LTC1921 Dual –48V Supply and Fuse Monitor U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC®1921 monitors two independent – 48V supplies, including their fuses, and drives up to three optoisolators to indicate status, in accordance with standard backplane specifications. Requiring only three noncritical resistors and optoisolators, the LTC1921 replaces multiple voltage comparators, a voltage reference and several precision resistors. Withstands Transient Voltages Up to 200V/–200V Requires No Precision External Components Independently Monitors Two –48V Supplies for – Undervoltage Faults: –38.5V ±1VMAX – Overvoltage Faults: –70V ±1.5VMAX Accurately Detects Undervoltage Fault Recovery: –43V ±0.5VMAX Monitors Two External Fuses Operates from –10V to –80V Tolerates DC Faults to –100V Tolerates Accidental Supply Reversal to 100V Small Footprint: 8-Lead MSOP Package Specified from – 40°C to 85°C The monitor features dual supply overvoltage and undervoltage detection circuits. The preset trip thresholds include overvoltage, undervoltage and undervoltage recovery that are guaranteed over temperature and meet or exceed common backplane specifications. Additional built-in circuitry detects the condition of supply fuses. Overvoltage and undervoltage detectors ignore fast supply transients, eliminating false detection. The LTC1921 operates from –10V to –80V with a typical power dissipation of less than 10mW. U APPLICATIO S ■ ■ ■ Telecom Backplanes or Switch Cards Networking Backplanes or Switch Cards High Voltage Fuse Monitoring The LTC1921 is available in 8-pin MSOP and SOIC packages. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO – 48V RETURN R1 100k 47k R2 100k 47k 47k FUSE GOOD LOGIC SUPPLY –48V LOAD 3 MOC207 RTN 1 8 VA OUT F 4 SUPPLY A GOOD SUPERVISOR µP VB LTC1921 2 7 FUSE B OUT A OUT B SUPPLY A –48V SUPPLY B –48V MOC207 FUSE A F1 D1 MURS320 F2 D2 MURS320 5 6 SUPPLY B GOOD LOGIC COMMON MOC207 R3 47k 1/4W 1921 TA01 1921f 1 LTC1921 W W U W ABSOLUTE AXI U RATI GS (Note 1) All voltages referred to RTN Supply Voltage (VA, VB, FUSE A, FUSE B) ....................... 100V to –100V Transient Voltage (VA, VB, FUSE A, FUSE B) (Note 2) ........................................................ 0V to 200V Transient Voltage (VA, VB, FUSE A, FUSE B) (Note 2) ...................................................... 0V to –200V OUT A, OUT B, OUT F Pins ......................... 0.3V to – 8V Maximum Junction Temperature ......................... 150°C Operating Temperature Range (Note 3) LTC1921C/LTC1921I .......................... – 40°C to 85°C Specified Temperature Range (Note 4) LTC1921C/LTC1921I .......................... – 40°C to 85°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C U W U PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER TOP VIEW VA FUSE A RTN OUT F 1 2 3 4 8 7 6 5 VB FUSE B OUT B OUT A MS8 PACKAGE 8-LEAD PLASTIC MSOP LTC1921CMS8 LTC1921IMS8 MS8 PART MARKING TJMAX = 150°C, θJA = 300°C/W LTZV LTZU ORDER PART NUMBER TOP VIEW VA 1 8 VB FUSE A 2 7 FUSE B RTN 3 6 OUT B OUT F 4 5 OUT A LTC1921CS8 LTC1921IS8 S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150°C, θJA = 190°C/W 1921 1921I Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 5) RTN = 0V, VA = –48V, VB = –48V, FUSE A = –48V, FUSE B = –48V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Power Supply Supply Voltage Range (RTN – VA, RTN –␣ VB) ● 10 Supply Current (IA + IB) –160 ● 80 V –250 –300 µA µA V Supply Monitor Undervoltage Threshold ● –39.5 –37.5 Undervoltage Recovery Threshold ● –43.5 –42.5 V Overvoltage Threshold ● –71.5 –68.5 V Overvoltage Threshold Hysteresis ● 1 1.6 V Fuse Monitor Input Resistance, FUSE A, FUSE B 11 MΩ Fuse Comparison Threshold |VFUSEA – VA|, |VFUSEB – VB| LTC1921C LTC1921I ● ● 0.9 0.5 4.5 4.5 V V V Output Propagation Delay COUT = 100pF, Overdrive = 1V Output Switch Resistance, OUT F, OUT A, OUT B VA = VB = –35V, VFUSEA = VFUSEB = 0V IOUT = 10mA µs 220 25 ● 50 Ω Ω 1921f 2 LTC1921 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 5) RTN = 0V, VA = –48V, VB = –48V, FUSE A = –48V, FUSE B = –48V, unless otherwise noted. PARAMETER CONDITIONS MIN Output Switch Off Leakage TYP MAX UNITS 500 Output Switch Resistance in Undervoltage Lockout, OUT F, OUT A, OUT B VA = VB = –10V, IOUT = 10mA VA = –10V, VB = 0V, IOUT = 10mA VA = 0V, VB = –10V, IOUT = 10mA Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Transient voltage for less than 10µs. This parameter is not 100% tested. Voltage should not exceed 200V between any two pins. Note 3: The LTC1921C and LTC1921I are guaranteed functional over the operating temperature range of –40°C to 85°C. pA Ω Ω Ω 60 80 80 ● ● ● Note 4: The LTC1921C is guaranteed to meet specified performance from 0°C to 70°C. The LTC1921C is designed, characterized and expected to meet specified performance from –40°C to 85°C but is not tested or QA sampled at these temperatures. The LTC1921I is guaranteed to meet specified performance from –40 t0 85°C. Note 5: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to RTN unless otherwise specified. U W TYPICAL PERFOR A CE CHARACTERISTICS Supply Current vs Supply Voltage IA + IB 160 300 140 250 200 150 100 50 0 10 20 30 40 50 60 70 80 90 100 SUPPLY VOLTAGE (V) 120 100 IA, IB 80 60 40 VA = –48V VB = –48V 20 VFUSEA = –48V VFUSEB = –48V 0 30 50 –50 –30 –10 10 TEMPERATURE (°C) 1921 G01 –37.9 –38.1 –38.3 –38.5 –38.7 –38.9 –39.1 –39.3 90 70 –39.5 –50 Overvoltage Threshold vs Temperature –68.5 1.45 –43.0 –43.1 –43.2 –43.3 –69.0 –69.5 –70.0 –70.5 –71.0 –43.4 –71.5 –43.5 –50 –72.0 –50 –30 –10 10 30 50 TEMPERATURE (°C) 70 90 1921 G04 OVERVOLTAGE HYSTERESIS (V) 1.50 OVERVOLTAGE THRESHOLD (V) –68.0 –42.9 70 90 Overvoltage Hysteresis vs Temperature –42.6 –42.8 –10 10 30 50 TEMPERATURE (°C) 1921 G04 –42.5 –42.7 –30 1921 G02 Undervoltage Recovery Threshold vs Temperature UNDERVOLTAGE RECOVERY THRESHOLD (V) –37.7 UNDERVOLTAGE THRESHOLD (V) 350 0 –37.5 180 VA = VB = VFUSEA = VFUSEB SUPPLY CURRENT (µA) SUPPLY CURRENT (µA) 400 Undervoltage Threshold vs Temperature Supply Current vs Temperature 1.40 1.35 1.30 1.25 1.20 1.15 1.10 1.05 –30 –10 10 30 50 TEMPERATURE (°C) 70 90 1921 G05 1.00 –50 –30 –10 10 30 50 TEMPERATURE (°C) 70 90 1921 G06 1921f 3 LTC1921 U W TYPICAL PERFOR A CE CHARACTERISTICS Fuse Window Positive Threshold vs Temperature Fuse Window Negative Threshold vs Temperature 2.3 2.1 1.9 1.7 1.5 –50 –30 –10 10 30 50 TEMPERATURE (°C) 70 90 –2.0 –2.2 25 OUT A (OUT F = 0V) –2.4 –2.6 –2.8 –3.2 –50 –30 –10 10 30 50 TEMPERATURE (°C) 70 OUT F, OUT B (OUT A = 0V) 15 10 90 VA = –35V VB = –35V I = –10mA 0 –50 –30 30 50 –10 10 TEMPERATURE (°C) 70 90 1921 G09 1921 G08 Undervoltage Response Time Overvoltage Response Time 10000 TA = 25°C RESPONSE TIME (µs) RESPONSE TIME (µs) TA = 25°C 1000 1000 100 4.5 20 5 –3.0 1921 G07 10000 Output RDS(ON) vs Temperature 30 OUTPUT RDS(ON) (Ω) 2.5 FUSE NEGATIVE THRESHOLD (V) FUSE POSITIVE THRESHOLD (V) 2.7 4.6 4.7 4.8 4.9 5.0 5.1 SUPPLY STEP FROM UNDERVOLTAGE RECOVERY THRESHOLD (V) 5.2 1921 G10 100 1.3 1.7 1.5 2.1 2.3 1.9 SUPPLY STEP FROM OVERVOLTAGE RECOVERY THRESHOLD (V) 2.5 1921 G11 1921f 4 LTC1921 U U U PI FU CTIO S VA (Pin 1): Supply to be Monitored. The voltage at this pin is compared to the valid supply voltage window and the result is output at OUT A (Pin 5). Supply current is drawn from VA as well as from VB (Pin 8). FUSE A (Pin 2): This pin monitors the state of a fuse by comparing the voltage at this pin to the voltage at VA (Pin␣ 1). The result is output at OUT F (Pin 4). RTN (Pin 3): Supply Return Reference. This pin must be at an equal or higher potential than the other pins and should be wired to the – 48V return. OUT F (Pin 4): This pin indicates the state of the external fuses by ORing the comparisons made to the FUSE A and FUSE B pins. If VFUSEA ≅ VA (VFUSEA is within the specified window around VA) and VFUSEB ≅ VB, then OUT F will exhibit a high internal impedance to the RTN pin. If VFUSEA ≠ VA or VFUSEB ≠ VB, then OUT F is shorted internally to the RTN pin and can shunt enough current to turn off an optoisolator or LED wired between these pins. OUT F should be clamped externally so that it cannot be driven more than 8V below RTN. This is done automatically by the optoisolator or LED diodes shown in the application circuits. OUT A (Pin 5): Indicates the state of VA. If VA is within the specified voltage window (neither undervoltage nor overvoltage), OUT A will exhibit a high internal impedance to the OUT F pin. If VA is outside the specified overvoltage or undervoltage limits, then OUT A is shorted internally to the OUT F pin and can shunt enough current to turn off an optoisolator or LED wired between these pins. OUT A should be clamped externally so that it cannot be driven more than 8V below RTN. This is done automatically by the optoisolator or LED diodes shown in the application circuits. OUT B (Pin 6): Indicates the state of VB. If VB is within the specified voltage window (neither undervoltage nor overvoltage), OUT B will exhibit a high internal impedance to the OUT A pin. If VB is outside the specified overvoltage or undervoltage limits, then OUT B is shorted internally to the OUT A pin and can shunt enough current to turn off an optoisolator or LED wired between these pins. OUT B should be clamped externally so that it cannot be driven more than 8V below RTN. This is done automatically by the optoisolator or LED diodes shown in the application circuits. FUSE B (Pin 7): This pin monitors the state of a fuse by comparing the voltage at this pin to the voltage at VB (Pin␣ 8). The result is output at OUT F (Pin 4). VB (Pin 8): Supply to be Monitored. The voltage at this pin is compared to the valid supply voltage window and the result is output at OUT B (Pin 6). Supply current is drawn from VB as well as from VA (Pin 1). 1921f 5 LTC1921 W BLOCK DIAGRA RTN 3 REGULATOR + – REF + – + – 4 OUT F + – + – + – 5 OUT A + – + – 1 8 VA VB 2 6 OUT B 7 1921 BD FUSE A FUSE B 1921f 6 LTC1921 U W U U APPLICATIO S I FOR ATIO Supply Monitoring The LTC1921 is designed to monitor dual – 48V power supplies. This is accomplished with precision window comparators and an accurate bandgap reference, as well as internal level shifting circuitry. The comparators are preset to standard voltage thresholds in order to accurately verify the status of each supply. These comparators also include precision hysteresis which allows accurate determination of voltage recovery. Status of the two supplies are indicated by the OUT A and OUT B pins. The supply window comparison works in a straightforward way (Figure 1). As long as each supply magnitude remains in the valid supply window (38.5V to 70V), the outputs will indicate a valid supply condition by exhibiting a high internal impedance. If a supply magnitude falls below the undervoltage threshold (38.5V), then its respective output will short internally (OUT A to OUT F or OUT B to OUT A) until that supply reaches the undervoltage recovery threshold, which is preset to –43V. At this time, the output will return to a high impedance state. If a supply magnitude rises above the overvoltage threshold (70V), then its respective output will short internally, just as with an undervoltage condition. The output will return to its nominal state when the supply overcomes the overvoltage hysteresis. Monitoring for each supply, VA and VB, is independent of the condition of the other supply. The LTC1921 can be powered equally from either VA, VB or both supplies. This allows the LTC1921 to provide correct information at its outputs as long as at least one supply is functional, whether or not the fuses are intact (see Figure 2). Undervoltage Lockout If both supplies are active and their magnitude falls below 13V, or if only one supply is active and its magnitude falls below 19V, the LTC1921 will lock all outputs into a fault condition by closing all three output switches. This state will be held until one supply magnitude is driven above 19V or both are driven above 13V. Fuse Monitoring In addition to monitoring two supplies, the LTC1921 can monitor the condition of two supply fuses via the FUSE A (Pin 2) and FUSE B (Pin 7) inputs. Fuse monitoring is accomplished by comparing the potential at FUSE A to the potential at supply VA and comparing the potential at FUSE␣ B to the potential at supply VB. If VFUSEA is within the specified voltage window around VA and VFUSEB is within the specified voltage window around VB, the OUT F pin will indicate that the fuses are intact by exhibiting a high TIME 0 SUPPLY VOLTAGE (V) NOMINAL VOLTAGE UNDERVOLTAGE FAULT –38.5 –43 –48 UNDERVOLTAGE RECOVERY –68.7 –70 OVERVOLTAGE FAULT OVERVOLTAGE RECOVERY 1921 F01 Figure 1. Supply Comparison 1921f 7 LTC1921 U W U U APPLICATIO S I FOR ATIO internal impedance to the return (RTN) pin. The application must be designed so that an open fuse condition will force the fuse input (FUSE A or FUSE B) to be outside the specified window around the supply pins, such as with a weak pull-up resistor to RTN, so that the LTC1921 can properly indicate a fault at OUT F. If supply diodes that exhibit high reverse leakage, such as Schottky diodes, are used, then the values of the pull-up resistors must be reduced accordingly. The FUSE A and FUSE B pins may also be used in conjunction with VA and VB for simple window comparison, provided that one of the circuit nodes to be compared can provide the small amount of supply current required to bias the IC. The LTC1921 is ideally suited for comparison functions in a circuit where only high supply voltages are available. Output Pins The output pins in the LTC1921 are designed to shunt external optoisolator diodes or LEDs during a supply or fuse fault condition. Up to three diodes may be used in series, one for each output. In this configuration (Figure␣ 2), a diode connected between OUT F and RTN will indicate the condition of both fuses. A diode connected between OUT A and OUT F will indicate the condition of supply A (VA) and a diode connected between OUT B and OUT A will indicate the condition of supply B (VB). A resistor connected from OUT B to the negative supply is required to bias the diodes. The LTC1921 is designed to allow the current from this resistor to flow through the diodes during normal supply conditions and intact fuses, and will shunt this current away from the proper diodes during a fault condition. These diodes will further clamp the output pin potentials to RTN in order to keep the outputs within rated voltages. If LEDs are used instead of optoisolators, they should be green since they will be lit when the supplies are within the proper voltage range. The LTC1921 may be connected in such a way as to OR various outputs to allow the use of fewer optocouplers or LEDs (Figures 3a and 3b). One and two diode circuits are shown. 47k 5V FUSE STATUS –48V RETURN R1 100k R2 100k MOC207 3 RTN 1 8 OUT F VA 5V SUPPLY A STATUS VB LTC1921 2 47k 4 FUSE B OUT A OUT B SUPPLY A –48V SUPPLY B –48V F1 D1 F2 D2 5V SUPPLY B STATUS 5 6 MOC207 R3 47k 1/4W 1921 F02 SUPPLY A STATUS 0 0 1 1 SUPPLY B STATUS 0 1 0 1 OK: WITHIN SPECIFICATION OV: OVERVOLTAGE UV: UNDERVOLTAGE MOC207 FUSE A 47k 7 VA VB OK OK OK UV OR OV UV OR OV OK UV OR OV UV OR OV –48V OUT VFUSE A = VA = VA ≠ VA ≠ VA VFUSE B = VB ≠ VB = VB ≠ VB FUSE STATUS 0 1 1 1* 0: LED/PHOTODIODE ON 1: LED/PHOTODIODE OFF *IF BOTH FUSES (F1 AND F2) ARE OPEN, ALL STATUS OUTPUTS WILL BE HIGH SINCE R3 WILL NOT BE POWERED = LOGIC COMMON Figure 2. 1921f 8 LTC1921 U W U U APPLICATIO S I FOR ATIO 47k 5V FUSE STATUS –48V RETURN R1 100k R2 100k 3 MOCD207 RTN 1 8 OUT F VA 4 VA VB OK OK OK UV OR OV UV OR OV OK UV OR OV UV OR OV 47k 5V SUPPLY STATUS OK: WITHIN SPECIFICATION OV: OVERVOLTAGE UV: UNDERVOLTAGE VB LTC1921 2 7 FUSE A FUSE B OUT A OUT B VFUSE A = VA = VA ≠ VA ≠ VA 5 R3 47k 1/4W 6 VFUSE B = VB ≠ VB = VB ≠ VB FUSE STATUS 0 1 1 1* 0: LED/PHOTODIODE ON 1: LED/PHOTODIODE OFF *IF BOTH FUSES (F1 AND F2) ARE OPEN, ALL STATUS OUTPUTS WILL BE HIGH SINCE R3 WILL NOT BE POWERED F1 SUPPLY A –48V SUPPLY STATUS 0 1 1 1 –48V OUT F2 SUPPLY B –48V = LOGIC COMMON 1921 F03a Figure 3a. Combined Supply Status 47k 5V STATUS –48V RETURN R1 100k R2 100k MOC207 3 RTN 1 8 VA OUT F 4 LOGIC COMMON VB LTC1921 2 7 VFUSE A VFUSE B VA VB STATUS OK OK 0 = VA = VB FUSE A FUSE B OUT A OUT B 1 6 R3 47k 1/4W SUPPLY A –48V SUPPLY B –48V ALL OTHER CONDITIONS OK: WITHIN SPECIFICATION 0: LED/PHOTODIODE ON 1: LED/PHOTODIODE OFF 5 –48V OUT 1921 F03b Figure 3b. All Outputs Combined 1921f 9 10 7 2 8 1 R10 10k 1W OUT F FUSE B OUT B OUT A LTC1921 RTN FUSE A VB VA 3 6 5 4 Hot Swap is a trademark of Linear Technology Corporation 3A 3A R9 10k 1W R11 47k 1/4W MOC207 MOC207 MOC207 * R6 10k 1% R5 6.49k 1% R4 549k 1% 2 3 4 VEE OV UV C8 100nF 100V = DIODES INC. B3100 * DIODES INC. SMAT70A SUPPLY B STATUS SUPPLY A STATUS FUSE STATUS R1 0.02Ω 5% 5 SENSE GATE DRAIN LT4250L PWRGD 8 VDD R8 100Ω 6 7 1 C1 470nF 25V C2 15nF 100V Q1 IRF530 R2 10Ω 5% R3 1k 5% 1N4003 C3 0.1µF 100V VOUT+ VOUT– CASE VIN– LUCENT FLTR100V10 VIN+ MOC207 R7 51k 5% C4 0.1µF 100V + C5 100µF 100V C6 0.1µF 100V 4 2 1 VIN– VOUT+ VOUT– SENSE – TRIM SENSE + 3 CASE ON/OFF VIN+ LUCENT JW050A1-E 1921 TA02 5 6 7 8 9 + U C7 100µF 16V 5V TYPICAL APPLICATIO S – 48V B – 48V A – 48V RTN Complete –48V Telecom Supply Monitor and Hot SwapTM Controller LTC1921 1921f LTC1921 U PACKAGE DESCRIPTIO MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 3.2 – 3.45 (.126 – .136) 0.42 ± 0.04 (.0165 ± .0015) TYP 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.65 (.0256) BSC 8 0.52 (.206) REF 7 6 5 RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 3.00 ± 0.102 (.118 ± .004) NOTE 4 4.90 ± 0.15 (1.93 ± .006) DETAIL “A” 0° – 6° TYP GAUGE PLANE 1 0.53 ± 0.015 (.021 ± .006) 4 2 3 1.10 (.043) MAX DETAIL “A” 0.86 (.034) REF 0.18 (.077) SEATING PLANE 0.22 – 0.38 (.009 – .015) TYP 0.13 ± 0.076 (.005 ± .003) 0.65 (.0256) BSC MSOP (MS8) 0802 NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 8 7 6 5 N N .245 MIN .160 ±.005 1 .030 ±.005 TYP .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) 2 3 N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) .008 – .010 (0.203 – 0.254) .053 – .069 (1.346 – 1.752) 0°– 8° TYP .016 – .050 (0.406 – 1.270) NOTE: 1. DIMENSIONS IN 1 .014 – .019 (0.355 – 0.483) TYP INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) 2 3 4 .004 – .010 (0.101 – 0.254) .050 (1.270) BSC SO8 0502 1921f Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 11 LTC1921 U TYPICAL APPLICATIO S Single 48V Supply Monitor Single –48V Supply Monitor V+ LOGIC V+ LOGIC V+ 3 3 47k RTN 1 8 VA OUT F 47k RTN 4 1 V– SUPPLY GOOD LTC1921 8 VB VA 4 OUT F SUPPLY GOOD LTC1921 VB MOC207 2 7 FUSE A OUT A FUSE B OUT B MOC207 5 2 LOGIC COMMON 6 7 FUSE A 5 OUT A FUSE B LOGIC COMMON 6 OUT B 47k 1/4W 47k 1/4W 1921 TA04 1921 TA06 Voltage and Fuse Monitor with LED Outputs –48V RETURN R1 100k D3 GREEN R2 100k 3 RTN 1 8 VA OUT F 4 D4 GREEN VB LTC1921 2 7 FUSE A FUSE B OUT A 5 D5 GREEN OUT B F1 SUPPLY A –48V 6 R3 5.1k 2W D1 –48V OUT F2 SUPPLY B –48V D2 1921 TA03 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT4250 –48V Hot Swap Controller in SO-8 Package Active Current Limiting, Supplies from –20V to –80V LTC4251 –48V Hot Swap Controller in SOT-23 Package Fast Active Current Limiting, Supplies from –15V (Floating) LTC4252 –48V Hot Swap Controller in MSOP Package Fast Active Current Limiting, Floating Supply, PWRGD Output LTC4253 –48V Hot Swap Controller with Sequencer Similar to LTC4252, Sequences Three DC/DC Converters 1921f 12 Linear Technology Corporation LT/TP 0902 2K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2002