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3A, 18V, 650kHz, ACOT™ Synchronous Step-Down Converter

RT6259A/RT6259B

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The RT6259A/B are high-performance 650kHz 3A step-down regulators with internal power switches and synchronous rectifiers. They feature quick transient response using their Advanced Constant On-Time (ACOTTM) control architecture that provides stable operation with small ceramic output capacitors and without complicated external compensation, among other benefits. The input voltage range is from 4.5V to 18V and the output is adjustable from 0.765V to 7V.

The proprietary ACOTTM control improves upon other fast-response constant on-time architectures, achieving nearly constant switching frequency over line, load, and output voltage ranges. Since there is no internal clock, response to transients is nearly instantaneous and inductor current can ramp quickly to maintain output regulation without large bulk output capacitance. The RT6259A/B are stable with and optimized for ceramic output capacitors.

With internal 70mΩ switches and 70mΩ synchronous rectifiers, the RT6259A/B display excellent efficiency and good behavior across a range of applications, especially for low output voltages and low duty cycles. Cycle-by-cycle current limit, input under-voltage lockout, externally-adjustable soft-start, output under- and over-voltage protection, and thermal shutdown provide safe and smooth operation in all operating conditions.

The RT6259A and RT6259B are each available in the WQFN-16L 3x3 package, with exposed thermal pads.The RT6259B switches continuously even at light loads to avoid low-frequency interference while the RT6259A features a power-saving discontinuous operating mode at light loads.

Applications

  • 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
Key Spec.
RT6259A RT6259B
Status Active Active
Vin (min) (V) 4.5 4.5
Vin (max) (V) 18 18
Number of Outputs 1 1
Vout (min) (V) 0.765 0.765
Vout (max) (V) 7 7
Preset Vout (V)
Output Adj. Method Resistor Resistor
Iout (max) (A) 3 3
Current Limit (typ) (A) 5 5
Freq (typ) (kHz) 650 650
Freq (min) (kHz)
Freq (max) (kHz)
Ext Sync No No
Ron_HS (typ) (mOhm) 70 70
Ron_LS (typ) (mOhm) 70 70
Iq (typ) (mA) 1 1
Features ACOT Control;Adjustable Soft-Start;COT Control;Cycle-by-Cycle Current Limit;PSM;Power Good;Stable with Ceramic Capacitor;UVP ACOT Control;Adjustable Soft-Start;COT Control;Cycle-by-Cycle Current Limit;Force PWM;Power Good;Stable with Ceramic Capacitor;UVP
Package Type WQFN3x3-16 WQFN3x3-16
Features
  • Fast Transient Response
  • Steady 650kHz Switching Frequency At all Load Current (RT6259B)
  • Discontinuous Operating Mode at Light Load (RT6259A)
  • 3A Output Current
  • Advanced Constant On-Time (ACOTTM) Control
  • Optimized for Ceramic Output Capacitors
  • 4.5V to 18V Input Voltage Range
  • Internal 70mΩ Switch and 70mΩ Synchronous Rectifier
  • 0.765V to 7V Adjustable Output Voltage
  • Externally-adjustable, Pre-biased Compatible Soft-Start
  • Cycle-by-Cycle Current Limit
  • Optional Output Discharge Function
  • Output Over- and Under-voltage Shut Down
  • Latched (RT6259ALGQW/RT6259BLGQW Only)
  • With Hiccup Mode (RT6259AHGQW/RT6259BHGQW Only)
  • Input Under-Voltage Lockout
  • Thermal Shutdown
  • RoHS Compliant and Halogen Free
Datasheet
TitleLast UpdateShareDownload
3A, 18V, 650kHz, ACOT™ Synchronous Step-Down Converter2015/12/18
Technical Documents
TitleLast UpdateShareDownload
ACOT™ Stability Testing2019/03/18
ACOT™ (Advanced Constant-On Time) Synchronous Step-Down Converters2018/11/15
Comparing Buck Converter Topologies2018/09/20
Buck Converter Selection Criteria2016/08/04
The Calculation of Output DC Offset for ACOT™ Control Buck Converter with Feed-forward Compensator2016/07/07
Videos
TitleLast UpdateShareViews
How to estimate control loop bandwidth from the transient response time?2017/03/30 522
Evaluation Boards
TitleLast UpdateShareDownload
RT6259BHGQW 3A, 18V, 650kHz, ACOT™ Synchronous Step-Down Converter2017/09/04
Reference Design
TitleLast UpdateShareDownload
Richtek Load Transient Tool2018/11/01
Part NumberPackage TypePackage Qty.Free SampleBuy From Authorized Distributor
RT6259AHGQWWQFN3x3-161500 Not available Buy from Distributor
RT6259ALGQWWQFN3x3-161500 Not available Buy from Distributor
RT6259BHGQWWQFN3x3-161500 Not available Buy from Distributor
RT6259BLGQWWQFN3x3-161500 Not available Buy from Distributor
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