RT9218APS

RT9218A Preliminary 5V/12V Synchronous Buck PWM DC-DC and Linear Power Controller General Description Features The RT9218A is a dual output with one synchronous buck Operating with 5V or 12V Supply Voltage PWM and one linear controller. The part is proposed to generate logic-supply voltages for PC based systems. The Drives All Low Cost N-Channel MOSFETs high-performance device includes internal soft-start, Voltage Mode PWM Control 300kHz Fixed Frequency Oscillator with specific sequence, and it comes all of the logic control, Fast Transient Response : nHigh-Speed GM Amplifier n output adjustment, power monitoring and protection functions into a small footprint package. The part is n nFull 0 to 100% Duty Ration Internal Soft-Start operated at fixed 300kHz frequeny providing an optimum compromise between efficiency, external component size, Power Good Indicator frequency-compensation networks, power good signaling and cost. The linear controller is implemented to drive an external MOSFET for regulation and it's adjustable by setting external resistors. Moreover the specific internal PGOOD sequence and indicator is also implemented to conform to Intel new platform requirement on FSB_VTT power plane. An adjustable over-current protection (OCP) is proposed to monitor the voltage drop across the RDS(ON) of the lower MOSFET for synchronous buck PWM DC-DC controller. Ordering Information RT9218A Package Type S : SOP-14 Operating Temperature Range C : Commercial Standard P : Pb Free with Commercial Standard Note : RichTek Pb-free products are : nRoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. nSuitable for use in SnPb or Pb-free soldering processes. Adaptive Non-Overlapping Gate Driver Over-Current Fault Monitor on MOSFET, No Current Sense Resistor Required Specific Power Good Indicator for Intel® Grantsdale FSB_VTT Power Sequence RoHS Compliant and 100% Lead (Pb)-Free Applications Graphic Card Motherboard, Desktop Servers IA Equipments Telecomm Equipments High Power DC-DC Regulators Pin Configurations (TOP VIEW) BOOT UGATE GND LGATE DRV NC NC 2 3 4 5 6 7 14 13 12 11 10 9 8 PHASE OPS FB VCC PGOOD FBL NC SOP-14 n100% matte tin (Sn) plating. DS9218A-02 October 2005 www.richtek.com 1 RT9218A Preliminary Typical Application Circuit D1 C8 PHASE C1 to C2 C3 to C4 1000uF x 2 1uF x 2 Q1 L1 MU 2.2uH C5 to C6 1000uF x 2 C7 1uF 1N4148 0.1uF RT9218A 1 BOOT 2 UGATE PHASE 3 Q2 ML 4 GND PHASE OPS FB 14 ROCSET 13 12 11 VCC LGATE 5 DRV PGOOD 10 9 6 FBL NC 8 7 NC NC Q3 R3 10R Q4 C10 1uF Disable 3904 R1 LVOUT 4k C9 470uF R2 8k R4 1k/NC R5 C11 0.1uF/NC R6 32R 68R www.richtek.com 2 DS9218A-02 October 2005 Preliminary RT9218A Functional Pin Description UGATE (Pin 2) VCC (Pin 11) Upper gate driver output. Connect to gate of the high-side Connect this pin to a well-decoupled 5V or 12V bias power N-Channel MOSFET. This pin is monitored by the supply. It is also the positive supply for the lower gate driver, LGATE. adaptive shoot-through protection circuitry to determine when the upper MOSFET has turned off. GND (Pin 3) BOOT (Pin 1) Both signal and power ground for the IC. All voltage levels Bootstrap supply pin for the upper gate driver. Connect are measured with respect to this pin. Ties the pin directly the bootstrap capacitor between BOOT pin and the PHASE to the low-side MOSFET source and ground plane with pin. The bootstrap capacitor provides the charge to turn the lowest impedance. on the upper MOSFET. DRV (Pin 5) PHASE (Pin 14) Connect this pin to the base/gate of an external transistor/ Connect this pin to the source of the upper MOSFET and MOSFET. This pin provides the drive for the linear the drain of the lower MOSFET. regulator's pass transistor/MOSFET. OPS (OCSET, POR and Shut-Down) (Pin 13) FBL (Pin 9) This pin provides multi-function of the over-current setting, UGATE turn-on POR sensing, and shut-down features. Linear regulator feedback voltage. This pin is the inverting Connecting a resistor (ROCSET) between OPS and PHASE pins sets the over-current trip point. this pin to the external resistor divider network of the linear regulator. Pulling the pin to ground resets the device and all external MOSFETs are turned off allowing the output voltage power rails to float. This pin is also used to detect VIN in power on stage and issues an internal POR signal. LGATE (Pin 4) Lower gate drive output. Connect to gate of the low-side power N-Channel MOSFET. This pin is monitored by the adaptive shoot-through protection circuitry to determine input of the error amplifier and protection monitor. Connect PGOOD (Pin 10) PGOOD is an open-drain output used to indicate that the regulator is within normal operating voltage ranges and it's implemented with a specific sequence as following chart. NC (Pin 6,7,8) No internal connection. when the lower MOSFET has turned off. FB (Pin 12) Switcher feedback voltage. This pin is the inverting input of the error amplifier. FB senses the switcher output through an external resistor divider network. DS9218A-02 October 2005 www.richtek.com 3 RT9218A Preliminary Function Block Diagram VCC EN + 0.15V - Bias & Regulators (3V_Logic & 3VDD_Analog) PH_M Power On Reset Reference + 0.6V VCC + - DRV 0.6V + - UV_S + - UV_L 1.5V - 0.8VREF 3V 40uA Soft-Start & Fault Logic OC + OPS 0.4V + - FBL PGOOD BOOT UGATE + +GM - FB PHASE EO + + - Gate Control Logic VCC LGATE Oscillator (300k/600kHz) GND Timing Diagram Specific Power Sequence for LDO 90% FSB_VTT (1.2V @ 5Amp) VTT_GD www.richtek.com 4 80% 1-10ms