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5A, 18V, 650kHz, ACOT™ Synchronous Step-Down Converter

RT7235/RT7236/RT7239/RT7240

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The RT7235/36/39/40 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 5A 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, RT7235/36/39/40 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 RT7235/36/39/40, output Under Voltage Protection (UVP) / Over Voltage Protection (OVP) for RT7235/36. When the UVP/OVP is triggered, the device will enter latch mode for TSSOP-14 (Exposed Pad), and hiccup mode for WDFN-10L 3x3.

The RT7235/36 are available in TSSOP-14 (Exposed Pad) and WDFN-10L 3x3 packages, and the RT7235 is operated in forced continuous conduction mode.

The RT7239/40 are available in the SOP-8 (Exposed Pad) package, and the RT7239 is operated in forced continuous conduction mode.

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.
RT7235 RT7236 RT7239 RT7240
Status Active Active Active Active
Vin (min) (V) 4.5 4.5 4.5 4.5
Vin (max) (V) 18 18 18 18
Number of Outputs 1 1 1 1
Vout (min) (V) 0.765 0.765 0.765 0.765
Vout (max) (V) 8 8 8 8
Output Adj. Method Resistor Resistor Resistor Resistor
Iout (max) (A) 5 5 5 5
Current Limit (typ) (A) 6.85 6.85 6.85 6.85
Freq (typ) (kHz) 650 650 650 650
Ext Sync No No No No
Ron_HS (typ) (mOhm) 120 120 120 120
Ron_LS (typ) (mOhm) 35 35 35 35
Iq (typ) (mA) 1 1 1 1
Features ACOT Control;Adjustable Soft-Start;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;Force PWM;OCP;OVP;Power Good;Stable with Ceramic Capacitor;UVP ACOT Control;Adjustable Soft-Start;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;OCP;OVP;PSM;Power Good;Stable with Ceramic Capacitor;UVP ACOT Control;Adjustable Soft-Start;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;Force PWM;OCP;Stable with Ceramic Capacitor ACOT Control;Adjustable Soft-Start;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;OCP;PSM;Stable with Ceramic Capacitor
Package Type TSSOP-14(PP);WDFN3x3-10 TSSOP-14(PP);WDFN3x3-10 PSOP-8 PSOP-8
Features
  • ACOTTM Mode Enables Fast Transient Response
  • 4.5V to 18V Input Voltage Range
  • 5A Output Current
  • 35mΩ 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 (RT7235, RT7239)
  • Discontinuous Operating Mode at Light Load (RT7236, RT7240)
  • 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
Datasheet
TitleLast UpdateShareDownload
5A, 18V, 650kHz, ACOT™ Synchronous Step-Down Converter2013/02/25
Technical Documents
TitleLast UpdateShareDownload
DC/DC Converter Testing with Fast Load Transient2019/06/04
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?2017/03/30 583
Introduction to Richtek's Advanced Constant On Time Buck Converters2013/05/14 50
Evaluation Boards
TitleLast UpdateShareDownload
RT7236GQW Evaluation Board2018/11/08
RT7235GQW Evaluation Board2018/11/08
Reference Design
TitleLast UpdateShareDownload
Richtek Load Transient Tool2019/01/09
Design Tool
TitleLast UpdateShare
Richtek Designer™ Web Simulation Tool : RT7239GSP2019/09/11
Richtek Designer™ Web Simulation Tool : RT7240GSP2019/09/11
Richtek Designer™ Web Simulation Tool : RT7235GCP2019/09/11
Richtek Designer™ Web Simulation Tool : RT7235GQW2019/09/11
Richtek Designer™ Web Simulation Tool : RT7236GCP2019/09/11
Richtek Designer™ Web Simulation Tool : RT7236GQW2019/09/11
Part NumberPackage TypePackage Qty.Free SampleBuy From Authorized Distributor
RT7235GCPTSSOP-14(PP)2500 Not available Buy from Distributor
RT7235GQWWDFN3x3-101500 Request Buy from Distributor
RT7236GCPTSSOP-14(PP)2500 Not available Buy from Distributor
RT7236GQWWDFN3x3-101500 Request Buy from Distributor
RT7240GSPPSOP-82500 Not available Buy from Distributor
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