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PDF RS2051 Data sheet ( Hoja de datos )
| Número de pieza | RS2051 | |
| Descripción | Novel Low Cost Green-Mode PWM Controller | |
| Fabricantes | Orister | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de RS2051 (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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RS2051
Novel Low Cost Green-Mode PWM Controller
with Soft Start & Latch Mode
Page No. : 1/13
Description
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 frequency jitter.
The RS2051 offers perfect protection like OVP(Over Voltage Protection)、OLP(Over Load Protection)、SCP(Short circuit
protection)、OTP、Sense Fault Protection 、LM (Latch Mode) and OCP(Over current protection). The RS2051’s output driver
is soft clamped to maximum 16.5V to protect the power MOSFET. RS2051 is offered in SOT-23-6L, SOT-8 and DIP-8 packages.
Features
Low Cost, PWM&PFM&CRM (Cycle Reset Mode)
Low Start-up Current (about 1.5μA)
Low Operating Current (about 2.2mA)
Current Mode Operation
Under Voltage Lockout (UVLO)
Built-in Synchronized Slope Compensation
Built-in fixed soft start with 1.2mS
Built-in Frequency jitter 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
Applications
Switching AC/DC Adaptor
Battery Charger
Open Frame Switching Power Supply
Standby Power Supplies
Set-Top Box Power Supplies
384X Replacement
SOT-23-6L、SOP8 and DIP-8 Pb-Free Packaging
Compatible with SG6848 (6849) / SG5701 / SG5848 /
LD7535 (7550) / OB2262 (2263) / OB2278（2279）
Soft Clamped GATE output voltage 16.5V
VDD over voltage protect 25.6V
Cycle-by-cycle current limiting
Sense Fault Protect ion
OTP (Over Temperature Protection)
Output SCP (Short circuit Protection)
Output OLP (Over Load Protection)
Latch mode After OLP&SCP
High-Voltage CMOS Process with ESD
Pin Configurations
DS-RS2051-02 September, 2007
www.Orister.com
1 page  
Page No. : 5/13
OPERATION DESCRIPTION
Current Mode
Compared to voltage mode control, current mode control has a current feedback loop. When the voltage of the Sense resistor
peak current of the primary winding reaches the internal setting value VTH, the register resets and the power MOSFET cuts off.
So, to detect and modulate the peak current cycle-by-cycle could control the output of the power supply. The current feedback
has a good linear modulation rate and a fast input and output dynamic impact, and avoid the pole that the output filter
inductance brings and the two-class system descends to the one-class. So it widens the frequency range and optimizes
overload protection and short circuit protection.
Startup Current and Under Voltage Lockout
The startup current of RS2051 is set to be very low so that a large value startup resistor can be used to minimize the power loss.
For AC to DC adaptor with universal input range design, a 2 MΩ, 1/8 W startup resistor and a 10uF/25V VDD hold capacitor
could be used.
The turn-on and turn-off threshold of the RS2051 is designed to 12.8V/7.8V. During startup, the hold-up capacitor must be
charge to 12.8V through the startup resistor. The hysteresis is implemented to prevent the shutdown from the voltage dip during
startup.
Internal Bias and OSC Operation
A resistor connected between RI pin and GND pin sets the internal constant current source to charge or discharge the internal
fixed capacitor. The charge time and discharge time determines the internal clock speed and the switching frequency.
Increasing the resistance will reduce the value of the input current and reduce the switching frequency. The relationship
between RI and PWM switching frequency follows the below equation within the RI allowed range.
FOSC
=
6000
RI (KΩ)
(kHz)
For example, a 100kΩ resistor RI could generate a 13uA constant current and a 60kHz PWM switching frequency.
The suggested operating frequency range of RS2051 is within 30KHz to 150KHz.
Green Power Operation
The power dissipation of switching mode power supply is very important in zero load or light load condition. The major
dissipation results from conduction loss、switching loss and consume of the control circuit. However, all of them relates to the
switching frequency. There are many difference topologies has been implemented in different chip. The basic operation theory
of all these approaches intends to reduce the switching frequency under light-load or no-load condition.
The RS2051`s green power function adapts PWM、PFM and CRM combining modulation. When RI resistor is 100kΩ, the
PWM frequency is 60kHz in medium or heavy load operation. Through modifying the pulse width, The RS2051 could control
output voltage. The current of FB pin increases when the load is in light condition and the internal mode controller enters
PFM&PWM when the feedback current is over 1.37mA. The operation frequency of oscillator is to descend gradually. When the
feedback current is over 1.43mA, the frequency of oscillator is invariable, namely 22kHz.
To decrease the standby consumption of the power supply, Chip-Rail introduces the Cycle Reset Mode technology (CRM). If the
feedback current is over 1.45mA, mode controller of the RS2051 would reset internal register all the time and cut off the GATE
pin. While the output voltage is lower than the set value, the register would be set, the GATE pin operate again. So the
frequency of the internal OSC is invariable, the register would reset some pulses so that the practical frequency is decreased at
the GATE pin.
RS2051 Green-Power Function
DS-RS2051-02 September, 2007
www.Orister.com
5 Page 
SOT-23-6L
Page No. : 11/13
Dimensions
Symbol
A
A1
B
b
C
D
e
H
L
Millimeters
Min.
Max.
0.700
1.000
0.000
0.100
1.397
1.803
0.300
0.559
2.591
3.000
2.692
3.099
0.838
1.041
0.080
0.254
0.300
0.610
Min.
0.028
0.000
0.055
0.012
0.102
0.106
0.033
0.003
0.012
Inches
Max.
0.039
0.004
0.071
0.022
0.118
0.122
0.041
0.010
0.024
Ordering Information
PART NUMBER
RS2051S
RS2051P
RS2051N
DS-RS2051-02 September, 2007
PIN-PACKAGE
SOP-8L
DIP-8L
SOT-23-6L
www.Orister.com
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet RS2051.PDF ] | |
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