RT9226BCS

Preliminary RT9226B Synchronous PWM Step-down DC/DC Converter Controller General Description The RT9226B is a low cost, high-efficiency voltagemode PWM controller for motherboard power supply application. Synchronous N-channel MOSFET driver, short-circuit protection, and soft start function are integrated in a single chip. A simple high power buck regulator with shutdown function can be implemented with minimum external components. The RT9226B provides current-limit protection by monitoring the voltage drop across N-channel MOSFET in over current condition, therefore, eliminates the current sensing resistor and minimizes the efficiency loss. The soft start function reduces the stress on power supply and components in power on duration. The 200 kHz operating frequency and high speed PWM control loop with Synchronous Nchannel speed. MOSFET Other driver provide output optimized compromise between efficiency, cost, and response features include voltage monitoring for power good indication and over voltage protection. Features Synchronous N-channel MOSFET Driver High Efficiency Fast Response with 200kHz Operating Frequency Adjustable Current Limit by Sensing MOSFET RDS(ON), Resistor Shutdown Function Power Good Indication Output and Overvoltage Protection without Extra Current Sensing Applications Low Cost CPU Power Supply Motherboard I/O Power Supply Add-On Card Power Supply DDR SDRAM Bus Terminator Power Supply Pin Configurations Part Number RT9226BCS (Plastic SOP-14) Pin Configurations TOP VIEW 1 2 3 4 5 6 PGNDH 7 VSEN OCSET SS FB EN GND 14 13 12 11 10 9 8 VCC LGATE PGNDL BOOT UGATE PHASE PGOOD Ordering Information RT9226B Package type S : SOP-14 Operating temperature range C: Commercial standard DS9226B-01 May 2001 www.richtek-ic.com.tw 1 RT9226B Absolute Maximum Ratings Supply Voltage Input, Output or I/O Voltage Ambient Temperature Range Operating Junction Temperature Range Storage Temperature Range Package Thermal Resistance SOP-14, θJA Lead Temperature (Soldering, 10 sec.) Preliminary 15V GND–0.3V to Vcc+0.3V 0°C to 70°C 0°C to 125°C −65°C to 150°C 160°C/W 300°C Electrical Characteristics (VCC = 12V, GND = 0V, TA = 25°C, unless otherwise specified) Parameter VCC Supply Current Nominal Supply Current Power-On Reset VCC Rising Threshold VCC Falling Threshold Enable Input Threshold Oscillator Frequency Ramp Amplitude Internal Voltage Reference Reference Voltage PWM Controller Error Amplifier DC Gain PWM Controller Gate Driver UGATE Source UGATE Sink LGATE Source LGATE Sink Protection OCSET Current Source Soft-start Current Over-voltage Trip (VSEN/VREF) Power Good Upper Threshold (VSEN/VREF) Lower Threshold (VSEN/VREF) PGOOD Voltage Low VPGOOD IPGOOD = -5mA ---108 92 0.5 ---% % V IOCSET ISS VOCSET = 4.5V VSS = 1.5V 170 --200 10 115 230 -120 µA µA % RUGATE IUGATE = 0.3A RUGATE IUGATE = 0.3A ILGATE VCC = 12V, VLGATE = 6V RLGATE ILGATE = 1V ----8 6 500 5 ----Ω Ω mA Ω -65 -dB VREF 0.785 0.800 0.815 V ∆VOSC 170 -200 1.9 230 -KHz V VEN VOCSET = 4.5V VOCSET = 4.5V --0.2 9.5 7.5 ---2.2 V V V ICC UGATE Open -3 -mA Symbol Test Conditions Min Typ Max Units www.richtek-ic.com.tw DS9226B-01 May 2001 2 Preliminary Function Block Diagram EN 10µA SS 4.5V GND ++ _ Vref FB PGOOD VSEN 47KΩ Error Amp + Oscillator Output Voltage Monitor _ Power-on Reset Over Current Comparator _ + 200µA RT9226B VCC OCSET Soft Start PHASE Control Logic PWM Comparator Gate Control Logic VCC LGATE PGNDL BOOT UGATE PGNDH Pin Description Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Pin Name VSEN OCSET SS FB EN GND PGNDH PGOOD PHASE UGATE BOOT PGNDL LGATE VCC Pin Function Output Voltage Monitoring Input Current Limit Set Pin with 200µA Current Sink Soft Start, connect a capacitor from this pin to GND Feedback Input Pin Regulator Enable with Low Shutdown Ground High Side Drive GND Power Good Indication Output Current Limit Sense Input High Side Driver Output Driver Power Low Side Driver GND Low Side Driver Output Power Supply Input DS9226B-01 May 2001 www.richtek-ic.com.tw 3 RT9226B Typical Application Circuit 12V R1 10 Ω Preliminary 11 C1 BOOT 1µF 14 VCC OCSET 5 EN Low Shutdown UGATE 3 SS C3 12 PGNDL PHASE 0.1µF 6 GND LGATE 7 PGNDH FB 8 PGOOD VSEN RT9226B D1 15V Power Good R5 10K 1% C2 1000pF 2 10 9 13 4 1 R3 R4 910 1% 510 1% Q2 R2 2.4k Q1 C6 1µF L1 1µH + C4 1000µF ×2 L2 + C5 - 1000 µF ×6 VIN 5 V 7µH D2 1N5817 VOUT 1.25V/10A C4, C5: Each 1000µF 6.3WV DC, Sanyo MV-GX or Equivalent. L1: Core: Micrometals T50-52; Winding: 5 turns of 18 AWG. L2: Core: Micrometals T60-52; Winding: 14 turns of 17 AWG. Q1, Q2: PHB83N03LT, PHB95N03LT www.richtek-ic.com.tw DS9226B-01 May 2001 4 Preliminary Package Information RT9226B H M B B J A C F D I Symbol A B C D F H I J M Dimensions In Millimeters Min 8.534 3.810 1.346 0.330 1.194 0.178 0.102 5.791 0.406 Max 8.738 3.988 1.753 0.508 1.346 0.254 0.254 6.198 1.270 Dimensions In Inches Min 0.336 0.150 0.053 0.013 0.047 0.007 0.004 0.228 0.016 Max 0.344 0.157 0.069 0.020 0.053 0.010 0.010 0.244 0.050 DS9226B-01 May 2001 www.richtek-ic.com.tw 5 RT9226B Preliminary RICHTEK TECHNOLOGY CORP. Headquarter 6F, No. 35, Hsintai Road, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5510047 Fax: (8863)5537749 RICHTEK TECHNOLOGY CORP. Taipei Office (Marketing) 8F-1, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek-ic.com.tw www.richtek-ic.com.tw DS9226B-01 May 2001 6