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LTC1921 Dual -48V Supply and Fuse Monitor
FEATURES
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DESCRIPTIO
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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 - 40C to 85C
The LTC(R)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. 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. The LTC1921 is available in 8-pin MSOP and SOIC packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
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Telecom Backplanes or Switch Cards Networking Backplanes or Switch Cards High Voltage Fuse Monitoring
TYPICAL APPLICATIO
- 48V RETURN R1 100k
R2 100k 3 RTN 1 8 2 7 VA VB LTC1921 FUSE A FUSE B OUT A 5 MOC207 OUT F MOC207 4
47k
47k
47k FUSE GOOD
SUPPLY A GOOD SUPERVISOR P
SUPPLY B GOOD
OUT B F1 F2 D1 MURS320 D2 MURS320
6
MOC207 R3 47k 1/4W
1921 TA01
SUPPLY A -48V SUPPLY B -48V
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LOGIC SUPPLY -48V LOAD LOGIC COMMON
1921f
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1
LTC1921
ABSOLUTE
AXI U RATI GS
Maximum Junction Temperature ......................... 150C Operating Temperature Range (Note 3) LTC1921C/LTC1921I .......................... - 40C to 85C Specified Temperature Range (Note 4) LTC1921C/LTC1921I .......................... - 40C to 85C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
(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
PACKAGE/ORDER I FOR ATIO
TOP VIEW VA FUSE A RTN OUT F 1 2 3 4 8 7 6 5 VB FUSE B OUT B OUT A
ORDER PART NUMBER
VA 1
LTC1921CMS8 LTC1921IMS8 MS8 PART MARKING LTZV LTZU
MS8 PACKAGE 8-LEAD PLASTIC MSOP
TJMAX = 150C, JA = 300C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. (Note 5) RTN = 0V, VA = -48V, VB = -48V, FUSE A = -48V, FUSE B = -48V, unless otherwise noted.
PARAMETER Power Supply Supply Voltage Range (RTN - VA, RTN - VB) Supply Current (IA + IB)
q q
ELECTRICAL CHARACTERISTICS
CONDITIONS
Supply Monitor Undervoltage Threshold Undervoltage Recovery Threshold Overvoltage Threshold Overvoltage Threshold Hysteresis Fuse Monitor Input Resistance, FUSE A, FUSE B Fuse Comparison Threshold |VFUSEA - VA|, |VFUSEB - VB| LTC1921C LTC1921I Output Propagation Delay Output Switch Resistance, OUT F, OUT A, OUT B COUT = 100pF, Overdrive = 1V VA = VB = -35V, VFUSEA = VFUSEB = 0V IOUT = 10mA
q q q q q q q
2
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TOP VIEW 8 7 6 5 VB FUSE B OUT B OUT A
ORDER PART NUMBER LTC1921CS8 LTC1921IS8 S8 PART MARKING 1921 1921I
FUSE A 2 RTN 3 OUT F 4
S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150C, JA = 190C/W
MIN 10
TYP
MAX 80
UNITS V A A V V V V M
-160
-250 -300 -37.5 -42.5 -68.5 1.6
-39.5 -43.5 -71.5 1 11 0.9 0.5 220 25
4.5 4.5
V V V s
50

1921f
LTC1921
ELECTRICAL CHARACTERISTICS
PARAMETER Output Switch Off Leakage 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
q q q
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. (Note 5) RTN = 0V, VA = -48V, VB = -48V, FUSE A = -48V, FUSE B = -48V, unless otherwise noted.
CONDITIONS MIN TYP 500 60 80 80 MAX UNITS pA
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 10s. 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 -40C to 85C.
Note 4: The LTC1921C is guaranteed to meet specified performance from 0C to 70C. The LTC1921C is designed, characterized and expected to meet specified performance from -40C to 85C but is not tested or QA sampled at these temperatures. The LTC1921I is guaranteed to meet specified performance from -40 t0 85C. 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.
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Supply Voltage
400 350 VA = VB = VFUSEA = VFUSEB 180 IA + IB
UNDERVOLTAGE THRESHOLD (V)
SUPPLY CURRENT (A)
SUPPLY CURRENT (A)
300 250 200 150 100 50 0 0 10 20 30 40 50 60 70 80 90 100 SUPPLY VOLTAGE (V)
1921 G01
Undervoltage Recovery Threshold vs Temperature
UNDERVOLTAGE RECOVERY THRESHOLD (V)
-42.5 -42.6 -42.7 -42.8 -42.9 -43.0 -43.1 -43.2 -43.3 -43.4 -43.5 -50 -30 -10 10 30 50 TEMPERATURE (C) 70 90
OVERVOLTAGE HYSTERESIS (V)
OVERVOLTAGE THRESHOLD (V)
UW
Supply Current vs Temperature
-37.5 -37.7 -37.9 -38.1 -38.3 -38.5 -38.7 -38.9 -39.1 -39.3
70 90 160 140 120 100 80 60 40 VA = -48V VB = -48V 20 VFUSEA = -48V VFUSEB = -48V 0 30 50 -50 -30 -10 10 TEMPERATURE (C) IA, IB
Undervoltage Threshold vs Temperature
-39.5 -50
-30
-10 10 30 50 TEMPERATURE (C)
70
90
1921 G02
1921 G04
Overvoltage Threshold vs Temperature
-68.0 -68.5 -69.0 -69.5 -70.0 -70.5 -71.0 -71.5 -72.0 -50 -30 -10 10 30 50 TEMPERATURE (C) 70 90 1.50 1.45 1.40 1.35 1.30 1.25 1.20 1.15 1.10 1.05
Overvoltage Hysteresis vs Temperature
1.00 -50
-30
-10 10 30 50 TEMPERATURE (C)
70
90
1921 G04
1921 G05
1921 G06
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3
LTC1921 TYPICAL PERFOR A CE CHARACTERISTICS
Fuse Window Positive Threshold vs Temperature
2.7 FUSE POSITIVE THRESHOLD (V) FUSE NEGATIVE THRESHOLD (V) 2.5 2.3 2.1 1.9 1.7 1.5 -50 -2.0 -2.2
OUTPUT RDS(ON) ()
-30
-10 10 30 50 TEMPERATURE (C)
Undervoltage Response Time
10000 TA = 25C
10000
RESPONSE TIME (s)
1000
RESPONSE TIME (s)
100 4.5
4.6 4.7 4.8 4.9 5.0 5.1 SUPPLY STEP FROM UNDERVOLTAGE RECOVERY THRESHOLD (V)
4
UW
70 90
1921 G07
Fuse Window Negative Threshold vs Temperature
30 25
Output RDS(ON) vs Temperature
OUT A (OUT F = 0V) 20 OUT F, OUT B (OUT A = 0V) 15 10 5 VA = -35V VB = -35V I = -10mA 30 50 -10 10 TEMPERATURE (C) 70 90
-2.4 -2.6 -2.8 -3.0 -3.2 -50
-30
-10 10 30 50 TEMPERATURE (C)
70
90
0 -50 -30
1921 G08
1921 G09
Overvoltage Response Time
TA = 25C
1000
5.2
100 1.3
1921 G10
1.7 1.5 2.1 2.3 1.9 SUPPLY STEP FROM OVERVOLTAGE RECOVERY THRESHOLD (V)
2.5
1921 G11
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LTC1921
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).
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5
LTC1921
BLOCK DIAGRA W
RTN 3 REF
REGULATOR
+ - + - + - + - + - + -
5 OUT A 4 OUT F
+ - + -
1 VA 8 VB 2 7
1921 BD
6 OUT B
FUSE A FUSE B
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LTC1921
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.
0 NOMINAL VOLTAGE
SUPPLY VOLTAGE (V)
-38.5 -43 -48 UNDERVOLTAGE RECOVERY -68.7 -70 OVERVOLTAGE FAULT
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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 UNDERVOLTAGE FAULT OVERVOLTAGE RECOVERY
1921 F01
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Figure 1. Supply Comparison
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LTC1921
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
-48V RETURN R1 100k R2 100k 1 8 2 7
3 RTN VA VB LTC1921 FUSE A OUT F 4
FUSE B
OUT A
OUT B F1 SUPPLY A -48V SUPPLY B -48V F2 D1 D2
8
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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 MOC207 47k 5V SUPPLY A STATUS MOC207 47k 5 5V SUPPLY B STATUS MOC207 R3 47k 1/4W VA VB OK OK OK UV OR OV UV OR OV OK UV OR OV UV OR OV SUPPLY A STATUS 0 0 1 1 SUPPLY B STATUS 0 1 0 1 OK: WITHIN SPECIFICATION OV: OVERVOLTAGE UV: UNDERVOLTAGE VFUSE A = VA = VA VA VA VFUSE B = VB VB = VB VB FUSE STATUS 0 1 1 1* 6 -48V OUT = LOGIC COMMON 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
1921 F02
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Figure 2.
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LTC1921
APPLICATIO S I FOR ATIO
-48V RETURN R1 100k R2 100k 1 8 2 7
3 RTN VA VB LTC1921 FUSE A FUSE B OUT A 5 OUT F MOCD207 4 47k 5V SUPPLY STATUS
OUT B SUPPLY A -48V SUPPLY B -48V F1
F2
1921 F03a
Figure 3a. Combined Supply Status
-48V RETURN R1 100k R2 100k 1 8 2 7
VA VB
FUSE A FUSE B OUT A 5
SUPPLY A -48V SUPPLY B -48V
1921 F03b
Figure 3b. All Outputs Combined
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47k 5V FUSE STATUS VA VB OK OK OK UV OR OV UV OR OV OK UV OR OV UV OR OV SUPPLY STATUS 0 1 1 1 OK: WITHIN SPECIFICATION OV: OVERVOLTAGE UV: UNDERVOLTAGE VFUSE A = VA = VA VA VA VFUSE B = VB VB = VB VB FUSE STATUS 0 1 1 1* 6 R3 47k 1/4W -48V OUT = LOGIC COMMON 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
W
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47k 5V STATUS
3 RTN OUT F 4
MOC207 LOGIC COMMON
LTC1921
VFUSE A VFUSE B VA VB STATUS OK OK 0 = VA = VB ALL OTHER CONDITIONS OK: WITHIN SPECIFICATION 0: LED/PHOTODIODE ON 1: LED/PHOTODIODE OFF 1
OUT B
6 R3 47k 1/4W
-48V OUT
9
LTC1921
TYPICAL APPLICATIO S
- 48V RTN R8 100 R7 51k 5% 8 VDD MOC207 3 UV 6 R3 1k 5% C2 15nF 100V DRAIN LT4250L 7 SUPPLY A STATUS PWRGD 1 R4 549k 1% LUCENT JW050A1-E MOC207 1 2 VIN+ VOUT+ LUCENT FLTR100V10 C3 0.1F 100V 1N4003 VIN- VOUT- CASE C4 0.1F 100V VIN+ ON/OFF VOUT+ SENSE + TRIM 9 8 7 5V
R9 10k 1W MOC207 4 FUSE STATUS C8 100nF 100V
R10 10k 1W
3
RTN OUT F
1
VA
8
VB
LTC1921
2 5 2 OV GATE SENSE 5 R1 0.02 5% VEE 4 SUPPLY B STATUS R6 10k 1% * C1 470nF 25V R2 10 5%
FUSE A OUT A
+ +
C5 100F 100V C6 0.1F 100V 4 SENSE - VIN- 3
1921 TA02
7
C7 100F 16V 6 VOUT- CASE 5
FUSE B
R5 6.49k 1%
OUT B R11 47k 1/4W * DIODES INC. SMAT70A = DIODES INC. B3100
6
MOC207
3A
- 48V A
3A
- 48V B
Q1 IRF530
Hot Swap is a trademark of Linear Technology Corporation
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10
Complete -48V Telecom Supply Monitor and Hot SwapTM Controller
1921f
LTC1921
PACKAGE DESCRIPTIO U
MS8 Package 8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
0.889 0.127 (.035 .005) 3.2 - 3.45 (.126 - .136) 0.65 (.0256) BSC 3.00 0.102 (.118 .004) (NOTE 3) 8 7 65 0.52 (.206) REF DETAIL "A" 0 - 6 TYP 4.90 0.15 (1.93 .006) 3.00 0.102 (.118 .004) NOTE 4 0.53 0.015 (.021 .006) DETAIL "A" 0.18 (.077) SEATING PLANE 0.22 - 0.38 (.009 - .015) TYP 0.13 0.076 (.005 .003)
MSOP (MS8) 0802
5.23 (.206) MIN
0.42 0.04 (.0165 .0015) TYP
RECOMMENDED SOLDER PAD LAYOUT
0.254 (.010) GAUGE PLANE
1 1.10 (.043) MAX
23
4 0.86 (.034) REF
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
0.65 (.0256) BSC
S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.045 .005 .050 BSC 8 N N .245 MIN .160 .005 .228 - .244 (5.791 - 6.197) 1 .030 .005 TYP 2 3 N/2 N/2 .150 - .157 (3.810 - 3.988) NOTE 3 .189 - .197 (4.801 - 5.004) NOTE 3 7 6 5
RECOMMENDED SOLDER PAD LAYOUT
1
2
3
4
.010 - .020 x 45 (0.254 - 0.508) .008 - .010 (0.203 - 0.254) 0- 8 TYP
.053 - .069 (1.346 - 1.752)
.004 - .010 (0.101 - 0.254)
.016 - .050 (0.406 - 1.270) NOTE: 1. DIMENSIONS IN
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)
.014 - .019 (0.355 - 0.483) TYP
.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.
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LTC1921
TYPICAL APPLICATIO S
Single 48V Supply Monitor
V+ LOGIC V+ 3 RTN 1 8 2 7 VA VB MOC207 FUSE A FUSE B 47k 1/4W
1921 TA04
OUT F LTC1921
4 SUPPLY GOOD
OUT A OUT B
5 6 LOGIC COMMON
SUPPLY A -48V SUPPLY B -48V
RELATED PARTS
PART NUMBER LT4250 LTC4251 LTC4252 LTC4253 DESCRIPTION -48V Hot Swap Controller in SO-8 Package -48V Hot Swap Controller in SOT-23 Package -48V Hot Swap Controller in MSOP Package -48V Hot Swap Controller with Sequencer COMMENTS Active Current Limiting, Supplies from -20V to -80V Fast Active Current Limiting, Supplies from -15V (Floating) Fast Active Current Limiting, Floating Supply, PWRGD Output Similar to LTC4252, Sequences Three DC/DC Converters
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
q
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Single -48V Supply Monitor
LOGIC V+ 3 RTN V- 1 8 2 7 VA VB MOC207 FUSE A FUSE B 47k 1/4W
1921 TA06
47k
47k OUT F 4 SUPPLY GOOD
LTC1921
OUT A OUT B
5 6 LOGIC COMMON
Voltage and Fuse Monitor with LED Outputs
-48V RETURN R1 100k R2 100k 1 8 2 7 D3 GREEN 3 RTN VA VB LTC1921 FUSE A FUSE B OUT A 5 D5 GREEN OUT B F1 D1 6 R3 5.1k 2W -48V OUT F2 D2
1921 TA03
OUT F
4
D4 GREEN
LT/TP 0902 2K * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2002

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