LT1424-5 Isolated Flyback Switching Regulator with 5V Output FEATURES DESCRIPTIO n No Transformer Third Winding or Optoisolator The LT 1424-5 is a monolithic high power switching Required regulator specifically designed for the isolated flyback n Designed for Use with 1:1 Ratio Transformers topology. No third winding or optoisolator is required n Fixed, Application Specific 5V Output Voltage the integrated circuit senses the isolated output voltage n Regulation Maintained Well into Discontinuous directly from the primary side flyback waveform. A high Mode (Light Load) current, high efficiency switch is included on the die along n Load Compensation Provides Excellent with all oscillator, control and protection circuitry. Load Regulation The LT1424-5 operates with input supply voltages from n Available in 8-Pin PDIP and SO Packages 3V to 20V and draws only 7mA quiescent current. It can n Operating Frequency: 285kHz deliver up to 400mA at 5V with no external power devices. By utilizing current mode switching techniques, it pro- U vides excellent AC and DC line regulation. APPLICATIO S The LT1424-5 has a number of features not found on other n Isolated Communication Supplies switching regulator ICs. Its unique control circuitry can n Industrial Automation maintain regulation well into discontinuous mode. Load n Instrumentation Systems compensation circuitry allows for improved load regula- tion. An externally activated shutdown mode reduces total supply current to 20m A typical for standby operation. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATIO 5V Output Isolated Power Supply Load Regulation 5.25 330pF 47W ISOLATION BARRIER MBRS130LT3 T1 5V 5V 400mA + C1 100m F 0.1m F 6 3 4 1N5248 47W 5.00 10V + C2 1 8 SHDN R 1.8k CCOMP 100m F 2 7 330pF 10V V V C IN MBR0540T4 7 LT1424-5 1 2 3 6 OUT SYNC V SW 1000pF COM 4 5 1424-5 TA01 SGND PGND 0.1m F C1, C2: AVX TPS D107M010R0080 INPUT 4.75 T1: DALE LPE-4841-A307 COM 0 100 200 300 400 OUTPUT CURRENT (mA) 1424-5 TA02 sn14245 14245fs 1 OUTPUT VOLTAGE (V) U ULT1424-5 ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) ORDER PART Supply Voltage (V ) ................................................ 20V IN TOP VIEW NUMBER Switch Voltage (V ) .............................................. 35V SW SHDN 1 8 R CCOMP SHDN, SYNC Pin Voltage........................................... 7V LT1424CN8-5 V 2 7 V C IN Operating Junction Temperature Range LT1424CS8-5 SYNC 3 6 V SW Commercial .......................................... 0 C to 125 C LT1424IN8-5 SGND 4 5 PGND Industrial ......................................... 40 C to 125 C LT1424IS8-5 N8 PACKAGE S8 PACKAGE Storage Temperature Range ................. 65 C to 150 C 8-LEAD PDIP 8-LEAD PLASTIC SO S8 PART MARKING Lead Temperature (Soldering, 10 sec).................. 300 C T = 145 C, q = 130 C/ W (N) JMAX JA 14245 T = 145 C, q = 110 C/ W (S) JMAX JA 1424I5 Consult factory for Military grade parts. The l denotes the specifications which apply over the full operating ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T = 25 C. V = 5V, V Open, V = 1.4V, unless otherwise specified. A IN SW C SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Power Supply V Minimum Operating Voltage l 2.8 3.1 V IN(MIN) I Supply Current l 7.0 9.5 mA CC Shutdown Mode Supply Current l 15 40 m A SHDN Pin Threshold l 0.3 0.9 1.3 V Feedback Amplifier V Reference Voltage Measured at V Pin (Note 2) 5.23 5.30 5.37 V REF SW l 5.18 5.30 5.42 V g Feedback Amplifier Transconductance D I = 10m A (Note 3) l 400 1000 1600 m mho m C I , I Feedback Amplifier Source or Sink Current l 30 50 80 m A SOURCE SINK V Feedback Amplifier Clamp Voltage 1.9 V CL Reference Voltage/Current Line Regulation 5V V 18V l 0.01 0.04 %/V IN Voltage Gain (Note 4) 500 V/V Output Switch BV Output Switch Breakdown Voltage I = 5mA l 35 50 V C V(V ) Output Switch ON Voltage I = 1A l 0.55 0.85 V SW SW I Switch Current Limit Duty Cycle = 50%, 0 C T 125 C l 1.35 1.6 1.95 A LIM J Duty Cycle = 50%, 40 C T 125 C l 1.20 1.6 1.95 A J Duty Cycle = 80% 1.3 A Current Amplifier Control Pin Threshold Duty Cycle = Minimum 0.95 1.2 1.3 V l 0.85 1.2 1.4 V Control Voltage to Switch Transconductance 2 A/V sn14245 14245fs 2 U W U W U WW