RT9204/A Preliminary Dual Regulators - Standard Buck PWM DC-DC and Linear Controller General Description Features 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. l 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. l l l l l l l l Applications l The RT9204/A protects the converter and regulator by monitoring the output under voltage. l l l Ordering Information RT9204/A l l l Package Type S : SOP-8 Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard) 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 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 UVP : Hiccup Mode UVP : Latch Mode Note : RichTek Pb-free and Green products are : }RoHS compliant and compatible with the current require- (TOP VIEW) GND 8 UGATE VCC 2 7 BOOT DRV 3 6 SD FBL 4 5 FB ments of IPC/JEDEC J-STD-020. }Suitable for use in SnPb or Pb-free soldering processes. SOP-8 }100%matte tin (Sn) plating. DS9204/A-08 March 2007 www.richtek.com 1 RT9204/A Preliminary Typical Application Circuit VAUX 3.3V R1 5V 10 Q1 2SD1802 1 2 1.6V 3 + R4 100 R5 100 UGATE VCC BOOT DRV SD FB FBL C5 1uF 8 C3 7 0.1uF VOUT1 2.5V R3 6 5 L1 MU 250 RT9204/A R2 120 C2 1uF C1 470uF 5uH + C6 220uF 4 GND + VOUT2 BAT54A C4 1000uF D1 SS34 C7 10nF Figure1. RT9204/A powered from 5V only 5V R1 0 VAUX 3.3V R6 C7 1uF C5 1uF Q1 1 Suggest use Transistor 2SD5706 2 1.6V 3 + R5 100 4 VCC BOOT DRV SD FBL RT9204/A FB 8 7 6 L1 VOUT1 2.5V 250 R2 120 MU C2 1uF C1 470uF 5uH R3 5 + C6 220uF R4 100 UGATE 5V + VOUT2 GND 12V 10 C4 1000uF D1 SS34 C7 10nF Figure2. RT9204/A powered from 12V www.richtek.com 2 DS9204/A-08 March 2007 RT9204/A Preliminary + MU COUT 1000uF D G S GND CVCC 1uF CBOOT C IN2 470uF Diode BOOT VCC CIN1 1uF + L 5uH 0.1uF RT9203/A GND Return 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 VCC BOOT Power on Reset + + DRV LDO - FBL Soft Start 0.8 Reference - UVP + 1V - OVP + 0.5V +UVP 0.8V FB GND DS9204/A-08 March 2007 + 35dB Error Amplifier SS Control Logic UGATE + +PWM - 600kHz Oscillator www.richtek.com 3 RT9204/A Preliminary Functional Pin Description GND (Pin 1) Signal and power ground for the IC. All voltage levels are measured with respect to this pin. Connect UGATE pin to the PWM converter's upper MOSFET gate. This pin provides the gate drive for the upper MOSFET. 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) www.richtek.com 4 DS9204/A-08 March 2007 RT9204/A Preliminary Absolute Maximum Ratings l l l l 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 Symbol Test Conditions Min Typ Max Units VCC Supply Current Nominal Supply Current ICC UGATE, LGATE open -- 3 -- mA VCC Regulated Voltage VCC VBOOT=12V -- 6 -- V 3.75 4.1 4.35 V -- 0.5 -- V 0.784 0.8 0.816 V 550 600 650 kHz -- 1.75 -- VP-P -- 35 -- dB Power-On Reset Rising VCC Threshold VCC Threshold Hysteresis Reference Reference Voltage Oscillator Both FB & FBL Free Running Frequency Ramp Amplitude ∆ VOSC PWM Error Amplifier DC Gain PWM Controller Gate Driver Upper Drive Source RUGATE VBOOT = 12V; VBOOT - VUGATE = 1V -- 7 -- Ω Upper Drive Sink RUGATE VUGATE = 1V -- 5 -- Ω 100 -- -- mA Linear Regulator DRV Driver Source VDRV = 2V To be continued DS9204/A-08 March 2007 www.richtek.com 5 RT9204/A Parameter Preliminary Symbol Test Conditions Min Typ Max Units Protection FB Over-Voltage Trip FB Rising -- 1 -- V FB & FBL Under-Voltage Trip FB & FBL Falling -- 0.5 -- V -- 1 -- ms Soft-Start Interval SD Pin Threshold VCC = 5V -- 1.5 -- V SD pin Sink Current VCC = 5V -- 40 -- µA www.richtek.com 6 DS9204/A-08 March 2007 RT9204/A Preliminary Typical Operating Characteristics Power On Power Off VCC = 5V VOUT = 2.2V VCC VCC = 5V VCC VOUT1 VOUT1 VOUT2 VOUT2 Time (1ms/Div) Time (50ms/Div) Load Transient Load Transient UGATE 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) Short Hiccup VCC = 5V VOUT = 2.2V VCC = 5V VOUT = 2.2V VOUT VOUT UGATE UGATE RT9204 Time (5ms/Div) DS9204/A-08 March 2007 RT9204A Time (2ms/Div) www.richtek.com 7 RT9204/A Preliminary POR (Rising/Falling) vs. Temperature 4.3 0.802 4.2 0.801 4.1 POR (V) Reference (V) Reference vs. Temperature 0.803 0.800 0.799 Rising 4.0 3.9 0.798 3.8 0.797 3.7 Falling 3.6 0.796 -50 0 50 100 150 Temperature (°C) -50 0 50 100 150 Temperature (°C) Oscillator Frequency vs. Temperature 315 Frequency (kHz) A 310 305 300 295 290 285 280 275 270 -50 0 50 100 150 Temperature (°C) www.richtek.com 8 DS9204/A-08 March 2007 RT9204/A Preliminary Application Information C2 1uF 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. UGATE 5V 0.1uF PHASE RT9204/A RT9204/A Power On Reset D1 + C2 1uF 12V C 1uF 10 Figure 4. Dual Power Supply Operation R1 BOOT R BOOT UGATE The Bootstrap Operation VCC 6.0V Regulation VCC 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. Figure 3. Single 5V power Supply Operation Under Voltage and Over Voltage Protection 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. DS9204/A-08 March 2007 5V + 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 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. www.richtek.com 9 RT9204/A Preliminary Shutdown Internal SS COUNT = 1 COUNT = 2 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. COUNT = 3 4V 2V 0V FB or FBL Voltage OVERLOAD APPLIED L Q VI T0T1 D R C VO T3 T2 TIME C.C.M. Figure 5 TS Inductor Selection Table 1 The RT9204/A was designed for VIN = 5V, step-down application mainly. Figure 6 shows the typical topology and waveforms of step-down converter. TON VI - VO VL The ripple current of inductor can be calculated as follows: ILRIPPLE = (5V - VOUT) L TOFF - VO × TON iL uQ Because operation frequency is fixed at 600kHz, TON = 3.33 × IL = IO uIL VOUT 5V The VOUT ripple is iQ VOUT RIPPLE = ILRIPPLE × ESR IQ ESR is COUT capacitor equivalent series resistor iD Table 1 shows the ripple voltage of VOUT : VIN = 5V *Refer to Sanyo low ESR series (CE, DX, PX......) ID The suggested L and C are as follows: 2µH with ≥ 1500µF COUT Figure 6 5µH with ≥ 1000µF COUT VOUT 3.3V 2.5V 1.5V Inductor 2µH 5µH 2µH 5µH 2µH 5µH 1000µF (ESR = 53mΩ) 100mV 40mV 110mV 44mV 93mV 37mV 1500µF (ESR = 33mΩ) 62mV 25mV 68mV 28mV 58mV 23mV 3000µF (ESR = 21mΩ) 40mV 16mV 43mV 18mV 37mV 15mV www.richtek.com 10 DS9204/A-08 March 2007 RT9204/A Preliminary Input / Output Capacitor 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. VOUT2 < 3.3V + 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. DRV VBOOT = 12V R3 BOOT 6V FBL R4 VCC R4<1K RT9204/A Figure 8 PWM Loop Stability The RT9204/A is a voltage mode buck controller designed for 5V step-down applications. The gain of error amplifier is fixed at 35dB for simplified design. The output amplitude of ramp oscillator is 1.6V, the loop gain and loop pole/zero are calculated as follows: DC loop gain GA = 35 dB × 5 1.6 × 0.8 VOUT 1 LC filter pole PO = 2π LC Error Amp pole PA = 300kHz ESR zero ZO = 1 2π ESR × C The RT9204/A Bode plot as shown Figure 9. is stable in most of application conditions. VOUT = 3.3V VOUT2 < 2.5V + DRV 40 R3 BOOT R4 VCC VCC = 5V 30 FBL RT9204/A R4<1K COUT = 1500uF(33mΩ) L = 2uH VOUT = 1.5V PO = 2.9kHz VOUT = 2.5V ZO = 3.2kHz VOUT = 3.3V 20 Loop Gain 10 100 Figure 7 DS9204/A-08 March 2007 1k 10k 100k 1M Figure 9 www.richtek.com 11 RT9204/A Preliminary Reference Voltage VIN L VOUT1 + DRV COUT 56K EA + I2 - 1K PWM PWM Layout Considerations RAMP Figure 10 0.82 VIN = 5V FB (V) 0.81 0.80 0.79 1 1.5 2 2.5 3 VOUT (V) 3.5 4 4.5 Figure 11 Feedback Divider The reference of RT9204/A is 0.8V. Both the PWM and LDO output voltages can be set using a resistor based divider as shown in Figure 12. Put the R1&R2 and R3&R4 as close as possible to FB pin and R2&R4 should be less than 1 kΩ to avoid noise coupling. The C1 capacitor is a speed-up capacitor for reducing output ripple to meet with the requirement of fast transient load. Typically a 1nF ~ 0.1µF is enough for C1. www.richtek.com 12 R4 R4<1K Figure 12 1.75V 0.78 0.5 R2 <1K R3 + - REP 0.8V RT9204/A FB FBL R3 VOUT2 = 0.8V (1+ R4 ) I3 + C1 R1 R1 VOUT1 = 0.8V (1+ R2 ) FB VOUT2 + Because RT9204/A use a low 35dB gain error amplifier, shown in Figure 10. The voltage regulation is dependent on VIN & VOUT setting. The FB reference voltage of 0.8V were trimmed at VIN = 5V & VOUT = 2.5V condition. In a fixed VIN = 5V application, the FB reference voltage vs. VOUT voltage can be calculated as Figure 11. 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 ocer-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 RT9204/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. DS9204/A-08 March 2007 Preliminary RT9204/A 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 13. shows the connections of the critical components in the converter. Note that the capacitors CIN 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 copper filled polygons on the top and bottom circuit layers for the PHASE node, but it is not necessary to oversize this particular island. Since the PHASE node is subjected to very high dV/dt voltages, the stray capacitance formed between these island and the surrounding circuitry will tend to couple switching noise. 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. IQ1 IL VOUT 5V + + + Q1 LOAD IQ2 GND VCC UGATE GND RT9204/A FB Figure 13 DS9204/A-08 March 2007 www.richtek.com 13 RT9204/A Preliminary Outline Dimension H A M J B F C I D 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 8-Lead SOP Plastic Package Richtek Technology Corporation Richtek Technology Corporation Headquarter Taipei Office (Marketing) 5F, No. 20, Taiyuen Street, Chupei City 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Hsinchu, Taiwan, R.O.C. Taipei County, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Tel: (8862)89191466 Fax: (8862)89191465 Email: [email protected] www.richtek.com 14 DS9204/A-08 March 2007