Page No. : 1/11
RS2051
Description
Green-Mode PWM Controller with Frequency Jiggling for Low EMI
The RS2051 is a highly integrated low cost current mode PWM controller, which is ideal for small power current mode of offline
AC-DC fly-back converter applications. Making use of external resistors, the IC changes the operating frequency and
automatically enters the PFM/CRM (Cycle Reset Mode) under light-load/zero-load conditions. This can minimize standby power
consumption and achieve power-saving functions. With a very low start-up current, the RS2051 could use a large value start-up
resistor (2Mohms). Built-in synchronized slope compensation enhances the stability of the system and avoids sub-harmonic
oscillation. Dynamic peak current limiting circuit minimizes output power change caused by delay time of the system over a
universal AC input range. Leading edge blanking circuit on current sense input could remove the signal glitch due to snubber
circuit diode reverse recovery and thus greatly reduces the external component count and system cost in the design. Cycle-by-
Cycle current limiting ensures safe operation even during short-circuit.
Excellent EMI performance is achieved built-in soft start with 1.2ms、soft driver and low EMI Technique.
The RS2051 offers perfect protection like OVP(Over Voltage Protection)、OLP(Over Load Protection)、SCP(Short circuit
protection)、Sense Fault Protection, LM (Latch Mode) and OCP(Over current protection). The RS2051’s output driver is soft
clamped to maximum 18V to protect the power MOSFET. RS2051 is offered in SOT-23-6, SOP-8 and DIP-8 packages.
Features
Low Cost, PWM, PFM&CRM (Cycle Reset Mode)
Low Start-up Current (about 3μA)
Low Operating Current (about 1.2mA)
Current Mode Operation
Under Voltage Lockout (UVLO)
Built-in Synchronized Slope Compensation
Built-in fixed soft start with 1.2ms
Built-in Frequency Jiggling for better EMI Signature
Programmable PWM Frequency
Audio Noise Free Operation
Leading edge Blanking on Sense input
Constant output power limiting for universal AC input
Range
SOT-26、SOP-8 and DIP-8 Pb-Free Packaging
Soft Clamped GATE output voltage 18V
VDD over voltage protect 34V
Cycle-by-cycle current limiting
Sense Fault Protect ion
Output SCP (Short circuit Protection)
Output OLP (Over Load Protection)
Latch mode After OLP&SCP
High-Voltage CMOS Process with ESD
Applications
Switching AC/DC Adaptor
Battery Charger
Open Frame Switching Power Supply
Standby Power Supplies
Set-Top Box Power Supplies
Pin Configurations
Name
GND
FB
RI
SEN
VDD
GATE
GND Pin
Voltage feedback pin. Output current of this pin could controls the PWM duty cycle、OLP and SCP.
This pin is to program the switching frequency. By connecting a resistor to ground to set the switching frequency
Current sense pin, connect to sense the MOSFET current
Supply voltage pin
Totem output to drive the external Power MOSFET.
www.Orister.com
Description
DS-RS2051-09 No v, 2010
ORISTER [ ORISTER CORPORATION ]
