Operating Conditions z z z −0.3V to 20V −0.8V to (VIN + 0.3V) −5V to 25V −0.3V to 6V −0.3V to 6V 1.333W 75°C/W 15°C/W 150°C 260°C −65°C to 150°C (Note 3) Supply Voltage, VIN ----------------------------------------------------------------------------------------------- 4.5V to 18V Junction Temperature Range ------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range ------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 12V, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Supply Current Shutdown Current ISHDN VEN = 0V -- 1 10 μA Quiescent Current IQ VEN = 3V, VFB = 1V -- 0.7 -- mA Logic-High 2 -- 5.5 Logic-Low -- -- 0.4 Logic Threshold EN Voltage V V REF Voltage and Discharge Resistance Feedback Reference Voltage VREF 4.5V ≤ V IN ≤ 18V 0.753 Feedback Input Current IFB VFB = 0.8V −0.1 0 0.1 VPVCC 6V ≤ VIN ≤ 18V, 0 < IPVCC < 5mA 0.765 0.777 V μA V PVCC Output V PVCC Output Voltage 4.7 5.1 5.5 V Line Regulation 6V ≤ VIN ≤ 18V, IPVCC = 5mA -- -- 20 mV Load Regulation 0 < IPVCC < 5mA -- -- 60 mV VIN = 6V, VPVCC = 4V -- 110 -- mA Output Current IPVCC RDS(ON) Switch On Resistance High Side RDS(ON)_H -- 90 -- Low Side RDS(ON)_L -- 60 -- 3.5 4.1 5.7 mΩ Current Limit Current limit ILIM Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 A is a registered trademark of Richtek Technology Corporation. DS7266-02 September 2012 RT7266 Parameter Thermal Shutdown Symbol Test Conditions Thermal Shutdown Threshold TSD Thermal Shutdown ΔTSD Hysteresis On-Time Timer Control VIN = 12V, VOUT = 1.05V Min Typ Max Unit -- 150 -- -- 20 -- -- 145 -- ns °C On-Time t ON Minimum On-Time t ON(MIN) -- 60 -- ns Minimum Off-Time t OFF(MIN) -- 230 -- ns Soft-Start SS Charge Current VSS = 0V 1.4 2 2.6 μA SS Discharge Current VSS = 0.5V 0.05 0.1 -- mA VIN Rising to Wake up VPVCC 3.55 3.85 4.15 -- 0.3 -- UVLO UVLO Threshold Hysteresis 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. The device is not guaranteed to function outside its operating conditions. Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS7266-02 September 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT7266 Typical Operating Characteristics Efficiency vs. Output Current Output Voltage vs. Output Current 100 1.07 90 Output Voltage (V) Efficiency (%) 80 70 VOUT = 5V VOUT = 3.3V VOUT = 1.05V 60 50 40 30 1.06 1.05 VIN = 4.5V VIN = 12V VIN = 17V 1.04 20 10 VOUT = 1.05V VIN = 12V 0 1.03 0 0.5 1 1.5 2 2.5 3 0 0.5 1 Output Current (A) 1.5 2 2.5 3 Output Current (A) Frequency vs. Input Voltage Output Voltage vs. Input Voltage 900 1.07 Frequency (kHz)1 Output Voltage (V) 800 1.06 1.05 IOUT = IOUT = IOUT = IOUT = 1.04 0A 1A 2A 3A 700 600 500 VOUT = 1.05V, ILOAD = 0.1A VOUT = 1.05V 400 1.03 4 6 8 10 12 14 16 4 18 6 8 Input Voltage (V) 14 16 18 Reference Voltage vs. Input Voltage Reference Voltage vs. Temperature 0.780 0.775 0.775 Reference Voltage (V) Reference Voltage (V) 12 Input Voltage (V) 0.780 0.770 0.765 VIN = 17V VIN = 12V VIN = 4.5V 0.760 10 0.755 0.770 0.765 0.760 0.755 No Load, VOUT = 1.05V No Load, VOUT = 1.05V 0.750 0.750 -50 -25 0 25 50 75 100 Temperature (°C) Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 125 4 6 8 10 12 14 16 18 Input Voltage (V) is a registered trademark of Richtek Technology Corporation. DS7266-02 September 2012 RT7266 Shutdown Current vs. Temperature 10 Quiescent Current vs. Temperature 0.8 VEN = 0V 0.8 Quiescent Current (mA) Shutdown Current (µA)1 9 8 7 6 5 VIN = 17V VIN = 12V VIN = 4.5V 4 3 2 0.7 0.7 0.6 0.5 0.5 0.4 1 0.4 0 0.3 -50 -25 0 25 50 75 100 VIN = 17V VIN = 12V VIN = 4.5V 0.6 125 VEN = 3V, VFB = 1V -50 -25 0 Temperature (°C) 50 75 8 7 7 6 6 Current Limit (A) 8 5 4 3 2 125 5 VIN = 17V VIN = 12V VIN = 4.5V 4 3 2 1 1 VOUT = 0V VOUT = 0V 0 0 4 6 8 10 12 14 16 18 -50 -25 0 25 50 75 Input Voltage (V) Temperature (°C) Load Transient Response Output Voltage Ripple VOUT (20mV/Div) VOUT (10mV/Div) IOUT (2A/Div) VSW (10V/Div) VIN = 12V, VOUT = 1.05V, IOUT = 0A to 3A Time (100μs/Div) Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS7266-02 100 Current Limit vs. Temperature Current Limit vs. Input Voltage Current Limit (A) 25 Temperature (°C) September 2012 100 125 VIN = 12V, VOUT = 1.05V, IOUT = 3A Time (500ns/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT7266 Power On from VIN Power Off from VIN VIN (20V/Div) VIN (20V/Div) VOUT (1V/Div) VOUT (1V/Div) VSW (10V/Div) VSW (10V/Div) IOUT (5A/Div) IOUT (5A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 3A VIN = 12V, VOUT = 1.05V, IOUT = 3A Time (5ms/Div) Time (10ms/Div) Power On from VEN Power Off from VEN VEN (5V/Div) VEN (5V/Div) VOUT (1V/Div) VOUT (1V/Div) VSW (10V/Div) IOUT (5A/Div) VSW (10V/Div) IOUT (5A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 3A Time (5ms/Div) Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 VIN = 12V, VOUT = 1.05V, IOUT = 3A Time (100μs/Div) is a registered trademark of Richtek Technology Corporation. DS7266-02 September 2012 RT7266 Application Information The RT7266 is a synchronous high voltage buck converter that can support the input voltage range from 4.5V to 18V and the output current can be up to 3A. It operates using adaptive on-time ACOTTM mode control and provides a very fast transient response with few external compensation components. The RT7266 allows low external component count configuration with both low ESR and ceramic output capacitors. PWM Operation It is suitable for low external component count configuration with appropriate amount of Equivalent Series Resistance (ESR) capacitor(s) at the output. The output ripple valley voltage is monitored at a feedback point voltage. The synchronous high side MOSFET is turned on at the beginning of each cycle. After the internal one shot timer expires, the MOSFET is turned off. The pulse width of this one shot is determined by the converter's input and output voltages to keep the frequency fairly constant over the entire input voltage range. Adaptive On-Time Control The RT7266 has a unique circuit to ensure the switching frequency on 700kHz over full input voltage range and full loading range. This circuit sets the on-time one-shot timer by monitoring the input voltage and SW signal. The switching frequency will keep constant if the duty ratio is VOUT/VIN. Chip Enable Operation The EN pin is the chip enable input. Pulling the EN pin low (2V,