RT9241CS

Preliminary RT9241 Two-Phase DC/DC Controller for CPU Core Power Supply General Description The RT9241 is a two-phase buck DC/DC controller integrated with all control functions for high performance processor VRM. The RT9241 drives 2 buck switching stages operating in 180 degree phase shift. The two-phase architecture provides high output current while maintaining low power dissipation on power devices and low stress on input and output capacitors. The high equivalent operating frequency also reduces the component dimension and the output voltage ripple in load transient. RT9241 regulates both easily set voltage and current loops. Precise current sharing for power stage is achieved by differential input current sense and processing circuit. The settings of current sense, droop tuning and over current protection are independent to compensation circuit of voltage loop. The feature greatly facilitates the flexibility of CPU power supply design and tuning. The RT9241 uses a 5-bit DAC of 1.1V to 1.85V (25mV/step) output with load current droop compensation to meet the strict VRM transient requirement. The IC monitors the VCORE voltage for PGOOD and over voltage protection. Soft start, over current protection and programmable under voltage lockout are also provided to assure the safety of microprocessor and power system. Features Two-Phase Power Conversion VRM 9.0 DAC Output with Active Droop Compensation for Fast Load Transient Precise Channel Current Sharing with Differential Sense Input Hiccup Mode Over Current Protection Programmable Under Voltage Lockout and Soft Start High Ripple Frequency, (Channel Frequency 200KHz) Times Channel Number Applications Power Supply for Server and Workstation Power Supply for High Current Microprocessor Pin Configurations Part Number RT9241CS (Plastic SOP-20) VID4 VID3 VID2 VID1 VID0 COMP FB ADJ DVD SS 1 2 3 4 5 6 7 8 9 10 Pin Configurations TOP VIEW 20 19 18 17 16 15 14 13 12 11 VDD PGOOD ISP1 PWM1 PWM2 ISP2 VSEN GND ISN1 ISN2 Ordering Information RT9241 Package Type S : SOP-20 Operating temperature range C: Commercial standard DS9241-00 November 2001 www.richtek-ic.com.tw 1 RT9241 Absolute Maximum Ratings Supply Voltage Input, Output or I/O Voltage Ambient Temperature Range Operating Junction Temperature Range Storage Temperature Range Power Dissipation, PD @ TA = 25°C SOP-20 Package Thermal Resistance SOP-20, θJA Lead Temperature (Soldering, 10 sec.) Preliminary 6V GND-0.3V ~ VDD+0.3V 0°C ~ 70°C 0°C ~ 125°C -65°C ~ 150°C 0.625W 60°C /W 260°C Electrical Characteristics (VDD = 5V, GND = 0V, TA = 25°C, unless otherwise specified) Parameter VDD Supply Current Nominal Supply Current Power-On Reset VDD Rising Threshold VDD Falling Threshold VDVD Rising Trip Threshold Oscillator Frequency Ramp Amplitude Ramp Valley Maximum On Time of Each Channel Reference and DAC DACOUT Voltage Accuracy DAC (VID0-VID4) Input Low Voltage DAC (VID0-VID4) Input High Voltage DAC (VID0-VID4) Bias Current PWM Controller Error Amplifier DC Gain Bandwidth Slew Rate Current Sense GM Amplifier ISP 1,2 Full Scale Source Current ISP 1,2 Current for OCP --50 75 --µA µA CL = 10pF ---85 10 5 ---dB MHz V/µS -1.0 -2.0 10 ---20 +1.0 0.8 -40 % V V µA For each phase 170 -1.0 -200 1 1.3 75 230 ---kHz V V % 4.2 3.7 1.19 4.35 3.85 1.25 4.5 4 1.31 V V V IDD PWM 1,2 Open -6 -mA Symbol Test Conditions Min Typ Max Units To be continued www.richtek-ic.com.tw DS9241-00 November 2001 2 Preliminary Parameter Protection SS Current Over-Voltage Trip (VSEN/DACOUT) Power Good Upper Threshold (VSEN/DACOUT) Lower Threshold (VSEN/DACOUT) VSEN Rising VSEN Rising --108 92 VSS = 1V -116 10 120 Symbol Test Conditions Min Typ RT9241 Max -124 --Units µA % % % Function Block Diagram DVD VDD PGOOD VID0 VID1 VID2 VID3 VID4 Power On Reset Oscillator 120% VDAC DAC 108% VDAC 92% VDAC INH +_ +_ INH OVP, PGOOD POR Logic Current Limit Current Balance PWM Logic & Driver PWM Logic & Driver PWM1 PWMCP INH +_ VSEN ADJ Droop Control EA SS Control CS1 _+ CS2 FB GND COMP SS DS9241-00 November 2001 _+ + _ +_ +_ PWM2 Processor PWMCP ISP1 ISN1 ISP2 ISN2 www.richtek-ic.com.tw 3 RT9241 Pin Name VID4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 VID3 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 VID2 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 Preliminary Table 1 Output Voltage Program Nominal Output Voltage DACOUT Off 1.100V 1.125V 1.150V 1.175V 1.200V 1.225V 1.250V 1.275V 1.300V 1.325V 1.350V 1.375V 1.400V 1.425V 1.450V 1.475V 1.500V 1.525V 1.550V 1.575V 1.600V 1.625V 1.650V 1.675V 1.700V 1.725V 1.750V 1.775V 1.800V 1.825V 1.850V VID1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 VID0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 Note: (1) 0:Connected to GND (2) 1:Open www.richtek-ic.com.tw DS9241-00 November 2001 4 +5V 2µH C7 1µF 1 VID4 VDD PGOOD PHASE 17 3 PWM GND 4 ISP1 2.4K 12 2.4K Typical 12V 6 7 C13 1µF 3 VCC PVCC C11 1µF 8 PHASE Q3 PHB83NO3LT L3 2µH 15 2.4K 11 2.4K R13 R2 R10 C8 1µF C9 100µF 18 R1 LGATE 5 Q2 PHB95NO3LT 19 PGOOD 8 C4 1µF VID3 VID2 2 3 4 VID1 VID0 COMP FB ADJ ISN1 PWM1 5 6 7 8 13 GND 14 VSEN ISP2 20 Typical 12V R3 10K 6 VCC 7 PVCC C3 1µF Q1 PHB83NO3LT L2 2µH 0.01µF C5 1000µF 2 BOOT 1 UGATE C1 1µF C2 100µF 12V DS9241-00 November 2001 L1 Typical Application Circuit VID4 VID3 VID2 R5 C10 6.6nF R 6 VID1 RT9600 C6 1000µF VCORE 2.4K R7 24K VID0 C12 Preliminary C14 R8 33pF R9 1K 12V DVD 10 SS PWM2 16 R12 9 ISN2 2 BOOT 1 UGATE 13K R14 2.4K RT9600 PWM GND 4 LGATE C17 0.1µF 5 Q4 PHB95NO3LT 0.01µF C15 1000µF C16 1000µF RT9241 RT9241 www.richtek-ic.com.tw 5 6 +5V D1 L1 12V 1.2µH C10 1000µF BOOT 12 13 C9 1µF 11 6 VDD PVCC 7 R4 10K PGOOD L3 R10 2H C17 ×1500µF Q5 HUF76129 3K R10 3K 14 13 R10 3K 11 3K 16 R10 L3 9 UGATE2 C10 1000µF C9 1µF 8 Q4 HUF76129 UGATE1 PHASE1 R20 10 C5 1µF C8 1µF 1 VID4 VDD PGOOD PWM1 ISP1 ISN1 VSEN GND 15 12 18 17 19 VID3 VID2 VID1 VID0 COMP FB ADJ 20 2 3 4 5 6 7 8 12V PWM1 1 4 LGATE1 PWM2 2 RT9241 www.richtek-ic.com.tw VID4 VID3 R6 R5 VID2 R7 VID1 2.4K C11 15K C13 VID0 C15 R9 66pF Preliminary R8 ISP2 12V 10 SS PWM2 ISN2 R7 9 DVD R10 2.4K GND 3 PHASE2 Q4 HUF76129 PGND 7 LGATE2 BOOT2 10 C9 1µF Q5 HUF76129 D3 6 18K R14 3K C18 0.1µF RT9241 2U C16 ×1500µF DS9241-00 November 2001 Preliminary Functional Pin Description VID4, VID3, VID2, VID1 and VID0 ( Pin1,2,3,4,5) DAC voltage identification inputs for VRM9.0. These pins are TTL-compatible and internally pulled to VDD if left open. COMP (Pin 6) Output of the error amplifier and input of the PWM comparator. FB (Pin 7) Inverting input of the internal error amplifier. ADJ (Pin 8) Current sense output for active droop adjust. Connect a resistor from this pin to GND to set the amount of load droop. DVD (Pin 9) Programmable power UVLO detection input. Trip threshold = 1.25V at V(DVD) rising SS (Pin 10) Connect this SS pin to GND with a capacitor to set the start time interval. Pull this pin below 1V(ramp valley of saw-tooth wave in pulse width modulator) to shutdown the converter output. ISEN1 (Pin 12), ISEN2 (Pin 11) Current sense inputs from the individual converter channel’s sense component GND nodes. GND (Pin 13) Ground for the IC. VSEN (Pin 14) Power good and over voltage monitor input. Connect to the microprocessor-CORE voltage. ISP1 (Pin 18), ISEN2 (Pin 15) Current sense inputs for individual converter channels. Tie this pin to the component sense node. PWM1 (Pin 17), PWM2 (Pin 16) RT9241 PWM outputs for each driven channel. Connect these pins to the PWM input of the MOSFET driver. PGOOD (Pin 19) Power good open-drain output. VDD (Pin 20) IC power supply. Connect this pin to a 5V supply. DS9241-00 November 2001 www.richtek-ic.com.tw 7 RT9241 Preliminary Simplified Block Diagram Control Loops for a Two Phase Converter VDAC ADJ Droop Control EA Current Balance FB GND SS Control COMP SS Processor + _ PWM Logic & Driver PWM Logic & Driver ISP1 ISN1 ISP2 ISN2 PWM1 CS1 CS2 VIN RT9600 R LOAD C OUT VIN RT9600 Voltage loop Current loop www.richtek-ic.com.tw _+ _+ + _ PWMCP PWM2 +_ PWMCP DS9241-00 November 2001 8 Preliminary Operation RT9241 is a two-phase DC/DC controller that precisely regulates CPU core voltage and balances the current of different power channels. The converter consists of RT9241 and its companion MOSFET driver provide high quality CPU power and all protection function to meet the requirement of modern VRM. Voltage control The reference of VCORE is provided by a 5-bit DAC of VRM9.0 specification. Control loop consists of error amplifier, two-phase pulse width modulator, driver and power components. Like conventional voltage mode PWM controller, the output voltage is locked at the VREF of error amplifier and the error signal is used as the control signal VC of pulse width modulator. The PWM signals of different channels are generated by comparison of EA output and spiltphase saw-tooth wave. Power stage transforms VIN to output by PWM signal on-time ratio. Current balance RT9241 senses the current of low side MOSFET in each synchronous rectifier when it is conducting for channel current balance and droop tuning. The differential sensing GM amplifier converts the voltage on the sense component (can be a sense resistor or the RDS(ON) of the low side MOSFET) to current signal into internal balance circuit. The current balance circuit sums and averages the current signals then produces the balancing signals injected to pulse width modulator. If the current of some power channel is greater than average, the balancing signal reduces the output pulse width to keep the balance. Load Droop The sensed power channel current signals regulate the reference of DAC to form a output voltage droop proportional to the load current. The droop or so call “active voltage positioning” can reduce the output voltage ripple at load transient and the LC filter size. Sample & Hold To Current Balance To Droop Tune 2/3 IX 2/3 IX To Over Current Detection 2/3 IX IX _ RT9241 Fault detection The chip detects VCORE for over voltage and power good detection. The “hiccup mode” operation of over current protection is adopted to reduce the short circuit current. The in-rush current at the start up is suppressed by the soft start circuit through clamping the pulse width and output voltage. Application Circuit setting MOSFET driver detection and converter start up RT9241 interface with companion MOSFET driver (like RT9600 or HIP660X series) for correct converter initialization. The tri-phase PWM output (high, low, high impedance) pins sense the interface voltage at IC POR acts (both VDD and DVD trip). The channel is enabled if the pin voltage is 1.2V less than VDD. Please tie the both PWM output to driver input for correct converter start-up. Current sensing setting RT9241 senses the current of low side MOSFET in each synchronous rectifier when it is conducting for channel current balance and droop tuning. The differential sensing GM amplifier converts the voltage on the sense component (can be a sense resistor or the RDS(ON) of the low side MOSFET) to current signal into internal circuit (see Fig.1). GM + IBP IBN ISPX RSP ISN X RSN RS IL Fig.1 Current Sense Circuit DS9241-00 November 2001 www.richtek-ic.com.tw 9 RT9241 The sensing circuit gets IX = Preliminary IL × RS by local feedback. RSP Protection and SS function For OVP, the RT9241 detects the VCORE by VSEN pin. Eliminate the parasitic delay and noise influence on the PCB path for fast and accurate detection. The trip point of OVP is 120% of normal output level. The PWM outputs are pulled low to turn on the low side MOSFET and turn off the high side MOSFET of the synchronous rectifier at OVP. The OVP latch can only be reset by VDD or DVD restart power on reset sequence. The PGOOD detection trip point of VCORE is ±8% out of the normal level. The PGOOD open drain output pulls low when VOCRE exceeds the range. Soft start circuit generates a ramp voltage by charging external capacitor with 10uA current after IC POR acts. The PWM pulse width and VCORE are RSP = RSN to cancel the voltage drop caused by GM amplifier input bias current. IX is sampled and held just before low side MOSFET turns off (See Fig.2). Therefore, I X ( S / H) = VO TOFF IL(S / H) × RS , IL(S / H) = IL( AVG) − , × L 2 RSP  VIN − VO  TOFF =   × 5µS , for operating frequency = 200kHz  VIN     VIN − VO  VO −   × 5µS    VIN   × RS = IL( AVG) −   RSP 2L     IX (S / H) Falling Slope = VO /L IL IL (AVG) IL (S/H) clamped by the rising ramp to reduce the in-rush current and protect the power devices. Over current protection trip point is set by the resistor Inductor Current PWM Signal & High Side MOSFET Gate Signal RIMAX connected to IMAX pin. OCP is triggered if one channel S/H current signal IX> forces PWM output latched at high impedance to turn 3 0.6 × . Controller 2 RIMAX Low Side MOSFET Gate Signal off both high and low side MOSFET in the power stage and initial the hiccup mode protection. The SS pin voltage is pulled low with a 10µA current after it is less than 90% VDD. The converter restarts after SS pin voltage < 0.2V. Three times of OCP disable the converter and only release the latch by POR acts (see Fig.4). COUNT = 1 COUNT = 2 4V 2V 0V VCORE OVERLOAD APPLIED IL 0A T0T1 T2 TIME T3T4 COUNT = 3 SS Fig. 2 Inductor Current and PWM Signal Droop Tuning The S/H current signals from power channels are injected to ADJ pin to create droop voltage. V ADJ = R ADJ × 2 ∑ IX 3 The DAC output voltage decreases by VADJ to form the VCORE load droop(see Fig.3). VDAC _ VADJ 2/3 IX1 _ + COMP EA FB + ∑ ∑ IX ADJ R ADJ 2/3 IX2 2/3 IX3 2/3 IX4 VDAC - VADJ Fig. 4 Fig. 3 Droop Tune Circuit www.richtek-ic.com.tw DS9241-00 November 2001 10 Preliminary Two-Phase Converter and Components Function Grouping RT9241 12V VCC PVCC BOOT UGATE PHASE RT9600 +5V PWM LGATE GND VDD VID Compensation & Offset PWM1 COMP FB VSEN ADJ ISP1 ISN1 VCC PVCC BOOT UGATE PHASE LGATE 12V +VCORE RT9600 PWM2 PWM GND Droop Setting 12V RT9241 DVD ISP2 SS GND ISN2 Driver Power UVLO Current Sense Components DS9241-00 November 2001 www.richtek-ic.com.tw 11 RT9241 Package Information Preliminary H M B B J A C F D I Symbol A B C D F H I J M Dimensions In Millimeters Min 12.598 7.391 2.362 0.330 1.194 0.229 0.102 10.008 0.381 Max 13.005 7.595 2.642 0.508 1.346 0.330 0.305 10.643 1.270 Dimensions In Inches Min 0.496 0.291 0.093 0.013 0.047 0.009 0.004 0.394 0.015 Max 0.512 0.299 0.104 0.020 0.053 0.013 0.012 0.419 0.050 20–Lead SOP Plastic Package www.richtek-ic.com.tw DS9241-00 November 2001 12 Preliminary RT9241 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 DS9241-00 November 2001 www.richtek-ic.com.tw 13