LTC3776 TM Dual 2-Phase, No R , SENSE Synchronous Controller for DDR/QDR Memory Termination FEATURES DESCRIPTIO No Current Sense Resistors Required The LTC 3776 is a 2-phase dual output synchronous step- Out-of-Phase Controllers Reduce Required down switching regulator controller for DDR/QDR memory Input Capacitance termination applications. The second controller regulates its output voltage to 1/2 V while providing symmetrical V Tracks 1/2 V REF OUT2 REF source and sink output current capability. Symmetrical Source/Sink Output Current Capability (V ) OUT2 The No R constant frequency current mode architec- SENSE Spread Spectrum Operation (When Enabled) ture eliminates the need for sense resistors and improves Wide V Range: 2.75V to 9.8V IN efficiency. Power loss and noise due to the ESR of the Constant Frequency Current Mode Operation input capacitance are minimized by operating the two 0.6V 1.5% Voltage Reference (V ) OUT1 controllers out of phase. Low Dropout Operation: 100% Duty Cycle The switching frequency can be programmed up to 750kHz, True PLL for Frequency Locking or Adjustment allowing the use of small surface mount inductors and ca- Internal Soft-Start Circuitry pacitors. For noise sensitive applications, the LTC3776 Power Good Output Voltage Monitor switching frequency can be externally synchronized from Output Overvoltage Protection 250kHz to 850kHz, or can be enabled for spread spectrum Micropower Shutdown: I = 9A Q operation. Forced continuous operation reduces noise and Tiny Low Profile (4mm 4mm) QFN and Narrow RF interference. Soft-start for V is provided internally OUT1 SSOP Packages and can be extended using an external capacitor. U APPLICATIO S The LTC3776 is available in the tiny thermally enhanced (4mm 4mm) QFN package or 24-lead SSOP narrow DDR, DDR II and QDR Memory package. SSTL, HSTL Termination Supplies , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. No R is a Servers, RAID Systems SENSE trademark of Linear Technology Corporation. All other trademarks are the property of their Distributed DC Power Systems respective owners. Protected by U.S. Patents including 5481178, 5929620, 6144194, 6580258, 6304066, 6611131, 6498466, patent pending on Spread Spectrum. TYPICAL APPLICATIO High Efficiency, 2-Phase, DDR Memory (V and V ) Supplies DDQ TT Efficiency vs Load Current V IN 3.3V 100 10F V IN 90 2 + + SENSE1 SENSE2 80 TG1 TG2 70 1.5H 1.5H SW1 SW2 60 LTC3776 50 BG1 BG2 40 PGND PGND 30 FIGURE 14 CIRCUIT V REF (V )V 187k V (V ) CHANNEL 2 (V = 3.3V) DDQ OUT1 OUT2 TT IN 20 CHANNEL 1 (V = 5V) 2.5V V V 1.25V FB1 FB2 IN 4A 10 CHANNEL 1 (V = 3.3V) 4A IN I I TH1 TH2 CHANNEL 2 (V = 5V) IN 470pF 2200pF 0 SGND 47F 47F 10 100 1000 10000 59k 15k 6.2k LOAD CURRENT (mA) 3776 TA01b 3776 TA01a 3776fa 1 EFFICIENCY (%) U ULTC3776 ABSOLUTE AXI U RATI GS (Note 1) Input Supply Voltage (V ) ........................ 0.3V to 10V TG1, TG2, BG1, BG2 Peak Output Current (<10s) ..... 1A IN PLLLPF, RUN/SS, SYNC/SSEN, Operating Temperature Range (Note 2) ... 40C to 85C + + V , SENSE1 , SENSE2 , V Storage Temperature Range .................. 65C to 125C REF FB2 IPRG1, IPRG2 Voltages ................. 0.3V to (V + 0.3V) Junction Temperature (Note 3) ............................ 125C IN V , I , I Voltages ........................... 0.3V to 2.4V Lead Temperature (Soldering, 10 sec) FB1 TH1 TH2 SW1, SW2 Voltages .............. 2V to V + 1V (10V Max) (LTC3776EGN) ..................................................... 300C IN PGOOD ..................................................... 0.3V to 10V UUW PACKAGE/ORDER I FOR ATIO TOP VIEW ORDER PART ORDER PART TOP VIEW NUMBER NUMBER + SW1 1 24 SENSE1 IPRG1 2 23 PGND 24 23 22 21 20 19 LTC3776EUF LTC3776EGN V 3 22 BG1 FB1 I 1 18 SYNC/SSEN TH1 I 4 21 SYNC/SSEN IPRG2 TH1 2 17 TG1 IPRG2 5 20 TG1 PLLLPF 3 16 PGND 25 PLLLPF 6 19 PGND SGND 4 15 TG2 V 5 14 RUN/SS SGND 7 18 TG2 IN V 6 13 BG2 V 8 17 RUN/SS REF IN UF PART MARKING V 9 16 BG2 7 8 9 10 11 12 REF V 10 15 PGND FB2 3776 + I 11 14 SENSE2 TH2 PGOOD 12 13 SW2 UF PACKAGE 24-LEAD (4mm 4mm) PLASTIC QFN GN PACKAGE T = 125C, = 37C/W JMAX JA 24-LEAD PLASTIC SSOP EXPOSED PAD (PIN 25) IS PGND T = 125C, = 130C/ W JMAX JA MUST BE SOLDERED TO PCB Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes specifications that apply over the full operating temperature range, otherwise specifications are at T = 25C. V = 4.2V unless otherwise specified. A IN PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loops Input DC Supply Current (Note 4) Normal Operation I = I = 1.3V 575 850 A TH1 TH2 Shutdown RUN/SS = 0V 9 20 A UVLO V < UVLO Threshold 200mV 3 10 A IN Undervoltage Lockout Threshold V Falling 1.95 2.25 2.55 V IN V Rising 2.15 2.45 2.75 V IN Shutdown Threshold at RUN/SS 0.45 0.65 0.85 V Start-Up Current Source RUN/SS = 0V 0.4 0.7 1 A Regulated Feedback Voltage (V)0C to 85C (Note 5) 0.591 0.6 0.609 V FB1 40C to 85C 0.588 0.6 0.612 V Regulated Feedback Voltage (V)V = 2.5V 1.232 1.250 1.268 V FB2 REF Output Voltage Line Regulation (V ) 2.75V < V < 9.8V (Note 5) 0.05 0.2 mV/V FB1 IN Output Voltage Line Regulation (V ) 0.02 0.1 mV/V FB2 3776fa 2 V V FB2 FB1 I IPRG1 TH2 PGOOD SW1 + SW2 SENSE1 + SENSE2 PGND PGND BG1 U WWW