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Step-Down (Buck) Converters

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Richtek Buck Product Family

  • Current Mode Buck converters

  • CMCOT Buck converters

  • ACOT product family

    The proprietary ACOT control scheme not only features ultra-fast transient response but also improves upon legacy constant on-time architectures, achieving constant average frequency over line, load and output ranges to minimize interference and noise problems. The ACOT Buck converters are stable with and optimized for ceramic output capacitors without external components or external ripple injection scheme. The ACOT family includes latch-off, hiccup and constant current protection modes. Richtek has introduced the whole range of ACOT Buck converters up to 12A output current capacity and the input range is from 4.5V to 23V. The ACOT Buck converters are ideal for Set Top Boxes, industrial and commercial low power systems, computer peripherals and LCD Monitors and TVs. See the list of ACOT products.
  • Wide Input Voltage Range DC-DC power solutions for industrial, Automotive and LED lighting applications

    Richtek offers comprehensive power conversion solutions for input voltages ranging up to 60V, suitable for a wide range of applications in the industrial, automotive, and professional lighting field. The key features for Buck converter parts in wide input range are: Robust control architectures for coping with noisy environments, PGOOD and adjustable Soft-start for power sequencing, thermally enhanced packages for operation in higher ambient temperatures, and fully stable with all ceramic input and output capacitors for extended operation life time. We also offer products qualified over -40°C to 85°C industrial temperature range as well as automotive AEC-Q100 standard qualified parts. See the list of selected products.



The following is a list of products released in the last

Part NumberDescriptionShareDatasheetFree Sample
RT6263A/RT6263B17V Input, 3A, ACOT® Buck Converter with Both FETs OC Protection Not available
RTQ634542VIN, 5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RTQ634342VIN, 3.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RT6272A/RT6272B17V Input, 2A, ACOT® Buck Converter with Both FETs OC Protection Not available
RT6273A/RT6273B17V Input, 3A, ACOT® Buck Converter with Both FETs OC Protection Not available
RT6256BH/RT6256CH6A, 23V Synchronous Step-Down Converter with 3.3V/5V LDO Not available
RTQ636560VIN, 5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RT58002.1MHz, 3 CHs, Step-Down Converter with I2C Interface Not available
RTQ636060VIN, 0.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RTQ634042VIN, 0.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RTQ636160VIN, 1.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RTQ634242VIN, 2.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RTQ636360VIN, 3.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RTQ634142VIN, 1.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RTQ636260VIN, 2.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RT6283B3A, 30V, 500kHz Synchronous Step-Down Converter Not available
RT634342VIN, 3.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RT6306A6A, 23V Synchronous Step-Down Converter Not available
RT80991.5MHz, 600mA, High Efficiency PWM Step-Down Converter Not available
RT634542VIN, 5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RT6308A8A, 23V Synchronous Step-Down Converter Not available
RTQ2823A/RTQ2823B8A, 17V, High Efficiency Synchronous Step-Down Converter Not available
RT636360VIN, 3.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RT636560VIN, 5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RT636160VIN, 1.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RT636060VIN, 0.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RT634242VIN, 2.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RT634042VIN, 0.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RT636260VIN, 2.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RTQ28166A, 18V, Synchronous Step-Down Converter Not available
RT634142VIN, 1.5A, Asynchronous Step-Down Converter with Low Quiescent Current Not available
RT6253A/RT6253B17V Input, 3A, ACOT® Buck Converter with Both FETs OC Protection Not available
RT6252A/RT6252B17V Input, 2A, ACOTTM Buck Converter with Both FETs OC Protection Not available
RT6264A/RT6264B18V Input, 4A, ACOTTM Buck Converter with Both FETs OC Protection Not available
RT57606V Input, 1A, ACOT® Buck Converter in Thin SOT-563 Package Not available
RT6258D8A, 23V Synchronous Step-Down Converter with 5V LDO Not available
RT6260C10A, 23V Synchronous Step-Down Converter with 5V LDO Not available
RTQ2822A/RTQ2822B12A, 17V, High Efficiency Synchronous Step-Down Converter Not available
RT6203E6A, 18V, 700kHz ACOTTM Synchronous Step-Down Converter with VID Control Not available
RT6243A/RT6243B12A, 17V, High Efficiency Synchronous Step-Down Converter Not available
RT6203F6A, 18V, 700kHz ACOTTM Synchronous Step-Down Converter with VID Control Not available
RTQ2105-QA36VIN, 3A, High Efficiency Synchronous Step-Down Converter with Low Quiescent Current Not available
RTQ2104-QA36VIN, 3A, High Efficiency, 2.1MHz, Synchronous Step-Down Converter with Low Quiescent Current Request
RTQ2106-QA36VIN, 3A, High Efficiency, 2.1MHz, Synchronous Step-Down Converter with Low Quiescent Current Not available
RT6215F2A, 24V, 800kHz, ACOT® Step-Down Converter Not available
RT57599A, 6.5V, 1MHz, ACOT® Synchronous Step-Down Converter with I2C Interface Not available
RTQ2132B-QT1.2A, 36V, 2.1MHz Synchronous Step-Down Converter Request
RT6280B23V, 10A, 500kHz ACOT® Synchronous Step-Down Converter Not available
RT6258B/RT6258C8A, 23V Synchronous Step-Down Converter with 3.3V/5V LDO Not available
RT57589A, 6.5V, 1MHz Synchronous Step-Down Converter Not available
RTQ2131B-QA1A, 36V, 2.1MHz Synchronous Step-Down Converter Request
RT5710F1A, 1MHz, 6V CMCOT Synchronous Step-Down Converte Not available
RTQ2130B-QT0.7A, 36V, 2.1MHz Synchronous Small Form Factor Step-Down Converter Request
RT5707/RT5707AUltra-Low Quiescent Current HCOT Buck Converter Request
RT725518V, 1.5A, 500kHz ACOTTM Step-down Converter in 8 Pin TSOT-23 Not available
RT6215A/RT6215B24V, 2A, 500kHz, ACOTTM Step-Down Converter in 8 Pin TSOT-23 Not available

Buck converter definition

Buck converters are switch-mode step-down converters which can provide high efficiency and high flexibility at higher VIN/VOUT ratios and higher load current.

Most Buck converters contain an internal high side MOSFET and synchronous rectifier MOSFET, which are in turn switched on and off via internal duty-cycle control circuit to regulate the average output voltage. The switching waveform is filtered via an external LC filter stage.

Buck converter features

Due to the fact that the MOSFETs are either ON or OFF, Buck converters dissipate very little power, and the duty-cycle control makes large VIN/VOUT ratios possible. The internal MOSFETs RDS(ON) mainly determines the current handling capabilities of the Buck converter, and the MOSFET voltage ratings determine the maximum input voltage. The switching frequency together with the external LC filter components will determine the ripple voltage on the output. Higher switching frequency buck converters can use smaller filter components, but switch losses will increase. Buck converters with Pulse Skipping Mode (PSM) will reduce their switching frequency at light load, thereby increasing light load efficiency, which can be important in applications with low power standby modes.

The Richtek DC/DC portfolio contains a wide range of Buck converters with different control topologies, including Current Mode (CM), Current Mode-Constant On Time (CMCOT) and Advanced Constant On Time (ACOT™) control topologies. Each topology is suitable for different applications and requirements. For example, Richtek unique ACOT™ family has extremely fast transient response compared to CM and CMCOT topologies, which makes it ideal for applications that exhibit very fast load transients, such as DDR, Core SoC, FPGA and ASIC supplies.

Comparison Table of Richtek Buck Topologies

Key features CM
Current Mode
CMCOT
Current Mode
Constant-On-Time
ACOT™
Advanced
Constant-On-Time
Topology BuckConverter BuckConverter BuckConverter
Steady-state &
Step load
BuckConverter BuckConverter BuckConverter
VIN/IOUT range
  • 2.5Vin to 5.5Vin / up to 6A for low Vin and battery-powered applications
  • Up to 36Vin / up to 10A
  • Up to 60Vin for Industrial and 36Vin for Automotive applications
  • 2.5Vin to 5.5Vin / up to 3A
  • Up to 23Vin / up to 12A
Response to
Load Steps
moderate fast extremely fast
Current Sense current sense limits min. ON time low side current sense Not required
Min. ON Time Larger, limits the min. achievable duty-cycle Small min. On time allows small duty-cycles Small min. On time allows small duty-cycles
Frequency stable fixed fSW constant average fSW constant average fSW
Stable with MLCC
Slope Compensation not required not required
Synchronized to ext. Clock X X
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Applications For applications with steady load conditions. Also for industrial and automotive applications. For applications with moderate load transients, or applications that require small minimum ON times
(i.e. high switching frequency in combination with larger step-down ratios)
For applications with severe fast load transients , such as DDR, Core SoC, FPGA and ASIC supplies

Buck Converter Selection Criteria

In order to select a suitable Buck converter for your application, some key criteria are important to be considered.


Application input voltage

Which upper bound of input voltage fits for your application best?
Richtek Buck converters can be divided into 3 main groups to fulfill different application requirements. Richtek LV Buck converters are suitable for running off single cell Li-Ion batteries as well as supplies from 5V rails. The 18V rated HV Buck converters are often used for applications that run from 12V. We also provide parts up to 36V input range for industrial supplies or automotive applications with large input voltage fluctuation.


Application current consumption

How to calculate the power loss and maximum applic