LTC1875 15m A Quiescent Current 1.5A Monolithic Synchronous Step-Down Regulator FEATURES DESCRIPTIO n High Efficiency: Up to 95% The LTC 1875 is a high efficiency 1.5A monolithic syn- n Low Quiescent Current: Only 15m A with No Load chronous buck regulator using a constant frequency, n 550kHz Constant Frequency Operation current mode architecture. Operating supply current is n 2.65V to 6V Input Voltage Range only 15m A with no load and drops to <1m A in shutdown. n V from 0.8V to V , I to 1.5A The input supply voltage range of 2.65V to 6V makes the OUT IN OUT n True PLL Frequency Locking from 350kHz to 750kHz LTC1875 ideally suited for single Li-Ion battery-powered n Power Good Output Voltage Monitor applications. 100% duty cycle provides low dropout op- n Low Dropout Operation: 100% Duty Cycle eration, extending battery life in portable systems. n Burst Mode or Pulse Skipping Operation The switching frequency is internally set to 550kHz, allow- n Current Mode Operation for Excellent Line and Load ing the use of small surface mount inductors and capaci- Transient Response tors. For noise sensitive applications, the LTC1875 can be n Shutdown Mode Draws <1m A Supply Current externally synchronized from 350kHz to 750kHz. Burst n 2% Output Voltage Accuracy Mode operation is inhibited during synchronization or n Overcurrent and Overtemperature Protected when the SYNC/MODE pin is pulled low. n Available in 16-Lead SSOP Package The internal synchronous switch increases efficiency and U eliminates the need for an external Schottky diode. Low APPLICATIO S output voltages are easily supported with a 0.8V feedback reference voltage. The LTC1875 is available in a 16-lead n Portable Computers SSOP package. n Portable Instruments , LTC and LT are registered trademarks of Linear Technology Corporation. n Wireless Modems Burst Mode is a registered trademark of Linear Technology Corporation. TYPICAL APPLICATIO High Efficiency Step-Down Converter Efficiency vs Output Load Current V IN 2.65V TO 6V 100 C IN V = 3.6V 22F IN 95 SV IN RUN/SS PV IN 90 L1 V = 4.2V 85 IN SYNC/MODE SWP 6.8H V * OUT V = 6V IN LTC1875 80 3.3V PGOOD SWN + 75 C OUT 150k 47F I PGND TH 70 88.7k 47pF 220pF 65 V FB Burst Mode OPERATION SGND 60 V = 3.3V 28.0k OUT L = 6.8H 55 1875 TA01 0.1 1 10 100 1000 C : TAIYO YUDEN CERAMIC JMK325BJ226MM IN OUPUT CURRENT (mA) C : SANYO POSCAP 6TPA47M OUT 1875 TA01a L1: TOKO 646CY-6R8M *V CONNECTED TO V (MINUS SWITCH AND L1 VOLTAGE DROP) FOR 2.65V < V < 3.3V OUT IN IN 1875f 1 EFFICIENCY (%) U ULTC1875 ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) ORDER PART Input Supply Voltage .................................. 0.3V to 7V TOP VIEW NUMBER I , PLL LPF Voltages ............................. 0.3V to 2.7V TH SGND 1 16 PLL LPF RUN/SS, V Voltages ............................... 0.3V to V FB IN RUN/SS 2 15 SYNC/MODE LTC1875EGN SYNC/MODE Voltage ................................. 0.3V to V IN V 3 14 PGOOD FB (V V ) Voltage............................... 0.3V to 7V PVIN SWP I 4 13 SV TH IN V Voltage .............................................. 0.3V to 7V SWN SWP1 5 12 SWP2 P-Channel Switch Source Current (DC) .................... 2A SWN1 6 11 SWN2 GN PART N-Channel Switch Sink Current (DC) ........................ 2A PGND1 7 10 PGND2 MARKING Peak Switching Sink and Source Current ................. 3A PV 8 9 PV IN1 IN2 Operating Ambient Temperature Range 1875 GN PACKAGE 16-LEAD PLASTIC SSOP (Note 2) ............................................. 40 C to 85 C T = 125 C, q = 110 C/ W, q = 40 C/ W JMAX JA JC Junction Temperature (Note 3, 6)........................ 125 C Storage Temperature Range ................ 65 C to 150 C Lead Temperature (Soldering, 10 sec)................. 300 C 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 = 3.6V unless otherwise noted. A IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I Feedback Current (Note 4) l 860 nA VFB V Regulated Output Voltage (Note 4) 0 C T 85 C 0.784 0.80 0.816 V FB A (Note 4) 40 C T 85 C l 0.740 0.80 0.840 V A D V Overvoltage Trip Limit with Respect to V D V = V V l 20 60 110 mV OVL FB OVL OVL FB D V Undervoltage Trip Limit with Respect to V D V = V V l 20 60 110 mV UVL FB UVL FB UVL D V /V Reference Voltage Line Regulation V = 2.65V to 6V (Note 4) 0.05 0.25 %/V FB FB IN V Output Voltage Load Regulation Measured in Servo Loop, V = 0.9V to 1.2V l 0.1 0.6 % LOADREG ITH Measured in Servo Loop, V = 1.6V to 1.2V l 0.1 0.6 % ITH V Input Voltage Range l 2.65 6 V IN I Input DC Bias Current (Note 5) Q Pulse Skipping Mode 2.65V < V < 6V, V = 0V, I = 0A 270 365 m A IN SYNC/MODE OUT Burst Mode Operation V = V , I = 0A 15 22 m A SYNC/MODE IN OUT Shutdown V = 0V, V = 6V 0 1 m A RUN IN f SYNC Capture Range 350 750 kHz SYNC f Oscillator Frequency V 0.7V 495 550 605 kHz OSC FB = 0V 80 kHz V FB I Phase Detector Output Current PLLLPF Sinking Capability f < f l 3 10 20 m A PLLIN OSC Sourcing Capability f > f l 3 10 20 m A PPLIN SOC R R of P-Channel FET I = 100mA, V = 5V 0.28 0.35 W PFET DS(ON) SW IN R R of N-Channel FET I = 100mA, V = 5V 0.35 0.4 W NFET DS(ON) SW IN I Peak Inductor Current V = 0.7V, Duty Cycle < 35%, V = 3V 1.6 2.15 2.75 A PK FB IN I SW Leakage V = 0V, V = 0V or 6V, V = 6V 0.01 2.5 m A LSW RUN SW IN V SYNC/MODE Threshold l 0.2 1.0 1.5 V SYNC/MODE I SYNC/MODE Leakage Current 0.01 1 m A SYNC/MODE 1875f 2 U W U U WWW