LTC1504A 500mA Low Voltage Step-Down Synchronous Switching Regulator DESCRIPTION FEATURES n 500mA Output Current at 3.3V Output The LTC 1504A is a self-contained, high efficiency syn- n Up to 92% Peak Efficiency chronous buck switching regulator. It includes a pair of n 100% Maximum Duty Cycle on-chip 1.3W power switches, enabling it to supply up to n Internal Reference Trimmed to 1% 500mA of load current. Efficiency peaks at 92%, minimiz- n Output Can Source or Sink Current ing heat and wasted power. The synchronous buck archi- n Requires as Few as Four External Components tecture allows the output to source or sink current as n Input Voltage Range: 4V to 10V required to keep the output voltage in regulation. 100% n Adjustable Current Limit duty cycle operation minimizes dropout voltage. n Small SO-8 Package The LTC1504A is available in adjustable and fixed 3.3V n 200kHz Switching Frequency Can Typically be output versions. An adjustable current limit circuit pro- Synchronized Up to 500kHz vides protection from overloads. The internal 1% refer- ence combined with a sophisticated voltage feedback loop U provides optimum output voltage accuracy and fast load APPLICATIONS Daisy-Chained Control Outputs transient response. The LTC1504A is specified to operate n Small Portable Digital Systems with input voltages between 4V and 10V. Contact the LTC n Active Termination factory for guaranteed specifications at 2.7V supply. n Auxiliary Output Voltage Supplies The LTC1504A is a pin-compatible, functional upgrade to n Minimum Part Count/Size Switchers the LTC1504. The LTC1504A is available in a plastic SO-8 package. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATION Minimum Part Count 5V to 3.3V Regulator 5V to 3.3V Efficiency 100 NC SHUTDOWN 90 L EXT I SHDN MAX 80 50H 3.3V AT 500mA 5V V SW CC 70 + C IN LTC1504A-3.3 60 22F GND SENSE 50 + C OUT SS COMP 40 47F 30 NC 1000pF C : AVX TPSC226M016R0375 IN C : AVX TAJC476M010 20 OUT L : COILTRONICS CTX50-1P 1504A TA01 EXT 10 0 10 100 500 LOAD CURRENT (mA) 1504 TA02 1 EFFICIENCY (%) U ULTC1504A ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART TOP VIEW Supply Voltage (V to GND)................................... 10V CC NUMBER I 1 8 COMP MAX Peak Output Current (SW) ....................................... 1A V 2 7 SS LTC1504ACS8 CC Input Voltage (All Other Pins) ...... 0.3V to (V + 0.3V) CC LTC1504ACS8-3.3 SW 3 6 SHDN Operating Temperature Range LTC1504AIS8 GND 4 5 FB/SENSE* LTC1504AC ............................................. 0 C to 70 C LTC1504AIS8-3.3 S8 PACKAGE LTC1504AI ......................................... 40 C to 85 C 8-LEAD PLASTIC SO Storage Temperature Range ................. 65 C to 150 C S8 PART MARKING *FB FOR LTC1504A, SENSE FOR LTC1504A-3.3 Lead Temperature (Soldering, 10 sec).................. 300 C T = 125 C, q = 90 C/W JMAX JA 1504A 1504AI 1504A33 04AI33 Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS V = 5V, T = 25 C unless otherwise specified. (Note 2) CC A SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Minimum Supply Voltage (Note 7) l4V CC V Feedback Voltage LTC1504ACS8 l 1.25 1.265 1.28 V FB LTC1504AIS8 l 1.23 1.265 1.29 V D V Feedback Voltage PSRR Figure 1, 4V V 10V, LTC1504ACS8 l 1.1 1.6 % FB CC Figure 1, 4V V 10V, LTC1504AIS8 l 1.1 1.8 % CC V Sense Pin Voltage LTC1504ACS8-3.3 l 3.20 3.30 3.40 V SENSE D V Sense Voltage PSRR Figure 1, 4V V 10V, LTC1504ACS8-3.3 l 1.2 1.8 % SENSE CC Figure 1, 4V V 10V, LTC1504AIS8-3.3 l 1.2 2.0 % CC I Supply Current Figure 1, V = V , I = 0 (Note 4) 3 mA CC SHDN CC OUT Figure 1, V = V , I = 0, V /V = V (Note 4) l 0.3 0.6 mA SHDN CC OUT FB SENSE CC V = 0V l 1.0 20 m A SHDN f Internal Oscillator Frequency Commercial l 150 200 250 kHz OSC Industrial l 130 200 300 kHz R Internal Switch Resistance Commercial l 1.3 2.0 W SW Industrial l 1.3 2.2 W V SHDN Input High Voltage l 2.4 V IH V SHDN Input Low Voltage l 0.8 V IL I SHDN Input Current l 0.1 1 m A IN V Error Amplifier Positive Swing Figure 2 l 4.5 4.95 V OH V Error Amplifier Negative Swing Figure 2 l 0.05 0.5 V OL I , I Error Amplifier Output Current Figure 2 l 50 100 200 m A OH OL g Error Amplifier Transconductance Commercial (Note 5) l 350 600 1100 m mho mV Industrial (Note 5) l 300 600 1200 m mho A Error Amplifier DC Gain (Note 5) l 40 48 dB V g I Amplifier Transconductance (Note 6) 2000 m mho mI LIM I I Sink Current V = V , Commercial l 812 16 m A MAX MAX IMAX CC V = V , Industrial l 812 17 m A IMAX CC 2 U WU U WWW