RT9204_07

Preliminary RT9204/A Dual Regulators - Standard Buck PWM DC-DC and Linear Controller General Description The RT9204/A is a dual power controllers designed for high performance graphics cards and computer applications. The IC integrates a standard buck controller, a linear regulator driver and protection functions into a small 8-pin package. The RT9204/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 600kHz oscillator reduce the component size for saving board area. The RT9204/A protects the converter and regulator by monitoring the output under voltage. Features l l l l l l l l l Operate from 5V 0.8V Internal Reference Voltage Mode PWM Control Fast Transient Response Fixed 600kHz Oscillator Frequency Full 0 to 100% Duty Cycle Internal Soft Start Internal PWM Loop Compensation RoHS Compliant and 100% Lead (Pb)-Free Applications l l l l Ordering Information RT9204/A Package Type S : SOP-8 Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard) UVP : Hiccup Mode UVP : Latch Mode Note : RichTek Pb-free and Green products are : }RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. }Suitable for use in SnPb or Pb-free soldering processes. }100%matte tin (Sn) plating. l l l l l Motherboard Power Regulation for Computers Subsystems Power Supplies Cable Modems, Set Top Box, and DSL Modems DSP and Core Communications Processor Supplies Memory Power Supplies Personal Computer Peripherals Industrial Power Supplies 5V-Input DC-DC Regulators Low Voltage Distributed Power Supplies Pin Configurations (TOP VIEW) GND VCC DRV FBL 2 3 4 8 7 6 5 UGATE BOOT SD FB SOP-8 DS9204/A-08 March 2007 www.richtek.com 1 RT9204/A Typical Application Circuit VAUX 3.3V Q1 2SD1802 VOUT2 1.6V R4 100 R5 100 C5 1uF + Preliminary R1 10 1 2 3 4 GND VCC DRV FBL RT9204/A UGATE BOOT SD FB 8 7 6 5 C3 + 5V BAT54A 0.1uF VOUT1 2.5V R3 + L1 5uH C4 1000uF MU D1 SS34 C2 1uF C1 470uF C6 220uF 250 R2 120 C7 10nF Figure1. RT9204/A powered from 5V only 5V R1 0 VAUX 3.3V Q1 Suggest use Transistor 2SD5706 VOUT2 1.6V R4 100 R5 100 + C7 1uF 1 2 3 4 8 7 R6 C5 1uF GND VCC DRV FBL RT9204/A UGATE BOOT SD FB 10 12V 5V + 6 5 VOUT1 2.5V R3 + L1 5uH C4 1000uF MU D1 SS34 C2 1uF C1 470uF C6 220uF 250 R2 120 C7 10nF Figure2. RT9204/A powered from 12V www.richtek.com 2 DS9204/A-08 March 2007 Preliminary MU COUT 1000uF GND CVCC 1uF CBOOT VCC BOOT 0.1uF RT9203/A GND Return Diode D L 5uH G S + + RT9204/A CIN1 1uF C IN2 470uF Layout Placement Layout Notes 1. Put C1 & C2 to be near the MU drain and ML source nodes. 2. Put RT9204/A to be near the COUT 3. Put CBOOT as close as to BOOT pin 4. Put CVCC as close as to VCC pin Function Block Diagram 6.0V Regulation Power on Reset DRV FBL 0.8 Reference + 1V + OVP UVP LDO VCC BOOT + - 0.8V FB + 35dB Error Amplifier GND DS9204/A-08 March 2007 + Soft Start 0.5V +UVP + +PWM - Control Logic UGATE SS 600kHz Oscillator www.richtek.com 3 RT9204/A Functional Pin Description GND (Pin 1) Preliminary Signal and power ground for the IC. All voltage levels are measured with respect to this pin. VCC (Pin 2) This is the main bias supply for the RT9204/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 6.0V regulator output powered from BOOT pin when BOOT pin is directly powered from ATX 12V. DRV (Pin 3) This pin is linear regulator output driver. Connect to external bypass NPN transistor base or NMOSFET gate terminal. FBL (Pin 4) This pin is connected to the linear regulator output divider. This pin also connects to internal linear regulator error amplifier inverting input and protection monitor. FB (Pin 5) 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. SD (Pin 6) Active low design with a 40µA pull low current source. Pull this pin to VCC to shutdown both PWM and linear regulator. BOOT (Pin 7) 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, an internal 6.0V regulator will supply to VCC pin for internal voltage bias. UGATE (Pin 8) Connect UGATE pin to the PWM converter's upper MOSFET gate. This pin provides the gate drive for the upper MOSFET. www.richtek.com 4 DS9204/A-08 March 2007 Preliminary Absolute Maximum Ratings l l l l RT9204/A l l l l l Supply Voltage VCC ------------------------------------------------------------------------------------------------ 7V BOOT & UGATE to GND ------------------------------------------------------------------------------------------- 15V Input, Output or I/O Voltage --------------------------------------------------------------------------------------- GND-0.3V to 7V Power Dissipation, PD @ TA = 25° C SOP-8 ------------------------------------------------------------------------------------------------------------------ 0.625W Package Thermal Resistance SOP-8, θJA ------------------------------------------------------------------------------------------------------------------------------------------------------- 160° C/W Ambient Temperature Range -------------------------------------------------------------------------------------- 0° C to +70° C Junction Temperature Range -------------------------------------------------------------------------------------- −40° C to +125° C Storage Temperature Range --------------------------------------------------------------------------------------- −65° C to +150° C Lead Temperature (Soldering, 10 sec.)-------------------------------------------------------------------------- 260° C 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. Electrical Characteristics (VCC = 5V, TA = 25° C, Unless otherwise specified.) Parameter VCC Supply Current Nominal Supply Current VCC Regulated Voltage Power-On Reset Rising VCC Threshold VCC Threshold Hysteresi s Reference Reference Voltage Oscillator Free Running Frequency Ramp Amplitude PWM Error Amplifier DC Gain PWM Controller Gate Driver Upper Drive Source Upper Drive Sink Linear Regulator DRV Driver Source Symbol Test Conditions Min Typ Max Units ICC VCC UGATE, LGATE open VBOOT=12V --- 3 6 --- mA V 3.75 -Both FB & FBL 0.784 550 ∆ VOSC -- 4.1 0.5 0.8 600 1.75 4.35 -0.816 650 -- V V V kHz VP-P -RUGATE RUGATE VBOOT = 12V; VBOOT - VUGATE = 1V VUGATE = 1V --- 35 7 5 ---- dB Ω Ω VDRV = 2V 100 -- -- mA To be continued DS9204/A-08 March 2007 www.richtek.com 5 RT9204/A Parameter Protection FB Over-Voltage Trip FB & FBL Under-Voltage Trip Soft-Start Interval SD Pin Threshold SD pin Sink Current Symbol Preliminary Test Conditions Min Typ Max Units FB Rising FB & FBL Falling VCC = 5V VCC = 5V ------ 1 0.5 1 1.5 40 ------ V V ms V µA www.richtek.com 6 DS9204/A-08 March 2007 Preliminary Typical Operating Characteristics Power On VCC = 5V VOUT = 2.2V VCC VCC RT9204/A Power Off VCC = 5V VOUT1 VOUT1 VOUT2 VOUT2 Time (1ms/Div) Time (50ms/Div) Load Transient UGATE Load Transient UGATE VOUT VOUT VCC = 5V VOUT = 2.2V COUT = 3000uF VCC = 5V VOUT = 2.2V COUT = 3000uF Time (5us/Div) Time (5us/Div) Short Hiccup (Latch Mode) VCC = 5V VOUT = 2.2V VCC = 5V VOUT = 2.2V Short Hiccup VOUT VOUT UGATE UGATE RT9204 RT9204A Time (5ms/Div) Time (2ms/Div) DS9204/A-08 March 2007 www.richtek.com 7 RT9204/A Reference vs. Temperature 0.803 0.802 0.801 Preliminary POR (Rising/Falling) vs. Temperature 4.3 4.2 4.1 Rising Reference (V) POR (V) 0.800 0.799 0.798 0.797 0.796 -50 0 50 100 150 4.0 3.9 3.8 3.7 3.6 -50 0 50 100 150 Falling Temperature (°C) Temperature (°C) Oscillator Frequency vs. Temperature 315 310 Frequency (kHz) A 305 300 295 290 285 280 275 270 -50 0 50 100 150 Temperature (°C) www.richtek.com 8 DS9204/A-08 March 2007 Preliminary Application Information The RT9204/A operates at either single 5V power supply with a bootstrap UGATE driver or 5V/12V dual-power supply form the ATX SMPS. The dual- power supply is recommended for high current application, the RT9204/A can deliver higher gate driving current while operating with ATX SMPS based on dual-power supply. The Bootstrap Operation In a single power supply system, the UGATE driver of RT9204/A is powered by an external bootstrap circuit, as the Figure 3. The boot capacitor, CBOOT , generates a floating reference at the PHASE node. Typically a 0.1µF CBOOT is enough for most of MOSFETs used with the RT9204/A. The voltage drop between BOOT and PHASE node is refreshed to a voltage of VCC−diode drop (VD) while the low side MOSFET turning on. R1 VCC C2 1uF D1 5V 0.1uF + 6.0V Regulation BOOT RT9204/A VCC R 12V C 1uF 10 5V + UGATE C2 1uF RT9204/A Figure 4. Dual Power Supply Operation Power On Reset The Power-On Reset (POR) monitors the supply voltage (normal +5V) at the VCC pin and the input voltage at the OCSET pin. The VCC POR level is 4.1V with 0.5V hysteresis and the normal level at OCSET pin is 1.5V (see over-current protection). The POR function initiates soft-start operation after all supply voltages exceed their POR thresholds. Soft Start A built-in soft-start is used to prevent surge current from power supply input during power on. The soft-start voltage is controlled by an internal digital counter. It clamps the ramping of reference voltage at the input of error amplifier and the pulse-width of the output driver slowly. The typical soft-start duration is 2ms. Under Voltage and Over Voltage Protection BOOT UGATE PHASE RT9204/A Figure 3. Single 5V power Supply Operation Dual Power Operation The RT9204/A was designed to regulate a 6.0V at VCC pin automatically when BOOT pin is powered by 12V. In a system with ATX 5V/12V power supply, the RT9204 is ideal for higher current application due to the higher gate driving capability, VUGATE = 7V. A RC (10Ω/1µF) filter is also recommended at BOOT pin to prevent the ringing induced from fast power on, as shown in Figure 4. The voltage at FB pin is monitored and protected against OC (over current), UV (under voltage), and OV (over voltage). The UV threshold is 0.5V and OV-threshold is 1.0V. Both UV/OV detection have 30µs triggered delay. When OC or UV trigged, a hiccup re-start sequence will be initialized, as shown in Figure 5. For RT9204, only 3 times of trigger are allowed to latch off. But for RT9204A, UVP will be kept hiccup mode. Hiccup is disabled during soft-start interval. DS9204/A-08 March 2007 www.richtek.com 9 RT9204/A COUNT = 1 In te r n a l SS Preliminary Shutdown COUNT = 2 COUNT = 3 4V 2V 0V OVERLOAD APPLIED F B o r F B L V o lt a g e Pulling high the SD pin by a small single transistor can shutdown the RT9204/A PWM controller as shown in typical application circuit. Normally SD pin can be floating because an internal 40µA current source will pull low the SD shutdown pin voltage. Q L VI T0T1 T2 TIME T3 D C R VO Figure 5 Inductor Selection The RT9204/A was designed for VIN = 5V, step-down application mainly. Figure 6 shows the typical topology and waveforms of step-down converter. The ripple current of inductor can be calculated as follows: ILRIPPLE = (5V - VOUT) L × TON iL VL C.C.M. TS Table 1 TON TOFF VI - VO - VO uQ uIL Because operation frequency is fixed at 600kHz, TON = 3.33 × VOUT 5V iQ IL = IO The VOUT ripple is VOUT RIPPLE = ILRIPPLE × ESR IQ ESR is COUT capacitor equivalent series resistor Table 1 shows the ripple voltage of VOUT : VIN = 5V *Refer to Sanyo low ESR series (CE, DX, PX......) The suggested L and C are as follows: 2µH with ≥ 1500µF COUT 5µH with ≥ 1000µF COUT VOUT Inductor 1000µF (ESR = 53mΩ) 1500µF (ESR = 33mΩ) 3000µF (ESR = 21mΩ) 2 µH 100mV 62mV 40mV 3.3V 5µ H 40mV 25mV 16mV 2µ H 110mV 68mV 43mV 2.5V 5µ H 44mV 28mV 18mV 2µ H 93mV 58mV 37mV 1.5V 5µ H 37mV 23mV 15mV iD ID Figure 6 www.richtek.com 10 DS9204/A-08 March 2007 Preliminary Input / Output Capacitor High frequency/long life decoupling capacitors should be placed as close to the power pins of the load as physically possible. Be careful not to add inductance to the PCB trace, as it could eliminate the performance from utilizing these low inductance components. Consult with the manuf acturer of the load on specific decoupling requirements. The output capacitors are necessary for filtering output and stabilizing the close loop (see the PWM loop stability). For powering advanced, high-speed processors, it is required to meet with the requirement of fast load transient, high frequency capacitors with low ESR/ESL capacitors are recommended. Another concern is high ESR induced ripple may trigger UV or OV protections. Linear Regulator Driver The linear regulator of RT9204/A was designed to drive bipolar NPN or MOSFET pass transistor. For MOSFET pass transistor, normally DRV need to provide minimum VOUT2+VT+gate-drive voltage to keep VOUT2 as setting voltage. When driving MOSFET operating at 5V power supply system, the gate-drive will be limited at 5V. In this situation shown in Figure 5, low VT threshold MOSFET (VT = 1V) and Vout2 setting below 2.5V were suggested. In VBOOT = 12V operation condition as Figure 8, VCC is regulated as higher to 6V providing more gate-drive for pass MOSFET transistor, VOUT2 can be set as ≤ 3.3V. RT9204/A VOUT2 < 3.3V + DRV VBOOT = 12V BOOT 6V FBL R4 VCC RT9204/A R3 R4