LTC1708-PG Dual Adjustable 5-Bit VID High Efficiency, 2-Phase Current Mode Synchronous Buck DC/DC Controller FEATURES DESCRIPTIO n Out-of-Phase Controllers Reduce Input Capacitance The LTC 1708 is a dual adjustable 5-bit VID program- and Power Supply Induced Noise mable step-down switching regulator controller that drives n OPTI-LOOP Compensation Minimizes C all N-Channel power MOSFET stages. A constant fre- OUT n Power Good Output Monitors Both Outputs quency current mode architecture allows adjustment of n 5-Bit Mobile VID Control, V : 0.9V to 2.0V the frequency up to 300kHz. Power loss and noise due to OUT n Dual N-Channel MOSFET Synchronous Drive the ESR of the input capacitance are minimized by oper- n 1% Output Voltage Accuracy ating the two main controller output stages out of phase. n DC Programmed Fixed Frequency 150kHz to 300kHz OPTI-LOOP compensation allows the transient response n Wide V Range: 3.5V to 36V Operation IN to be optimized over a wide range of output capacitance n Very Low Dropout Operation: 99% Duty Cycle and ESR values. The precision 0.8V reference is compat- n Adjustable Soft-Start Current Ramping ible with future microprocessor generations, and a wide n Foldback Output Current Limiting 3.5V to 30V (36V maximum) input supply range that n Latched Short-Circuit Shutdown with Defeat Option encompasses all battery chemistries. A power good out- n Output Overvoltage Protection put indicates when the output voltages are within 7.5% of n Remote Output Voltage Sense their programmed value. n Low Shutdown Current: 20m A n A RUN/SS pin for each controller provides both soft-start 5V and 3.3V Standby Regulators n and an optional timed, short-circuit shutdown. Other Selectable Constant Frequency, Burst Mode and protection features include: internal foldback current lim- Continuous Operation U iting and an output overvoltage crowbar. The forced APPLICATIO S continuous control pin (FCB) can be used to inhibit Burst Mode operation or to regulate a third, flyback output. n Notebook and Palmtop Computers, PDAs , LTC and LT are registered trademarks of Linear Technology Corporation. n Portable Instruments Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATIO V IN 4.75V TO 28V C + IN 1F 4.7F 10F D3 CERAMIC D4 50V V VIDV INTV IN CC CC CERAMIC M3a M1 TG1 TG2 4 L1 L2 C 0.47F C 0.1F B1 B2 BOOST1 BOOST2 1H 2.2H SW1 SW2 LTC1708-PG M2 BG1 BG2 M3b D1 D2 5 VID BITS VID0 TO VID4 PGND + + SENSE1 SENSE2 R R SENSE1 SENSE2 1000pF 1000pF PGOOD 0.003 0.01 SENSE1 SENSE2 V OUT2 1.5V ATTNIN EAIN2 V OUT1 4A R4 0.925V TO C I I TH1 TH2 OUT1 63.4k C OUT1a C C 2.00V M1: IRF7811 + 270F C1 C2 C OUT 1% 10F RUN/SS1 SGND RUN/SS2 R3 1500pF 220pF 14.1A 2V M2: 1RF7809 180F 6.3V 20k R R M3a, M3b: FDS6982 SP C1 C C C2 4V SS1 SS2 CERAMIC 1% 22k 15k 4 0.1F 0.1F SP L1: VISHAY 5050CE ATTNOUT CONNECTED TO EAIN1 1628 F01 Figure 1. High Efficiency VID Controlled, 2-Output Step-Down Converter 1708f 1 + U ULTC1708-PG UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW Input Supply Voltage (V ).........................36V to 0.3V IN ORDER PART Topside Driver Voltages 1 36 PGOOD RUN/SS1 NUMBER + (BOOST1, BOOST2) ...................................42V to 0.3V 2 35 TG1 SENSE1 LTC1708EG-PG 3 34 SW1 Switch Voltage (SW1, SW2) .........................36V to 5V SENSE1 4 33 BOOST1 EAIN1 INTV EXTV , RUN/SS1, RUN/SS2, CC, CC 5 32 V FREQSET IN (BOOST1-SW1), (BOOST2-SW2), ...............7V to 0.3V + + 6 31 BG1 STBYMD SENSE1 , SENSE2 , SENSE1 , 7 30 EXTV FCB CC SENSE2 Voltages....................... (1.1)INTV to 0.3V CC 8 29 INTV I CC TH1 FREQSET, STBYMD, FCB, VIDV , VID0-4, CC 9 28 PGND SGND PGOOD Voltages..........................................7V to 0.3V 10 27 BG2 3.3V OUT I I , EAIN1, EAIN2, ATTNIN, TH1, TH2 11 26 BOOST2 I TH2 ATTNOUT Voltages ...................................2.7V to 0.3V 12 25 SW2 EAIN2 Peak Output Current <10m s (TG1, TG2, BG1, BG2) ... 3A 13 24 TG2 SENSE2 INTV Peak Output Current ................................ 50mA + CC 14 23 RUN/SS2 SENSE2 Operating Ambient Temperature Range ATTNOUT 15 22 VIDV CC (Note 2) ...................................................40 C to 85 C ATTNIN 16 21 VID4 VID0 17 20 VID3 Junction Temperature (Note 3)............................. 125 C VID1 18 19 VID2 Storage Temperature Range ................. 65 C to 150 C Lead Temperature (Soldering, 10 sec).................. 300 C G PACKAGE 36-LEAD PLASTIC SSOP T = 125 C, q = 85 C/W JMAX JA Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25 C. V = 15V, V = 5V unless otherwise noted. A IN RUN/SS1, 2 SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loops V Regulated Feedback Voltage (Note 4) I Voltage = 1.2V l 0.792 0.800 0.808 V EAIN1, 2 TH1, 2 at EAIN Pin I Feedback Current (Note 4) 5 50 nA EAIN1, 2 V Reference Voltage Line Regulation V = 3.6V to 30V (Note 4) 0.002 0.02 %/V REFLNREG IN V Output Voltage Load Regulation (Note 4) LOADREG Measured in Servo Loop I Voltage = 1.2V to 0.7V l 0.1 0.5 % TH1, 2 Measured in Servo Loop I Voltage = 1.2V to 2.0V l 0.1 0.5 % TH1, 2 g Transconductance Amplifier g I = 1.2V Sink/Source 5m A (Note 4) 1.3 mmho m1, 2 m TH1, 2 g Transconductance Amplifier GBW I = 1.2V (g Z , No Ext Load) (Note 4) 3 MHz mOL1, 2 TH1, 2 m L I Input DC Supply Current (Note 5) Q Normal Mode EXTV Tied to GND VID Inputs Open Circuit 850 m A CC Standby V = 0V, V > 2V 125 m A RUN/SS1, 2 STBYMD Shutdown V = 0V, V = Open 20 35 m A RUN/SS1, 2 STBYMD V Forced Continuous Threshold l 0.760 0.800 0.840 V FCB I Forced Continuous Current V = 0.85V 0.3 0.18 0.1 m A FCB FCB V Burst Inhibit Threshold Measured at FCB pin 4.3 4.8 V BINHIBIT UVLO Undervoltage Lockout V Ramping Down 3.5 4 V IN 1708f 2 U WWW