RT5789BGJ8F

® RT5789A/B 6V, 6A, 1.5MHz ACOT® Synchronous Step-Down Converter in 2.5mm x 2mm Package General Description Features The RT5789A/B is a simple, easy-to-use, 6A synchronous step-down DC-DC converter with an input supply voltage range of 2.5V to 6V. The device build-in an accurate 0.6V (±1.5%) reference voltage and can operate in 100% duty cycle as a very low dropout voltage regulator. the RT5789A/B integrates low RDS(ON) power MOSFETs to achieve high efficiency and is available in TSOT-23-8 (FC) package and UDFN-8L 2.5x2(FC) package.  Ω/16mΩ Ω Low RDS(ON) 6A Converter With Built-In 18mΩ Power FETs  Input Supply Voltage Range : 2.5V to 6V  Output Voltage Range : 0.6V to 6V  Operates Up to 100% Duty Cycle ®  Advanced Constant On-Time (ACOT ) Control  Ultrafast Transient Response  No Needs For External Compensations  Optimized for Low-ESR Ceramic Output Capacitors  0.6V ± 1.5% High-Accuracy Feedback Reference Voltage  35μ μA Operation Quiescent Current (RT5789A)  Robust Over-Current Protection for Both FETs  Optional for Operation Modes :  Power Saving Mode (PSM) (RT5789A)  Forced PWM Mode (RT5789B)  Fixed Switching Frequency : 1.5MHz  Monotonic Start-Up for Pre-Biased Output  Individual Enable Control Input  Power Good Indicator  Built-In Internally Fixed Soft-Start (Typ. 1.5ms)  100% Duty Cycle Mode  Internal Output Discharge  Input Under-Voltage Lockout (UVLO)  Output Under-Voltage Protection (UVP) with Hiccup Mode  Over-Temperature Protection  Available in TSOT-23-8 (FC) Package and UDFN-8L 2.5x2 (FC) Package The RT5789A/B adopts Advanced Constant On-Time (ACOT®) control architecture to provide an ultrafast transient response with few external components and to operate in nearly constant switching frequency over the line, load, and output voltage range. The RT5789A/B is designed to operate at 1.5MHz fixed frequency. While the RT5789A automatically enters power saving mode (PSM) operation at light load to maintain high efficiency. RT5789B operates in Forced PWM over the loading range, that helps meet tight voltage regulation accuracy requirements. The RT5789A/B senses both FETs current for a robust over-current protection. It prevents the device from the catastrophic damage in output short circuit, over current or inductor saturation. The individual enable control input and power good indicator provides flexible system power sequence control a built-in soft-start function prevents inrush current during start-up. The device also includes input under-voltage lockout, output under-voltage protection, and over-temperature protection (thermal shutdown) to provide safe and smooth operation in all operating conditions. Simplified Application Circuit VIN VIN RPGOOD PGOOD Enable LX L VOUT CIN R1 RT5789A/B PGOOD COUT FB R2 EN VOUT PGND Copyright © 2020 Richtek Technology Corporation. All rights reserved. DS5789A/B-04 August 2020 AGND is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT5789A/B Ordering Information Pin Configuration Richtek products are : EN FB AGND VOUT Suitable for use in SnPb or Pb-free soldering processes. Applications     AGND VOUT 6 5 2 3 4 LX TSOT-23-8 (FC) RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.  7 PGND Note :  8 PGOOD PWM Operation Mode A : Automatic PSM B : Forced PWM FB Lead Plating System G : Green (Halogen Free and Pb Free) VIN Package Type J8F : TSOT-23-8 (FC) QUF: UDFN-8L 2.5x2 (FC) (U-Type) EN (TOP VIEW) RT5789A/B 1 8 2 7 3 6 4 5 PGOOD VIN LX PGND UDFN-8L 2.5x2 (FC) WLAN ASIC Power / Storage (SSD and HDD) Mobile Phones and Handheld Devices STB, Cable Modem, and xDSL Platforms General Purpose for POL LV Buck Converter Marking Information RT5789AGQUF RT5789AGJ8F 16= : Product Code 16=DNN DNN : Date Code 01 : Product Code 01W W : Date Code RT5789BGJ8F 15= : Product Code 15=DNN DNN : Date Code RT5789BGQUF 00 : Product Code 00W Copyright © 2020 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 W : Date Code is a registered trademark of Richtek Technology Corporation. DS5789A/B-04 August 2020 RT5789A/B Functional Pin Description Pin No. TSOT-23-8 (FC) UDFN-8L 2.5x2 (FC) 1 8 Pin Name Pin Function PGOOD Open-drain power-good indication output. The power-good function is activated after soft-start is finished. 2 7 VIN Power input. The input voltage range is from 2.5V to 6V. Connect a suitable input bypass capacitor (typically of greater than 10F) between this pin and PGND. The bypass capacitor should be placed as close to the IC as possible. 3 6 LX Switch node between the internal switch and the synchronous rectifier. Connect the output LC filter from this pin to the output load. 4 5 PGND Power ground. This pin, connected to analog ground, must be soldered to a large PCB copper area for maximum power dissipation. 5 4 VOUT Output voltage sense input. This pin is used to monitor and adjust output voltage to enhance load transient regulation. 6 3 AGND Analog ground. It provides a ground return path for the control circuitry and internal reference. Connect AGND to a clean inner GND point with separate trace. 7 2 FB Feedback voltage input. Connect this pin to the midpoint of the external feedback resistive divider to set the output voltage of the converter to the desired regulation level. The device regulates the FB voltage at a feedback reference voltage, typically 0.6V. 8 1 EN Enable control input. A logic-high enables the converter; a logic-low forces the device into shutdown mode. Copyright © 2020 Richtek Technology Corporation. All rights reserved. DS5789A/B-04 August 2020 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT5789A/B Functional Block Diagram EN UVLO AGND Shutdown Control OTP FB VOUT Error Amplifier + + VREF TON Comparator + - Ramp Generator LX VIN Logic Control Current Limit Detector PGOOD AZC Driver LX LX LX FB PGND + Operation The RT5789A/B is a low-voltage, high-efficiency, synchronous step-down DC-DC converter that can deliver up to 6A output current from a 2.5V to 6V input supply. The RT5789A/B adopts ACOT® control mode, which can reduce the output capacitance and provide ultrafast transient responses, and allow minimal component sizes without any additional external compensation network. The device includes a built-in ramp voltage generator, which takes up the virtual inductor current as an input. With the internal ramp signal, the device can be compensated to achieve good stability even with low-ESR ceramic capacitors, since the need for the output capacitor's ESR to generate an ESR ramp voltage can be eliminated. Low VIN ACOT® One-Shot Operation For a low VIN ACOT® converter, a built-in error amplifier is used to keep track of the feedback voltage, as shown in the Functional Block Diagram. In steady state, the error amplifier compares the feedback voltage VFB and an internal reference voltage. If the virtual inductor current ramp voltage is lower than the output of the error amplifier, a new pre-determined fixed on-time will be triggered by the on-time one-shot generator, provided that minimumoff-time one-shot is cleared and the measured inductor current through the synchronous rectifier (low-side switch) Copyright © 2020 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is below the current limit ILIM_L. During the on-time, the high-side switch is turned on 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. If the output voltage has not reached its nominal level, another on-time, however, can only be generated after a short blanking time, or called minimum off-time, which is triggered by the minimum-off-time one-shot generator. It is to prevent another immediate on-time being triggered during the noisy switching time and allow the feedback voltage and current sense signals to settle. The minimum off-time tOFF_MIN is kept short so that the inductor current can be raised up quickly by rapidly repeated on-times when needed. Such feature makes reaction speed of the ACOT® -based converters to load transients extremely fast. Enable Control The RT5789A/B provides an EN pin, as an external chip enable control, to enable or disable the device. If VEN is held below a logic-low threshold voltage (VENL) of the enable input (EN), the converter will enter into shutdown mode, that is, the converter is disabled and switching is inhibited even if the VIN voltage is above VIN under-voltage lockout threshold (VUVLO). During shutdown mode, the is a registered trademark of Richtek Technology Corporation. DS5789A/B-04 August 2020 RT5789A/B supply current can be reduced to ISHDN (1μA or below). If the EN voltage rises above the logic-high threshold voltage (VENH) while the VIN voltage is higher than UVLO threshold (VUVLO), the device will be turned on, that is, switching being enabled and soft-start sequence being initiated. Input Under-Voltage Lockout In addition to the EN pin, the RT5789A/B also provides enable control through the VIN pin. It features an undervoltage lockout (UVLO) function that monitors the internal linear regulator (VCC). If VEN rises above VENH first, switching will still be inhibited until the VIN voltage rises above VUVLO. It is to ensure that the internal regulator is ready so that operation with not-fully-enhanced internal MOSFET switches can be prevented. After the device is powered up, if the input voltage VIN goes below the UVLO falling threshold voltage (VUVLO − ΔVUVLO), this switching will be inhibited; if VIN rises above the UVLO-rising threshold (VUVLO), the device will resume switching. Over-Current Protection The RT5789A/B is protected from over current conditions by cycle-by-cycle current limiting on both the high-side MOSFET and the low-side MOSFET. The robust over current protection mechanism prevents the converter to be damaged from a catastrophic condition, i.e. the inductor is shorted or saturated. High-Side MOSFET Over-Current Protection The device senses high-side current after a deglitch time when the high-side MOSFET is turned-on. Each cycle when the sensed current is higher than the high-side switch peak current limit threshold, ILIM_H, then the device enters high side over current protection. At the same time, the high-side MOSFET is turned off and the low-side MOSFET is turned on. Low-Side MOSFET Over-Current Protection The RT5789A/B detects low side current after a minimumoff-time while the low-side MOSFET is turned on. If the detected low-side current is higher than the low-side switch valley current limit threshold, ILIM_L, the on-time one-shot will be inhibited until the inductor current ramps down to the current limit level (ILIM). That is, another on-time can only be triggered when the inductor current goes below Copyright © 2020 Richtek Technology Corporation. All rights reserved. DS5789A/B-04 August 2020 the low-side current limit. If the output load current exceeds the available inductor current (clamped by the above-mentioned low-side current limit), the output capacitor needs to supply the extra current such that the output voltage will begin to drop. If it drops below the output under-voltage protection trip threshold, the IC will stop switching to avoid excessive heat. Output Under-Voltage Protection The RT5789A/B includes output under-voltage protection (UVP) against over-load or short-circuited condition by constantly monitoring the feedback voltage VFB. If VFB drops below the under-voltage protection trip threshold (typically 50% of the internal reference voltage), the UV comparator will go high to turn off both the internal highside and low-side MOSFET switches. Hiccup Mode If the output under-voltage condition continues for a period of time, the RT5789A/B will enter output under-voltage protection with hiccup mode. During hiccup mode, the device remains shut down. After a period of time, a softstart sequence for auto-recovery will be initiated. Upon completion of the soft-start sequence, if the fault condition is removed, the converter will resume normal operation; otherwise, such cycle for auto-recovery will be repeated until the fault condition is cleared. Hiccup mode allows the circuit to operate safely with low input current and power dissipation, and then resume normal operation as soon as the over-load or short-circuit condition is removed. Soft-Start (SS) The soft-start function is used to prevent large inrush currents while the converter is being powered up. The RT5789A/B provides an internal soft-start feature for inrush control. During the start-up sequence, the internal capacitor is charged by an internal current source ISS to generate a soft-start ramp voltage as a reference voltage to an error amplifier. The device will initiate switching and the output voltage will smoothly ramp up to its targeted regulation voltage only after this ramp voltage is greater than the feedback voltage VFB to ensure the converters have a smooth start-up. The typical soft-start time is 1.5ms. is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT5789A/B Power Good Indication The RT5789A/B provides a power-good (PGOOD) opendrain output pin. It is to be connected to an external voltage source through a pull-up resistor. The power-good function is activated after soft-start is finished and is controlled by a comparator connected to the feedback signal VFB. If VFB rises above a power-good threshold (V TH_PGLH) (typically 95% of the target value), the PGOOD pin will be in high impedance and VPGOOD will be held high after a certain delay elapsed. When VFB drops by a power-good hysteresis (ΔVTH_PGLH) (typically 5% of the target value) or exceeds VTH_PGHL (typically 110% of the target value), the PGOOD pin will be pulled low. For VFB higher than VTH_PGHL, VPGOOD can be pulled high again if VFB drops back by a power-good hysteresis (ΔVTH_PGHL) (typically 5% of the target value). Once being started-up, if any internal protection is triggered, PGOOD will be pulled low to GND. Over-Temperature Protection (Thermal Shutdown) The RT5789A/B includes an over-temperature protection (OTP) circuitry to prevent overheating due to excessive power dissipation. The OTP will shut down switching operation when junction temperature exceeds a thermal shutdown threshold TSD. Once the junction temperature cools down by a thermal shutdown hysteresis (ΔTSD), the IC will resume normal operation with a complete soft-start. Copyright © 2020 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS5789A/B-04 August 2020 RT5789A/B Absolute Maximum Ratings          (Note 1) Supply Input Voltage, VIN ----------------------------------------------------------------------------------------LX Pin Switch Voltage ---------------------------------------------------------------------------------------------