LTC1929/LTC1929-PG 2-Phase, High Efficiency, Synchronous Step-Down Switching Regulators FEATURES DESCRIPTIO n 2-Phase Single Output Controller The LTC 1929/LTC1929-PG are 2-phase, single output, n Reduces Required Input Capacitance and Power synchronous step-down current mode switching regula- Supply Induced Noise tor controllers that drive N-channel external power MOSFET n Current Mode Control Ensures Current Sharing stages in a phase-lockable fixed frequency architecture. n Phase-Lockable Fixed Frequency: 150kHz to 300kHz The 2-phase controllers drive their two output stages out n True Remote Sensing Differential Amplifier of phase at frequencies up to 300kHz to minimize the RMS TM n OPTI-LOOP Compensation Improves Transient ripple currents in both input and output capacitors. The Response 2-phase technique effectively multiplies the fundamental n 1% Output Voltage Accuracy frequency by two, improving transient response while n Power Good Output Voltage Monitor (LTC1929-PG) operating each channel at an optimum frequency for n Wide V Range: 4V to 36V Operation efficiency. Thermal design is also simplified. IN n Very Low Dropout Operation: 99% Duty Cycle An internal differential amplifier provides true remote n Adjustable Soft-Start Current Ramping sensing of the regulated supplys positive and negative n Internal Current Foldback output terminals as required by high current applications. n Short-Circuit Shutdown Timer with Defeat Option n The RUN/SS pin provides soft-start and a defeatable, Overvoltage Soft-Latch Eliminates Nuisance Trips n timed, latched short-circuit shutdown to shut down both Available in 28-Lead SSOP Package channels. Internal foldback current limit provides protec- U APPLICATIO S tion for the external synchronous MOSFETs in the event of an output fault. OPTI-LOOP compensation allows the n Desktop Computers transient response to be optimized over a wide range of n Internet/Network Servers output capacitance and ESR values. n Large Memory Arrays , LTC and LT are registered trademarks of Linear Technology Corporation. n DC Power Distribution Systems OPTI-LOOP is a trademark of Linear Technology Corporation. TYPICAL APPLICATIO 10 V IN 5V TO 28V 10F 0.1F 35V CERAMIC V TG1 IN 4 BOOST1 0.1F 0.47F LTC1929 SW1 L1 0.002 RUN/SS 1H BG1 D1 PGND 1000pF + SENSE1 I TH SENSE1 10k 100pF TG2 SGND BOOST2 V OUT 0.47F 1.6V/40A SW2 L2 16k 0.002 1H V BG2 DIFFOUT D2 EAIN INTV CC 10F C OUT + + V SENSE2 OS 1000F 16k + 4V V SENSE2 OS 2 C : T510E108K004AS L1, L2: CEPH149-1ROMC OUT 1929 F01 Figure 1. High Current 2-Phase Step-Down Converter 1 + U ULTC1929/LTC1929-PG UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW ORDER PART Input Supply Voltage (V ).........................36V to 0.3V IN 1 NC NUMBER RUN/SS 28 Topside Driver Voltages (BOOST1,2).........42V to 0.3V + 2 TG1 SENSE1 27 Switch Voltage (SW1, 2) .............................36V to 5 V LTC1929CG 3 SW1 + + SENSE1 26 SENSE1 , SENSE2 , SENSE1 , LTC1929CG-PG 4 BOOST1 EAIN 25 SENSE2 Voltages ........................ (1.1)INTV to 0.3V CC LTC1929IG 5 V PLLFLTR 24 IN + EAIN, V , V , EXTV , INTV , OS OS CC CC 6 BG1 LTC1929IG-PG PLLIN 23 RUN/SS, AMPMD Voltages..........................7V to 0.3V 7 EXTV NC 22 CC Boosted Driver Voltage (BOOST-SW) ..........7V to 0.3V 8 INTV I 21 CC TH PLLFLTR, PLLIN, V Voltages .... INTV to 0.3V DIFFOUT CC 9 PGND SGND 20 I Voltage ................................................2.7V to 0.3V TH 10 BG2 V 19 DIFFOUT Peak Output Current <1m s(TGL1,2, BG1,2)................ 3A 11 BOOST2 V 18 OS INTV RMS Output Current................................ 50mA + 12 SW2 V 17 CC OS 13 TG2 Operating Ambient Temperature Range SENSE2 16 + 14 AMPMD* SENSE2 15 LTC1929C .................................................. 0 C to 85 C LTC1929I .............................................. 40 C to 85 C G PACKAGE 28-LEAD PLASTIC SSOP Junction Temperature (Note 2)............................. 125 C *PGOOD ON LTC1929-PG Storage Temperature Range ................. 65 C to 150 C T = 125 C, q = 95 C/W JMAX JA Lead Temperature (Soldering, 10 sec).................. 300 C Consult factory for Military grade parts. 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/SS SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loop V Regulated Feedback Voltage (Note 3) I Voltage = 1.2V l 0.792 0.800 0.808 V EAIN TH V Maximum Current Sense Threshold V = 5V l 62 75 88 mV SENSEMAX SENSE V = 5V, LTC1929 Only 65 75 85 mV SENSE1, 2 I Feedback Current (Note 3) 5 50 nA INEAIN V Output Voltage Load Regulation (Note 3) LOADREG Measured in Servo Loop I Voltage = 0.7V l 0.05 0.5 % TH Measured in Servo Loop I Voltage = 2V l 0.1 0.5 % TH V Reference Voltage Line Regulation V = 3.6V to 30V (Note 3) 0.002 0.02 %/V REFLNREG IN V Output Overvoltage Threshold Measured at V 0.84 0.86 0.88 V OVL EAIN UVLO Undervoltage Lockout V Ramping Down 3 3.5 4 V IN g Transconductance Amplifier g I = 1.2V Sink/Source 5m A (Note 3) 3 mmho m m TH g Transconductance Amplifier Gain I = 1.2V (g xZ No Ext Load) (Note 3) 1.5 V/mV mOL TH m L I Input DC Supply Current (Note 4) Q Normal Mode EXTV Tied to V V = 5V 470 m A CC OUT OUT Shutdown V = 0V 20 40 m A RUN/SS I Soft-Start Charge Current V = 1.9V 0.5 1.2 m A RUN/SS RUN/SS V RUN/SS Pin ON Threshold V Rising 1.0 1.5 1.9 V RUN/SS RUN/SS V RUN/SS Pin Latchoff Arming V Rising from 3V 4.1 4.5 V RUN/SSLO RUN/SS 2 U WWW