INPUT CURRENT (mA) LT1579 300mA Dual Input Smart Battery Backup Regulator DESCRIPTION FEATURES n Maintains Output Regulation with Dual Inputs The LT 1579 is a dual input, single output, low dropout n Dropout Voltage: 0.4V regulator. This device is designed to provide an n Output Current: 300mA uninterruptible output voltage from two independent input n 50A Quiescent Current voltage sources on a priority basis. All of the circuitry n No Protection Diodes Needed needed to switch smoothly and automatically between n Two Low-Battery Comparators inputs is incorporated. n Status Flags Aid Power Management The LT1579 can supply 300mA of output current from n Adjustable Output from 1.5V to 20V either input at a dropout voltage of 0.4V. Quiescent current n Fixed Output Voltages: 3V, 3.3V and 5V is 50A, dropping to 7A in shutdown. Two comparators n 7A Quiescent Current in Shutdown are included to monitor input voltage status. Two addi- n Reverse-Battery Protection tional status flags indicate which input is supplying power n Reverse Current Protection and provide an early warning against loss of output n Remove, Recharge and Replace Batteries Without regulation when both inputs are low. A secondary select Daisy-Chained Control Outputs Loss of Regulation pin is provided so that the user can force the device to switch from the primary input to the secondary input. U Internal protection circuitry includes reverse-battery pro- APPLICATIONS tection, current limiting, thermal limiting and reverse- n Dual Battery Systems current protection. n Battery Backup Systems The device is available in fixed output voltages of 3V, 3.3V n Automatic Power Management for and 5V, and as an adjustable device with a 1.5V reference Battery-Operated Systems voltage. The LT1579 regulators are available in narrow , LTC and LT are registered trademarks of Linear Technology Corporation. 16-lead SO and 16-lead SSOP packages with all features, and in SO-8 with limited features. TYPICAL APPLICATION 5V Dual Battery Supply Automatic Input Switching 12 5V IN1 OUT V = 10V IN2 300mA V 10 + + IN1 SWITCHOVER I = 50mA LOAD 2.7M POINT 1F 4.7F 8 80 LBI1 I I 6 60 IN1 IN2 1M LT1579-5 4 40 SS 2 20 IN2 SHDN + TO 0 0 2.7M LBO1 1F POWER LB02 5.05 LBI2 MANAGEMENT BACKUP 1M 5.00 DROPOUT 4.95 BIASCOMP 02146 8 10 12 14 168 20 GND 0.01F TIME (ms) 1579 TA01 1578 TA02 1 OUTPUT VOLTAGE (V) INPUT VOLTAGE (V) U ULT1579 ABSOLUTE MAXIMUM RATINGS Power Input Pin Voltage ...................................... 20V* BIASCOMP Pin Voltage ...............................6.5V, 0.6V Output Pin Voltage BIASCOMP Pin Current .......................................... 5mA Fixed Devices............................................. 6.5V, 6V Logic Flag Output Voltage............................ 6.5V, 0.6V Adjustable Device ............................................ 20V* Logic Flag Input Current ......................................... 5mA Output Pin Reverse Current .................................... 5mA Output Short-Circuit Duration .......................... Indefinite ADJ Pin Voltage ..............................................2V, 0.6V Storage Temperature Range ................. 65C to 150C ADJ Pin Current ...................................................... 5mA Operating Junction Temperature Range .... 0C to 125C Control Input Pin Voltage ............................ 6.5V, 0.6V Lead Temperature (Soldering, 10 sec).................. 300C Control Input Pin Current ....................................... 5mA *For applications requiring input voltage ratings greater than 20V, consult factory. PACKAGE/ORDER I FOR ATIO ORDER PART ORDER PART TOP VIEW TOP VIEW NUMBER NUMBER GND 1 16 GND GND 1 16 GND LT1579CGN-3 LT1579CGN V 2 15 OUT V 2 15 OUT POWER IN1 POWER IN1 INPUTS INPUTS 3 14 LT1579CGN-3.3 V 3 14 ADJ LT1579CS V BACKUP IN2 IN2 SS 4 13 DROPOUT SS 4 13 BACKUP LOGIC LT1579CGN-5 LOGIC OUTPUTS 5 12 SHDN 5 12 LBO1 SHDN LBO1 CONTROL CONTROL OUTPUTS LT1579CS-3 INPUTS INPUTS LBI1 6 11 LBO2 LBI1 6 11 LBO2 LT1579CS-3.3 LBI2 7 10 LBI2 7 10 BIASCOMP BIASCOMP LT1579CS-5 GND 8 9 GND GND 8 9 GND GN PACKAGE S PACKAGE GN PACKAGE S PACKAGE GN PART MARKING 16-LEAD PLASTIC SSOP 16-LEAD PLASTIC SO 16-LEAD PLASTIC SSOP 16-LEAD PLASTIC SO GN PART MARKING SEE APPLICATION INFORMATION SECTION SEE APPLICATION INFORMATION SECTION 15793 1579 T = 125C, = 95C/W (GN) T = 125C, = 95C/W (GN) JMAX JA JMAX JA 157933 T = 125C, = 68C/W (S) T = 125C, = 68C/W (S) JMAX JA JMAX JA 15795 ORDER PART ORDER PART NUMBER NUMBER TOP VIEW TOP VIEW V 1 8 OUT V 1 8 OUT IN1 POWER IN1 POWER LT1579CS8 LT1579CS8-3 INPUTS INPUTS V 2 7 BACKUP V 2 7 ADJ IN2 IN2 LOGIC LT1579CS8-3.3 CONTROL LOGIC CONTROL OUTPUTS SHDN 3 6 DROPOUT SHDN 3 6 BACKUP INPUT OUTPUT INPUT LT1579CS8-5 GND 4 5 BIASCOMP GND 4 5 BIASCOMP S8 PACKAGE S8 PACKAGE S8 PART MARKING S8 PART MARKING 8-LEAD PLASTIC SO 8-LEAD PLASTIC SO SEE APPLICATION INFORMATION SECTION SEE APPLICATION INFORMATION SECTION 15793 1579 T = 125C, = 90C/W T = 125C, = 90C/W JMAX JA JMAX JA 157933 15795 Consult factory for Industrial and Military grade parts. 2 U WU U WWW