Datasheet SC4150 Datasheet (SEMTECH)

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POWER MANAGEMENT

Description Features

SC4150

Negative Voltage

Hot Swap Controller

The SC4150 is a negative voltage hotswap controller that
allows the insertion of line cards into a live backplane.

The inrush current is programmable and closed loop op­eration limits the maximum current even under short cir­cuit conditions. A built in timing circuit prevents false shut­down. The signal from the drain voltage is fed to the
timer, providing safety for the MOSFET when in linear
mode. The SC4150 latches off under abnormal condi­tion and attempts to restart after a time out period.

The device comes in two options, PWRGD (SC4150H)
and PWRGD (SC4150L). These signals can be directly
used to enable power modules.

Typical Application Circuit

 Programmable slew of the inrush current when

used for hot insertion in the negative 24V and 48V
backplane

 Closed loop operation limits the maximum current

even in short circuit condition

 Built in timer prevents false shutdown, when the

closed loop operation limits the current.

 Sensing the drain voltage allows for immediate

shutdown in short circuit condition, where current
spikes and noise is ignored.

 Power good signal
 Input UVLO and OVLO sensing
 SO-8 package

Applications

 Central office switching
 -48V Distributed power systems
 Power supply hotswap & inrush control

GND

PWRG D/PWRG D

GND(remote)

-- 48V

R1

562k

R2

9.31k

R3

10.2k

C2

0.001

VEE

Vee

C1

0.1

C4

R6
18k

3.3nF

R5
10

Q1

C5

150

U1

SC4150

1

PWRGD

/PWRGD

2

OV

3

UV

4

VEE

R4

0.01

DRAIN

VCC

GATE

SEN SE

8

7

6

5

C3

0.33

Figure 1

Revision: October 10, 2003

1 www.semtech.com

SC4150

POWER MANAGEMENT

Absolute Maximum Ratings

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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Electrical Characteristics

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

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8.83C°

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051ot56-C°

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evirDetaGlanretxE

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egatloVdlohserhTwoLniPVUV

sisretsyHniPVUV

tnerruCtupnIniPVUI

egatloVdlohserhThgiHniPVOV

egatloVdlohserhTwoLniPVOV

sisretsyHniPVOV

∆V

CC

BC

UP

DP

ESNES

ETAG

HVU

LVU

YHVU

VUNI

HVO

LVO

YHVO

V

V(

V-

ETAG

V(

V-

ETAG

V=V0,V3=VU

EE

BC

V

EE

V(=

ESNES

EE

VVUV=

V-EE) 050607 Vm

ESNES

V,NOevirdetaG

ETAG

Vm05=50.0-Aµ

V02,) < VDD≤ V08 93161 V

V01,) ≤ VDD≤ V02 8

EE

V=ESNES,

EE

V=

EE

47 Am

05-Aµ

noitidnoctluafynA04Am

noitisnarthgiHotwoLVU 142.1372.1503.1 V

noitisnartwoLothgiHVU 291.1322.1352.1 V

05 Vm

1.0-Aµ

noitisnarthgiHotwoLVO 291.1322.1352.1 V

noitisnartwoLothgiHVO 351.1881.1322.1 V

53Vm

tnerruCtupnIniPVOI

VONI

V

≥ V5.150.0-Aµ

VO

2 2003 Semtech Corp. www.semtech.com

POWER MANAGEMENT

Electrical Characteristics (Cont.)

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

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SC4150

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GP

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NIARD

LO

HO

V

V-

NIARD

EE

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4.0V

V

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LO

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NIARD

V,L0514CS

V@

NIARD

V,H0514CS

V-

NIARD

V,L0514CS

V84= 5105 Aµ

NIARD

V-DGRWP=

I,V5=

O

LO

I,V1=

O

EE

V,V1=

V-

NIARD

EE

NIARD

Am1=

V-DGRWP=

EE

Am1=

V08= 0.101 Aµ

DGRWP

V5= 0.101 Aµ

1V

1V

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VULHP

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5.1sµ

5.5sµ

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3sµ

sµ

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

3 2003 Semtech Corp. www.semtech.com

5.0sµ

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yrterotroirp,trohsretfA,004-0514CS004

POWER MANAGEMENT

Pin Configuration Ordering Information

)1(

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SC4150

egakcaP

Pin Descriptions

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TOP VIEW

1

2

3

4

8

7

6

5

(SO-8)

RTSIH0514CS

RTSIL0514CS

VCCPWRGD/PWRGD

DRAINOV

GATEUV

SENSEVEE

Note:

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

RT4-SIH0514CS

RT4-SIL0514CS

8-OS

contains 2500 devices.

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4 2003 Semtech Corp. www.semtech.com

POWER MANAGEMENT

Block Diagram

Active High PWRGD

Vcc

UV

SC4150

PWRG D

12.5V Reg 1.223V

50uA

_

+

Active Low PWRGD

UV

OV

60mV

Vcc

_

+

Dela y

_

+

12.5V Reg 1.223V

_

+

_

+7V

+

Timer

_

+

1.75V

DRAINGATESENSEVee

PWRG D

50uA

OV

60mV

_

+

_

+7V

+

Dela y

_

+

Timer

_

+

1.75V

DRAINGATESENSEVee

5 2003 Semtech Corp. www.semtech.com

POWER MANAGEMENT

C

Applications Information

SC4150

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 SC4150. 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

+48V

1

-48V

Vcc

12.5V Reg 1.223V

R1

UV

R2

OV

R3

60mV

_

+

_

+

_

+

R4

Delay

_

+7V

+

DRAINGATESENSEVee

C3

R5

R6

C2

Q1

50uA

Timer

PWRGD

_

+

1.75V

Cloa d
150uF

Figure 2

6 2003 Semtech Corp. www.semtech.com

POWER MANAGEMENT

Applications Information (Cont.)

SC4150

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=9.31k

Ω. With these values the accuracy is about 1%

10.2k

Ω and R3 =

which is quite acceptable for those functions.
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 m

Ω.

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 SC4150
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.

The inrush can be calculated using the following equation:
I

= (50µA • C

MAX

LOAD

) / C3

With the values shown in the schematic the actual inruch
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.

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
SC4150 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 ·

dt = Cload ·

∆Vmax /dt

∆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 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.

7 2003 Semtech Corp. www.semtech.com

SC4150

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

Figure 3. Start-up with no load.

DRAIN

; Ch2: V

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

GATE

Figure 4. Start-up in over load.

Figure 5. Start-up with 1Amp load.

Figure 6. From 3A load into “short circuit”.

8 2003 Semtech Corp. www.semtech.com

SC4150

POWER MANAGEMENT

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

Figure 7. Short circuit hiccup.

DRAIN

; Ch2: V

; Ch3: PWRGD (referenced to V

GATE

); Ch4: VR4 (Input current)

DRAIN

Figure 8. Inrush limit.

Figure 9. Inrush limit.

Figure 10. Inrush limit.

9 2003 Semtech Corp. www.semtech.com

POWER MANAGEMENT

Evaluation Board Schematic

SC4150

GND

GND(remote)

-- 48V

Evaluation Board

R1

562k

R2

9.31k

R3

10.2k

C2(opt)

0.01

R7
(opt)

U1

SC4150H/L

1

2

3

4

PWRGD/PWRGD

OV

UV

VEE

R4

0.01

C1

0.1

DRAI N

GATE

SENSE

VCC

8

7

C4

R6
18k

R5
10

Q1

IRF1310

3.3nF

6

5

C3

0.33

150

C6(opt)

C5

ON/OFF

+Vin

POWER

0.1

MODUL E

-Vin

+Vout

-Vout

0.1

Copt

10 2003 Semtech Corp. www.semtech.com

POWER MANAGEMENT

Evaluation Board - Bill of Materials

feRytQrotangiseDeulaVnoitpircseDtnirptooF

111CV001/1.0paccimareC0121

21 ).tpo(2C10.0paccimareC5080

313C33.0paccimareCS6021

414CV001/3300.0paccimareC5080

515CV08/051pacmunimulAH-LA-PAC

61 ).tpo(6CV001/1.0paccimareC0121

711Q0131FRITEFSOMKAP2D

811Rk265rotsiseR5080

912Rk13.9rotsiseR5080

SC4150

0113Rk2.01rotsiseR5080

1114R10.0rotsiseRSC0102

2115R01rotsiseR5080

3116Rk81rotsiseR5080

4117Rk1.5rotsiseRS6021

5111U0514CSCIhcetmeS8-OS

11 2003 Semtech Corp. www.semtech.com

POWER MANAGEMENT

Outline Drawing - SO-8

SC4150

JEDEC REF: MS-012AA

Minimum Land Pattern - SO-8

Contact Information

Semtech Corporation

Power Management Products Division

200 Flynn Road, Camarillo, CA 93012

Phone: [phone] FAX [phone]

12 2003 Semtech Corp. www.semtech.com