Datasheet sc1104 Datasheet

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Description

SC1104A/B

Simple, Synchronous

Voltage Mode PWM Controller

Features

The SC1104A/B is a versatile voltage-mode PWM controller designed for use in single ended DC/DC power supply applications. A simple, fixed frequency high efficiency buck regulator can be implemented using the SC1104A/B with a minimum of external components. Internal level shift and drive circuitry eliminates the need for an expensive P-channel, high-side switch. The small device footprint allows for compact circuit design.

SC1104A/B features include temperature compensated voltage reference, triangle wave oscillator, current limit comparator and an externally compensated error amplifier. Current limit is implemented by sensing the voltage drop across the top FET’s R

DS(ON)

.

The SC1104 operates at fixed frequencies of 300kHz(A) or 600kHz(B) providing an optimum compromise between efficiency, external component size, and cost. 600kHz switching frequency is reserved for the SC1104B, +5VCC operation only.

SC1104A/B has a thermal protection circuit, which is activated if the junction temperature exceeds 150°C.

 Up to +14V input, 300kHz operation (SC1104A)  Up to +7V input, 600kHz operation (SC1104B)  High efficiency (>90%)  1% Reference voltage accuracy  Hiccup mode over current protection  Robust output drive  R

Current sensing

DS(ON)

 Industrial temperature range  8-Lead SOIC package. Pb-free package available,

fully WEEE and RoHS compliant

Applications

 Termination supplies  Low cost microprocessor supplies  Peripheral card supplies  Industrial power supplies  High density DC/DC conversion

Typical Application Circuit

Typical Distributed Power Supply

C1

510-1500pF

U1

COMP /SS

GND

DL

DH

SC1104A/B

SENSE

VCC

PHASE

BST

R1 200-2k

C2

0.01

1

2

3

4

C3 1

8

7

6

5

R6 1-5.1

R7 1-5.1

Q1

Si4884DY

Q2

Si4874DY

R3

1.00k

D1

MBRA130L

C9

0.1

(opt)

+

C4

10.0

R4

2.32k

R5

0.1-0.33

L1

1.5-6.8uH

C8

C10 220/4V

200-1k

R8 opt

D2

C5 47/16V

C11 220/4V

C6 47/16V

C12 220/4V

C7 47/16V

C13 220/4V

Vin 5 to 12V

_

+

C14-17

3.3V

1.0

_

Revision: November 22, 2006

Figure 1

1

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SC1104A/B

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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. Exposure to Absolute Maximum rated conditions for extended periods of time may affect device reliability.

retemaraPlobmySmumixaMstinU

V

CC

DNGot 02+V

ESAHPotTSB 02+V

DNGotESAHP 02+ot5.0-V

DNGotSS/PMOC 7+V

DNGotESNES 7+V

egnaRerutarepmeTegarotST

Electrical Characteristics

Unless specified: A: VCC = 12 ± 0.6V, V

retemaraPlobmySsnoitidnoCniMpyTxaMstinU

esaCotnoitcnuJecnatsiseRlamrehT

tneibmAotnoitcnuJecnatsiseRlamrehT

egnaRerutarepmeTnoitcnuJgnitarepOT

egnaRerutarepmeTtneibmAgnitarepOT

.ceS01)gniredloS(erutarepmeTdaeLT

)ledoMydoBnamuH(gnitaRDSEV

= 23 ± 1V, V

BST

= 3.3V, TJ = TA = 25oC.

OUT

θ

CJ

θ

AJ

J

A

GTS

daeL

DSE

B: V

= 5 ± 0.25V, V

CC

04W/C°

061W/C°

521+ot04-C°

58+ot04-C°

051+ot56-C°

003C°

2Vk

= 12 ± 0.6V, V

BST

= 2.0V, TJ = TA = 25oC

OUT

ylppuSrewoP

egatloVylppuSV

tnerruCylppuSI

CC

V

CC

F

WS

F

WS

reifilpmArorrE

)1(

ecnatcudnocsnarTA/E

)1(

niaGCDpooLnepO

)1(

Bd3-htdiwdnaB

tnerruCsaiBtupnII

tnerruCkniStuptuO

tnerruCecruoS

g

m

A

O

F

WB

BF

I

KIS

I

CS

V

rotallicsO

ycneuqerFgnihctiwSF

CSO

A4011CS,).mon(zHk003=5.441V

B4011CS,).mon(zHk006=5.47

V

≤ V4.01141Am

PMOC

21Sm

24Bd

004zHk

13 Aµ

≥ V;V1.1

ESNES

V5.1=56.07.0

PMOC

Am

≥ V;V9.0

ESNES

V

CC

V5.1=59.01.1

PMOC

V6.0±V21=552003543

zHk

V

CC

V52.0±V5=015006096

2

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Electrical Characteristics

Unless specified: A: VCC = 12 ± 0.6V, V

retemaraPlobmySsnoitidnoCniMpyTxaMstinU

)1(

egatloVkaePpmaR

)1(

egatloVyellaVpmaR

)2(

elcyCytuDmumixaM

srevirDTEFSOM

= 23 ± 1V, V

BST

V

K-P

V

cd

SC1104A/B

= 3.3V, TJ = TA = 25oC.

OUT

V57.4 ≤ VCC≤ V6.210.2V V57.4 ≤ VCC≤ V6.210.1V

XAM

V

CC

V

CC

B: VCC = 5 ± 0.25V, V

)A4011CS,zHk003(V21=0959%

)B4011CS,zHk006(V5=5809

= 12 ± 0.6V, V

BST

= 2.0V, TJ = TA = 25oC

OUT

tnerruCecruoS/kniSHD

A4011CS

tnerruCecruoS/kniSLD

A4011CS

tnerruCecruoS/kniSHD

B4011CS

tnerruCecruoS/kniSLD

B4011CS

emiTllaF/esiRHDft,rtC

emiTllaF/esiRLDft,rtC

emiTdaeDt

emiTffOmuminiMHDt

I

HD

V

I

LD

I

HD

V

I

LD

td

FFO

V

L

t,%2<.c.d

WP

SG

t,%2<.c.d

WP

SG

V57.4 ≤ ccV ≤ V6.21061

noitceSecnerefeR

egatloVecnerefeRV

ecnairaVpmeT

∆V

FER

ytilibatSmreTgnoLT

V57.4 ≤ ccV ≤ V6.21099.0000.1010.1V

T<0

J

T<04-

J

timiLtnerruC

sµ001<

6.08.0A

)crs(V5.4=

)kns(V5.2=

sµ001<

6.07.0

54.06.0A

)crs(V5.4=

)kns(V5.2=

54.06.0

2.giFeeS,Fp0003=05sn

2.giFeeS,Fp0004=05

2.giFeeS08sn

C°07+<1-1%

C°58+<5.1-5.1

.srh0001,C°521=5Vm

egatloVpirTV

elbanE/tratS-tfoS

tnerruCecruoSSSI

tnerruCkniSSSI

PIRT

CRS

KNS

V57.4<ccV< V6.21

V

prt

V

PMOC

V

PMOC

V-ccV=

ESAHP

V5.2<5.08.1Aµ

V5.0>5.08.1Aµ

081002022Vm

dlohserhTtupnIelbanE 00.153.1V

tnerruCtupnIelbanEV

V8.0=2Am

PMOC

3

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Electrical Characteristics

Unless specified: A: VCC = 12 ± 0.6V, V

retemaraPlobmySsnoitidnoCniMpyTxaMstinU

tuokcoLegatloVrednU

= 23 ± 1V, V

BST

= 3.3V, TJ = TA = 25oC.

OUT

B: V

CC

= 5 ± 0.25V, V

= 12 ± 0.6V, V

BST

SC1104A/B

= 2.0V, TJ = TA = 25oC

OUT

dlohserhTOLVUV

nwodtuhSlamrehT

)2(

tnioPpirTerutarepmeTrevO

Notes: (1) Guaranteed by design. (2) Not tested, by characterization.

ht

T

PTO

T<04-

C°58<9.351.45.4V

J

041061C°

Figure 2

Block Diagram

Figure 3

4

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SC1104A/B

Pin Configuration

(8-Pin SOI

Pin Descriptions

niP

#

1SS/PMOC.elbane/tratstfos,noitasnepmoC.tuptuoreifilpmarorrE

2DNG.dnuorG

emaNniPnoitcnuFniP

Top View

C)

Ordering Information

)2(

eciveD

)1(

RTSIX4011CS

)3()1(

TRTSIX4011CS

BVEX4011CSdraoBnoitaulavE

Notes: (1) In place of “X”: A = 300kHz, V B = 600kHz, V (2) Only available in tape and reel packaging. A reel contains 2500 devices. (3) Lead free product. This product is fully WEEE and RoHS compliant.

egakcaPT(egnaRpmeT

8-CIOSC°521ot°04-

= 5V to 12V.

CC

= 5V.

CC

)

J

3LDtuptuorevirdediswoL

4HDtuptuorevirdedishgiH

5TSB.revirdedishgih,partstooB

6ESAHP.sTEFSOMehtneewtebedonesahpehtmorftupnI

7CCV.egatlovylppussaibpihC

8ESNES.tupniesnesegatlovtuptuO

Marking Information

yyww = Date Code (Example: 0012) xxxxxxxx = Semtech Lot No. (Example: E90101-1)

5

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Theory of Operation

Synchronous Buck Converter

SC1104A/B

The output voltage of the synchronous converter is set and controlled by the output of the error amplifier. The inverting input of the error amplifier receives its voltage from the SENSE pin. The non-inverting input of the error amplifier is connected to an internal 1V reference.

The error amplifier output is connected to the COMPensation pin. The error amplifier generates a current proportional to (Vsense – 1V), which is the COMP pin output current (Transconductance ~ 12mS). The voltage on the COMP pin is the integral of the error amplifier current. The COMP voltage is the non-inverting input to the PWM comparator and controls the duty cycle of the MOSFET drivers. The size of capacitor Ccomp controls the stability and transient response of the regulator. The larger the capacitor, the slower the COMP voltage changes, and the slower the duty cycle changes.

The inverting input voltage of the PWM comparator is the triangular output of the oscillator.

When the oscillator output voltage drops below the COMP voltage, the comparator output goes high. This pulls DL low, turning off the low-side FET. After a short delay (“dead time”), DH is pulled high, turning on the high-side FET. When the oscillator voltage rises back above the error amplifier output voltage, the comparator output goes low. This pulls DH low, turning off the high-side FET, and after a dead time delay, DL is pulled high, turning on the lowside FET. The dead time delay is determined by a monostable on the chip.

The triangle wave minimum is about 1V, and the maximum is about 2V. Thus, if Vcomp = 0.9V, high side duty cycle is the minimum (~0%) , but if Vcomp is 2.0V, duty cycle is at maximum ( ~90%).The internal oscillator uses an on-chip capacitor and trimmed precision current sources to set the oscillation frequency to 300kHz (SC1104A) or 600kHz (SC1104B).

Figure 1 shows a 3.3V output converter. If the Vout <3.3V, then the SENSE voltage < 1V. In this case the error amplifier will be sourcing current into the COMP pin so that COMP voltage and duty cycle will gradually increase. If Vout > 3.3V, the error amplifier will sink current and reduce the COMP voltage, so that duty cycle will decrease.

The circuit will be in steady state when Vout =3.3V , Vsense = 1V, Icomp = 0 . The COMP voltage and duty cycle depend on Vin.

Under Voltage Lockout

The under voltage lockout circuit of the SC1104A/B assures that both high-side and low-side MOSFET driver outputs remain in the off state whenever the supply voltage drops below set parameters. Lockout occurs if V falls below 4.2V typ.

R

Current Limiting

DS(ON)

In case of a short circuit or overload, the high-side (HS) FET will conduct large currents. To prevent damage, in this situation, large currents will generate a fault condition and begin a soft start cycle.

While the HS driver is on, the phase voltage is compared to the Vcc pin voltage. If the phase voltage is 200mV lower than Vcc, a fault is latched and the soft start cycle begins.

The voltages are compared during the middle of the HS pulse, to prevent transients from affecting the accuracy.

The sampling of the voltage across the top FET occurs after a time delay t

= 100ns_typ from the time the

DELAY

DH is pulled high. This delay prevents the measurement to be effected by ringing on the leading edge of the phase node pulse. The duration of the sampling is t

SAMPLE

= 100ns_typ. It is being disabled at very low duty cycle when tON < 300ns_typ. This feature allows for the orderly startup during the inrush of the current charging output capacitor and the fault free operation with extremely high input/output voltage ratio, e.g., VIN = 12V and V

OUT

= 1V.

The over-current comparator (OC) is only active if the phase node is > 3.3V. This means that in the case of power source being < 3V the OC will be disabled even though the rest of the circuitry is completely functional. SC1104 still can be used for stepping down, e.g. 2.8V to

2.5V, 2V, 1.8V, etc.

CC

6

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Theory of Operation (Cont.)

SC1104A/B

When choosing OC trip point one should consider the Tempco of the MOSFETs Rds_on and SC1104’s Vtrip. Also, any ringing on the Vcc and Phase nodes due to parasitic L and C will have some effect on the OC Vtrip.

Example:

Iout_nom = 6A; assume I_max = 125% • Iout_nom =

7.5A

Rds_on = 0.014Ω; assume Rds_on_max

≈ 150% •

Rds_on = 0.02Ω Voc = 7.5A • 0.02Ω = 150mV.

This proves that MOSFETs with R

= 0.014Ω @ 25°C

DS_ON

is the right choice.

Soft Start

The soft start (or hiccup) circuitry is activated when a fault occurs. Faults occur for three reasons:

Closing the Loop

In order to have a stable closed loop system with optimum transient response one should make sure that open-loop frequency response has an adequate Gain & Phase margins. The Bode plot of log. Gain vs Freq. and Phase vs Freq. provide the necessary means for the circuit evaluation. Loop stability defined by compensation networks around transconductance error amplifier (EA) and output divider, see below and output capacitor Cout and inductor Lout.

Vout

Cn

Rn

EA

_

C

R

C

Gm

+

Cp

Vref

Ra

Rb

1) Under voltage (VCC < 4.2V)

2) Over temperature (die temperature > 150°C)

3) Over current in high side FET.

All faults are handled the same way. Both DH and DL are forced low. The error amplifier is turned off, but a 2µA current flows into the comp pin (soft start current). The sink current reduces the Comp voltage down to 0.6V over a period of a few milliseconds. When Vcomp ~ 0.6V, the fault is cleared and the DL goes high. Also, the soft start current changes polarity and begins to increase the voltage on the Comp capacitor. The DH remains low, because Vcomp is less than the lowest excursion of the oscillator ramp (1.0V). After a few ms, the Vcomp increases to about 1.0V and the DH will start to switch. The duty cycle will gradually increase, and Vsns will increase. When Vsns ~ 1.00V, the error amplifier turns on again. The circuit has now reached its operating point. If a fault occurs during the soft start, the cycle will begin again (drivers low, Vcomp decreasing down to 0.6V).

Typical transconductance error amplifier

The inductor and output capacitor form a “double pole” at the frequency:

∏

1

•••

CoLo2

=

f

LC

The ESR of the output capacitor and the output capacitor value create a “zero” at the frequency.

f

ESR

=

∏

1

•••

CoESR2

The “zero” and “pole” from the EA compensation network are:

∏

1

•••

CcRc2

=

f

P

=

f

Z

∏

1

•••

CpRc2

The additional “lead” network RA, CN, RN can be used to improve phase margin in case when output capacitors with extra-low ESR are used and there is a need to compensate for “high quality” output Lo, Co filter.

7

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POWER MANAGEMENT

Theory of Operation (Cont.)

SC1104A/B

f

NET

=

∏

1

•••

CnRa2

Value for the resistor RN should be 1/10 of the output divider upper resistor RA.

Example. Switching frequency fSW = 300kHz

Output capacitance C

Output capacitor ESR = 45mΩ/each

Output inductance L

= 3 x 330µF

OUT

= 4.7µH

OUT

Input voltage VIN = 12V Output voltage V

= 3.3V

OUT

Let’s choose crossover frequency f

= 1/20 • f

CO

= 15kHz

SW

The compensation values used in this example are based on the following criteria:

f

= fLC; f

Z

= 1/10 • f

NET

; f

LC

= 10 • f

P

= 150kHz

CO

attenuation due to the LO, CO filter and the output resistor divider R

, RB is compensated by the gain of

A

the PWM modulator and the gain of the transconductance error amplifier (Gm

• Z

EA

COMP

).

Shown below is a typical Bode plot of the open-loop frequency response of SC1104 based buck converter.

80.0

-50.0

40.0

-150

0

-250

Plot1

vpherr in degrees

vdberr in db(volts)

-40.0

-80.0

-350

-450

2

1

Therefore,

f

LC

f

ESR

=

1

∏

=

1

∏

=

µ•••

F990H4.7µ2

=

F990015.02

µ•••

kHz33.2

kHz72.10

Since, the EA can sink/source about 1mA, let’s choose

Rc = 680Ω, then

∏

1

•••

RcFz2

1

=

RcFp2

•••

F1.0

pF1500

C µ=

=

C

=

P

Assuming the output divider lower resistor RB = 1k, then for V

= 3.3V the RA = 2.32k.

OUT

=

C

N

∏

1

NET

µ=

•••

Raf2

F3.0

At the closed-loop crossover frequency fCO, the

1 10 100 1k 10k 100k 1Meg

1 vdberr 2 vpherr

frequency in hertz

8

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Typical Characteristics

SC1104A/B

Reference Voltage vs. Temp

0.5%

0.4%

0.3%

0.2%

0.1%

0.0%

-0.1 %

-0.2 %

-0.3 %

Vref, %

-0.4 %

-0.5 %

-0.6 %

-0.7 %

-0.8 %

-0.9 %

-1.0 %

-40-20020406080100120

Temp, °C

Trip Voltage vs. Temp

25%

20%

15%

10%

5%

0%

Vtrip, %

-5%

-10%

-15%

-20%

-25%

-40-20 0 20406080100120

Temp, °C

Switching Frequency vs. Temp

25%

20%

15%

10%

5%

0%

Freq, %

-5%

-10%

-15%

-20%

-25%

-40-200 20406080100120

Temp, °C

Under Voltage Lockout vs. Temp

10%

8%

6%

4%

2%

0%

UVLO, %

-2%

-4%

-6%

-8%

-10%

-40-200 20406080100120

Temp, °C

9

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0

Evaluation Board Schematic - V

C3

1.0

C1

C2

0.1

1500p

R1 1k

1

2

3

SC11 04A ISTR

COMP/SS

GND

DL

U1

8

SENSE

7

VCC

PHASE

MBRA13 0L(o pt)

6

D2

= 5V

IN

D1

MBRA13 0L

C7

10.0

R7

1.0k

C8 47/6.3V

R9 150

R8

1.50k

C9 47/6.3V

C11

0.47

SC1104A/B

+

C10

47/6.3V

Vin=5V

_

4

DH

R3 1

R4

2.2

BST

5

Q1

Si44 10DY

Q2

Si44 10DY

Evaluation Board Schematic - VIN = 12V

C3

1.0

C1

C2

0.1

1500p

R1 680

1

2

3

SC11 04A ISTR

COMP/SS

GND

DL

U1

8

SENSE

D2

7

VCC

PHASE

MBRA13 0L(o pt)

6

R5 0

C4

0.1

D1

LL4148

C5 6800p

R6

2.2

C7

10.0

L1

3.9uH

R7

1.0k

C8 33/16V

C15 330/4V

R8

2.32k

R9 220

C16 330/4V

C9 33/16V

C11

0.33

C17

330/4V

C10

33/16V

C18 10

+

Vout=2.5@6A

_

+

Vin=12V

_

4

DH

R3

2.2

R4

2.2

BST

5

Q1

Si44 10DY

Q2

Si44 10DY

R5

5.1opt

C4

0.1

10

C5 3300p

R6

3.3

L1

4.7uH

C15 330/4V

C16 330/4V

C17

330/4V

C18 10

Vout=3.3@6A

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+

_

POWER MANAGEMENT

Evaluation PC Board

SC1104A/B

Top View

Top Layer

Bottom Layer

11

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POWER MANAGEMENT

Typical Characteristics

100%

95%

90%

SC1104A/B

Efficiency

1.0%

0.8%

0.6%

0.4%

0.2%

0.0%

-0.2%

-0.4%

Regulation

-0.6%

-0.8%

-1.0%

85%

80%

75%

70%

65%

60%

024681012

Current, A

024681012

12V = Vin

3.3V = Vout

12A = Iout

Current, A

12

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Typical Characteristics (Cont.)

100%

95%

90%

85%

80%

75%

Efficiency

70%

65%

60%

024681012

SC1104A/B

5V = Vin

2V = Vout

12A = Iout

Current, A

-0.2%

Regula tion

-0.4%

-0.6%

-0.8%

-1.0%

1.0%

0.8%

0.6%

0.4%

0.2%

0.0%

024681012

Current, A

13

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,

Outline Drawing - SOIC - 8

SC1104A/B

A

N

E/2

2X

12

ccc C

2X N/2 TIPS

aaa C

SEATING PLANE

NOTES:

CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).

1.

DATUMS AND TO BE DETERMINED AT DATUM PLANE

2.

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

REFERENCE JEDEC STD MS-012, VARIATION AA.

4.

C

SIDE VIEW

-A- -H-

-B-

e/2

B

D

bxN

bbb C A-B D

e

E1

A2

A1

SEE DETAIL

D

E

A

PLANE

A

DIM

GAGE

0.25

A1 A2

D

E1

L1 N

01 aaa bbb ccc

A

b c

E e

h L

H

DIMENSIONS

INCHES

NOM

MIN MAX MAXNOM

-

.053

-

.004

-

.049

-

.012

-

.007 .189

.193

.150

.154 .236 BSC .050 BSC

-

.010 .020 0.50

.028

.016

(.041)

8

-

0°

.004

.010

.008

h

DETAIL

MILLIMETERS

MIN

.069

1.35

0.10

.010

1.25

.065 .020 0.31 .010

0.17

.197

4.80

.157

3.80

0.25

.041

0.40

8° 0°

h

L

(L1)

A

-

4.90

3.90

6.00 BSC

1.27 BSC

-

0.72-1.04

(1.04)

8

-

0.10

0.25

0.20

01

c

1.75

0.25

1.65

0.51

0.25

5.00

4.00

8°

Minimum Land Pattern - SOIC - 8

X

(C)

P

NOTES:

1.

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

2.

REFERENCE IPC-SM-782A

Contact Information

Power Management Products Division

200 Flynn Road, Camarillo, CA 93012

Phone: (805)498-2111 FAX (805)498-3804

INCHES

G

Z

Y

RLP NO. 300A.

DIM

C G P X Y Z

(.205) (5.20)

.118 .050

Semtech Corporation

DIMENSIONS

MILLIMETERS

3.00

1.27

0.60.024

2.20.087

7.40.291

14

www.semtech.com