RT9209 RICHTEK | Alldatasheet

Document overview

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Technical content

Features

zzzzz 0.8V Internal Reference zzzzz Drives Two N-MOSFET zzzzz Voltage Mode PWM Control zzzzz Fast Transient Response zzzzz Fixed 260kHz/400kHz Oscillator Frequency zzzzz Dynamic 0 to 100% Duty Cycle zzzzz Internal PWM Loop Compensation zzzzz Internal Soft-Start zzzzz Adaptive Non-Overlapping Gate Driver zzzzz Over-Voltage Protection Uses Lower MOSFET zzzzz RoHS Compliant and 100% Lead (Pb)-Free Pin Configurations

Applications

z Motherboard Power Regulation for Computers z Subsystems Power Supplies z Cable Modems, Set Top Box, and DSL Modems z DSP and Core Communications processor Supplies z Memory Power Supplies z Personal Computer Peripherals z Industrial Power Supplies z 5V-Input DC-DC Regulators z Low Voltage Distributed Power Supplies Synchronous Buck PWM DC-DC with Enable & PGOOD

Ordering Information

The RT9209/A is a single power supply PWM DC-DC converter controller designed to drive N-MOSFET in a synchronous buck topology. The IC integrates the control, output adjustment, monitoring and protection functions into a small 8-pin package. The RT9209/A uses an internal compensated voltage mode PWM control for simple application design. An internal 0.8V reference allows the output voltage to be precisely regulated to low voltage requirement. A fixed 260kHz/ 400kHz oscillator reduce the component size for saving board area. The RT9209/A future a enable control pin to shutdown PWM switching and a 90% power good flag indicator. The FB pin under voltage detection function monitor the output short circuit which trigger a three time hiccup sequence to latch off the chip function. (TOP VIEW) SOP-8 FB SS UGATEGND LGATE VCC BOOT PGOOD2 4 5 Note : RichTek Pb-free and Green products are : \RoHS compliant and compatible with the current require- ments of IPC/JEDEC J-STD-020. \Suitable for use in SnPb or Pb-free soldering processes. \`100%matte tin (Sn) plating. RT9209/A Package Type S : SOP-8 Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commer- cial Standard) 400kHz 260kHz

DS9209/A-08 March 2007www.richtek.com Typical Application Circuit Figure A. RT9209/A Booted from 5V Figure B. RT9209/A Booted from 12V VOUT R1 R2 120 250 10K 1uF 0.1uF PGOOD FB VCC PGOOD SS BOOT UGATE LGATE GND 0.1uF MU ML 470uF 1000uF 5uH RT9209/A CBOOT A R1 R2 120 250 1uF 0.1uF FB VCC PGOOD SS BOOT UGATE LGATE GND MU ML 470uF 1000uF 5uH VOUT 12V 10 C5 1uF 10K RT9209/A PGOOD A

DS9209/A-08 March 2007 www.richtek.com Function Block Diagram GND VCC RT9209/A BOOT CVCC 1uF CBOOT 0.1uF COUT 1000uF L 5uH MU D G S Diode CIN1 1uF CIN2 470uF GND Return Layout Placement Layout Notes 1. Put CIN1 & CIN2 to be near the MU drain and ML source nodes. 2. Put RT9209/A to be near the C OUT 3. Put CBOOT as close as to BOOT pin 4. Put C VCC as close as to VCC pin 0.8 Reference Power on Reset Soft Start OVP UVP 0.8V 0.5V Error Amplifier PWM 260kHz/300kHz Oscillator Control Logic VCC 6.5V Regulation GND FB VCC BOOT UGATE LGATE +SS PGOOD PWM Loop Compensation - SSPGOOD 0.72V

DS9209/A-08 March 2007www.richtek.com Absolute Maximum Ratings z Power Dissipation, PD @ TA = 25°C z Package Thermal Resistance CAUTION: Stresses beyond the ratings specified in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Functional Pin Description FB (Pin1) This pin is connected to the PWM converter's output divider. This pin also connects to internal PWM error amplifier inverting input and protection monitor. VCC (Pin 2) This is the main bias supply for the RT9209/A. This pin also provides the gate bias charge for the lower MOSFETs gate. The voltage at this pin monitored for power-on reset (POR) purpose. This pin is also the internal 6.5V regulator output powered from BOOT pin when BOOT pin is directly powered from ATX 12V. LGATE (Pin 3) Connect LGATE to the PWM converter's lower MOSFET gate. This pin provides the gate drive for the lower MOSFET. GND (Pin 4) Signal and power ground for the IC. All voltage levels are measured with respect to this pin. UGATE (Pin 5) Connect UGATE pin to the PWM converter's upper MOSFET gate. This pin provides the gate drive for the upper MOSFET. BOOT (Pin 6) This pin provides ground referenced bias voltage to the upper MOSFET driver. A bootstrap circuit is used to create a voltage suitable to drive a logic-level N-Channel MOSFET when operating at a single 5V power supply. This pin also could be powered from ATX 12V, in this situation, a internal 6.5V regulator will supply to VCC pin for internal voltage bias. PGOOD (Pin 7) PGOOD is an open collector output used to indicate the status of the PWM converter output voltage. This pin is pulled low when the FB is not over 90% of the reference voltage. SS (Pin 8) Connect a capacitor from this pin to ground. This capacitor, along with an internal 22μA current source, sets the soft- start internal of the synchronous PWM converter.

DS9209/A-08 March 2007 www.richtek.com

Electrical Characteristics

(VCC = 5V, TA = 25°C, Unless otherwise specified.) Parameter Symbol Test Conditions Min Typ Max Units VCC Supply Current Nominal Supply Current ICC UGATE, LGATE open -- 3 6 mA Power-On Reset Rising VCC Threshold 3.7 4.1 4.5 V VCC Threshold Hysteresis 0.3 0.5 0.7 V Reference Reference Voltage 0.784 0.8 0.816 V Oscillator RT9209 210 260 310 Free Running Frequency RT9209A 350 400 450 kHz Ramp Amplitude Δ VOSC -- 1.75 -- VP-P Error Amplifier DC gain 33 35 40 dB PWM Controller Gate Driver Upper Drive Source RUGATE BOOT= 12V BOOT-VUGATE = 1V -- 7 12 Ω Upper Drive Sink RUGATE V UGATE = 1V -- 7 7.5 Ω Lower Drive Source RLGATE V CC - VLGATE = 1V, -- 7 6 Ω Lower Drive Sink RLGATE V LGATE = 1V -- 3 4 Ω Protection FB Over-Voltage Trip FB Rising -- 1 -- V FB Under-Voltage Trip FB Falling -- 0.6 -- V Power Good Threshold FB pin Rising 86 90 95 % Power Good Hysteresis -- 2 -- % Power Good Sink Capability IPGOOD = 1mA -- 0.4 V SS Source Current 12 20 32 μA

DS9209/A-08 March 2007www.richtek.com Typical Operating Characteristics Time (50ns/Div) UGATE Dead Time Booted from 5V IOUT = 0A LGATE Time (50ns/Div) Booted from 12V IOUT = 0A UGATE Dead Time LGATE Time (50ns/Div) UGATE Dead Time Booted from 12V IOUT = 0A LGATE Time (50ns/Div) UGATE Dead Time Booted from 5V IOUT = 0A LGATE Load Transient VCC = 5V VOUT = 2.5V COUT = 1000uF IOUT = 0A to 10A Time (10us/Div) UGATE IOUT VOUT Load Transient VCC = 5V VOUT = 2.5V COUT = 1000uF IOUT = 10A to 0A Time (10us/Div) UGATE IOUT VOUT

DS9209/A-08 March 2007 www.richtek.com Power Off Time (50ms/Div) VCC Booted from 12V IOUT = 10A VOUT Power On Time (2.5ms/Div) Booted from 12V IOUT = 10A VCC VOUT Time (1us/Div) UGATE Boostrap Waveform Booted from 12V,A node LGATE Power Off Time (10ms/Div) VCC Booted from 5V IOUT = 10A VOUT Power On Time (2.5ms/Div) Booted from 5V I OUT = 10A CSS = 0.1uF VCC VOUT Time (1us/Div) UGATE Boostrap Waveform Booted from 5V A node LGATE

DS9209/A-08 March 2007www.richtek.com Reference vs. Temperature 0.788 0.79 0.792 0.794 0.796 0.798 0.8 0.802 0.804 0.806 0.808 -35 -15 5 25 45 65 85 105 125 Temperature Reference (V) (°C) (°C) Oscillator Frequency vs. Temperature 350 360 370 380 390 400 410 -35 -15 5 25 45 65 85 105 125 Temperature Frequency (kHz) RT9209A Short Hiccup Time (25ms/Div) VOUT UGATE Booted from 12V Short Hiccup Time (500ms/Div) VOUT UGATE Booted from 5V PGOOD vs. VOUT Time (25ms/Div) PGOOD VOUT VCC vs. V SS Time (5ms/Div) VCC VSS IOUT = 10A CSS = 0.1uF

DS9209/A-08 March 2007 www.richtek.com POR(Rising/Falling) vs. Temperature 3.5 3.6 3.7 3.8 3.9 4.1 4.2 -35 -15 5 25 45 65 85 105 125 Temperature POR (V) (°C) Rising Falling

DS9209/A-08 March 2007 www.richtek.com Figure 9 PWM Layout Considerations MOSFETs switch very fast and efficiently. The speed with which the current transitions from one device to another causes voltage spikes across the interconnecting impedances and parasitic circuit elements. The voltage spikes can degrade efficiency and radiate noise, that results in over-voltage stress on devices. Careful component placement layout and printed circuit design can minimize the voltage spikes induced in the converter. Consider, as an example, the turn-off transition of the upper MOSFET prior to turn-off, the upper MOSFET was carrying the full load current. During turn-off, current stops flowing in the upper MOSFET and is picked up by the low side MOSFET or Schottky diode. Any inductance in the switched current path generates a large voltage spike during the switching interval. Careful component selections, layout of the critical components, and use shorter and wider PCB traces help in minimizing the magnitude of voltage spikes. There are two sets of critical components in a DC-DC converter using the RT9209/A. The switching power components are most critical because they switch large amounts of energy, and as such, they tend to generate equally large amounts of noise. The critical small signal components are those connected to sensitive nodes or those supplying critical bypass current. The power components and the PWM controller should be placed firstly. Place the input capacitors, especially the high-frequency ceramic decoupling capacitors, close to the power switches. Place the output inductor and output capacitors between the MOSFETs and the load. Also locate the PWM controller near by MOSFETs. A multi-layer printed circuit board is recommended. Figure 9 shows the connections of the critical components in the converter. Note that the capacitors C IN and COUT each of them represents numerous physical capacitors. Use a dedicated grounding plane and use vias to ground all critical components to this layer. Apply another solid layer as a power plane and cut this plane into smaller islands of common voltage levels. The power plane should support the input power and output power nodes. Use the remaining printed circuit layers for small signal routing. The PCB traces between the PWM controller and the gate of MOSFET and also the traces connecting source of MOSFETs should be sized to carry 2A peak currents. LOAD VCC GND RT9209/A FB LGATE UGATE ILIQ1 VOUT IQ2 GND CIN COUT A

DS9209/A-08 March 2007www.richtek.com Richtek Technology Corporation Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Richtek Technology Corporation Taipei Office (Marketing) 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com Outline Dimension A BJ F H M C D I 8-Lead SOP Plastic Package Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 4.801 5.004 0.189 0.197 B 3.810 3.988 0.150 0.157 C 1.346 1.753 0.053 0.069 D 0.330 0.508 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.170 0.254 0.007 0.010 I 0.050 0.254 0.002 0.010 J 5.791 6.200 0.228 0.244 M 0.400 1.270 0.016 0.050