RT6215EHGJ8F

® RT6215E 2A, 24V, 500kHz, ACOTTM Step-Down Converter General Description Features The RT6215E is a high-efficiency, monolithic synchronous step-down DC-DC converter that can deliver up to 2A output current from a 4.5V to 24V input supply. The RT6215E adopts advanced constant on-time (ACOTTM) architecture to provides a very fast transient response with few external components and keep in constant frequency. Cycle-by-cycle current limit provides protection against shorted outputs and soft-start eliminates input current surge during start-up. Input under-voltage lock-out, output under-voltage protection, over-current protection, and overtemperature protection offer completely safe and smooth operation in all applied conditions.  4.5V to 24V Input Voltage Range  2A Output Current 500kHz Switching Frequency Advanced Constant On-Time Control Fast Transient Response Stable with Low ESR Ceramic Output Capacitors Adjustable Output Voltage from 0.791V to 5V Integrated 100mΩ Ω/85mΩ Ω MOSFETs Monotonic Start-Up into Pre-Biased Outputs Enable Control Cycle-by-Cycle Over Current Limit Protection Input Under-Voltage Lockout Output Under-Voltage Protection with Hiccup Mode Over-Temperature Protection RoHS Compliant and Halogen Free            Ordering Information  RT6215E  Package Type J8F : TSOT-23-8 (FC) Applications Lead Plating System G : Green (Halogen Free and Pb Free)    UVP Option H : Hiccup   Set Top Box Portable TV Access Point Router DSL Modem LCD TV Note : Richtek products are :  RoHS compliant and compatible with the current require-  Suitable for use in SnPb or Pb-free soldering processes. Marking Information 1L= : Product Code 1L=DNN ments of IPC/JEDEC J-STD-020. DNN : Date Code Simplified Application Circuit RT6215E VIN VIN BOOT CIN R3 CBOOT L Enable EN SW VOUT R1 Mode MODE FB GND Copyright © 2022 Richtek Technology Corporation. All rights reserved. DS6215E-01 March 2022 CFF COUT R2 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT6215E Pin Configuration NC EN BOOT 8 7 6 5 2 3 4 VIN SW GND MODE FB (TOP VIEW) TSOT-23-8 (FC) Functional Pin Description Pin No. Pin Name Pin Function 1 MODE Mode selection input. Set MODE pin high will force the RT6215E into CCM. Connect MODE to VIN with a 100k resistor for CCM application. Connect MODE pin to ground to force the RT6215E into Pulse Skipping Mode for light load. Do not float MODE pin. 2 VIN Input voltage. Support 4.5 to 24V input voltage. Must bypass with a suitable large ceramic capacitor at this pin. 3 SW Switch node. Connected to external L-C filter. 4 GND System ground. 5 BOOT Bootstrap supply for high-side gate driver. Connect a 0.1F ceramic capacitor between the BOOT and SW pins. 6 EN Buck enable. High = enable. 7 NC This pin is left to float. 8 FB Feedback input. The pin is used to set the output voltage of the converter to regulate to the desired via a resistive divider. Copyright © 2022 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS6215E-01 March 2022 RT6215E Functional Block Diagram NC VIN MODE BOOT VIN VCC Minoff Reg 3.5V VCC UGATE OC VIBIAS Control Driver SW VREF LGATE UV GND GND SW VCC SW Ripple Gen. EN + + Comparator FB Copyright © 2022 Richtek Technology Corporation. All rights reserved. DS6215E-01 March 2022 EN VIN On Time SW is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT6215E Operation The RT6215E is a high-efficiency, monolithic synchronous step-down DC-DC converter that can deliver up to 2A output current from a 4.5V to 24V input supply. Using the ACOTTM control mode can reduce the output capacitance and perform fast transient response. It can minimize the component size without additional external compensation network. Current Protection The inductor current is monitored via the internal switches cycle-by-cycle. Once the output voltage drops under UV threshold, the RT6215E will enter hiccup mode. operation when the junction temperature exceeds the OTP threshold value. Once the junction temperature cools down and is lower than the OTP lower threshold, the IC will resume normal operation. UVP Protection The RT6215E detects under-voltage conditions by monitoring the feedback voltage on FB pin. When the feedback voltage is lower than 50% of the target voltage, the UVP comparator will go high to turn off both internal high-side and low-side MOSFETs. Hiccup Mode The RT6215E use hiccup mode for UVP. When the protection function is triggered, the IC will shut down for a period of time and then attempt to recover automatically. Hiccup mode allows the circuit to operate safely with low input current and power dissipation, and then resume normal operation as soon as the overload or short circuit is removed. Input Under-Voltage Lockout 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. Shut-Down, Start-Up and Enable (EN) The enable input (EN) has a logic-low level. When VEN is below this level the IC enters shutdown mode. When VEN exceeds its logic-high level the IC is fully operational. External Bootstrap Capacitor Connect a 0.1μF 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 RT6215E includes an over-temperature protection (OTP) circuitry to prevent overheating due to excessive power dissipation. The OTP will shut down switching Copyright © 2022 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS6215E-01 March 2022 RT6215E Absolute Maximum Ratings (Note 1) Supply Input Voltage and EN Voltage, VIN, EN -------------------------------------------------------------------- −0.3V to 28V Switch Voltage, SW ------------------------------------------------------------------------------------------------------ −0.3V to 28V SW (t ≤ 10ns) -------------------------------------------------------------------------------------------------------------- −5V to 30V  BOOT to SW, VBOOT − VSW ------------------------------------------------------------------------------------------------------------------------------------- −0.3V to 6V  BOOT Voltage ------------------------------------------------------------------------------------------------------------- −0.3V to 34V  Other Pins ------------------------------------------------------------------------------------------------------------------ −0.3V to 6V  Power Dissipation, PD @ TA = 25°C TSOT-23-8 (FC) ------------------------------------------------------------------------------------------------------------ 1.428W  Package Thermal Resistance (Note 2) TSOT-23-8 (FC), θJA ------------------------------------------------------------------------------------------------------- 70°C/W TSOT-23-8 (FC), θJC ------------------------------------------------------------------------------------------------------ 15°C/W  Junction Temperature ---------------------------------------------------------------------------------------------------- 150°C  Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- 260°C  Storage Temperature Range -------------------------------------------------------------------------------------------- −65°C to 150°C  ESD Susceptibility (Note 3) HBM (Human Body Model) --------------------------------------------------------------------------------------------- 2kV   Recommended Operating Conditions    (Note 4) Supply Input Voltage ----------------------------------------------------------------------------------------------------- 4.5V to 24V 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 4.5 -- 24 V 3.9 4.1 4.3 V -- 550 -- mV Supply Voltage VIN Supply Input Operating Voltage VIN VIN Under-Voltage Lockout Threshold VUVLO VIN Under-Voltage Lockout Threshold-Hysteresis VUVLO VIN rising Supply Current Supply Current (Shutdown) ISHDN VEN = 0V -- -- 10 A Supply Current (Quiescent) IQ VEN = 2V, VFB = 1V -- 170 270 A tSS VFB from 0% to 100% -- 1500 -- s Soft-Start Internal Soft-Start Period Enable Voltage EN Rising Threshold VENH 1.2 1.4 1.6 V EN Falling Threshold VENL 1.1 1.25 1.4 V VFB 779 791 803 mV Feedback Voltage Feedback Threshold Voltage Copyright © 2022 Richtek Technology Corporation. All rights reserved. DS6215E-01 March 2022 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT6215E Parameter Symbol Test Conditions Min Typ Max Unit Mode Input Voltage Mode Input High Voltage VMODEH 2 -- -- V Mode Input Low Voltage VMODEL -- -- 0.4 V -- 100 -- m -- 85 -- m 2.2 2.7 -- A -- 4 -- A f SW -- 500 -- kHz Maximum Duty Cycle DMAX -- 90 -- % Minimum On-Time tON(MIN) -- 60 -- ns Thermal Shutdown TSD -- 160 -- C Thermal Hysteresis TSD -- 25 -- C UVP detected -- 50 -- % Hysteresis -- 10 -- % Internal MOSFET High-Side Switch-On Resistance RDS(ON)_H Low-Side Switch-On Resistance RDS(ON)_L VBOOTVSW = 4.8V Current Limit Low-Side Switch Valley Current Limit ILIM_L High-Side Switch Peak Current Limit ILIM_H Switching Frequency Switching Frequency On-Time Timer Control Thermal Shutdown Output Under-Voltage Protection UVP Trip Threshold 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 under natural convection (still air) at TA = 25°C with the component mounted on a high effectivethermal-conductivity four-layer test board on a JEDEC 51-7 thermal measurement standard. The first layer is filled with copper. θJC is measured at the lead of the package. Note 3. Devices are ESD sensitive. Handling precautions are recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2022 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS6215E-01 March 2022 RT6215E Typical Application Circuit 2 VIN 4.5V to 24V CIN 22µF Enable Mode RT6215E BOOT VIN SW 6 1 5 R3 20 3 CBOOT 0.1µF L 1.8µH EN MODE GND 4 FB R1 6.49k CFF Option C1 22µF C2 22µF VOUT 1.05V 8 R2 20k Table 1. Suggested Component Values VOUT (V) R1 (k) R2 (k) L (H) COUT (F) CFF (pF) 1.05 6.49 20 1.8 44 -- 1.2 10.5 20 2.2 44 -- 1.8 25.5 20 3.6 44 -- 2.5 43.2 20 4.7 44 22 to 68 3.3 63.4 20 4.7 44 22 to 68 5 107 20 6.8 44 22 to 68 Note : (1) All the input and output capacitors are the suggested values, referring to the effective capacitances, subject to any derating effect, like a DC bias. (2) For low output voltage application, it can optimize the load transient response of the device by adding feedforward capacitor (CFF, 22pF to 68pF). Copyright © 2022 Richtek Technology Corporation. All rights reserved. DS6215E-01 March 2022 is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT6215E Typical Operating Characteristics Efficiency vs. Output Current Output Voltage vs. Output Current 1.20 100 90 1.15 Output Voltage (V) Efficiency (%) 80 70 VIN = 4.5V VIN = 12V VIN = 19V VIN = 24V 60 50 40 30 1.05 10 VOUT = 1.05V VOUT = 1.05V 0.95 0.01 0.1 1 0 10 0.75 1 1.25 1.5 Load Transient Response Output Ripple Voltage 1.75 2 VIN = 12V, VOUT = 1.05V, IOUT = 2A, L = 1.8μH VOUT (20mV/Div) IOUT (1A/Div) VSW (5V/Div) Time (100μs/Div) Time (2μs/Div) Power On from EN Power Off from EN VOUT (1V/Div) VIN = 12V, VOUT = 1.05V, IOUT = 2A, L = 1.8μH VIN = 12V, VOUT = 1.05V, IOUT = 2A, L = 1.8μH VEN (2V/Div) VEN (2V/Div) VSW (10V/Div) VSW (10V/Div) IOUT (2A/Div) Time (5ms/Div) Copyright © 2022 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 0.5 Output Current (A) VOUT (20mV/Div) IOUT (2A/Div) 0.25 Output Current (A) VIN = 12V, VOUT = 1.05V, IOUT = 1.25A to 2A, L = 1.8μH VOUT (1V/Div) VIN = 4.5V VIN = 12V VIN = 19V VIN = 24V 1.00 20 0 0.001 1.10 Time (200μs/Div) is a registered trademark of Richtek Technology Corporation. DS6215E-01 March 2022 RT6215E Power On from VIN VOUT (1V/Div) VIN = 12V, VOUT = 1.05V, IOUT = 2A, L = 1.8μH Power Off from VIN VOUT (1V/Div) VIN = 12V, VOUT = 1.05V, IOUT = 2A, L = 1.8μH VIN (10V/Div) VIN (10V/Div) VSW (10V/Div) VSW (10V/Div) IOUT (2A/Div) IOUT (2A/Div) Time (10ms/Div) Copyright © 2022 Richtek Technology Corporation. All rights reserved. DS6215E-01 March 2022 Time (10ms/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT6215E Application Information Inductor Selection The consideration of inductor selection includes inductance, RMS current rating and, saturation current rating. The inductance selection is generally flexible and is optimized for the low cost, low physical size, and high system performance. Choosing lower inductance to reduce physical size and cost, and it is useful to improve the transient response. However, it causes the higher inductor peak current and output ripple voltage to decrease system efficiency. Conversely, higher inductance increase system efficiency, but the physical size of inductor will become larger and transient response will be slow because more transient time is required to change current (up or down) by inductor. A good compromise between size, efficiency, and transient response is to set a inductor ripple current (ΔIL) about 20% to 50% of the desired full output load current. Calculate the approximate inductance by the input voltage, output voltage, switching frequency (fSW), maximum rated output current (IOUT(MAX)) and inductor ripple current (ΔIL). L= VOUT   VIN  VOUT  VIN  fSW  IL Once the inductance is chosen, the inductor ripple current (ΔIL) and peak inductor current can be calculated. VOUT   VIN  VOUT  VIN  fSW  L IL(PEAK) = IOUT(MAX)  1 IL 2 IL(VALLY) = IOUT(MAX)  1 IL 2 IL = For the typical operating circuit design, the output voltage is 1.05V, maximum rated output current is 2A, input voltage is 12V, and inductor ripple current is 1A which is 50% of the maximum rated output current, the calculated inductance value is : L= 1.05  12  1.05  12  500  103  1 = 1.92μH Copyright © 2022 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 The inductor ripple current set at 1A and so we select 1.8μH inductance. The actual inductor ripple current and required peak current is shown as below : IL = 1.05  12  1.05  12  500  103  1.8  10-6 = 1.06A IL(PEAK) = IOUT(MAX)  1 IL = 2 + 1.06 = 2.53A 2 2 Inductor saturation current should be chosen over IC's current limit. Input Capacitor Selection The input filter capacitors are needed to smooth out the RMS input ripple current drawn from the input power source and ripple voltage seen at the input of the converter. The voltage rating of the input filter capacitors must be greater than the maximum input voltage. It's also important to consider the ripple current capabilities of capacitors. The RMS input ripple current (IRMS) is a function of the input voltage (VIN), output voltage (VOUT), and rated output current (IOUT) : IRMS = IOUT(MAX)  VOUT VIN VIN 1 VOUT The maximum RMS input ripple current occurs at maximum output load and it needs to be concerned about the ripple current capabilities of capacitors at maximum output load. Ceramic capacitors are most often used because of their low cost, small size, high RMS current ratings, and robust surge current capabilities. It should pay attention that value of capacitors change as temperature, bias voltage, and operating frequency change. For example the capacitance value of a capacitor decreases as the dc bias across the capacitor increases. However, take care when these capacitors are used at the input of circuits supplied by a wall adapter or other supply connected through long and thin wires. Current surges through the inductive wires can induce ringing at the IC's power input which could potentially cause large, damaging voltage spikes at VIN pin. If this phenomenon is observed, some bulk input capacitance may be required. Ceramic capacitors can be placed in parallel with is a registered trademark of Richtek Technology Corporation. DS6215E-01 March 2022 RT6215E other types such as tantalum, electrolytic, or polymer to reduce voltage ringing and overshoot. very quick load changes. Typically, load changes occur slowly with respect to the IC's 500kHz switching frequency. Choose capacitors rated at higher temperatures than required. Several ceramic capacitors may be paralleled to meet the RMS current, size, and height requirements of the application. The typical operating circuit use 22μF and one 0.1μF low ESR ceramic capacitors on the input. But some modern digital loads can exhibit nearly instantaneous load changes and the following section shows how to calculate the worst-case voltage swings in response to very fast load steps. Output Capacitor Selection The RT6215E is optimized for output terminal with ceramic capacitors application and best performance will be obtained using them. The total output capacitance value is usually determined by the desired output ripple voltage level and transient response requirements for sag which is undershoot on positive load steps and soar which is overshoot on negative load steps. Output Ripple Voltage Output ripple voltage at the switching frequency is caused by the inductor current ripple and its effect on the output capacitor's ESR and stored charge. These two ripple components are called ESR ripple and capacitive ripple. Since ceramic capacitors have extremely low ESR and relatively little capacitance, both components are similar in amplitude and both should be considered if ripple is critical. VRIPPLE = VRIPPLE(ESR)  VRIPPLE(C) VRIPPLE(ESR) = IL  RESR VRIPPLE(C) = IL 8  COUT  fSW Output Transient Undershoot and Overshoot In addition to output ripple voltage at the switching frequency, the output capacitor and its ESR also affect the voltage sag (undershoot) and soar (overshoot) when the load steps up and down abruptly. The ACOTTM transient response is very quick and output transients are usually small. However, the combination of small ceramic output capacitors (with little capacitance), low output voltages (with little stored charge in the output capacitors), and low duty cycle applications (which require high inductance to get reasonable ripple currents with high input voltages) increases the size of voltage variations in response to Copyright © 2022 Richtek Technology Corporation. All rights reserved. DS6215E-01 March 2022 The output voltage transient undershoot and overshoot each have two components : the voltage steps caused by the output capacitor's ESR, and the voltage sag and soar due to the finite output capacitance and the inductor current slew rate. Use the following formulas to check if the ESR is low enough (typically not a problem with ceramic capacitors) and the output capacitance is large enough to prevent excessive sag and soar on very fast load step edges, with the chosen inductor value. The amplitude of the ESR step up or down is a function of the load step and the ESR of the output capacitor : VESR_STEP = IOUT  RESR The amplitude of the capacitive sag is a function of the load step, the output capacitor value, the inductor value, the input-to-output voltage differential, and the maximum duty cycle. The maximum duty cycle during a fast transient is a function of the on-time and the minimum off-time since the ACOTTM control scheme will ramp the current using on-times spaced apart with minimum off-times, which is as fast as allowed. Calculate the approximate on-time (neglecting parasitics) and maximum duty cycle for a given input and output voltage as : t ON = VOUT tON and DMAX = VIN  fSW tON  t OFF(MIN) The actual on-time will be slightly longer as the IC compensates for voltage drops in the circuit, but we can neglect both of these since the on-time increase compensates for the voltage losses. Calculate the output voltage sag as : L  (IOUT )2 VSAG = 2  COUT   VIN(MIN)  DMAX  VOUT  is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT6215E The amplitude of the capacitive soar is a function of the load step, the output capacitor value, the inductor value and the output voltage : L  (IOUT )2 VSOAR = 2  COUT  VOUT Feed-Forward Capacitor (CFF) EN VIN REN EN RT6215E CEN GND Figure 2. External Timing Control The RT6215E is optimized for ceramic output capacitors and for low duty cycle applications. However for high-output voltages, with high feedback attenuation, the circuit's transient response can be slowed. The high-output voltage circuits transient response could be improved by adding a small “feedforward” capacitor (CFF) across the upper FB divider resistor (Figure 1). Choose a suitable capacitor value that following suggested component BOM. VIN REN 100k EN Q1 Enable RT6215E GND Figure 3. Digital Enable Control Circuit VOUT VIN R1 CFF REN1 EN REN2 RT6215E FB RT6215E GND R2 GND Figure 1. CFF Capacitor Setting Enable Operation (EN) There is an internal 1MEG resister from EN to GND. For automatic start-up the high-voltage EN pin can be connected to VIN, through a 100kΩ resistor. Its large hysteresis band makes EN useful for simple delay and timing circuits. 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. An external MOSFET can be added to implement digital control of EN when no system voltage above 2V is available (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). Copyright © 2022 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 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  0.791V  (1 + R1 ) R2 VOUT R1 FB RT6215E R2 GND Figure 5. Output Voltage Setting is a registered trademark of Richtek Technology Corporation. DS6215E-01 March 2022 RT6215E Place the FB resistors within 5mm of the FB pin. To minimize power consumption without excessive noise pick-up, considering typical application, fix R2 = 20kΩ and calculate R1 as follows : Mode Selection setting For output voltage accuracy, use divider resistors with 1% or better tolerance. The RT6215E has MODE Selection function to set Pulse Skipping Mode for light load. To connect MODE pin to ground to force the RT6215E into Pulse Skipping Mode for light load efficiency improvement. Pulling the MODE pin high (i.e. > 2V) will force the RT6215E into CCM. In order to avoid the abnormal operation caused by noise, MODE pin can't be floated. External BOOT Bootstrap Diode Thermal Considerations When the input voltage is lower than 5.5V it is recommended to add an external bootstrap diode between VIN 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. The junction temperature should never exceed the absolute maximum junction temperature TJ(MAX), listed under Absolute Maximum Ratings, to avoid permanent damage to the device. The maximum allowable power dissipation depends on the thermal resistance of the IC package, the PCB layout, the rate of surrounding airflow, and the difference between the junction and ambient temperatures. The maximum power dissipation can be calculated using the following formula : R1  R2  (VOUT  VREF ) VREF External BOOT Capacitor Series Resistance 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 (