9-4590; Rev 1; 7/09 KIT ATION EVALU E L B AVAILA 1-Phase Quick-PWM GPU Controller Features o 1-Phase Quick-PWM Controller o ±6mV VOUT Accuracy Over Line, Load, and Temperature The MAX17409 is a 1-phase Quick-PWM™ step-down VID power-supply controller for high-performance graphics processors. The Quick-PWM control provides instantaneous response to fast-load current steps.
MAX17409 1-Phase Quick-PWM GPU Controller ABSOLUTE MAXIMUM RATINGS VCC, VDD to GND .....................................................-0.3V to +6V G0–G5 to GND .........................................................-0.3V to +6V CSP, CSN to GND ....................................................-0.3V to +6V ILIM, THRM, VRHOT, PWRGD to GND ....................-0.3V to +6V SKIP to GND.............................................................-0.3V to +6V CCV, FB, IMON, REF to GND .....................
1-Phase Quick-PWM GPU Controller (Circuit of Figure 1, VIN = 12V, VDD = VCC = 5V, SHDN = ILIM = VCC, SKIP = GNDS = PGND = GND, VFB = VCSP = VCSN = 1.05V; G5–G0 set for 1.05V (G0–G5 = 100110); TA = 0°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C.) (Note 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS BIAS CURRENTS Quiescent Supply Current (VCC) ICC Measured at VCC, SKIP = 5V, FB forced above the regulation point 1.
MAX17409 1-Phase Quick-PWM GPU Controller ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VIN = 12V, VDD = VCC = 5V, SHDN = ILIM = VCC, SKIP = GNDS = PGND = GND, VFB = VCSP = VCSN = 1.05V; G5–G0 set for 1.05V (G0–G5 = 100110); TA = 0°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C.) (Note 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 29.2 30 30.
1-Phase Quick-PWM GPU Controller (Circuit of Figure 1, VIN = 12V, VDD = VCC = 5V, SHDN = ILIM = VCC, SKIP = GNDS = PGND = GND, VFB = VCSP = VCSN = 1.05V; G5–G0 set for 1.05V (G0–G5 = 100110); TA = 0°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C.) (Note 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Gm(IMON) I IMON/ (VCSP - VCSN), VCSN = 0.5V to 1.0V 4.9 5.0 51 mS I IMON = 0 -1.0 +1.0 mV I IMON = -1.0mA 1.05 1.15 V 2.
MAX17409 1-Phase Quick-PWM GPU Controller ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VIN = 12V, VDD = VCC = 5V, SHDN = ILIM = VCC, SKIP = GNDS = PGND = GND, VFB = VCSP = VCSN = 1.05V; G5–G0 set for 1.05V (G0–G5 = 100110); TA = -40°C to +105°C, unless otherwise specified.
1-Phase Quick-PWM GPU Controller (Circuit of Figure 1, VIN = 12V, VDD = VCC = 5V, SHDN = ILIM = VCC, SKIP = GNDS = PGND = GND, VFB = VCSP = VCSN = 1.05V; G5–G0 set for 1.05V (G0–G5 = 100110); TA = -40°C to +105°C, unless otherwise specified.) (Note 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS GATE DRIVERS DH Gate-Driver On-Resistance R ON(DH) DL Gate-Driver On-Resistance R ON(DL) Internal BST Switch On-Resistance RBST BST - LX forced to 5V High state (pullup) 2.5 Low state (pulldown) 2.
Typical Operating Characteristics (Circuit of Figure 1, VIN = 12V, VCC = VDD = 5V, SHDN = VCC, G0–G5 set for 1.05V (G0–G5 = 100110), TA = +25°C, unless otherwise specified.) 0.9V OUTPUT VOLTAGE vs. LOAD CURRENT 0.9V OUTPUT EFFICIENCY vs. LOAD CURRENT OUTPUT VOLTAGE (V) EFFICIENCY (%) 12V 80 20V 70 60 MAX17409 toc02 7V 90 0.92 MAX17409 toc01 100 SKIP MODE 0.91 0.90 PWM MODE 0.89 50 SKIP MODE PWM MODE 40 0.88 0.
1-Phase Quick-PWM GPU Controller Gm(IMON) TRANSCONDUCTANCE DISTRIBUTION SOFT-START WAVEFORM 80 MAX17409 toc07 SAMPLE SIZE = 100 +85°C +25°C 5V 0 60 A 0.95V A 0 B 0 B 0.95V 50 C C 40 0 0 30 D D 0 0 20 10 E 5.10 5.08 5.06 5.04 5.02 5.00 4.98 4.96 4.94 0 4.92 0 MAX17409 toc09 5V 0 70 4.90 SAMPLE PERCENTAGE (%) 90 SOFT-SHUTDOWN WAVEFORM MAX17409 toc08 100 E 0 1ms/div A. SHDN, 5V/div B. ILX, 10A/div C. VOUT, 500mV/div TRANSCONDUCTANCE (mS) 100µs/div D.
1-Phase Quick-PWM GPU Controller MAX17409 Pin Description PIN NAME FUNCTION Current Monitor Output. The MAX17409 IMON output sources a current that is directly proportional to the current-sense voltage as defined by: I IMON = Gm(IMON) x (VCSP - VCSN) where Gm(IMON) = 5mS (typ). The IMON current is unidirectional (sources current out of IMON only) for positive current-sense values. For negative current-sense voltages, the IMON current is zero.
1-Phase Quick-PWM GPU Controller PIN 7 NAME THRM FUNCTION Comparator Input for Thermal Protection. THRM connects to the positive input of an internal comparator. The comparator’s negative input connects to an internal resistive voltage-divider that accurately sets the THRM threshold to 30% of the VCC voltage. Connect the output of a resistordivider and thermistor-divider (between VCC and GND) to THRM with the values selected so the voltage at THRM falls below 30% of VCC (1.
1-Phase Quick-PWM GPU Controller MAX17409 Pin Description (continued) 12 PIN NAME 22 DH FUNCTION 23 GND 24 VRHOT 25 REF Buffered 2V Reference Output. Bypass REF with a 100pF to 1000pF capacitor. Do not exceed 1000pF. 26 ILIM Valley Current-Limit Adjustment Input. The valley current-limit threshold voltage at CSP to CSN equals precisely 1/10 of the differential REF to ILIM voltage over a 0.1V to 0.5V range (10mV to 50mV current-sense range).
1-Phase Quick-PWM GPU Controller 6 11 12 13 14 VID INPUTS 15 16 SHDN R3 R2 VDD G0 G1 G2 G3 G4 G5 TON DH LX ILIM REF PGND CSP 24 R6 7.
MAX17409 1-Phase Quick-PWM GPU Controller CSP IMON CSN ILIM MINIMUM OFF-TIME Q REF TRIG ONE-SHOT VCC ON-TIME ONE SHOT TON FB REF (2.0V) Q SLEW CONTROL GND G0–G5 TRIG BST R DAC Q DH S SHDN LX TARGET S Q PGND LX 1mV R VDD SKIP FAULT REF DL CCV PGND Gm(CCV) TARGET +200mV 7R BLANK R 5ms STARTUP DELAY TARGET -300mV FB SKIP PWRGD TARGET +300mV CSP FAULT Gm(FB) CSN THRM TARGET -400mV GNDS VRHOT Gm(GNDS) MAX17409 0.3 x VCC Figure 2.
1-Phase Quick-PWM GPU Controller MAX17409 Table 1. Component Selection for Standard Applications DESIGN PARAMETERS 14A DESIGN 9A DESIGN 5A DESIGN Input Voltage Range 8V to 20V 8V to 20V 8V to 20V Maximum Load Current 14A 9A 5A Transient Load Current 10A 7A 4A TON Resistance (RTON) 200k (fSW = 300kHz) 170k (fSW = 350kHz) 150k (fSW = 390kHz) Inductance (L1) 0.6µH, 17A, 2.3m NEC-TOKIN MPC0750LR60C 0.75µH, 10.7A, 6.2m TOKO FDVE0630-R75M 1.50µH, 8A, 12.
MAX17409 1-Phase Quick-PWM GPU Controller Detailed Description Free-Running, Constant On-Time PWM Controller with Input Feed-Forward The Quick-PWM control architecture is a pseudo-fixedfrequency, constant-on-time, current-mode regulator with voltage feed-forward (Figure 2). This architecture relies on the output filter capacitor’s ESR to act as the current-sense resistor, so the output ripple voltage provides the PWM ramp signal.
1-Phase Quick-PWM GPU Controller fSW = ( VOUT + VDROP1) t ON ( VIN + VDROP1 - VDROP2 ) where VDROP1 is the sum of the parasitic voltage drops in the inductor discharge path, including synchronous rectifier, inductor, and PCB resistances; VDROP2 is the sum of the parasitic voltage drops in the inductor charge path, including high-side switch, inductor, and PCB resistances; and tON is the on-time as determined above.
MAX17409 1-Phase Quick-PWM GPU Controller INPUT (VIN) DH NH CIN SENSE RESISTOR L LESL RSENSE R1 CEQ L CEQR1 = SENSE RSENSE LX MAX17409 DL NL DL COUT PGND CSP CSN A) OUTPUT SERIES RESISTOR SENSING INPUT (VIN) DH NH CIN INDUCTOR L RDCR RCS = LX MAX17409 DL NL DL R1 PGND R2 CEQ R2 RDCR R1 + R2 COUT L RDCR = C EQ [ R11 + R21 ] CSP CSN B) LOSSLESS INDUCTOR SENSING FOR THERMAL COMPENSATION: R2 SHOULD CONSIST OF AN NTC RESISTOR IN SERIES WITH A STANDARD THIN-FILM RESISTOR. Figure 3.
1-Phase Quick-PWM GPU Controller where Gm(CCV) is the integrator’s maximum transconductance (320µs) and fSW is the switching frequency set by the TON resistance. The MAX17409 disables the integrator by connecting the amplifier inputs together at the beginning of all VID transitions done in pulse-skipping mode (SKIP = high). The integrator remains disabled until 20µs after the transition is completed (the internal target settles) and the output is in regulation (edge detected on the error comparator).
MAX17409 1-Phase Quick-PWM GPU Controller Table 4. Output Voltage VID DAC Codes G5 G4 G3 G2 G1 G0 OUTPUT VOLTAGE (V) G5 G4 G3 G2 G1 G0 OUTPUT VOLTAGE (V) 1 0 0 0 0 0 1.1250 0 0 0 0 0 0 0.7250 1 0 0 0 0 1 1.1125 0 0 0 0 0 1 0.7125 1 0 0 0 1 0 1.1000 0 0 0 0 1 0 0.7000 1 0 0 0 1 1 1.0875 0 0 0 0 1 1 0.6875 1 0 0 1 0 0 1.0750 0 0 0 1 0 0 0.6750 1 0 0 1 0 1 1.0675 0 0 0 1 0 1 0.6625 1 0 0 1 1 0 1.
1-Phase Quick-PWM GPU Controller OVP LEVEL The slew rate is not dependent on the total output capacitance, as long as the surge current is less than the current limit. For all dynamic VID transitions, the transition time (tTRAN) is given by: t TRAN = VNEW - VOLD 12.5mVµs where VOLD is the original output voltage, and VNEW is the new target voltage. See Slew-Rate Accuracy in the Electrical Characteristics for slew-rate limits.
Forced-PWM Operation (Normal Mode) During soft-shutdown and normal operation—when the CPU is actively running (SKIP = low, Table 3) — the MAX17409 operates with the low-noise, forced-PWM control scheme. Forced-PWM operation disables the zero-crossing comparator, forcing the low-side gatedrive waveforms to constantly be the complement of the high-side gate-drive waveforms.
1-Phase Quick-PWM GPU Controller t TRAN(START) = VBOOT (1.56mV / µs) where VBOOT is the initial VID target. The soft-start circuitry does not use a variable current limit, so full output current is available immediately. PWRGD becomes high impedance approximately 5ms after the target output voltage is reached. The MAX17409 automatically uses pulse-skipping mode during soft-start and uses forced-PWM mode during soft-shutdown, regardless of the SKIP configuration.
MAX17409 1-Phase Quick-PWM GPU Controller Shutdown When SHDN goes low, the MAX17409 enters low-power shutdown mode. PWRGD is pulled low immediately, and the output voltage ramps down with a 1.56mV/µs slew rate: t TRAN(SHDN) = VOUT (1.
1-Phase Quick-PWM GPU Controller The internal pulldown transistor that drives DL low is robust, with a 0.25Ω (typ) on-resistance. This helps DL from being pulled up due to capacitive coupling from the drain to the gate of the low-side MOSFETs when the inductor node (LX) quickly switches from ground to VIN. Applications with high input voltages and long inductive driver traces might require that rising LX edges do not pull up the low-side MOSFETs’ gate, causing shootthrough currents.
MAX17409 1-Phase Quick-PWM GPU Controller capacitor selection, inductor saturation rating, and the design of the current-limit circuit. The continuous load current (ILOAD) determines the thermal stresses and thus drives the selection of input capacitors, MOSFETs, and other critical heat-contributing components. Modern notebook CPUs generally exhibit ILOAD = ILOAD(MAX) x 80%. • • Switching frequency: This choice determines the basic trade-off between size and efficiency.
1-Phase Quick-PWM GPU Controller (RESR + RPCB ) ≤ ∆I VSTEP LOAD(MAX) V I VALLEY = LIMIT = R SENSE VLIMIT R DCR × CSP -CSN R LX -C CSN where RSENSE is the sensing resistor and RCSP-CSN/ RLX-CSN is the ratio of resistor-divider with DCR-sensing approach. In nonprocessor applications, the output capacitor’s size often depends on how much ESR is needed to maintain an acceptable level of output ripple voltage.
MAX17409 1-Phase Quick-PWM GPU Controller In applications that require DC droop, RDROOP(AC) is the same as the DC droop setting (R DROOP(AC) = RDROOP(DC)). In applications that do not require DC droop, this AC signal is generated by capacitively coupling the inductor ripple current signal to the FB pin. In this case, RDROOP(AC) = RSENSE, where RSENSE is the effective sense resistance seen at the CSP-CSN pins. In Figure 1, C3 couples the inductor ripple current signal to the FB pin.
1-Phase Quick-PWM GPU Controller MOSFET Power Dissipation Worst-case conduction losses occur in the high-side MOSFET (NH) is a function of the duty factor, with the worst-case power dissipation occurring at the minimum input voltage: ⎛V ⎞ PD (NH Resistive) = ⎜ OUT ⎟ ILOAD 2R DS(O ON) ⎝ VIN ⎠ Generally, a small high-side MOSFET is desired to reduce switching losses at high input voltages. However, the RDS(ON) required to stay within package power dissipation often limits how small the MOSFET can be.
MAX17409 1-Phase Quick-PWM GPU Controller Applications Information • When trade-offs in trace lengths must be made, it is preferable to allow the inductor charging path to be made longer than the discharge path. For example, it is better to allow some extra distance between the input capacitors and the high-side MOSFET than to allow distance between the inductor and the lowside MOSFET or between the inductor and the output filter capacitor.
1-Phase Quick-PWM GPU Controller MAX17409 KELVIN SENSE VIAS UNDER THE INDUCTOR (SEE MAX17409 EVALUATION KIT) POWER STAGE LAYOUT (TOP SIDE OF PCB) OUTPUT INDUCTOR L COUT COUT CSP CSN CEQ RNTC R2 R1 POWER GROUND CIN1 KELVIN SENSE VIAS TO INDUCTOR PAD INDUCTOR DCR SENSING INPUT SMPS Figure 8. PCB Layout Example Chip Information PROCESS: BiCMOS Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
MAX17409 1-Phase Quick-PWM GPU Controller Revision History REVISION NUMBER REVISION DATE 0 4/09 Initial release 1 7/09 Remove all NVIDIA references; change CPU to GPU DESCRIPTION PAGES CHANGED — 1–32 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.