LINEAR TECHNOLOGY LTC1921, LTC1921i Technical data

Final Electrical Specifications

查询LTC1921CMS8供应商

LTC1921

Dual –48V Supply

and Fuse Monitor

FEATURES

■

Independently Monitors Two –48V Supplies for
– Undervoltage Faults: –38.5V ±1V
– Overvoltage Faults: –70V ±1.5V

■

Accurately Detects Undervoltage Fault Recovery:
–43V ±0.5V

■

Monitors Two External Fuses

■

Operates from –10V to –80V

■

Tolerates DC Faults to –100V

■

Tolerates Accidental Supply Reversal to 100V

■

Withstands Transient Voltages Up to 200V/–200V

■

Small Footprint: 8-Lead MSOP Package

■

Requires No Precision External Components

■

Specified from –40°C to 85°C

MAX

MAX

MAX

U

APPLICATIO S

■

Telecom Backplanes or Switch Cards

■

Networking Backplanes or Switch Cards

■

High Voltage Fuse Monitoring

U

May 2002

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.

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 an 8-pin MSOP package.

, LTC and LT are registered trademarks of Linear Technology Corporation.

TYPICAL APPLICATIO

–48V

RETURN

R1

100k

SUPPLY A

–48V

SUPPLY B

–48V

F1

F2

U

R2
100k

1

8

2

RTN

A

V

B

LTC1921
FUSE A
FUSE B

D1 MURS320

D2 MURS320

3

OUT FV

OUT A

OUT B

47k 47k

47k

MOC207

4

MOC207

57

MOC207

6

R3
47k
1/4W

FUSE GOOD

SUPPLY A GOOD

SUPPLY B GOOD

LOGIC

SUPPLY

SUPERVISOR

µP

LOGIC

COMMON

–48V LOAD

1921 TA01

1921i

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.

1

LTC1921

1
2
3
4

V

A

FUSE A

RTN

OUT F

8
7
6
5

V

B

FUSE B
OUT B
OUT A

TOP VIEW

MS8 PACKAGE

8-LEAD PLASTIC MSOP

WWWU

ABSOLUTE AXI U RATI GS

PACKAGE/ORDER I FOR ATIO

UU

W

(Note 1) All voltages referred to RTN

Supply Voltage

(VA, VB, FUSE A, FUSE B) ....................... 100V to –100V

ORDER PART

NUMBER

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

LTC1921CMS8 ........................................ 0°C to 70°C

T

= 150°C, θJA = 250°C/W

JMAX

Consult LTC Marketing for parts specified with wider operating temperature ranges.

LTC1921CMS8
LTC1921IMS8

MS8 PART MARKING

LTZV
LTZU

LTC1921IMS8 .................................... –40°C to 85°C

Storage Temperature Range ................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec)..................300°C

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. (Note 3) 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 80 V
Supply Current (IA + IB) –160 –250 µA

Supply Monitor

Undervoltage Threshold ● –39.5 –37.5 V
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 |V

Output

Propagation Delay C
Output Switch Resistance, OUT F, OUT A, OUT B VA = VB = –35V, V

Output Switch Off Leakage 500 pA
Output Switch Resistance in Undervoltage Lockout, VA = VB = –10V, I

OUT F, OUT A, OUT B V

FUSEA

– VA|, |V

– VB| 2.5 V

FUSEB

The ● denotes specifications which apply over the full operating

● –300 µA

LTC1921C ● 0.9 4.5 V
LTC1921I

= 100pF, Overdrive = 1V 220 µs

OUT

= V

I

= 10mA ● 50 Ω

OUT

= –10V, VB = 0V, I

A

VA = 0V, VB = –10V, I

FUSEA

= 10mA ● 60 Ω

OUT

OUT
OUT

= 0V 25 Ω

FUSEB

= 10mA ● 80 Ω
= 10mA ● 80 Ω

● 0.5 4.5 V

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.

2

Note 3: All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to RTN unless otherwise
specified.

1921i

UW

TEMPERATURE (°C)

–50

OUTPUT R

DS(ON)

(Ω)

20

25

30

10 50

1921 G03

15

10

–30 –10

30 70 90

5

0

OUT A (OUT F = 0V)

OUT F, OUT B (OUT A = 0V)

VA = –35V
V

B

= –35V

I = –10mA

TYPICAL PERFOR A CE CHARACTERISTICS

Supply Current vs Supply Voltage

SUPPLY CURRENT (µA)

400

350

300

250

200

150

100

50

VA = VB = V

0

0

= V

FUSEA

FUSEB

20 40 60 1007010 30 50 90

SUPPLY VOLTAGE (V)

80

1921 G01

180

160

140

120

100

80

60

SUPPLY CURRENT (µA)

VA = –48V

40

= –48V

V

B

= –48V

V

20

FUSEA

= –48V

V

FUSEB

0

–30 –10 10 30 50 70

–50

+ I

I

A

B

IA, I

B

TEMPERATURE (°C)

1921 G02

Undervoltage Threshold
vs TemperatureSupply Current vs Temperature

–37.5
–37.7
–37.9
–38.1
–38.3
–38.5
–38.7
–38.9
–39.1

UNDERVOLTAGE THRESHOLD (V)

–39.3
–39.5

90

–50 –30 –10 10

LTC1921

30 50 70

TEMPERATURE (°C)

90

1921 G04

Undervoltage Recovery Threshold
vs Temperature

–42.5
–42.6
–42.7
–42.8
–42.9
–43.0
–43.1
–43.2
–43.3
–43.4

UNDERVOLTAGE RECOVERY THRESHOLD (V)

–43.5

–50 –30 –10 10

TEMPERATURE (°C)

30 50 70

Fuse Window Positive Threshold
vs Temperature

2.7

2.5

2.3

1921 G05

Overvoltage Threshold
vs Temperature

–68.0

–68.5

–69.0

–69.5

–70.0

–70.5

–71.0

OVERVOLTAGE THRESHOLD (V)

–71.5

–72.0

90

–50 –30 –10 10

Fuse Window Negative Threshold
vs Temperature

–2.0

–2.2

–2.4

TEMPERATURE (°C)

30 50 70

1921 G06

Overvoltage Hysteresis
vs Temperature

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

OVERVOLTAGE HYSTERESIS (V)

1.05

90

1.00
–50 –30 –10 10

Output R

TEMPERATURE (°C)

DS(ON)

30 50 70

vs Temperature

90

1921 G07

2.1

1.9

FUSE POSITIVE THRESHOLD (V)

1.7

1.5
–50 –30 –10 10

TEMPERATURE (°C)

30 50 70

1921 G08

–2.6

–2.8

–3.0

FUSE NEGATIVE THRESHOLD (V)

90

–3.2

–50 –30 –10 10

TEMPERATURE (°C)

30 50 70

90

1921 G09

1921i

3

LTC1921

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Undervoltage Response Time

10000

TA = 25°C

1000

RESPONSE TIME (µs)

100

U

4.5

4.6

SUPPLY STEP FROM UNDERVOLTAGE

RECOVERY THRESHOLD (V)

4.8

4.9 5.0 5.1

UU

5.24.7

1921 G10

PI FU CTIO S

VA (Pin 1):
is compared to the valid supply voltage window and the
result is output at OUT A (Pin 5). Supply current is drawn
from this pin 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 V
(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 V
window around VA) and V
exhibit a high internal impedance to the RTN pin. If
V

FUSEA

internally to the RTN pin and can shunt enough current to
turn off an optocoupler 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 optocoupler 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

Supply to be Monitored. The voltage at this pin

FUSEA

≠ VA or V

≅ VA (V

FUSEB

≠ VB, then OUT F is shorted

FUSEB

is within the specified

FUSEA

≅ VB, then OUT F will

A

Overvoltage Response Time

10000

TA = 25°C

1000

RESPONSE TIME (µs)

100

1.3

1.5

SUPPLY STEP FROM OVERVOLTAGE

RECOVERY THRESHOLD (V)

1.9

2.1 2.3

2.51.7

1921 G11

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
optocoupler 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
optocoupler 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
optocoupler 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
optocoupler 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 V

B

(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 this pin as well as from VA (Pin 1).

1921i

4

BLOCK DIAGRA

W

LTC1921

RTN

3

+

REFREGULATOR

–
+

–

+
–

OUT F

4

+
–

+
–

+
–

OUT A

5

+
–

+
–

1

V

A

8

V

B

FUSE A

72

FUSE B

1921 BD

OUT B

6

1921i

5

LTC1921

WUUU

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 V
specified voltage window around VA and V

FUSEA

FUSEB

is within the

is within
the specified voltage window around VB, the OUT F pin will
indicate that the fuses are intact by exhibiting a high

6

0

–38.5

–43
–48

UNDERVOLTAGE

RECOVERY

–68.7

SUPPLY VOLTAGE (V)

–70

0

(A)

V

SUPPLY

OUT

I

R3

Figure 1. Supply Comparison

NOMINAL

VOLTAGE

TIME

UNDERVOLTAGE

OVERVOLTAGE

FAULT

FAULT

OVERVOLTAGE
RECOVERY

1921 F01

1921i

WUUU

APPLICATIO S I FOR ATIO

LTC1921

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 optocoupler 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
optocouplers, 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.

SUPPLY A

–48V

SUPPLY B

–48V

–48V

RETURN

F1

F2

R1
100kR2100k

1

8

2

V

A

V

B

FUSE A

FUSE B

3

RTN

LTC1921

D1

D2

OUT F

OUT A

OUT B

4

57

6

1921 F02

MOC207

MOC207

MOC207

R3
47k
1/4W

Figure 2

47k

5V
FUSE

STATUS

47k

5V
SUPPLY A

STATUS

47k

5V
SUPPLY B

STATUS

–48V OUT

= LOGIC COMMON

SUPPLY A

V

A

OK

UV OR OV

OK
UV OR OV
UV OR OV

OK: WITHIN SPECIFICATION
OV: OVERVOLTAGE
UV: UNDERVOLTAGE

FUSE A

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

= V
= V

≠ V
≠ V

A
A
A
A

UV OR OV

FUSE B

= V
≠ V
= V
≠ V

V

OK

OK

B

B
B
B
B

STATUS

0
0
1
1

FUSE STATUS

0
1
1

1*

SUPPLY B

STATUS

0
1
0
1

1921i

7

LTC1921

WUUU

APPLICATIO S I FOR ATIO

–48V

RETURN

R1

R2

100k

SUPPLY A

–48V

SUPPLY B

–48V

100k

1

8

2

F1

F2

V

A

V

B

FUSE A

FUSE B

3

RTN

OUT F

LTC1921

OUT A

OUT B

4

57

6

1921 F03a

47k

MOCD207

R3
47k
1/4W

= LOGIC COMMON

47k

5V
FUSE STATUS

5V
SUPPLY

STATUS

–48V OUT

V

A

OK

OK
UV OR OV
UV OR OV

OK: WITHIN SPECIFICATION
OV: OVERVOLTAGE
UV: UNDERVOLTAGE

FUSE A

= V
= V

≠ V
≠ V

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

A
A
A
A

V

B

OK

UV OR OV

OK

UV OR OV

FUSE B

= V

B

≠ V

B

= V

B

≠ V

B

SUPPLY STATUS

0
1
1
1

FUSE STATUS

0
1
1

1*

SUPPLY A

–48V

SUPPLY B

–48V

–48V

RETURN

Figure 3a. Combined Supply Status

100k

100k

1

8

2

A

V

B

FUSE A

FUSE B

RTN

LTC1921

3

OUT A

OUT B

4

OUT FV

57

6

1921 F03b

MOC207

COMMON

48k
1/2W

LOGIC

47k

5V
STATUS

FUSE B

FUSE A

OK: WITHIN SPECIFICATION
0: LED/PHOTODIODE ON
1: LED/PHOTODIODE OFF

–48V OUT

= V

= V

A

ALL OTHER CONDITIONS

V

V

STATUS

A

B

OK

OK

B

0
1

8

Figure 3b. All Outputs Combined

1921i

TYPICAL APPLICATIO S

+

V

EE

V

DD

C8

100nF

100V

LT4250L

PWRGD

SENSE

C1

470nF

25V

C2

15nF

100V

C3

0.1µF

100V

C4

0.1µF

100V

C6

0.1µF

100V

C5

100µF

100V

C7

100µF

16V

Q1

IRF530

R2

10Ω

5%

R31k5%

R8

100Ω

R4

549k

1%

R5

6.49k

1%

R6

10k

1%

R1

0.02Ω

5%

4

OV

3

2

–48V A

–48V

RTN

–48V B

UV

5

6

8

7

1

GATE

DRAIN

LUCENT

JW050A1-E

V

OUT

+

SENSE

+

TRIM

SENSE

–

V

OUT

–

V

IN

+

9

5V

1921 TA02

8

7

6

5

3

1

2

4

ON/OFF

CASE

V

IN

–

V

OUT

+

V

OUT

–

V

IN

+

CASE

V

IN

–

1N4003

+

LUCENT

FLTR100V10

*

* DIODES INC. SMAT70A

MOC207

R7

51k

5%

MOC207

MOC207

MOC207

FUSE

STATUS

SUPPLY A

STATUS

R11

47k

1/4W

SUPPLY B

STATUS

OUT FV

A

3

4

57

2

8

1

6

V

B

FUSE A

3A

3A

RTN

LTC1921

FUSE B

OUT A

OUT B

R10

10k

1W

R9

10k

1W

= DIODES INC. B3100

Controller

TM

LTC1921

U

Complete –48V Telecom Supply Monitor and Hot Swap

Hot Swap is a trademark of Linear Technology Corporation.

1921i

9

LTC1921

TYPICAL APPLICATIO S

U

1

8

2

7

Single 48V Supply Monitor

+

V

3

A

V

B

FUSE A

FUSE B

RTN

LTC1921

47k

1/4W

OUT FV

OUT A

OUT B

4

5

6

LOGIC V

MOC207

COMMON

1921 TA04

+

47k

SUPPLY GOOD

LOGIC

Single –48V Supply Monitor

+

3

A

V

B

FUSE A

FUSE B

RTN

LTC1921

47k

1/4W

–

V

1

8

2

7

OUT FV

OUT A

OUT B

4

5

6

LOGIC V

MOC207

COMMON

1921 TA06

47k

SUPPLY GOOD

LOGIC

10

1921i

PACKAGE DESCRIPTIO

U

MS8 Package

8-Lead Plastic MSOP

(Reference LTC DWG # 05-08-1660)

0.889

± 0.127

(.035 ± .005)

LTC1921

5.23

(.206)

MIN

0.42 ± 0.04

(.0165 ± .0015)

TYP

RECOMMENDED SOLDER PAD LAYOUT

0.254

(.010)

GAUGE PLANE

0.18

(.077)

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

DETAIL “A”

(.126 – .136)

(.0256)

° – 6° TYP

0

DETAIL “A”

3.2 – 3.45

0.65

BSC

0.53 ± 0.015
(.021 ± .006)

SEATING

PLANE

3.00 ± 0.102
(.118 ± .004)

(NOTE 3)

4.88

± 0.1

(.192 ± .004)

0.22 – 0.38

(.009 – .015)

1.10

(.043)

MAX

8

12

0.65

(.0256)

BCS

7

0.52

5

4

(.206)

REF

3.00 ± 0.102

(.118 ± .004)

NOTE 4

0.86

(.034)

REF

0.13 ± 0.05

(.005 ± .002)

MSOP (MS8) 1001

6

3

1921i

11

LTC1921

TYPICAL APPLICATIO

U

Voltage and Fuse Monitor with LED Outputs

–48V RETURN

R2

R1

100k

100k

1

8

2

V

A

V

B

FUSE A

3

RTN

LTC1921

OUT F

D3
GREEN

4

D4
GREEN

SUPPLY A

–48V

SUPPLY B

–48V

FUSE B

F1

F2

D1

D2

OUT A

OUT B

57

6

1921 TA03

R3

5.1k
2W

D5
GREEN

–48V OUT

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

1921i

LT/TP 0502 1.5K • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 2002

12

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

●

www.linear.com