LTC1921 Dual 48V Supply and Fuse Monitor FEATURES DESCRIPTIO n Withstands Transient Voltages Up to 200V/200V The LTC 1921 monitors two independent 48V supplies, n Requires No Precision External Components including their fuses, and drives up to three optoisolators n Independently Monitors Two 48V Supplies for to indicate status, in accordance with standard backplane Undervoltage Faults: 38.5V 1V specifications. Requiring only three noncritical resistors MAX Overvoltage Faults: 70V 1.5V and optoisolators, the LTC1921 replaces multiple voltage MAX n Accurately Detects Undervoltage Fault Recovery: comparators, a voltage reference and several precision 43V 0.5V resistors. MAX n Monitors Two External Fuses The monitor features dual supply overvoltage and under- n Operates from 10V to 80V voltage detection circuits. The preset trip thresholds in- n Tolerates DC Faults to 100V clude overvoltage, undervoltage and undervoltage recovery n Tolerates Accidental Supply Reversal to 100V that are guaranteed over temperature and meet or exceed n Small Footprint: 8-Lead MSOP Package common backplane specifications. Additional built-in cir- n Specified from 40 C to 85 C cuitry detects the condition of supply fuses. Overvoltage U and undervoltage detectors ignore fast supply transients, APPLICATIO S eliminating false detection. The LTC1921 operates from 10V to 80V with a typical power dissipation of less than n Telecom Backplanes or Switch Cards 10mW. n Networking Backplanes or Switch Cards n High Voltage Fuse Monitoring The LTC1921 is available in 8-pin MSOP and SOIC pack- ages. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATIO 48V RETURN 47k 47k 47k LOGIC R1 R2 FUSE GOOD SUPPLY 48V LOAD 100k 100k 3 MOC207 RTN 4 1 V OUT F A SUPPLY A GOOD SUPERVISOR P 8 V B LTC1921 MOC207 2 FUSE A 7 5 LOGIC SUPPLY B GOOD FUSE B OUT A COMMON MOC207 6 OUT B R3 47k D1 MURS320 F1 1/4W SUPPLY A 48V 1921 TA01 D2 MURS320 F2 SUPPLY B 48V 1921f 1 U ULTC1921 ABSOLUTE AXI U RATI GS (Note 1) All voltages referred to RTN Maximum Junction Temperature ......................... 150 C Supply Voltage Operating Temperature Range (Note 3) (V , V , FUSE A, FUSE B) ....................... 100V to 100V A B LTC1921C/LTC1921I .......................... 40 C to 85 C Transient Voltage (V , V , FUSE A, FUSE B) A B Specified Temperature Range (Note 4) (Note 2) ........................................................ 0V to 200V LTC1921C/LTC1921I .......................... 40 C to 85 C Transient Voltage (V , V , FUSE A, FUSE B) A B Storage Temperature Range ................. 65 C to 150 C (Note 2) ...................................................... 0V to 200V Lead Temperature (Soldering, 10 sec).................. 300 C OUT A, OUT B, OUT F Pins ......................... 0.3V to 8V UUW PACKAGE/ORDER I FOR ATIO ORDER PART ORDER PART TOP VIEW NUMBER NUMBER TOP VIEW V 1 8 V A B V 1 8 V A B LTC1921CMS8 FUSE A 2 7 FUSE B LTC1921CS8 FUSE A 2 7 FUSE B RTN 3 6 OUT B LTC1921IMS8 RTN 3 6 OUT B LTC1921IS8 OUT F 4 5 OUT A OUT F OUT A 4 5 MS8 PACKAGE MS8 PART MARKING S8 PART MARKING 8-LEAD PLASTIC MSOP S8 PACKAGE T = 150 C, q = 300 C/W JMAX JA 8-LEAD PLASTIC SO LTZV 1921 T = 150 C, q = 190 C/W JMAX JA LTZU 1921I 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 at T = 25 C. (Note 5) RTN = 0V, V = 48V, V = 48V, FUSE A = 48V, A A B FUSE B = 48V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Power Supply Supply Voltage Range (RTN V , RTN V ) l 10 80 V A B Supply Current (I + I ) 160 250 m A A B l 300 m A Supply Monitor Undervoltage Threshold l 39.5 37.5 V Undervoltage Recovery Threshold l 43.5 42.5 V Overvoltage Threshold l 71.5 68.5 V Overvoltage Threshold Hysteresis l 1 1.6 V Fuse Monitor Input Resistance, FUSE A, FUSE B 11 MW Fuse Comparison Threshold V V , V V V FUSEA A FUSEB B LTC1921C l 0.9 4.5 V LTC1921I l 0.5 4.5 V Output Propagation Delay C = 100pF, Overdrive = 1V 220 m s OUT Output Switch Resistance, OUT F, OUT A, OUT B V = V = 35V, V = V = 0V 25 W A B FUSEA FUSEB I = 10mA l 50 W OUT 1921f 2 U WWW