RT7281

RT7274 RICHTEK | Alldatasheet

Document overview

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Technical content

Features

zzzzz ACOTTM Mode Enables Fast Transient Response zzzzz 4.5V to 18V Input Voltage Range zzzzz 2A Output Current zzzzz High Efficient Internal N-MOSFET Optimized for Lower Duty Cycle Applications zzzzz 105mΩΩΩΩΩ Internal Low Side N-MOSFET zzzzz Advanced Constant On-Time Control zzzzz Allows Ceramic Output Capacitor zzzzz 700kHz Switching Frequency zzzzz Adjustable Output Voltage from 0.765V to 8V zzzzz Adjustable and Pre-biased Soft-Start zzzzz Cycle-by-Cycle Current Limit zzzzz Input Under Voltage Lockout zzzzz Thermal Shutdown zzzzz RoHS Compliant and Halogen Free

Applications

z Industrial and Commercial Low Power Systems z Computer Peripherals z LCD Monitors and TVs z Green Electronics/Appliances z Point of Load Regulation for High-Performance DSPs, FPGAs, and ASICs Simplified Application Circuit General Description The RT7274/79/80/81 is a synchronous step-down DC/ DC converter with Advanced Constant On-Time (ACOT TM) mode control. It achieves high power density to deliver up to 2A output current from a 4.5V to 18V input supply. The proprietary ACOT TM mode offers an optimal transient response over a wide range of loads and all kinds of ceramic capacitors, which allows the device to adopt very low ESR output capacitor for ensuring performance stabilization. In addition, RT7274/79/80/81 keeps an excellent constant switching frequency under line and load variation and the integrated synchronous power switches with the ACOT TM mode operation provides high efficiency in whole output current load range. Cycle-by-cycle current limit provides an accurate protection by a valley detection of low side MOSFET and external soft-start setting eliminates input current surge during startup. Protection functions indude thermal shutdown for RT7274/79/80/81; output under voltage protection and output over voltage protection for RT7279/80 only. RT7274/79/80/81 PVCC PGND* VINVIN SS VOUT GND ENInput Signal PGOOD* Power Good BOOT SW FB VOUT* VINR* * : VINR pin for TSSOP-14 (Exposed Pad) only. VOUT pin for TSSOP-14 (Exposed Pad) only. PGND pin for TSSOP-14 (Exposed Pad) only. PGOOD pin for TSSOP-14 (Exposed Pad) only.

DS7274/79/80/81-01 February 2013www.richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.

Ordering Information

Discontinuous Operating Mode Forced PWM Mode RT7274 Package Type SP : SOP-8 (Exposed Pad-Option 2) Lead Plating System G : Green (Halogen Free and Pb Free) RT7280 Package Type CP : TSSOP-14 (Exposed Pad) Lead Plating System G : Green (Halogen Free and Pb Free) RT7279 Package Type CP : TSSOP-14 (Exposed Pad) Lead Plating System G : Green (Halogen Free and Pb Free) RT7281 Package Type SP : SOP-8 (Exposed Pad-Option 2) Lead Plating System G : Green (Halogen Free and Pb Free) FB VIN PGND GND SS PVCC PGOOD EN PGND SW SW BOOT VOUT VINR PGND Marking Information RT7281GSP : Product Number YMDNN : Date Code RT7281GSP RT7279GCP : Product Number YMDNN : Date Code RT7279GCP RT7280GCP : Product Number YMDNN : Date Code RT7280GCP RT7274GSP : Product Number YMDNN : Date Code RT7274GSP RT7274 GSPYMDNN RT7279 GCPYMDNN RT7281 GSPYMDNN EN FB PVCC SS VIN BOOT GND SW GND 4 5 Pin Configurations (TOP VIEW) TSSOP-14 (Exposed Pad) SOP-8 (Exposed Pad) RT7280 GCPYMDNN

DS7274/79/80/81-01 February 2013 www .richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Pin No. TSSOP-14 (Exposed Pad) SOP-8 (Exposed Pad) Pin Name Pin Function 1 -- VOUT Output Voltage Sense Input. This terminal is used for On-Time Adjustment. 2 2 FB Feedback Input Voltage. Connect with feedback resistive divider to the output voltage. 3 3 PVCC 5.1V Power Supply Output. Connect a 1μF capacitor from this pin to GND. 4 4 SS Soft-Start Control. Connect an external capacitor between this pin and GND to set the soft- start time. 5 5, 9 (Exposed Pad) GND Analog Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. 6 -- PGOOD Open Drain Power Good Output. 7 1 EN Enable Control Input. 8, 9, 15 (Exposed pad) -- PGND Power Ground. The exposed pad must be soldered to a large PCB and connected to PGND for maximum power dissipation. 10, 11 6 SW Switch Node. 12 7 BOOT Bootstrap Supply for High Side Gate Driver. Connect a 0.1 μF capacitor between the BOOT and SW pin. 13 8 VIN Power Input. It is connected to the drain of the internal high side MOSFET. 14 -- VINR Supply Input for Internal Li near Regulator to the Control Circuitry. Functional Pin Description

DS7274/79/80/81-01 February 2013www.richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Function Block Diagram For TSSOP-14 (Exposed Pad) Package For SOP-8 (Exposed Pad) Package UGATE LGATE Driver SW BOOT PVCC Switch Controller On-Time Over Current Protection EN FB Comparator SW PGND Internal Regulator PVCC VIBIAS VREF VINR GND PVCC Under & Over Voltage Protection FB

0.9 VREF +-

+-- 2µA PVCC Ripple Gen. VIN EN VOUT Discharge FB PGOOD Comparator SS UGATE LGATE Driver SW BOOT PVCC Switch Controller On-Time Over Current Protection EN FB Comparator SW Internal Regulator PVCC VIBIAS VREF GND PVCC +-- 2µA PVCC Ripple Gen. VIN EN FB SS

DS7274/79/80/81-01 February 2013 www .richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Detailed Description The RT7274/79/80/81 are high-performance 700kHz 2A step-down regulators with internal power switches and synchronous rectifiers. They feature an Advanced Constant On-Time (ACOT TM) control architecture that provides stable operation with ceramic output capacitors without complicated external compensation, among other benefits. The input voltage range is from 4.5V to 18V and the output is adjustable from 0.765V to 8V. The proprietary ACOT TM control scheme improves upon other constant on-time architectures, achieving nearly constant switching frequency over line, load, and output voltage ranges. The RT7274/79/80/81 are optimized for ceramic output capacitors. Since there is no internal clock, response to transients is nearly instantaneous and inductor current can ramp quickly to maintain output regulation without large bulk output capacitance. Constant On-Time (COT) Control The heart of any COT architecture is the on-time one- shot. Each on-time is a pre-determined “fixed” period that is triggered by a feedback comparator. This robust arrangement has high noise immunity and is ideal for low duty cycle applications. After the on-time one-shot period, there is a minimum off-time period before any further regulation decisions can be considered. This arrangement avoids the need to make any decisions during the noisy time periods just after switching events, when the switching node (SW) rises or falls. Because there is no fixed clock, the high-side switch can turn on almost immediately after load transients and further switching pulses can ramp the inductor current higher to meet load requirements with minimal delays. Traditional current mode or voltage mode control schemes typically must monitor the feedback voltage, current signals (also for current limit), and internal ramps and compensation signals, to determine when to turn off the high-side switch and turn on the synchronous rectifier. Weighing these small signals in a switching environment is difficult to do just after switching large currents, making those architectures problematic at low duty cycles and in less than ideal board layouts. Because no switching decisions are made during noisy time periods, COT architectures are preferable in low duty cycle and noisy applications. However, traditional COT control schemes suffer from some disadvantages that preclude their use in many cases. Many applications require a known switching frequency range to avoid interference with other sensitive circuitry. True constant on-time control, where the on-time is actually fixed, exhibits variable switching frequency. In a step-down converter, the duty factor is proportional to the output voltage and inversely proportional to the input voltage. Therefore, if the on-time is fixed, the off-time (and therefore the frequency) must change in response to changes in input or output voltage. Modern pseudo-fixed frequency COT architectures greatly improve COT by making the one-shot on-time proportional to V OUT and inversely proportional to VIN. In this way, an on-time is chosen as approximately what it would be for an ideal fixed-frequency PWM in similar input/output voltage conditions. The result is a big improvement but the switching frequency still varies considerably over line and load due to losses in the switches and inductor and other parasitic effects. Another problem with many COT architectures is their dependence on adequate ESR in the output capacitor, making it difficult to use highly-desirable, small, low-cost, but low-ESR ceramic capacitors. Most COT architectures use AC current information from the output capacitor, generated by the inductor current passing through the ESR, to function in a way like a current mode control system. With ceramic capacitors the inductor current information is too small to keep the control loop stable, like a current mode system with no current information. ACOT TM Control Architecture Making the on-time proportional to V OUT and inversely proportional to V IN is not sufficient to achieve good constant-frequency behavior for several reasons. First, voltage drops across the MOSFET switches and inductor cause the effective input voltage to be less than the measured input voltage and the effective output voltage to be greater than the measured output voltage. As the load

DS7274/79/80/81-01 February 2013www.richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. changes, the switch voltage drops change causing a switching frequency variation with load current. Also, at light loads if the inductor current goes negative, the switch dead-time between the synchronous rectifier turn-off and the high-side switch turn-on allows the switching node to rise to the input voltage. This increases the effective on- time and causes the switching frequency to drop noticeably. One way to reduce these effects is to measure the actual switching frequency and compare it to the desired range. This has the added benefit eliminating the need to sense the actual output voltage, potentially saving one pin connection. ACOT TM uses this method, measuring the actual switching frequency and modifying the on-time with a feedback loop to keep the average switching frequency in the desired range. To achieve good stability with low-ESR ceramic capacitors, ACOT TM uses a virtual inductor current ramp generated inside the IC. This internal ramp signal replaces the ESR ramp normally provided by the output capacitor's ESR. The ramp signal and other internal compensations are optimized for low-ESR ceramic output capacitors. ACOT TM One-shot Operation The RT7274/79/80/81 control algorithm is simple to understand. The feedback voltage, with the virtual inductor current ramp added, is compared to the reference voltage. When the combined signal is less than the reference the on-time one-shot is triggered, as long as the minimum off-time one-shot is clear and the measured inductor current (through the synchronous rectifier) is below the current limit. The on-time one-shot turns on the high-side switch and the inductor current ramps up linearly. After the on-time, the high-side switch is turned off and the synchronous rectifier is turned on and the inductor current ramps down linearly. At the same time, the minimum off- time one-shot is triggered to prevent another immediate on-time during the noisy switching time and allow the feedback voltage and current sense signals to settle. The minimum off-time is kept short (230ns typical) so that rapidly-repeated on-times can raise the inductor current quickly when needed. Discontinuous Operating Mode (RT7274/80 Only) After soft start, the RT7279/81 operates in fixed frequency mode to minimize interference and noise problems. The RT7274/80 uses variable-frequency discontinuous switching at light loads to improve efficiency. During discontinuous switching, the on-time is immediately increased to add “hysteresis” to discourage the IC from switching back to continuous switching unless the load increases substantially. The IC returns to continuous switching as soon as an on- time is generated before the inductor current reaches zero. The on-time is reduced back to the length needed for 700kHz switching and encouraging the circuit to remain in continuous conduction, preventing repetitive mode transitions between continuous switching and discontinuous switching. Current Limit The RT7274/79/80/81 current limit is a cycle-by-cycle “valley” type, measuring the inductor current through the synchronous rectifier during the off-time while the inductor current ramps down. The current is determined by measuring the voltage between source and drain of the synchronous rectifier, adding temperature compensation for greater accuracy. If the current exceeds the upper current limit, the on-time one-shot is inhibited until the inductor current ramps down below the upper current limit plus a wide hysteresis band of about 1A and drops below the lower current limit level. Thus, only when the inductor current is well below the upper current limit is another on- time permitted. This arrangement prevents the average output current from greatly exceeding the guaranteed upper current limit value, as typically occurs with other valley-type current limits. If the output current exceeds the available inductor current (controlled by the current limit mechanism), the output voltage will drop. If it drops below the output under-voltage protection level (see next section) the IC will stop switching to avoid excessive heat. The RT7279/81 also includes a negative current limit to protect the IC against sinking excessive current and possibly damaging the IC. If the voltage across the synchronous rectifier indicates the negative current is too

DS7274/79/80/81-01 February 2013 www .richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Input Under-voltage Lock-out In addition to the enable function, the RT7274/79/80/81 feature an under-voltage lock-out (UVLO) function that monitors the internal linear regulator output (PVCC). To prevent operation without fully-enhanced internal MOSFET switches, this function inhibits switching when PVCC drops below the UVLO-falling threshold. The IC resumes switching when PVCC exceeds the UVLO-rising threshold. Soft-Start (SS) The RT7274/79/80/81 soft-start uses an external pin (SS) to clamp the output voltage and allow it to slowly rise. After V EN is high and PVCC exceeds its UVLO threshold, the IC begins to source 2μA from the SS pin. An external capacitor at SS is used to adjust the soft-start timing. The available capacitance range is from 2.7nF to 220nF. Do not leave SS unconnected. During start-up, while the SS capacitor charges, the RT7274/79/80/81 operate in discontinuous switching mode with very small pulses. This prevents negative inductor currents and keeps the circuit from sinking current. Therefore, the output voltage may be pre-biased to some positive level before start-up. Once the V SS ramp charges enough to raise the internal reference above the feedback voltage, switching will begin and the output voltage will smoothly rise from the pre-biased level to its regulated level. After V SS rises above about 2.2V output over-and under-voltage protections are enabled and the RT7279/81 begins continuous-switching operation. Internal Regulator (PVCC) An internal linear regulator (PVCC) produces a 5.1V supply from VIN that powers the internal gate drivers, PWM logic, reference, analog circuitry, and other blocks. If VIN is 6V or greater, PVCC is guaranteed to provide significant power for external loads. PGOOD Comparator PGOOD is an open drain output controlled by a comparator connected to the feedback signal. If FB exceeds 90% of the internal reference voltage, PGOOD will be high impedance. Otherwise, the PGOOD output is connected to PGND. high, the synchronous rectifier turns off until after the next high-side on-time. RT7274/80 does not sink current and therefore does not need a negative current limit. Output Over-voltage Protection and Under-voltage Protection The RT7279/80 include output over-voltage protection (OVP). If the output voltage rises above the regulation level, the high-side switch naturally remains off and the synchronous rectifier turns on. If the output voltage remains high the synchronous rectifier remains on until the inductor current reaches the negative current limit (RT7279) or until it reaches zero (RT7280). If the output voltage remains high, the IC's switches remain off. If the output voltage exceeds the OVP trip threshold for longer than 5 μs (typical), the IC's OVP is triggered. The RT7279/80 include output under-voltage protection (UVP). If the output voltage drops below the UVP trip threshold for longer than 250μs (typical) the IC's UVP is triggered. There are two different behaviors for OVP and UVP events for the TSSOP-14 (Exposed Pad) packages. \ Latch-Off Mode (TSSOP-14 (Exposed Pad) Only) \ The RT7280GCP/RT7279GCP, use latch-off mode OVP and UVP. When the protection function is triggered the IC will shut down. The IC stops switching, leaving both switches open, and is latched off. To restart operation, toggle EN or power the IC off and then on again. Shut-down, Start-up and Enable (EN) The enable input (EN) has a logic-low level of 0.4V. When V EN is below this level the IC enters shutdown mode and supply current drops to less than 10μA. When VEN exceeds its logic-high level of 1.6V the IC is fully operational. Between these 2 levels there are 2 thresholds (1.2V typical and 1.4V typical). When VEN exceeds the lower threshold the internal bias regulators begin to function and supply current increases above the shutdown current level. Switching operation begins when V EN exceeds the upper threshold. Unlike many competing devices, EN is a high voltage input that can be safely connected to VIN (up to 18V) for automatic start-up.

DS7274/79/80/81-01 February 2013www.richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. External Bootstrap Capacitor (C6) Connect a 0.1 μF low ESR ceramic capacitor between BOOT and SW. This bootstrap capacitor provides the gate driver supply voltage for the high side N-channel MOSFET switch. Over Temperature Protection The RT7274/79/80/81 includes an over temperature protection (OTP) circuitry to prevent overheating due to excessive power dissipation. The OTP will shut down switching operation when the junction temperature exceeds 150 °C. Once the junction temperature cools down by approximately 25°C the IC will resume normal operation with a complete soft-start. For continuous operation, provide adequate cooling so that the junction temperature does not exceed 150°C.

DS7274/79/80/81-01 February 2013 www .richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. (VIN = 12V, TA = 25°C, unless otherwise specified)

Electrical Characteristics

Recommended Operating Conditions (Note 4) Absolute Maximum Ratings (Note 1) z Power Dissipation, PD @ TA = 25°C z Package Thermal Resistance (Note 2) z ESD Susceptibility (Note 3) Parameter Symbol Test Conditions Min Typ Max Unit Supply Current Supply Current (Shutdown) V EN = 0V -- 1 10 μA Supply Current (Quiescent) V EN = 3V, VFB = 1V -- 0.7 -- mA Logic Threshold Logic High V IH 1.6 -- 18 EN Voltage Logic Low V IL -- -- 0.4 V EN Pin Resistance to GND (RT7274/81) V EN = 12V 220 440 880 k Ω VFB Voltage and Discharge Resistance Feedback Threshold Voltage V FB_TH 4.5V ≤ VIN ≤ 18V 0.757 0.765 0.773 V Feedback Input Current I FB V FB = 0.8V −0.1 0 0.1 μA VOUT Discharge Resistance R DIS EN = 0V, V VOUT = 0.5V -- 50 100 Ω

DS7274/79/80/81-01 February 2013www.richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. 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. θJC is measured at the exposed pad of the package. The PCB copper area of exposed pad is 70mm 2. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Parameter Symbol Test Conditions Min Typ Max Unit VPVCC Output VPVCC Output Voltage V PVCC 6V ≤ VIN ≤ 18V, 0 < IPVCC < 5mA 4.7 5.1 5.5 V Line Regulation 6V ≤ VIN ≤ 18V, IPVCC = 5mA -- -- 20 mV Load Regulation 0 < IPVCC < 5mA -- -- 100 mV Output Current I PVCC V IN = 6V, VPVCC = 4V -- 110 -- mA RDS(ON) High Side R DS(ON) _H -- 150 -- Switch On Resistance Low Side R DS(ON) _L -- 105 -- mΩ Current Limit Current Limit ILIM LSW = 2μH 2.5 3.5 4.7 A Thermal Shutdown Thermal Shutdown Threshold T SD -- 150 -- °C Thermal Shutdown Hysteresis ΔTSD -- 25 -- °C On-Time Timer Control On-Time t ON V IN = 12V, VOUT = 1.05V -- 145 -- ns Minimum Off-Time t OFF(MIN) -- 230 -- ns Soft-Start SS Charge Current V SS = 0V 1.4 2 2.6 μA SS Discharge Current V SS = 0.5V 0.05 0.1 -- mA UVLO Wake up V PVCC 3.55 3.85 4.15 UVLO Threshold Hysteresis -- 0.3 -- V Power Good (RT7279/80) FB Rising 85 90 95 PGOOD Threshold FB Falling -- 85 -- PGOOD Sink Current PGOOD = 0.5V -- 5 -- mA Output Under Voltage and Over Voltage Protection (RT7279/80) OVP Trip Threshold OVP Detect 115 120 125 % OVP Delay Time -- 5 -- μs UVP Detect 65 70 75 UVP Trip Threshold Hysteresis -- 10 -- UVP Delay Time -- 250 -- μs

©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Table 1. Suggested Component Values

DS7274/79/80/81-01 February 2013www.richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. VFB Threshold Voltage vs. Temperature 0.740 0.745 0.750 0.755 0.760 0.765 0.770 0.775 0.780 -50 -25 0 25 50 75 100 125 Temperature (°C) VFB Threshold Voltage (V) Typical Operating Characteristics Efficiency vs. Output Current 100 0.001 0.01 0.1 1 10 Output Current (A) Efficiency (%) VIN = 12V, VOUT = 1.05V, IOUT = 0 to 2A RT7279/81 RT7274/80 Output Voltage vs. Input Voltage 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 468 1 0 1 2 1 4 1 6 1 8 Input Voltage (V) Output Voltage (V) RT7279 RT7274 RT7280 RT7281 VIN = 4.5V to 18V, V OUT = 1.05V, IOUT = 1A Efficiency vs. Output Current 100 0.001 0.01 0.1 1 10 Output Current (A) Efficiency (%) VIN = 12V, VOUT = 5V, IOUT = 0 to 2A RT7279/81 RT7274/80 Output Voltage vs. Output Current 1.030 1.035 1.040 1.045 1.050 1.055 1.060 1.065 1.070 Output Current (A) Output Voltage (V) VIN = 12V, VOUT = 1.05V, IOUT = 0 to 2A RT7279/81 RT7274/80 Output Voltage vs. Output Current 4.92 4.94 4.96 4.98 5.00 5.02 5.04 5.06 5.08 5.10 Output Current (A) Output Voltage (V) VIN = 12V, VOUT = 5V, IOUT = 0 to 2A RT7279/81 RT7274/80

DS7274/79/80/81-01 February 2013 www .richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. UVLO Threshold vs. Temperature 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 -50 -25 0 25 50 75 100 125 Temperature (°C) UVLO Threshold (V) Falling Rising Enable Voltage vs. Temperature 1.0 1.1 1.2 1.3 1.4 1.5 1.6 -50 -25 0 25 50 75 100 125 Temperature (°C) Enable Voltage (V) Falling Rising Switching Frequency vs. Input Voltage 630 640 650 660 670 680 690 700 468 1 0 1 2 1 4 1 6 1 8 Input Voltage (V) Switching Frequency (kHz) 1 VIN = 12V, VOUT = 1.05V, IOUT = 0.7A Switching Frequency vs. Temperature 600 610 620 630 640 650 660 670 680 690 700 -50 -25 0 25 50 75 100 125 Temperature (°C) Switching Frequency (KHz) 1 VIN = 12V, VOUT = 1.05V, IOUT = 0.7A Current Limit vs. Temperature 2.0 2.5 3.0 3.5 4.0 4.5 5.0 - 5 0 - 2 50 2 55 07 5 1 0 0 1 2 5 Temperature (°C) Current Limit(A) VIN = 12V, VOUT = 1.05V RT7281 RT7280 RT7279 RT7274 Current Limit vs. Input Voltage 2.0 2.5 3.0 3.5 4.0 4.5 5.0 4 6 8 1 01 21 41 61 8 Input Voltage (V) Current Limit (A) VIN = 12V, VOUT = 1.05V RT7281 RT7280 RT7279 RT7274

DS7274/79/80/81-01 February 2013www.richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Quiescent Current vs. Temperature 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 -50 -25 0 25 50 75 100 125 Temperature (°C) Quiescent Current (mA ) VIN = 12V Time (100 μs/Div) Load Transient Response IOUT (1A/Div) VOUT (20mV/Div) RT7279/81 VOUT = 12V, VOUT = 1.05V, IOUT = 1A to 2A Time (100 μs/Div) Load Transient Response IOUT (1A/Div) VOUT (20mV/Div) VOUT = 12V, VOUT = 1.05V, IOUT = 1A to 2A RT7274/80 VOUT = 12V, VOUT = 1.05V, IOUT = 1A to 2A Shutdown Current vs. Temperature -50 -25 0 25 50 75 100 125 Temperature (°C) Shutdown Current (μA) 1 VIN = 12V VOUT = 12V, VOUT = 1.05V, IOUT = 10mA to 2A Time (100 μs/Div) Load Transient Response IOUT (1A/Div) VOUT (20mV/Div) RT7279/81 Time (100 μs/Div) Load Transient Response IOUT (1A/Div) VOUT (50mV/Div) RT7274/80 VOUT = 12V, VOUT = 1.05V, IOUT = 10mA to 2A

DS7274/79/80/81-01 February 2013 www .richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Time (5ms/Div) Power Off from VIN VOUT (1V/Div) IOUT (1A/Div) VIN (20V/Div) VIN = 12V, VOUT = 1.05V, IOUT = 2A VLX (20V/Div) Time (2.5ms/Div) Power On from VIN VIN = 12V, VOUT = 1.05V, IOUT = 2A VOUT (1V/Div) IOUT (1A/Div) VIN (20V/Div) VLX (20V/Div) VIN = 12V, VOUT = 1.05V, IOUT = 2A Time (1 μs/Div) Output Ripple Voltage VOUT (10mV/Div) VLX (10V/Div) VIN = 12V, VOUT = 1.05V, IOUT = 1A Time (1 μs/Div) Output Ripple Voltage VOUT (10mV/Div) VLX (10V/Div) Time (1ms/Div) Power On from EN VLX (20V/Div) VEN (10V/Div) VIN = 12V, VOUT = 1.05V, IOUT = 2A VOUT (1V/Div) IOUT (1A/Div) Time (25 μs/Div) Power Off from EN VLX (20V/Div) VOUT (1V/Div) IOUT (1A/Div) VEN (10V/Div) VIN = 12V, VOUT = 1.05V, IOUT = 2A

DS7274/79/80/81-01 February 2013www.richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Time (10 μs/Div) Power Good from EN Off VOUT (1V/Div) VEN (5V/Div) VIN = 12V, VOUT = 1.05V, IOUT = 2A VPGOOD (5V/Div) RT7279/80 Time (1ms/Div) Power Good from EN On VOUT (1V/Div) VEN (5V/Div) VIN = 12V, VOUT = 1.05V, IOUT = 2A VPGOOD (5V/Div) RT7279/80

©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. voltage as shown in Figure 4. Figure 4. Output Voltage Setting Protection (UVLO) that monitors the voltage of PVCC pin. voltage, the RT7274/79/80/81 will be turned off in this state. This is non-latch protection. temperature should be prevented from rising above 150°C. and decreases with higher inductance. use 1% tolerance or better divider resistors. trapezoidal current at the source of the high side MOSFET. deviations do not offer much relief. for COUT selection to ensure that the control loop is stable. and RMS current handling requirements.

©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Figure 5. External Bootstrap Diode stable temperature characteristics. voltage is lower than 5.5V or duty ratio is higher than 65%.

DS7274/79/80/81-01 February 2013 www .richtek.com ©Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Outline Dimension Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 1.000 1.200 0.039 0.047 A1 0.000 0.150 0.000 0.006 A2 0.800 1.050 0.031 0.041 b 0.190 0.300 0.007 0.012 D 4.900 5.100 0.193 0.201 e 0.650 0.026 E 6.300 6.500 0.248 0.256 E1 4.300 4.500 0.169 0.177 L 0.450 0.750 0.018 0.030 U 1.900 2.900 0.075 0.114 V 1.600 2.600 0.063 0.102 14-Lead TSSOP (Exposed Pad) Plastic Package

DS7274/79/80/81-01 February 2013www.richtek.com Richtek Technology Corporation 5F, No. 20, Taiyuen 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. A BJ F H M C D I Y X EXPOSED THERMAL PAD (Bottom of Package) 8-Lead SOP (Exposed Pad) Plastic Package Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 4.801 5.004 0.189 0.197 B 3.810 4.000 0.150 0.157 C 1.346 1.753 0.053 0.069 D 0.330 0.510 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.170 0.254 0.007 0.010 I 0.000 0.152 0.000 0.006 J 5.791 6.200 0.228 0.244 M 0.406 1.270 0.016 0.050 X 2.000 2.300 0.079 0.091 Option 1 Y 2.000 2.300 0.079 0.091 X 2.100 2.500 0.083 0.098 Option 2 Y 3.000 3.500 0.118 0.138