LINEAR TECHNOLOGY LT4250L, LT4250H Technical data

FEATURES

■

Allows Safe Board Insertion and Removal
from a Live –48V Backplane

■

Circuit Breaker Immunity to Voltage Steps and
Current Spikes

■

Programmable Inrush and
Short-Circuit Current Limits

■

Pin Compatible with LT1640L/LT1640H

■

Operates from –20V to –80V

■

Programmable Overvoltage Protection

■

Programmable Undervoltage Lockout

■

Power Good Control Output

■

Bell-Core Compatible ON/OFF Threshold

U

APPLICATIO S

LT4250L/LT4250H

Negative 48V

Hot Swap Controller

U

DESCRIPTIO

The LT®4250L/LT4250H are 8-pin, negative 48V Hot Swap
controllers that allow a board to be safely inserted and
removed from a live backplane. Inrush current is limited to
a programmable value by controlling the gate voltage of an
external N-channel pass transistor. The pass transistor is
turned off if the input voltage is less than the program­mable undervoltage threshold or greater than the over­voltage threshold. A programmable current limit protects
the system against shorts. After a 500µs timeout the
current limit activates the electronic circuit breaker. The
PWRGD (LT4250L) or PWRGD (LT4250H) signal can be
used to directly enable a power module. The LT4250L is
designed for modules with a low enable input and the
LT4250H for modules with a high enable input.

TM

■

Central Office Switching

■

–48V Distributed Power Systems

■

Negative Power Supply Control

TYPICAL APPLICATIO

–48V RTN

(SHORT PIN)

–48V RTN

UV =

38.5V
UV

RELEASE
AT 43V

OV =
71V

*

–48V

INPUT 1

–48V

INPUT 2

* DIODES INC. SMAT70A

†

THESE COMPONENTS ARE APPLICATION
SPECIFIC AND MUST BE SELECTED BASED
UPON OPERATING CONDITIONS AND DESIRED
PERFORMANCE. SEE APPLICATIONS
INFORMATION.

R4

549k

1%

R5

6.49k
1%

R6
10k

1%

0.1µF
10V

†

3

UV

†

2

OV

†

V

SENSE

EE

4

56

†

R1

0.02Ω

5%

U

8

V

DD

LT4250L

GATE DRAIN

†

R3

1k, 5%

†

R2

C1

10Ω

470nF

5%

25V

Q1

IRF530

C3

0.1µF
100V

C4

+

100µF
100V

C2
15nF
100V

PWRGD

†

1

4

7

+

V

IN

–

V

IN

LUCENT

JW050A1-E

The LT4250L/LT4250H are available in 8-pin PDIP and SO
packages.

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

Hot Swap is a trademark of Linear Technology Corporation.

Voltage Step On Input Supply

1

VEE AND

DRAIN

20V/DIV

(Q1)

I

D

5A/DIV

2

ON/OFF

V

OUT

SENSE

TRIM

SENSE

V

OUT

9

+

8

+

7
6

–

5

–

5V

C5

+

100µF
16V

4250 TA01

500µs/DIV

4250lhf

1

LT4250L/LT4250H

WW

W

ABSOLUTE MAXIMUM RATINGS

U

(Note 1), All Voltages Referred to V

Supply Voltage (VDD – VEE) .................... –0.3V to 100V

PWRGD, PWRGD Pins ........................... –0.3V to 100V

SENSE, GATE Pins.................................... –0.3V to 20V

UV, OV Pins .............................................. –0.3V to 60V

DRAIN Pin .................................................. –2V to 100V

Maximum Junction Temperature ......................... 125°C

WU

/

PACKAGE

PWRGD

1

OV

2

UV

3

V

4

EE

N8 PACKAGE
8-LEAD PDIP

T

= 125°C, θJA = 120°C/W (N8)

JMAX

T

= 125°C, θJA = 150°C/W (S8)

JMAX

O

RDER I FOR ATIO

TOP VIEW

V

8

DD

DRAIN

7

GATE

6

SENSE

5

S8 PACKAGE

8-LEAD PLASTIC SO

S8 PART MARKING

ORDER PART

NUMBER

LT4250LCN8
LT4250LCS8
LT4250LIN8
LT4250LIS8

4250L
4250LI

EE

Operating Temperature Range

LT4250LC/LT4250HC ............................. 0°C to 70°C

LT4250LI/LT4250HI .......................... – 40°C to 85°C

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

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

U

ORDER PART

NUMBER

LT4250HCN8
LT4250HCS8
LT4250HIN8
LT4250HIS8

S8 PART MARKING

4250H
4250HI

PWRGD

OV
UV

V

EE

N8 PACKAGE
8-LEAD PDIP

T

JMAX

T

JMAX

TOP VIEW

1

2

3

4

8-LEAD PLASTIC SO

= 125°C, θJA = 120°C/W (N8)
= 125°C, θJA = 150°C/W (S8)

V

8

DRAIN

7

GATE

6

SENSE

5

S8 PACKAGE

DD

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

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. (Note 2), VDD = 48V, VEE = 0V unless otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
DC

V

DD

I

DD

V

UVL

V

CL

I

PU

I

PD

I

SENSE

∆V
V

UVH

V

UVL

V

UVHY

I

INUV

V

OVH

V

OVL

GATE

Supply Voltage Operating Range ● 20 80 V
Supply Current UV = 3V, OV = VEE, SENSE = V
Undervoltage Lockout ● 15.4 V
Current Limit Trip Voltage VCL = (V
GATE Pin Pull-Up Current Gate Drive On, V
GATE Pin Pull-Down Current Gate Drive OFF 24 50 70 mA
SENSE Pin Current V
External Gate Drive (V
UV Pin High Threshold Voltage UV Increasing ● 1.240 1.255 1.270 V
UV Pin Low Threshold Voltage UV Decreasing ● 1.105 1.125 1.145 V
UV Pin Hysteresis 130 mV
UV Pin Input Current VUV = V
OV Pin High Threshold Voltage OV Increasing ● 1.235 1.255 1.275 V
OV Pin Low Threshold Voltage OV Decreasing ● 1.210 1.235 1.255 V

SENSE

GATE

– VEE) ● 40 50 60 mV

SENSE

= V

GATE

= 50mV –20 µA

– VEE), 20V ≤ VDD ≤ 80V ● 10 13.5 18 V

EE

EE

EE

● 1.6 5 mA

● –30 –45 –60 µA

● –0.02 –0.5 µA

2

4250lhf

LT4250L/LT4250H

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. (Note 2), VDD = 48V, VEE = 0V unless otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

OVHY

I

INOV

V

DL

V

GH

I

DRAIN

V

OL

I

OH

AC

t

PHLOV

t

PHLUV

t

PLHOV

t

PLHUV

t

PHLSENSE

t

PHLCB

t

PHLDL

t

PHLGH

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

OV Pin Hysteresis 20 mV
OV Pin Input Current VOV = V
DRAIN Low Threshold V
GATE High Threshold ∆V
Drain Input Bias Current V

EE

– VEE, DRAIN Decreasing 1.1 1.6 2.3 V

DRAIN

– V

GATE

DRAIN

Decreasing 1.3 V

GATE

= 48V ● 10 80 500 µA

PWRGD Output Low Voltage PWRGD (LT4250L), (V

I

= 1mA ● 0.48 0.8 V

OUT

= 5mA ● 1.2 3.0 V

I

OUT

PWRGD Output Low Voltage PWRGD (LT4250H), V
(PWRGD – DRAIN) I

= 1mA ● 0.75 1.0 V

OUT

Output Leakage PWRGD (LT4250L), V

PWRGD (LT4250H), V

DRAIN

DRAIN

DRAIN

DRAIN

– VEE) < V

= 5V

= 48V, V

= 0V, V

DL

= 80V ● 0.05 10 µA

PWRGD

= 80V ● 0.05 10 µA

PWRGD

● – 0.03 –0.5 µA

OV High to GATE Low Figures 1a, 2 1.7 µs
UV Low to GATE Low Figures 1a, 3 1.5 µs
OV Low to GATE High Figures 1a, 2 5.5 µs
UV High to GATE High Figures 1a, 3 6.5 µs
SENSE High to Gate Low Figures 1a, 4a 1 3 µs
Current Limit to GATE Low Figures 1b, 4b 500 µs
DRAIN Low to PWRGD Low (LT4250L) Figures 1a, 5a 1 µs

DRAIN Low to (PWRGD – DRAIN) High (LT4250H) Figures 1a, 5a 1 µs
GATE High to PWRGD Low (LT4250L) Figures 1a, 5b 1.5 µs

GATE High to (PWRGD – DRAIN) High (LT4250H) Figures 1a, 5b 1.5 µs

Note 2: All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to V

unless otherwise

EE

specified.

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Supply Current vs Supply Voltage

1.8
TA = 25°C

1.7

1.6

1.5

1.4

1.3

SUPPLY CURRENT (mA)

1.2

1.1

0

20 40 80

0

SUPPLY VOLTAGE (V)

60

100

1640 G01

Supply Current vs Temperature

1.6
VDD = 48V

1.5

1.4

1.3

1.2

SUPPLY CURRENT (mA)

1.1

1.0

–50 –25

0255075

TEMPERATURE (°C)

1640 G02

100

Gate Voltage vs Supply Voltage

15

TA = 25°C

14

13

12

11

10

9

GATE VOLTAGE (V)

8

7

6

0

20 60

40

SUPPLY VOLTAGE (V)

100

80

1640 G03

4250lhf

3

LT4250L/LT4250H

TEMPERATURE (°C)

–50

2

OUTPUT IMPEDANCE (kΩ)

3

4

5

6

7

8

–25 2505075

1640 G09

100

V

DRAIN

– VEE > 2.4V

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Gate Voltage vs Temperature

15.0
VDD = 48V

14.5

14.0

13.5

13.0

GATE VOLTAGE (V)

12.5

12.0

–25 0 75

TEMPERATURE (°C)

Gate Pull-Down Current
vs Temperature

55

V

= 2V

GATE

52

49

1640 G04

Current Limit Trip Voltage
vs Temperature

55

54

53

52

51

TRIP VOLTAGE (mV)

50

49

100–50 25 50

48

–50

–25

TEMPERATURE (°C)

50

250

100

75

1640 G05

PWRGD Output Low Voltage
vs Temperature (LT4250L)

0.5
I

= 1mA

OUT

0.4

0.3

Gate Pull-Up Current
vs Temperature

48

V

= 0V

GATE

47

46

45

44

43

42

GATE PULL-UP CURRENT (µA)

41

40

–25 10050250

–50

TEMPERATURE (°C)

PWRGD Output Impedance
vs Temperature (LT4250H)

75

1640 G06

46

43

GATE PULL-DOWN CURRENT (mA)

40

–25 0

–50

25

TEMPERATURE (°C)

50

75

100

1640 G07

0.2

0.1

PWRGD OUTPUT LOW VOLTAGE (V)

0

–25 25050

–50

TEMPERATURE (°C)

75

100

1640 G08

UUU

PIN FUNCTIONS

PWRGD/PWRGD (Pin 1): Power Good Output Pin. This pin
will latch a power good indication when V
of V

and V

EE

connected directly to the enable pin of a power module.
When the DRAIN pin of the LT4250L is above VEE by more

than V

DL

PWRGD pin will be high impedance, allowing the pull-up

is within VGH of ∆V

GATE

or V

is more than VGH from ∆V

GATE

GATE

is within V

DRAIN

. This pin can be

, the

GATE

current of the module’s enable pin to pull the pin high and
turn the module off. When V
V

rises above VGH, the PWRGD pin sinks current to

GATE

VEE, pulling the enable pin low and turning on the module.

drops below V

DRAIN

DL

and

This condition is latched until the GATE pin is turned off via
the UV, OV, UVLO or the electronic circuit breaker.

DL

When the DRAIN pin of the LT4250H is above VEE by more
than VDL or V

is more than VGH from ∆V

GATE

PWRGD pin will sink current to the DRAIN pin which pulls
the module’s enable pin low, forcing it off. When V
drops below VDL and V

rises above VGH, the PWRGD

GATE

sink current is turned off, allowing the module’s pull-up
current to pull the enable pin high and turn on the module.
This condition is latched until the GATE pin is turned off via
the UV, OV, UVLO or the electronic circuit breaker.

GATE

, the

DRAIN

4250lhf

4