Datasheet SC4250 Datasheet (SEMTECH)

查询SC4250供应商

2 2005 Semtech Corp. www.semtech.com

SC4250

POWER MANAGEMENT

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DP

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ESNES

V

ESNES

Vm05=50.0-Aµ

evirDetaGlanretxE

∆V

ETAG

V(

ETAG

V-

EE

V02,) < VDD≤ V08 93161 V

V(

ETAG

V-

EE

V01,) ≤ VDD≤ V02 8

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HVU

noitisnarthgiHotwoLVU 142.1372.1503.1 V

egatloVdlohserhTwoLniPVUV

LVU

noitisnartwoLothgiHVU 291.1322.1352.1 V

sisretsyHniPVUV

YHVU

05 Vm

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VUNI

VVUV=

EE

1.0-Aµ

egatloVdlohserhThgiHniPVOV

HVO

noitisnarthgiHotwoLVO 291.1322.1352.1 V

egatloVdlohserhTwoLniPVOV

LVO

noitisnartwoLothgiHVO 351.1881.1322.1 V

sisretsyHniPVOV

YHVO

53Vm

tnerruCtupnIniPVOI

VONI

V

VO

≥ V5.150.0-Aµ

Unless specified: TA = 25°C, VCC = 48V, VEE = 0V.
Values in bold apply over full operating temperature range.

Absolute Maximum Ratings

Electrical Characteristics

Exceeding the specifications below may result in permanent damage to the device or device malfunction. Operation outside of the parameters
specified in the Electrical Characteristics section is not implied.

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DAEL

003C°

3 2005 Semtech Corp. www.semtech.com

POWER MANAGEMENT

SC4250

Electrical Characteristics (Cont.)

Unless specified: TA = 25°C, VCC = 48V, VEE = 0V.
Values in bold apply over full operating temperature range.

Note:
(1) This device is ESD sensitive. Use of standard ESD handling precaution is required.

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GP

V

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YHGP

4.0V

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NIARD

V

NIARD

V84= 5105 Aµ

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LO

V,H0524CS

LO

V-DGRWP=

NIARD

V@

NIARD

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O

Am1=

1V

V,L0524CS

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EE

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NIARD

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Am1=

1V

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EE

V,V1=

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NIARD

V-

EE

V5= 0.101 Aµ

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t

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4 2005 Semtech Corp. www.semtech.com

SC4250

POWER MANAGEMENT

Notes:

(1) Only available in tape and reel packaging. A reel
contains 2500 devices.

(2) Lead free product. This product is fully WEEE and RoHS
compliant.

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)1(

RTSIH0524CS

8-OS

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)2(

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TRTSIL0524CS

)2(

Pin Configuration Ordering Information

Pin Descriptions

1

2

3

4

VCCPWRGD/PWRGD

TOP VIEW

(SO-8)

5

6

7

8

DRAINOV

GATEUV

SENSEVEE

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5 2005 Semtech Corp. www.semtech.com

POWER MANAGEMENT

SC4250

Block Diagrams

Active High PWRGD

Active Low PWRGD

60mV

+

_

_

+

_

+

_

+

+

_

+7V

Dela y

DRAINGATESENSEVee

Vcc

12.5V Reg 1.223V

1.75V

PWRG D

50uA

UV

OV

60mV

+

_

_

+

_

+

_

+

+

_

+7V

Dela y

DRAINGATESENSEVee

Vcc

12.5V Reg 1.223V

1.75V

PWRG D

50uA

UV

OV

6 2005 Semtech Corp. www.semtech.com

SC4250

POWER MANAGEMENT

Applications Information

Insertion of a power circuit board into a live backplane
would draw enormous inrush currents. This is mostly due
to the charging of the bulk electrolytic capacitors at the
input of the power module being plugged in.

The transient currents would send glitches all over the
power system and could cause corruption of the signals
and even a power down if the source isn’t able to handle
these high surges.

This section describes the components selection needed
for a typical application utilizing the SC4250. Let’s assume
the following requirements for a representative system:

Input voltage range: 36V to 72V

Nominal current: 2A typ.

Over-current condition: 5A

Bulk capacitance: Cload = 150µF

The schematic in Figure 2 combines internal function
blocks along with the external components of the
application circuit.

Resistors R1, R2 and R3 make up a voltage divider to
set the Under-Voltage (UV) and Over-Voltage (OV) trip
points.

When the input power supply ramps up the UV trips at

1.273V and OV trips at 1.223V; during the ramp down
transition the UV trips at 1.223V and OV trips at 1.198V.

The 50mV hysteresis for UV and 25mV hysteresis for OV
provide the necessary guard-bands to prevent false
tripping during power up and power down conditions.

As an additional noise killing and stabilizing measure, the
capacitor C1 should be placed at the OV terminal with
the value in range from 1,000 to 10,000pF.

For the UV=38V and OV=70V the values of the resistor
can be calculated as follows:

Vuv = 1.273V · (R1+R2+R3) ÷ (R2+R3)

Vov = 1.223V · (R1+R2+R3) ÷ R3

With the input bias current of the UV and OV comparators
in the range of 20-30nA, let’s choose the R1 to be

562kΩ. This yields the values of R2=9.31kΩ and R3 =

10.2kΩ. With these values the accuracy is about 1%

which is quite acceptable for those functions.

Figure 2

60mV

+

_

_

+

_

+

_

+

+

_

+7V

Delay

Q1

DRAINGATE

R4

SENSEVee

Vcc

12.5V Reg 1.223V

1.75V

PWRGD

50uA

Cloa d
150uF

C3

R5

R1

R2

R3

C2

UV

OV

-48V

+48V

C

1

R6

7 2005 Semtech Corp. www.semtech.com

POWER MANAGEMENT

SC4250

Applications Information (Cont.)

Resistor R4 sets the over-current trip. To choose R4,
the user must determine the level of the current where
it should trip. As a rule of thumb, the over-current is set
to be 200-300% of the nominal value. In our case, we
assumed this value to be 5A.

Considering the minimum trip voltage is 50mV the value

of R4 is 50mV ÷ 5A = 10 mΩ.

The tolerance of this resistor is usually price driven and
5% is an adequate range of accuracy.

The actual position and layout of the circuitry around the
sense resistor R4 is critical to avoid a false over-current
tripping. The trace routing between R4 and SC4250
should be as short as possible and wide enough to handle
the maximum current with zero current in the sense lines
– ideally “Kelvin” like. Additionally, there is a short delay
circuit at the comparator to filter out unwanted noise
and otherwise induced transients.

Inrush Current

is being controlled by the R5C3 network

and swamping capacitor C2.

When a board is plugged into a live backplane, the input
bulk capacitance of the board’s power supply produces
large current transients due to the rush of the currents
charging those capacitors. The main feature of the
SC4250 is to provide an orderly and well-controlled inrush
current.

Since the minimum trip voltage is 50mV, let’s choose
the inrush current to be 3A.

Imax = Cload ·

∆Vmax /dt

dt = Cload ·

∆Vmax /Imax = 150µF · 70V / 3A = 3.5ms

This would be the minimum time for the gate voltage
plateau during which the Vdd linearly decreases
maintaining 3A charge current of the Cload.
The inrush can be calculated using the following equation:

I

MAX

= (50µA • C

LOAD

) / C3

With the values shown in the schematic the actual inrush
current will be about 2A, which is within the limits we
have chosen.

Resistor R5 will produce a time constant which prevents
Q1 from turning on when power is initially applied and
the circuit is not ready to actively pull the gate low. It’s
value is not critical and 18k ensures the adequate delay.

The value of C2 is chosen to prevent false turn-on of the
FET due to the current flowing via C3 into the gate of the
FET when the circuit initially connects to the power source.
Capacitors C2 and C3 form a divider from Vin to GND.
C2 must keep the initial voltage at the gate below Vth
minimum.

For the typical FET, this threshold is around 1V to 2V,
therefore C2 = 100 • C3 will keep gate voltage at 0.7V,
even at the ”worst” case of Vin = 70V.
The choice of the Q1 is quite straightforward and is guided
mostly by thermal considerations due to the power
dissipation in the steady state.

For instance, in our case, the nominal current is 2A, the
power dissipation due to the conducting losses will be

Pdis = Inom² • Rds_on.

The MOSFET should be able to withstand Vdss

≥ 100V

with continuous drain current Id ≥ 6A. Device SUD06N10
or similar fits this application. It has an Rds_on = 0.2Ω,

and will dissipate

Pdis = 2² • 0.2 = 0.8W, which can be handled by this
DPAK device.

If there is a consideration of reducing the temperature
of the MOSFET then the lower Rds_on device should be
chosen or a different style (D2PAK) which has lower
Junction-to-Ambient thermal characteristics.

The R6

has a function of dumping high frequency

oscillations. The value of it is not critical and can be in

the range of 5Ω to 20Ω.

8 2005 Semtech Corp. www.semtech.com

SC4250

POWER MANAGEMENT

Typical Characteristics

Below are the snap-shots taken at start-up with different loading conditions and during the application of the over­current at the output of the circuit.

For all figures, Ch1: V

DRAIN

; Ch2: V

GATE

; Ch3: PWRGD; Ch4: VR4 (Input current)

Figure 3. Start-up with no load.

Figure 4. Start-up with 1A load.

Figure 5. Start-up with “over the limit” load. Figure 6. Over-current/Short circuit.

9 2005 Semtech Corp. www.semtech.com

POWER MANAGEMENT

SC4250

Typical Characteristics (Cont.)

The following set of snapshots demonstrates effectiveness of SC4250 circuit in the case where connection to the
live back plane is very “bouncy”, which is usually the situation with manual replacements of the power cards.

For all figures, Ch1: V

DRAIN

; Ch2: V

GATE

; Ch3: PWRGD (referenced to V

DRAIN

); Ch4: VR4 (Input current)

Figure 7. Start-up with no load.

Figure 8. Start-up with 1A load.

Figure 9. Start-up with “over the limit” load.

Figure 10. Over-current/Short circuit.

10 2005 Semtech Corp. www.semtech.com

SC4250

POWER MANAGEMENT

Evaluation Board Schematic

Figure 12

Evaluation Board

C3

0.33

C5

150

+Vout

-Vout

GND

-- 48V

R5
10

R1

562k

R3

10.2k
R4

0.01

R6
18k

R2

9.31k

C4

3.3nF

DRAIN

7

UV

3

VEE

4

GATE

6

PWRGD/PWRGD

1

SENSE

5

VCC

8

OV

2

U1

SC4250H/L

GND(remote)

C2(opt)

0.01

+Vin

-Vin

ON/OFF

POWER

MODULE

C1

0.1

C6(opt)

0.1

R7
(opt)

Copt

0.1

Q1

IRF1310

Figure 11

11 2005 Semtech Corp. www.semtech.com

POWER MANAGEMENT

SC4250

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2115R01rotsiseR5080

3116Rk81rotsiseR5080

4117Rk1.5rotsiseRS6021

5111U0524CSCIhcetmeS8-OS

Evaluation Board - Bill of Materials

12 2005 Semtech Corp. www.semtech.com

SC4250

POWER MANAGEMENT

Outline Drawing - SO-8

Minimum Land Pattern - SO-8

Semtech Corporation

Power Management Products Division

200 Flynn Road, Camarillo, CA 93012

Phone: [phone] FAX [phone]

Contact Information

SEE DETAIL

DETAIL

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h

h

3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS
OR GATE BURRS.

-B-

CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).

DATUMS AND TO BE DETERMINED AT DATUM PLANE

NOTES:

1.

2.

-A-

-H-

SIDE VIEW

A

B

C

D

e

H

PLANE

REFERENCE JEDEC STD MS-012, VARIATION AA.

4.

L1

N

01

bbb

aaa

ccc

A

b

A2

A1

D

E

E1

L

h

e

c

DIM

MIN

MILLIMETERS

NOM

DIMENSIONS

INCHES

MIN MAX MAXNOM

E

(.205) (5.20)

Z

G

Y

P

(C)

3.00

.118

1.27

.050

0.60.024

2.20.087

7.40.291

X

INCHES

DIMENSIONS

Z

P

Y

X

DIM

C
G

MILLIMETERS

THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.

NOTES:

1.

REFERENCE IPC-SM-782A, RLP NO. 300A.

2.