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The RT2859A/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 (ACOT®) 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 ACOT® 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 RT2859A/B are stable with and optimized for ceramic output capacitors.

With internal 70mΩ switches and 70mΩ synchronous rectifiers, the RT2859A/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 RT2859A and RT2859B are each available in
the WQFN-16L 3x3 package, with exposed thermal pads. The RT2859B switches continuously even at light loads to avoid low-frequency interference while the RT2859A 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.
RT2859A RT2859B
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
Output Adj. Method Resistor Resistor
Iout (max) (A) 3 3
Current Limit (typ) (A) 5 5
Freq (typ) (kHz) 650 650
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;Enable Input;Fast Transient Response;OCP;OTP;OVP;PSM;Power Good;SCP;Stable with Ceramic Capacitor;UVP ACOT Control;Adjustable Soft-Start;COT Control;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;OCP;OTP;OVP;Power Good;SCP;Stable with Ceramic Capacitor;UVP
Package Type WQFN3x3-16 WQFN3x3-16
Features
  • Fast Transient Response
  • Steady 650kHz Switching Frequency at all Load Current (RT2859B)
  • Discontinuous Operating Mode at Light Load (RT2859A)
  • 3A Output Current
  • Advanced Constant On-Time (ACOT®) 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 (RT2859ALGQW/RT2859BLGQW Only)
  • With Hiccup Mode (RT2859AHGQW/RT2859BHGQW Only)
  • Input Under-Voltage Lockout
  • Thermal Shutdown
Technical Documents
TitleItem TypeLast UpdateDownload
Richtek Product Selection Guide [Jan., 2024] Selection Guide2024/01/18
Richtek Featured Product Tree [Aug., 2023] Selection Guide2023/08/07
Part NumberPackage TypePackage Qty.Free SampleDistributorStockBuy From Authorized Distributor
RT2859ALGQWWQFN3x3-161,500 Request Digikey 23 Buy
Mouser Lead-Time: 14 weeks Not Available
WPG Lead-Time: 14 weeks Not Available
Evaluation Board
Part NumberDistributorStockBuy From Authorized Distributor
EVB_RT2859BHGQW Digikey 5 Buy
Mouser Lead-Time: 14 weeks Not Available
WPG Lead-Time: 14 weeks Not Available
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