RT2810BHGQUF

Reference Design ® Sample & Buy RT2810A/B 10A, 18V, 500kHz, ACOTTM Synchronous Step-Down Converter General Description Features The RT2810A/B is a synchronous step-down converter with Advanced Constant On-Time (ACOTTM) mode control. The ACOTTM provides a very fast transient response with few external components. The low impedance internal MOSFET supports high efficiency operation with wide input voltage range from 4.5V to 18V. The proprietary circuit of the RT2810A/B enables to support all ceramic capacitors. The output voltage can be adjustable between 0.7V and 8V. The soft-start is adjustable by an external capacitor.          Ordering Information  RT2810A/B   Package Type QUF : UQFN-16JL 3x3 (U-Type) (FC)  Lead Plating System G : Green (Halogen Free and Pb Free)  UVP Option H : Hiccup Mode UVP L : Latched OVP & UVP   Applications A : PSM B : PWM  Note :  Richtek products are :    4.5V to 18V Input Voltage Range 10A Output Current Ω 12mΩ Ω Internal High-Side N-MOSFET and 5.4mΩ Internal Low-Side N-MOSFET Advanced Constant On-Time Control Fast Transient Response Support All Ceramic Capacitors Up to 95% Efficiency Adjustable Switching Frequency from 300kHz to 700kHz Adjustable Output Voltage from 0.7V to 8V Adjustable Soft-Start Pre-bias Start Up Adjustable Current Limit from 6A to 16A Cycle-by-Cycle Over Current Protection Power Good Output Input Under-Voltage Lockout Hiccup/Latched Mode Under-Voltage Selection RoHS compliant and compatible with the current require-  ments of IPC/JEDEC J-STD-020.  Suitable for use in SnPb or Pb-free soldering processes. 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 Simplified Application Circuit VIN RT2810A/B SW VIN VOUT BOOT EN Signal Power Good EN PGOOD PVCC SS GND Copyright © 2019 Richtek Technology Corporation. All rights reserved. DS2810A/B-07 April 2019 FB RT RLIM is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT2810A/B Marking Information RT2810BLGQUF 7H= : Product Code Pin Configuration YMDNN : Date Code 7F=YM DNN SW 15 14 13 1 12 SW FB 2 11 SW PVCC 3 10 SW RT 4 9 BOOT 5 6 7 8 PGOOD 7F= : Product Code 16 AGND GND RT2810BHGQUF SW (TOP VIEW) YMDNN : Date Code 7G=YM DNN EN 7G= : Product Code YMDNN : Date Code RLIM RT2810ALGQUF 7E=YM DNN VIN YMDNN : Date Code 7H=YM DNN 7E= : Product Code SS RT2810AHGQUF UQFN-16JL 3x3 (FC) Functional Pin Description Pin No. Pin Name Pin Function 1 AGND Analog ground. 2 FB Feedback voltage 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 0.7V typically. 3 PVCC Internal regulator output. Connect a 1F capacitor to GND to stabilize output voltage. 4 RT 5 SS 6 VIN An external timing resistor adjusts the switching frequency of the device. Soft-start time setting. An external capacitor should be connected between this pin and GND. Power input. The input voltage range is from 4.5V to 18V. Must bypass with a suitably large (10F x 2) ceramic capacitor. 7 GND Ground. 8 PGOOD Power good indicator open-drain output. After PVCC voltage raising up, it is pulled low if the feed-back voltage is out of PGOOD threshold after soft start is finished, IC shutdown from OTP and EN goes low. The PGOOD should be pulled high to PVCC through a pull-up resistor if this function is used. 9 BOOT Bootstrap. This capacitor is needed to drive the power switch's gate above the supply voltage. It is connected between SW and BOOT pins to form a floating supply across the power switch driver. A 0.1F capacitor is recommended for use. 10 to 14 SW Switch node. Connect this pin to an external L-C filter. 15 EN Enable control input. A logic-high enables the converter; a logic-low forces the IC into shutdown mode reducing the supply current to less than 10A. 16 RLIM An external resistor adjusts the current limit of the device. Copyright © 2019 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS2810A/B-07 April 2019 RT2810A/B Functional Block Diagram BOOT PVCC EN POR & Reg VBIAS Min. Off-Time PVCC VIN VREF OC UGATE Control Driver SW LGATE UV & OV PVCC 6µA SS GND Ripple Gen. FB VIN + + Comparator ZC Comparator 0.9 VREF FB PGOOD + - On-Time Operation The RT2810A/B is a synchronous step-down converter with advanced Constant On-Time control mode. Using the ACOTTM control mode can reduce the output capacitance and fast transient response. It can minimize the component size without additional external compensation network. Soft-Start Power Good Current Protection The PGOOD pin is an open-drain power-good indication which is connected to PVCC through a pull-up resistor. After PVCC raises up, the PGOOD is actively held low and only allowed to transition high after soft-start is over. If VFB rises above a power-good threshold VTH_PGH The inductor current is monitored via the internal switches cycle-by-cycle. Once the output voltage drops under UV threshold, the RT2810A/B will enter hiccup mode or latch off mode. (typically 90% of the target value), the PGOOD pin will be in high impedance and VPGOOD will be held high. When VFB drops under a VFB falling threshold VTH_PGL (typically 80% of the target value) or exceeds OVP threshold VOVP (typically 120% of the target value), the PGOOD pin will be pulled low. UVLO Protection Once being started-up, if any protection is triggered (UVP and OTP) or EN is from high to low, PGOOD will be pulled to GND. PVCC The regulator provides 5V power to supply the internal control circuit. 1μF ceramic capacitor for decoupling and stability is required. Copyright © 2019 Richtek Technology Corporation. All rights reserved. DS2810A/B-07 April 2019 In order to prevent the converter output voltage from overshooting during the startup period, the soft-start function is necessary. The soft-start time is adjustable by an external capacitor. To protect the chip from operating at insufficient supply voltage, the UVLO is needed. When the input voltage of VIN is lower than the UVLO falling threshold voltage, the device will be lockout. Thermal Shutdown When the junction temperature exceeds the OTP threshold value, the IC will shut down the switching operation. Once the junction temperature cools down and is lower than the OTP lower threshold, the converter will autocratically resume switching. is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT2810A/B Absolute Maximum Ratings             (Note 1) Supply Voltage, VIN -----------------------------------------------------------------------------------------------Switch Voltage, SW -----------------------------------------------------------------------------------------------SW, ( 3.3V) transient response is improved by adding a small “feed-forward” capacitor (Cff) across the upper FB divider resistor (Figure 1), to increase the circuit's Q and reduce damping to speed up the transient response without affecting the steady-state stability of the circuit. Choose a suitable capacitor value that following below step.  Get the BW the quickest method to do transient response form no load to full load. Confirm the damping frequency. The damping frequency is BW. VOUT Cff FB RT2810A/B ISS μA  Following below equation to get the minimum capacitance range in order to avoid UV occur. COUT  VOUT  0.6  1.2 (ILIM  Load Current)  0.8 T  6μA CSS  VREF T Do not leave SS unconnected. Enable Operation (EN) For automatic start-up, the low-voltage EN pin must be connected to VIN with a 100kΩ resistor. EN can be externally pulled to VIN by adding a resistor-capacitor delay (REN and CEN in Figure 2). Calculate the delay time using EN's internal threshold where switching operation begins (1.2V, typical). An external MOSFET can be added to implement digital control of EN (Figure 3). In this case, a 100kΩ pull-up resistor, REN, is connected between VIN and the EN pin. MOSFET Q1 will be under logic control to pull down the EN pin. To prevent enabling circuit when VIN is smaller than the VOUT target value or some other desired voltage level, a resistive voltage divider can be placed between the input voltage and ground and connected to EN to create an additional input under voltage lockout threshold (Figure 4). BW R1 CSS  nF   0.7 R2 GND EN VIN REN CEN EN RT2810A/B GND Figure 1. Cff Capacitor Setting  Figure 2. External Timing Control Cff can be calculated base on below equation : Cff  1 2  3.1412  R1 BW  0.8 Copyright © 2019 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 is a registered trademark of Richtek Technology Corporation. DS2810A/B-07 April 2019 RT2810A/B VIN REN 100k External BOOT Bootstrap Diode EN Q1 Enable RT2810A/B GND Figure 3. Digital Enable Control Circuit VIN REN1 External BOOT Capacitor Series Resistance EN REN2 RT2810A/B GND Figure 4. Resistor Divider for Lockout Threshold Setting Output Voltage Setting Set the desired output voltage using a resistive divider from the output to ground with the midpoint connected to FB. The output voltage is set according to the following equation : VOUT = 0.7 x (1 + R1 / R2) VOUT R1 FB RT2810A/B When the input voltage is lower than 5.5V it is recommended to add an external bootstrap diode between VIN (or VINR) and the BOOT pin to improve enhancement of the internal MOSFET switch and improve efficiency. The bootstrap diode can be a low cost one such as 1N4148 or BAT54. R2 GND The internal power MOSFET switch gate driver is optimized to turn the switch on fast enough for low power loss and good efficiency, but also slow enough to reduce EMI. Switch turn-on is when most EMI occurs since VSW rises rapidly. During switch turn-off, SW is discharged relatively slowly by the inductor current during the dead time between high-side and low-side switch on-times. In some cases it is desirable to reduce EMI further, at the expense of some additional power dissipation. The switch turn-on can be slowed by placing a small (