RT7231GQW

Reference Design Design Tools Sample & Buy ® RT7231/32/33/34 4A, 18V, 650kHz, ACOTTM Synchronous Step-Down Converter General Description Features The RT7231/32/33/34 is a synchronous step-down DC/ DC converter with Advanced Constant On-Time (ACOTTM) mode control. It achieves high power density to deliver up to 4A output current from a 4.5V to 18V input supply. The proprietary ACOTTM 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, RT7231/32/33/34 keeps an excellent constant switching frequency under line and load variation and the integrated synchronous power switches with the ACOTTM 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 include thermal shutdown for RT7231/32/33/34, output Under Voltage Protection (UVP) / Over Voltage Protection (OVP) for RT7231/32. When the UVP/OVP is triggered, the device will enter latch mode for TSSOP-14 (Exposed Pad), and hiccup mode for WDFN-10L 3x3. z The RT7231/32 are available in TSSOP-14 (Exposed Pad) and WDFN-10L 3x3 packages, and the RT7231 is operated in forced continuous conduction mode. z The RT7233/34 are available in the SOP-8 (Exposed Pad) package, and the RT7233 is operated in forced continuous conduction mode. z z z z z z z z z z z z z z ACOTTM Mode Enables Fast Transient Response 4.5V to 18V Input Voltage Range 4A Output Current 50mΩ Ω Internal Low Site N-MOSFET Advanced Constant On-Time Control Support All Ceramic Capacitors Up to 95% Efficiency 650kHz Switching Frequency at all Load Current (RT7231, RT7233) Discontinuous Operating Mode at Light Load (RT7232, RT7234) Adjustable Output Voltage from 0.765V to 8V Adjustable Soft-Start Cycle-by-Cycle Current Limit Input Under Voltage Lockout Thermal Shutdown RoHS Compliant and Halogen Free Applications z z z z 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 RT7231/32/33/34 VIN Enable Power GOOD * : VCC pin for TSSOP-14 (Exposed Pad) only. VIN SW VCC* BOOT EN PGOOD* PGND VREG5 SS GND* VOUT FB VS* VS pin for TSSOP-14 (Exposed Pad) only. GND pin for TSSOP-14 (Exposed Pad) only. PGOOD pin for TSSOP-14 (Exposed Pad) and WDFN-10L 3x3 only. Copyright © 2018 Richtek Technology Corporation. All rights reserved. DS7231/32/33/34-10 February 2018 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT7231/32/33/34 Ordering Information Marking Information Continuous Switching Mode RT7231GCP RT7231GCP : Product Number RT7231 RT7231GCP YMDNN Package Type CP : TSSOP-14 (Exposed Pad) QW : WDFN-10L 3x3 (W-Type) Lead Plating System G : Green (Halogen Free and Pb Free) YMDNN : Date Code RT7231GQW 1Q= : Product Code 1Q=YM DNN RT7233 YMDNN : Date Code Package Type SP : SOP-8 (Exposed Pad-Option 2) Lead Plating System G : Green (Halogen Free and Pb Free) RT7233GSP RT7233GSP : Product Number RT7233 GSPYMDNN YMDNN : Date Code Discontinuous Operating Mode RT7232 RT7232GCP Package Type CP : TSSOP-14 (Exposed Pad) QW : WDFN-10L 3x3 (W-Type) RT7232GCP : Product Number RT7232GCP YMDNN YMDNN : Date Code Lead Plating System G : Green (Halogen Free and Pb Free) RT7232GQW RT7234 1P= : Product Code 1P=YM DNN Package Type SP : SOP-8 (Exposed Pad-Option 2) YMDNN : Date Code Lead Plating System G : Green (Halogen Free and Pb Free) RT7234GSP Note : RT7234GSP : Product Number RT7234 GSPYMDNN Richtek products are : ` RoHS compliant and compatible with the current require- YMDNN : Date Code ments of IPC/JEDEC J-STD-020. ` Suitable for use in SnPb or Pb-free soldering processes. Pin Configurations 14 2 13 3 4 12 PGND 11 5 10 6 9 7 15 8 VCC VIN BOOT SW SW PGND PGND EN FB VREG5 SS PGOOD TSSOP-14 (Exposed Pad) Copyright © 2018 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 1 2 3 4 5 11 10 9 8 7 9 VS FB VREG5 SS GND PGOOD EN PGND (TOP VIEW) VIN VIN BOOT SW SW WDFN-10L 3x3 8 EN FB 2 VREG5 3 SS 4 PGND VIN 7 BOOT 6 SW 5 PGND 9 SOP-8 (Exposed Pad) is a registered trademark of Richtek Technology Corporation. DS7231/32/33/34-10 February 2018 RT7231/32/33/34 Functional Pin Description Pin No. Pin Name TSSOP-14 SOP-8 WDFN-10L 3x3 (Exposed Pad) (Exposed Pad) 1 -- -- Pin Function VS Output Voltage Sense Input. 2 2 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 threshold voltage is 0.765V typically. 3 3 3 VREG5 Internal Regulator Output. Connect a 1µF capacitor to GND to stabilize output voltage. 4 4 4 SS Soft-Start Time Setting. Connect an external capacitor between this pin and GND to set the soft- start time. 5 -- -- GND Analog Ground. 6 5 -- PGOOD Open Drain Power Good Indicator Output. 7 1 1 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 10µA. 8, 9, 15 11 5, 9 PGND (Exposed pad) (Exposed pad) (Exposed Pad) Power Ground. The exposed pad must be soldered to a large PCB and connected to PGND for maximum power dissipation. 10, 11 6, 7 6 SW Switch Node. Connect this pin to an external L-C filter. 12 8 7 BOOT Bootstrap Supply for High Side Gate Driver. Connect a 0.1µF capacitor between the BOOT and SW pin. 13 9, 10 8 VIN Power Input. The input voltage range is from 4.5V to 18V. Must bypass with a suitably large ( ≥10µF x 2) ceramic capacitor. 14 -- -- VCC Supply Voltage Input for Internal Linear Regulator to the Control Circuitry. Copyright © 2018 Richtek Technology Corporation. All rights reserved. DS7231/32/33/34-10 February 2018 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT7231/32/33/34 Function Block Diagram VCC* EN VREG5 POR & Reg BOOT Min. Off-Time VBIAS VREG5 VIN VREF OC Control Driver SW UV & OV PGND SW VREG5 ZC Ripple Gen. GND* 6µA SS VIN FB VS* FB + Comparator FB 0.9 x VREF Comparator - PGOOD* + On-Time * : VCC pin for TSSOP-14 (Exposed Pad) only. GND pin for TSSOP-14 (Exposed Pad) only. VS pin for TSSOP-14 (Exposed Pad) only. PGOOD pin for TSSOP-14 (Exposed Pad) and WDFN-10L 3x3 only. Operation The RT7231/32/33/34 is a synchronous step-down converter with advanced constant on-time control mode. Using the ACOTTM control mode can reduce the output capacitance and provide 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 in cycle-by-cycle. Once the output voltage drops under UV threshold, the device will enter latch mode for TSSOP14 (Exposed Pad), and hiccup mode for WDFN-10L 3x3. UVLO Protection Power Good (for TSSOP-14 (Exposed Pad) and WDFN-10L 3x3 only) After soft-start is finished, the power good function will be activated. When the FB is activated, the PGOOD will become an open-drain output. If the FB is below, the PGOOD pin will be pulled low. To protect the chip from operating at insufficient supply voltage, the UVLO is needed. When the input voltage of VCC is lower than the UVLO falling threshold voltage, the device will be latch-off. Output Discharge Control (for TSSOP-14 (Exposed Pad) only) Internal Regulator The regulator provides 5V power to supply the internal control circuit. Connecting a 1µF ceramic capacitor for decoupling and stability is required. When EN pin is low, the RT7231/32 will discharge the output with an internal 50Ω MOSFET connected between VOUT to GND pin. Thermal Shutdown Soft-Start 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 and can be set by an external capacitor. Copyright © 2018 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 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 automatically resume switching is a registered trademark of Richtek Technology Corporation. DS7231/32/33/34-10 February 2018 RT7231/32/33/34 Absolute Maximum Ratings z z z z z z z z z z z (Note 1) Supply Voltage, VIN, VCC --------------------------------------------------------------------------------------- −0.3V to 20V Switch Voltage, SW ----------------------------------------------------------------------------------------------- −0.8V to (VIN + 0.3V) < 10ns ---------------------------------------------------------------------------------------------------------------- −5V to 25V BOOT to SW -------------------------------------------------------------------------------------------------------- −0.3V to 6V EN ---------------------------------------------------------------------------------------------------------------------- −0.3V to 20V Other Pins ------------------------------------------------------------------------------------------------------------ −0.3V to 6V Power Dissipation, PD @ TA = 25°C TSSOP-14 (Exposed Pad) --------------------------------------------------------------------------------------- 2.50W WDFN-10L 3x3 ------------------------------------------------------------------------------------------------------ 1.67W SOP-8 (Exposed Pad) -------------------------------------------------------------------------------------------- 2.174W Package Thermal Resistance (Note 2) TSSOP-14 (Exposed Pad), θJA --------------------------------------------------------------------------------- 40°C/W WDFN-10L 3x3, θJA ------------------------------------------------------------------------------------------------ 60°C/W WDFN-10L 3x3, θJC ------------------------------------------------------------------------------------------------ 7.5°C/W SOP-8 (Exposed Pad), θJA --------------------------------------------------------------------------------------- 46°C/W SOP-8 (Exposed Pad), θJC -------------------------------------------------------------------------------------- 7°C/W Junction Temperature Range ------------------------------------------------------------------------------------- 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) ---------------------------------------------------------------------------------------- 3kV MM (Machine Model) ----------------------------------------------------------------------------------------------- 250V Recommended Operating Conditions z z z (Note 4) Supply Voltage, VIN ----------------------------------------------------------------------------------------------- 4.5V to 18V 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 Supply Current Shutdown Current ISHDN VEN = 0V -- 1 10 µA Quiescent Current IQ VEN = 5V, VFB = 0.8V -- 1 1.3 mA Logic-High 1.25 -- 18 Logic-Low -- -- 0.85 Logic Threshold EN Input Voltage V VFB Voltage and Discharge Resistance Feedback Threshold Voltage VFB Feedback Input Current IFB VOUT Discharge Resistance RDIS TA = 25°C 0.757 0.765 0.773 TA = −40°C to 85°C 0.755 -- 0.775 VFB = 0.8V -- 0.01 0.1 µA VEN = 0V, VS = 0.5V -- 50 100 Ω Copyright © 2018 Richtek Technology Corporation. All rights reserved. DS7231/32/33/34-10 February 2018 V is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT7231/32/33/34 Parameter Symbol Test Conditions Min Typ Max Unit 4.8 5.1 5.4 V VREG5 Output VREG5 Output Voltage VREG5 6V ≤ VIN ≤ 18V, 0 < IVREG5 < 5mA Line Regulation 6V ≤ VIN ≤ 18V, IVREG5 = 5mA -- -- 20 mV Load Regulation 0 < IVREG5 < 5mA -- -- 100 mV IVREG5 VIN = 6V, VREG5 = 4V -- 70 -- mA High-Side RDS(ON)_H (VBOOT − VSW ) = 5.5V -- 120 -- Low-Side RDS(ON)_L -- 50 -- 4.9 5.85 6.8 -- 150 -- -- 20 -- Output Current RDS(ON) Switch On Resistance Current Limit Current Limit Thermal Shutdown Thermal Shutdown Threshold ILIM TSD Shutdown Temperature Thermal Shutdown Hysteresis ∆TSD mΩ A °C On-Time Timer Control On-Time tON VIN = 12V, VOUT = 1.05V -- 135 -- ns Minimum Off-Time tOFF(MIN) VFB = 0.7V -- 260 310 ns SS Charge Current VSS = 0V 5 6 8 µA SS Discharge Current VSS = 0.5V 0.1 0.2 -- mA Wake Up VREG5 3.6 3.85 4.1 0.16 0.35 0.47 VFB Rising 85 90 95 VFB Falling -- 85 -- Soft-Start UVLO UVLO Threshold Hysteresis V Power Good PGOOD Threshold % PGOOD Sink Current PGOOD = 0.5V Output Under Voltage and Over Voltage Protection OVP Trip Threshold OVP Detect 2.5 5 -- mA 115 120 125 % OVP Prop Delay UVP Trip Threshold -65 5 70 -75 µs UVP Hysteresis -- 10 -- UVP Prop Delay -- 250 -- µs -- tSS x 1.7 -- ms UVP Enable Delay tUVPEN Relative to Soft-Start Time % 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 at TA = 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. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2018 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS7231/32/33/34-10 February 2018 RT7231/32/33/34 Typical Application Circuit RT7231/32/33/34 VIN C1 10µF x 2 C2 0.1µF VIN VCC* BOOT C6 0.1µF C5 3.9nF C7 22µF x 2 R1 8.25k R2 22k R3 100k C4 1µF C3 FB PGOOD* Power GOOD VOUT 1.05V/4A SW EN Input Signal L1 1.4µH VREG5 SS GND* VS* PGND * : VCC pin for TSSOP-14 (Exposed Pad) only. VS pin for TSSOP-14 (Exposed Pad) only. GND pin for TSSOP-14 (Exposed Pad) only. PGOOD pin for TSSOP-14 (Exposed Pad) and WDFN-10L 3x3 only. Table 1. Suggested Component Values (VIN = 12V) VOUT (V) R1 (kΩ) R2 (kΩ) C3 (pF) L1 (µH) C7 (µF) 1 6.81 22.1 -- 1.4 22 to 68 1.05 8.25 22.1 -- 1.4 22 to 68 1.2 12.7 22.1 -- 1.4 22 to 68 1.8 30.1 22.1 5 to 22 2 22 to 68 2.5 49.9 22.1 5 to 22 2 22 to 68 3.3 73.2 22.1 5 to 22 2 22 to 68 124 22.1 5 to 22 3.3 22 to 68 12 2.16 50 to 220 3.3 22 to 68 180 22.1 5 to 22 3.3 22 to 68 5 7 Copyright © 2018 Richtek Technology Corporation. All rights reserved. DS7231/32/33/34-10 February 2018 is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT7231/32/33/34 Typical Operating Characteristics Efficiency vs. Output Current Efficiency vs. Output Current 100 RT7231/33 90 90 80 80 70 VIN = 5V VIN = 12V VIN = 18V 60 Efficiency (%) Efficiency (%) 100 50 40 30 RT7232/34 70 VIN = 5V VIN = 12V VIN = 18V 60 50 40 30 20 20 10 10 VOUT = 1.05V 0 0.001 0.01 0.1 1 VOUT = 1.05V 0 0.001 10 0.01 Output Current (A) Output Voltage vs. Input Voltage 10 Feedback Threshold Voltage (V) 0.780 1.058 Output Voltage (V) 1 Feedback Threshold Voltage vs. Temperature 1.060 1.056 1.054 1.052 1.050 1.048 1.046 1.044 1.042 VIN = 4.5V to 18V, VOUT = 1.05V 1.040 0.775 0.770 0.765 0.760 0.755 VIN = 12V, VOUT = 1.05V, IOUT = 0A 0.750 4 6 8 10 12 14 16 18 -50 -25 0 Input Voltage (V) RT7231/33 1.09 1.08 1.08 Output Voltage (V) 1.09 1.07 1.06 1.05 VIN = 18V VIN = 12V VIN = 5V 1.03 50 75 100 125 Output Voltage vs. Output Current 1.10 1.04 25 Temperature (°C) Output Voltage vs. Output Current 1.10 Output Voltage (V) 0.1 Output Current (A) 1.02 RT7232/34 1.07 1.06 1.05 VIN = 18V VIN = 12V VIN = 5V 1.04 1.03 1.02 1.01 1.01 VOUT = 1.05V 1.00 VOUT = 1.05V 1.00 0 0.5 1 1.5 2 2.5 3 3.5 Output Current (A) Copyright © 2018 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 4 0 0.5 1 1.5 2 2.5 3 3.5 4 Output Current (A) is a registered trademark of Richtek Technology Corporation. DS7231/32/33/34-10 February 2018 RT7231/32/33/34 Switching Frequency vs. Temperature 700 690 690 Switching Frequency (kHz)1 Switching Frequency (kHz)1 Switching Frequency vs. Input Voltage 700 680 670 660 650 640 630 620 610 680 670 660 650 640 630 620 610 600 600 4 6 8 10 12 14 16 18 -50 -25 0 Input Voltage (V) Current Limit vs. Temperature 50 75 100 125 Current Limit vs. Input Voltage 7.0 7.0 6.5 6.5 Current Limit (A) Current Limit (A) 25 Temperature (°C) 6.0 5.5 5.0 4.5 6.0 5.5 5.0 4.5 VIN = 12V, VOUT = 1.05V 4.0 4.0 -50 -25 0 25 50 75 100 125 4 6 8 10 12 14 16 Temperature (°C) Input Voltage (V) Load Transient Response Load Transient Response RT7231/33 VOUT (5mV/Div) VIN = 12V, VOUT = 1.05V, IOUT = 0A to 4A Time (100µs/Div) Copyright © 2018 Richtek Technology Corporation. All rights reserved. DS7231/32/33/34-10 20 RT7231/32/33/34 VOUT (20mV/Div) IOUT (2A/Div) 18 February 2018 IOUT (2A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 1A to 4A Time (100µs/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT7231/32/33/34 Switching Switching VSW (10V/Div) VSW (10V/Div) VOUT (5mV/Div) VOUT (5mV/Div) IL (1A/Div) IL (2A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 1A Time (1µs/Div) Time (1µs/Div) Power On from VIN Power Off from VIN VIN (5V/Div) VIN (5V/Div) VOUT (1V/Div) VOUT (1V/Div) IOUT (5A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 4A IOUT (5A/Div) Time (10ms/Div) Power On from EN Power Off from EN VEN (5V/Div) VOUT (500mV/Div) VOUT (500mV/Div) VIN = 12V, VOUT = 1.05V, IOUT = 4A Time (500µs/Div) Copyright © 2018 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 VIN = 12V, VOUT = 1.05V, IOUT = 4A Time (2.5ms/Div) VEN (5V/Div) IOUT (2A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 4A IOUT (2A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 4A Time (500µs/Div) is a registered trademark of Richtek Technology Corporation. DS7231/32/33/34-10 February 2018 RT7231/32/33/34 EN Threshold Voltage vs. Temperature UVLO Voltage vs. Temperature 4.0 1.4 3.9 1.3 1.2 UVLO Voltage (V) EN Threshold Voltage (V) 1.5 Rising 1.1 Falling 1.0 0.9 Rising 3.8 3.7 3.6 Falling 3.5 0.8 VIN = 12V, VOUT = 1.05V 0.7 3.4 -50 -25 0 25 50 75 100 125 -50 -25 0 25 50 75 100 Temperature (°C) Temperature (°C) Power Good from EN Turn On Power Good from EN Turn Off RT7231/32 RT7231/32 VEN (5V/Div) VEN (5V/Div) VPGOOD (5V/Div) VPGOOD (5V/Div) VOUT (1V/Div) VOUT (1V/Div) IOUT (5A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 4A Time (250µs/Div) Copyright © 2018 Richtek Technology Corporation. All rights reserved. DS7231/32/33/34-10 125 February 2018 IOUT (5A/Div) VIN = 12V, VOUT = 1.05V, IOUT = 4A Time (2.5ms/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT7231/32/33/34 Application Information The RT7231/32/33/34 is a synchronous high voltage Buck converter that can support the input voltage range from 4.5V to 18V and the output current up to 4A. It adopts ACOTTM mode control to provide a very fast transient response with few external compensation components. the EN pin can also be externally pulled high by adding a REN resistor and CEN capacitor from the VIN pin (see Figure 1). EN VIN Advanced Constant On-Time Control The RT7231/32/33/34 has a unique circuit which sets the on-time by monitoring the input voltage and SW signal. The circuit ensures the switching frequency operating at 650kHz over input voltage range and loading range. Soft-Start The RT7231/32/33/34 contains an external soft-start clamp that gradually raises the output voltage. The soft-start timing can be programmed by the external capacitor between the SS and GND pins. The chip provides a 6µA charge current for the external capacitor. If a 3.9nF capacitor is used, the soft-start will be 0.87ms (typ.). The available capacitance range is from 2.7nF to 220nF. t SS (ms) = C5 (nF) × 1.365 ISS (µ A) Chip Enable Operation The EN pin is the chip enable input. Pulling the EN pin low (