LT1123 Low Dropout Regulator Driver FEATURES DESCRIPTIO Extremely Low Dropout The LT 1123 is a 3-pin bipolar device designed to be used Low Cost in conjunction with a discrete PNP power transistor to Fixed 5V Output, Trimmed to 1% form an inexpensive low dropout regulator. The LT1123 700A Quiescent Current consists of a trimmed bandgap reference, error amplifier, 1mV Line Regulation and a driver circuit capable of sinking up to 125mA from 5mV Load Regulation the base of the external PNP pass transistor. The LT1123 Thermal Limit is designed to provide a fixed output voltage of 5V. 4A Output Current Guaranteed The drive pin of the device can pull down to 2V at 125mA Available in a 3-Pin TO-92 Package (1.4V at 10mA). This allows a resistor to be used to reduce the base drive available to the PNP and minimize the power dissipation in the LT1123. The drive current of the LT1123 is folded back as the feedback pin approaches ground to further limit the available drive current under short-circuit conditions. Total quiescent current for the LT1123 is only 700A. The device is available in a low cost TO-92 package. , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIO 5V Low Dropout Regulator Dropout Voltage 0.5 620 SEALED + LEAD ACID MOTOROLA 10F* 0.4 5.4 TO 7.2V MJE1123 20 0.3 DRIVE *REQUIRED IF DEVICE IS LT1123 FB OUTPUT = 5V/4A 0.2 MORE THAN 6 FROM MAIN + FILTER CAPACITOR GND 10F REQUIRED FOR STABILITY 0.1 (LARGER VALUES INCREASE LT1123 TA01 STABILITY) 0 0 1 2 3 4 5 OUTPUT CURRENT (A) LT1123 TA02 1123fb 1 DROPOUT VOLTAGE (V) U ULT1123 ABSOLUTE AXI U RATI GS (Note 1) Drive Pin Voltage (V to Ground) ..................... 30V Storage Temperature Range ................. 65C to 150C DRIVE Feedback Pin Voltage (V to Ground) .................... 30V Lead Temperature (Soldering, 10 sec)................. 300C FB Operating Junction Temperature Range ... 0C to 125C UUW PACKAGE/ORDER I FOR ATIO BOTTOM VIEW FRONT VIEW ORDER PART ORDER PART NUMBER NUMBER 3 FB DRIVE FB GND TAB IS LT1123CST LT1123CZ 2 GND GND 1 DRIVE ST PART MARKING Z PACKAGE ST PACKAGE 3-LEAD TO-92 PLASTIC 3-LEAD PLASTIC SOT-223 1123 AT TAB 20C/W T = 125C, = 220C/W JMAX JA JA Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25C. A PARAMETER CONDITIONS MIN TYP MAX UNITS Feedback Voltage I = 10mA, T = 25C 4.90 5.00 5.10 V DRIVE J 5mA I 100mA DRIVE 3V V 20V 4.80 5.00 5.20 V DRIVE Feedback Pin Bias Current V = 5.00V, 2V V 15V 300 500 A FB DRIVE Drive Current V = 5.20V, 2V V 15V 0.45 1.0 mA FB DRIVE V = 4.80V, V = 3V 125 170 FB DRIVE V = 0.5V, V = 3V, 0C T 100C 25 100 150 FB DRIVE J Drive Pin Saturation Voltage I = 10mA, V = 4.5V 1.4 V DRIVE FB I = 125mA, V = 4.5V 2.0 DRIVE FB Line Regulation 5V < V < 20V 1.0 20 mV DRIVE Load Regulation I = 10 to 100mA 5 50 mV DRIVE Temperature Coefficient of V 0.2 mV/C OUT Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. 1123fb 2 U WWW