LTC3717-1 Wide Operating Range, TM No R Step-Down Controller SENSE for DDR/QDR Memory Termination FEATURES DESCRIPTIO n V = 1/2 V OUT REF The LTC 3717-1 is a synchronous step-down switching n Adjustable and Symmetrical Sink/Source regulator controller for double data rate (DDR) and Quad TM TM Current Limit up to 20A Data Rate (QDR ) memory termination. The controller n True Current Mode Control with Optional Use of uses a valley current control architecture to deliver very Sense Resistor low duty cycles with or without a sense resistor. Operating n V and I Pins Allow Constant Frequency ON ON frequency is selected by an external resistor and is com- Operation During Input and Output Voltage Changes pensated for variations in V and V . IN OUT n 0.65% Output Voltage Accuracy Forced continuous operation reduces noise and RF inter- n Up to 97% Efficiency ference. Output voltage is internally set to half of V , REF n Ultrafast Transient Response which is user programmable. n 2% to 90% Duty Cycle at 200kHz n t 100ns Fault protection is provided by an output overvoltage ON(MIN) n Stable with Ceramic C comparator and optional short-circuit shutdown timer. OUT n Power Good Output Voltage Monitor Soft-start capability for supply sequencing is accom- n Wide V Range: 4V to 36V plished using an external timing capacitor. The regulator IN n Adjustable Switching Frequency up to 1.5MHz current limit level is symmetrical and user programmable. n Output Overvoltage Protection Wide supply range allows operation from 4V to 36V at the n Optional Short-Circuit Shutdown Timer V input. CC n Available in a 5mm 5mm QFN Package , LTC and LT are registered trademarks of Linear Technology Corporation. No R is a trademark of Linear Technology Corporation. SENSE U QDR RAMs and Quad Data Rate RAMs comprise a new family of products developed by Cypress APPLICATIO S Semiconductor, Hitachi, IDT, Micron Technology, Inc. and Samsung. n Bus Termination: DDR and QDR Memory, SSTL, HSTL, ... n Notebook Computers, Desktop Servers n Tracking/Margining Power Supply TYPICAL APPLICATIO V CC 5V TO 28V Efficiency vs Load Current 715k 1F V V CC IN I ON 2.5V TO 5.5V 100 V = 1.25V + 150F OUT 0.1F V V = 2.5V REF DD 90 6.3V RUN/SS TG Si7840DP B320A 2 V = 5V 80 IN LTC3717-1 SW V 70 OUT 470pF V = 2.5V IN + 20k SENSE 1.25V 0.22F 0.68H 60 I BOOST 10A TH + 180F 4V 50 CMDSH-3 DRV CC 2 SGND INTV CC 40 V BG Si7840DP ON B320A 30 + 4.7F 20 PGOOD PGND 10 SENSE 37171 F01a 0 V FB 0 2 4 6 8 10 12 14 LOAD CURRENT (A) 37171 F01b Figure 1. High Efficiency DDR Memory Termination Supply sn37171 37171fs 1 EFFICIENCY (%) U ULTC3717-1 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW Boosted Topside Driver Supply Voltage (BOOST) ............................................... 42V to 0.3V + V , I , SW, SENSE Voltage .................. 36V to 0.3V IN ON 32 31 30 29 28 27 26 25 EXTV , DRV , RUN/SS, PGOOD, CC CC V 1 24 SW ON (BOOST SW) Voltages ............................ 7V to 0.3V + PGOOD 2 23 SENSE V , V , V Voltages .......(INTV + 0.3V) to 0.3V ON REF RNG CC V 3 22 NC RNG I , V Voltages...................................... 2.7V to 0.3V TH FB I SENSE 4 21 TH 33 TG, BG, INTV , EXTV , DRV Peak Currents ....... 2A CC CC CC SGND PGND 5 20 TG, BG, INTV , EXTV , DRV RMS Currents .. 50mA I 6 19 BG CC CC CC ON V 7 18 DRV Operating Ambient Temperature FB CC NC 8 17 INTV CC Range (Note 4) ................................... 40 C to 85 C 9 10 11 12 13 14 15 16 Junction Temperature (Note 2)............................ 125 C Storage Temperature Range ................. 65 C to 125 C Reflow Peak Body Temperature ............................ 260 C UH PACKAGE 32-LEAD (5mm 5mm) PLASTIC QFN T = 125 C, q = 34 C/ W JMAX JA EXPOSED PAD IS SGND (PIN 33) MUST BE SOLDERED TO PCB ORDER PART NUMBER QFN PART MARKING LTC3717EUH-1 37171 Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T = 25 C. V = 15V, unless otherwise noted. A IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Buck Regulator I Input DC Supply Current (V ) Q(VIN) IN Normal 1000 2000 m A Shutdown Supply Current V = 0V 15 30 m A RUN/SS V Feedback Voltage Accuracy I = 1.2V (Note 3), V = 2.4V l 0.65 0.1 0.65 % FB TH REF D V Feedback Voltage Line Regulation V = 4V to 36V, I = 1.2V (Note 3) 0.002 %/V FB(LINE) IN TH D V Feedback Voltage Load Regulation I = 0.5V to 1.9V (Note 3) l 0.05 0.3 % FB(LOAD) TH g Error Amplifier Transconductance I = 1.2V (Note 3) 0.93 1.13 1.33 mS m(EA) TH t On-Time I = 30m A, V = 0V 186 233 280 ns ON ON ON I = 60m A, V = 0V 95 115 135 ns ON ON t Minimum On-Time I = 180m A 50 100 ns ON(MIN) ON t Minimum Off-Time 300 400 ns OFF(MIN) V Maximum Current Sense Threshold V = 1V, V = V /2 50mV l 108 135 162 mV SENSE(MAX) RNG FB REF V V (Source) V = 0V, V = V /2 50mV l 76 95 114 mV PGND SW RNG FB REF V = INTV , V = V /2 50mV l 148 185 222 mV RNG CC FB REF V Minimum Current Sense Threshold V = 1V, V = V /2 + 50mV l 140 165 190 mV SENSE(MIN) RNG FB REF V V (Sink) V = 0V, V = V /2 + 50mV l 97 115 133 mV PGND SW RNG FB REF V = INTV , V = V /2 + 50mV l 200 235 270 mV RNG CC FB REF sn37171 37171fs 2 NC NC V RUN/SS REF NC NC NC NC NC BOOST NC TG EXTV NC CC V NC IN U WWW