RT5797ALGQW

RT5797A 3A, 1MHz, 6V CMCOT Synchronous Step-Down Converter General Description Features The RT5797A is a high efficiency synchronous stepdown DC-DC converter. Its input voltage range is from 2.7V to 6V and provides an adjustable regulated output voltage from 0.6V to 3.4V while delivering up to 3A of output current.      Constant-On-time (CMCOT) operation with internal compensation allows the transient response to be optimized over a wide range of loads and output capacitors. The RT5797A is available in the WDFN-8L 2x2 and WDFN-8SL 2x2 packages. for Best Transient Response, Robust Loop Stability with Low-ESR (MLCC) COUT The internal synchronous low on-resistance power switches increase efficiency and eliminate the need for an external Schottky diode. The Current Mode Efficiency Up to 95% RDS(ON) 100m HS / 70m LS VIN Range 2.7V to 6V VREF 0.6V with 1% Accuracy at 25C CMCOT ™ Control Loop Design   Soft-Start 1.2ms Power Saving in Light Load Applications    STB, Cable Modem, & xDSL Platforms LCD TV Power Supply & Metering Platforms General Purpose Point of Load (POL) Ordering Information RT5797A RT5797A Package Type QW : WDFN-8L 2x2 (W-Type) Package Type QWA : WDFN-8SL 2x2 (W-Type) (Exposed Pad-Option 2) Lead Plating System G : Green (Halogen Free and Pb Free) UVP Option H : Hiccup L : Latched-Off Lead Plating System G : Green (Halogen Free and Pb Free) UVP Option H : Hiccup Note : Richtek products are :  RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.  Suitable for use in SnPb or Pb-free soldering processes. Simplified Application Circuit RT5797A LX VIN VIN CIN May 2021 VOUT EN R1 FB PG SGND PGND R2 Copyright © 2021 Richtek Technology Corporation. All rights reserved. DS5797A-10 L COUT is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT5797A Marking Information Pin Configuration RT5797ALGQW 2U : Product Code W : Date Code (TOP VIEW) 1 2 3 4 PGND FB PG VIN PGND 9 8 7 6 5 SGND EN LX NC 2UW WDFN-8L 2x2 / WDFN-8SL 2x2 RT5797AHGQW 2V : Product Code W : Date Code 2VW RT5797AHGQWA 4A : Product Code W : Date Code 4AW Functional Pin Description Pin No. Pin Name WDFN-8L 2x2 WDFN-8SL 2x2 Pin Function 1 FB Feedback voltage input. An external resistor divider from the output to GND, tapped to the FB pin, sets the output voltage. 2 PG Power good indicator. The output of this pin is an open-drain with external pull-up resistor. PG is pulled up when the FB voltage is within 90%, otherwise it is LOW. 3 VIN Supply voltage input. The RT5797A operates from a 2.7V to 6V input. PGND Power ground. The exposed pad must be soldered to a large PCB and connected to PGND for maximum power dissipation. 5 NC No internal connection. 6 LX Switch node. 7 EN Enable control input. 8 SGND Signal GND. 4, 9 (Exposed Pad) Copyright © 2021 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS5797A-10 May 2021 RT5797A Functional Block Diagram EN VIN UVLO Shut Down Control OTP - FB VREF Ton Error Amplifier Comparator + + RC CCOMP PGOOD Comparotor - Logic Control LX VIN Driver Current Limit Detector Current Sense LX GND LX SS PG Operation The RT5797A is a synchronous low voltage step-down track the internal ramp voltage during soft-start interval. converter that can support the input voltage range from 2.7V to 6V and the output current can be up to 3A. The RT5797A uses a constant on-time, current mode architecture. In normal operation, the high side PMOSFET is turned on when the switch controller is set by the comparator and is turned off when the Ton The typical soft-start time is 1.2ms. comparator resets the switch controller. output will be high impedance. The internal PG MOSFET is typical 100. The PGOOD signal delay time is defined from EN high to the internal soft-start function end which is about 2ms (Typ.). Low side MOSFET peak current is measured by internal RSENSE. The error amplifier EA adjusts COMP voltage by comparing the feedback signal (VFB) from the output voltage with the internal 0.6V reference. When the load current increases, it causes a drop in the feedback voltage relative to the reference, then the COMP voltage rises to allow higher inductor current to match the load current. PGOOD Comparator When the feedback voltage (VFB) is higher than threshold voltage 0.54V and the internal soft-start function has been finished, the PGOOD open drain EN 0.54V (Typ.) FB 0.54V (Typ.) SS (Internal) 1.2ms (Typ.) UV Comparator If the feedback voltage (VFB) is lower than threshold voltage 0.2V, the UV comparator's output will go high and the switch controller will turn off the high side MOSFET. The output under voltage protection is designed to operate in Hiccup mode for the RT5797AH, Latch mode for the RT5797AL. Soft-Start (SS) An internal current source charges an internal capacitor to build the soft-start ramp voltage. The VFB voltage will Copyright © 2021 Richtek Technology Corporation. All rights reserved. DS5797A-10 May 2021 PG 2ms (Typ.) Enable Comparator A logic-high enables the converter; a logic-low forces the IC into shutdown mode. Over-Current Protection (OCP) The RT5797A provides over-current protection by detecting low side MOSFET valley inductor current. If is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT5797A the sensed valley inductor current is over the current limit threshold (3.7A typ.), the OCP will be triggered. When OCP is tripped, the RT5797A will keep the over current threshold level then cause the UV protection. Thermal Shutdown (OTP) The device implements an internal thermal shutdown function when the junction temperature exceeds 150C. The thermal shutdown forces the device to stop switching when the junction temperature exceeds the thermal shutdown threshold. Once the die temperature decreases below the hysteresis of 20C, the device reinstates the power up sequence. Maximum Duty Cycle The maximum duty cycle (70%, min.) can be calculated by minimum off time (180ns, max.), dead time (60ns, max.) and switching frequency (1.2MHz, max.). DMAX = 1 - ( tOFF_MIN + tD ) x f SW Where tOFF_MIN is minimum off time, tD is dead time and f SW is switching frequency. If input voltage and output voltage are closed, RT5797A operates at high duty cycle. Once the operational duty cycle is larger than the maximum duty cycle (70%, min.), RT5797A keeps minimum off time (180ns, max.) and deadtime (60ns, max.), then the output voltage starts to drop. The input voltage at which the devices enter dropout changes depending on the input voltage, output voltage, switching frequency, load current, and the efficiency of the design. tOFF_MIN 180ns High-Side MOSFET Deadtime 30ns Deadtime 30ns Low-Side MOSFET Copyright © 2021 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS5797A-10 May 2021 RT5797A Absolute Maximum Ratings (Note 1)  Supply Input Voltage -------------------------------------------------------------------------------------------0.3V to 6.5V  LX Pin Switch Voltage----------------------------------------------------------------------------------------- 0.3V to (VIN + 0.3V)