LTC3874EUFD#TRPBF datasheet, PDF

LTC3874

PolyPhase Step-Down

Synchronous Slave Controller with

Sub-Milliohm DCR Sensing

FEATURES

n

DESCRIPTION

The

LTC

®

3874

is a dual PolyPhase

®

current mode synchro-

nous step-down slave controller. It enables high current,

multi-phase applications when paired with a companion

master controller by extending the phase count. Compat-

ible master controllers include the LTC3884, LTC3866,

LTC3875, LTC3877 and LTC3774. The LTC3874 employs a

unique architecture that enhances the signal-to-noise ratio

of the current sense signal, allowing the use of sub-milliohm

DC resistance power inductors to maximize efficiency while

reducing switching jitter. Its peak current mode architecture

allows for accurate phase to phase current sharing even

for dynamic loads.

Effectively working with a master controller, the LTC3874

supports all the programmable features as well as fault

protection.

L,

LT, LTC, LTM, Linear Technology, the Linear logo, PolyPhase and Burst Mode are registered

trademarks of Analog Devices, Inc. All other trademarks are the property of their respective

owners. Protected by U.S. Patents, including 5481178, 5705919, 5929620, 6100678, 6144194,

6177787, 6304066, 6580258.

n

Phase Extender for High Phase Count Voltage Rails

Accurate Phase-to-Phase Current Sharing

Sub-Milliohm DCR Current Sensing

Phase-Lockable Fixed Frequency 250kHz to 1MHz

Immediate Response to Master IC's Fault

Up to 12 Phase Operation

Wide V

IN

Range: 4.5V to 38V

V

OUT

Range: Up to 3.5V (LOWDCR Pin = INTV

CC

)

Up to 5.5V (LOWDCR Pin = OV)

Proprietary Current Mode Control Loop

Programmable CCM/DCM Operation

Programmable Phase Shift Control

Dual N-Channel MOSFET Gate Drivers

28-Lead (4mm

×

5mm) QFN Package

APPLICATIONS

n

High Current Distributed Power Systems

Telecom, Datacom, and Storage Systems

Intelligent Energy Efficient Power Regulation

TYPICAL APPLICATION

High Efficiency, 4-Phase 1.8V/120A Step-Down Supply

V

IN

7V TO 14V

4.7µF

V

IN

INTV

CC

LTC3874 TG0

PHASMD BOOST0

LOWDCR

90k

EXTV

CC

FREQ

ILIM

SW0

BG0

I

SENSE0+

I

SENSE0

LTC3884

RUN0

RUN1

GPIO0

GPIO1

PGOOD0

PGOOD1

I

TH0

I

TH1

SYNC

RUN0

RUN1

FAULT0

FAULT1

MODE0

MODE1

I

TH0

I

TH1

SYNC

–

Dual Phase Efficiency and Power Loss

vs Output Current, Sub-Milliohm DCR

vs Traditional DCR

0.1µF

0.33µH

(0.32m DCR)

100

V

OUT

1.8V

120A

EFFICIENCY (%)

95

90

85

POWER LOSS

80

75

0.32m

1.5m

0.32m

1.5m

0

10

20

30

40

LOAD CURRENT (A)

50

6

4

2

0

60

V

IN

= 12V

V

OUT

= 1.8V

CCM

EFFICIENCY

14

12

10

8

POWER LOSS (W)

+

931

0.22µF

470µF

×2

TG1

BOOST1

SW1

BG1

GND

I

SENSE1+

I

SENSE1–

0.1µF

0.33µH

(0.32m DCR)

V

SENSE0+

V

SENSE1

+

931

0.22µF

470µF

×2

70

3874 TA01b

3874 TA02

3874fb

For more information

www.linear.com/LTC3874

1

LTC3874

ABSOLUTE MAXIMUM RATINGS

(Note 1)

PIN CONFIGURATION

TOP VIEW

LOWDCR

FAULT0

FAULT1

SW0

22 BOOST0

21 BG0

20 V

IN

29

GND

19 INTV

CC

18 EXTV

CC

17 BG1

16 BOOST1

15 SW1

9 10 11 12 13 14

FREQ

ILIM

SYNC

PHASMD

I

TH1

TG1

I

TH0

TG0

V

IN

............................................................. −0.3V to 40V

BOOST0, BOOST1 ...................................... −0.3V to 46V

SW0, SW1 .................................................... −5V to 40V

(BOOST0-SW0), (BOOST1-SW1) ................. −0.3V to 6V

I

SENSE0+

, I

SENSE0 –

, I

SENSE1+

, I

SENSE1–

... −0.3V to INTV

CC

EXTV

CC

, INTV

CC

, RUN0, RUN1 .................... −0.3V to 6V

MODE0, MODE1, ILIM, LOWDCR,

PHASMD, FREQ .................................... −0.3V to INTVcc

SYNC,

FAULT0, FAULT1,

I

TH0

, I

TH1

......... −0.3V to INTVcc

INTV

CC

Peak Output Current ................................100mA

Operating Junction Temperature Range

(Note 2) .................................................. −40°C to 125°C

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

28 27 26 25 24 23

MODE0 1

I

SENSE0

I

SENSE0

+

–

2

3

RUN0 4

RUN1 5

I

SENSE1–

6

I

SENSE1+

7

MODE1 8

UFD PACKAGE

28-LEAD (4mm

×

5mm) PLASTIC QFN

θ

JA

= 43°C/W,

θ

JC

= 3.4°C/W

EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

LTC3874EUFD#PBF

LTC3874IUFD#PBF

TAPE AND REEL

LTC3874EUFD#TRPBF

LTC3874IUFD#TRPBF

PART MARKING*

3874

PACKAGE DESCRIPTION

28-Lead (4mm

×

5mm) Plastic QFN

28-Lead (4mm

×

5mm) Plastic QFN

TEMPERATURE RANGE

–40°C to 125°C

Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.

For more information on lead free part marking, go to:

http://www.linear.com/leadfree/

For more information on tape and reel specifications, go to:

http://www.linear.com/tapeandreel/.

Some packages are available in 500 unit reels through

designated sales channels with #TRMPBF suffix.

2

3874fb

For more information

www.linear.com/LTC3874

LTC3874

The

l

denotes the specifications which apply over the specified operating

junction temperature range, otherwise specifications are at T

A

= 25°C (Note 2). V

IN

= 12V, V

RUN0,1

= 3.3V unless otherwise specified.

SYMBOL

Input Voltage

V

IN

V

OUT

I

Q

V

UVLO

Control Loop

I

ISENSE0,1

I

SENSE

Pins Bias Current

V

ISENSE0,1

< (V

INTVCC

– 3.3V)

V

ISENSE0,1

> (V

INTVCC

– 3.3V)

(Table 3)

ILIM = INTV

CC

, LOWDCR = INTV

CC

,

V

ISENSE0,1

= 1.2V, V

ITH

= 2.18V

ILIM = 0V, LOWDCR = INTV

CC

,

V

ISENSE0,1

= 1.2V, V

ITH

= 2.18V

ILIM = INTV

CC

, LOWDCR = 0V,

V

ISENSE0,1

= 1.2V, V

ITH

= 2.18V

ILIM = 0V, LOWDCR = 0V,

V

ISENSE0,1

= 1.2V, V

ITH

= 2.18V

Gate Drivers

TG R

UP

TG R

DOWN

BG R

UP

BG R

DOWN

TG0,1

t

r

t

f

BG0,1

t

r

t

f

TG/BG t

1D

BG/TG t

2D

t

ON(MIN)

V

INTVCC

V

LDO

INT

V

EXTVCC

V

LDO

EXT

V

LDOHYS

TG Pull-Up R

DS(ON)

TG Pull-Down R

DS(ON)

BG Pull-Up R

DS(ON)

BG Pull-Down R

DS(ON)

TG Transition Time:

Rise Time

Fall Time

BG Transition Time:

Rise Time

Fall Time

Top Gate Off to Bottom Gate on Delay Time

Bottom Gate Off to Top Gate On Delay Time

Minimum On-Time

Internal V

CC

Voltage No Load

INTV

CC

Load Regulation

EXTV

CC

Switchover Voltage

EXTV

CC

Voltage Drop

EXTV

CC

Hysteresis

TG High

TG Low

BG High

BG Low

(Note 5)

C

LOAD

= 3300pF

C

LOAD

= 3300pF

(Note 5)

C

LOAD

= 3300pF

C

LOAD

= 3300pF

C

LOAD

= 3300pF Each Driver (Note 5)

C

LOAD

= 3300pF Each Driver (Note 5)

(Note 6)

6V < V

IN

< 38V

I

CC

= 0mA to 20mA

EXTV

CC

Ramping Positive (Note 7)

I

CC

= 20mA, V

EXTVCC

= 5V

l

ELECTRICAL CHARACTERISTICS

PARAMETER

Input Voltage Range

Output Voltage Range

Input DC Supply Current

Normal Operation

Shutdown

Undervoltage Lockout Threshold

CONDITIONS

MIN

4.5

TYP

MAX

38

3.5

5.5

UNITS

V

mA

V

LOWDCR = INTV

CC

(Note 3)

LOWDCR = 0V

(Note 4)

V

RUN0,1

= 3.3V

V

RUN0,1

= 0V

V

INTVCC

Falling

V

INTVCC

Rising

4.6

1.8

3.5

3.8

±0.15

±1

26.8

14.5

65

33

28.8

16

72

40

±0.4

±3

30.8

17.5

79

47

µA

mV

V

ISENSE(MAX)

Maximum Current Sense Threshold

2.6

1.5

2.4

1.1

30

60

5.25

4.5

5.5

0.5

4.7

50

300

100

5.75

2

Ω

ns

V

%

V

mV

INTV

CC

Regulator

3874fb

For more information

www.linear.com/LTC3874

3

LTC3874

The

l

denotes the specifications which apply over the specified operating

junction temperature range, otherwise specifications are at T

A

= 25°C (Note 2). V

IN

= 12V, V

RUN0,1

= 3.3V unless otherwise specified.

SYMBOL

f

RANGE

f

NOM

I

FREQ

θ

SYNC-θ0

PARAMETER

PLL SYNC Range

Nominal Frequency

Frequency Setting Current

SYNC to Ch0 Phase Relationship Based on

the Falling Edge of SYNC and Rising Edge

of TG0

SYNC to Ch1 Phase Relationship Based on

the Falling Edge of SYNC and Rising Edge

of TG1

PHASMD = 0

PHASMD = 1/3 • INTV

CC

PHASMD = 2/3 • INTV

CC

PHASMD = INTV

CC

PHASMD = 0

PHASMD = 1/3 • INTV

CC

PHASMD = 2/3 • INTV

CC

PHASMD = INTV

CC

l

ELECTRICAL CHARACTERISTICS

CONDITIONS

l

MIN

250

TYP

MAX

1000

UNITS

kHz

µA

Deg

Oscillator and Phase-Locked Loop

V

FREQ

= 0.9V

9

500

10

180

60

120

90

0

300

240

270

2.0

1.4

11

θ

SYNC-θ1

Digital Inputs RUN0, RUN1, MODE0, MODE1,

FAULT0, FAULT1,

LOWDCR

V

IH

V

IL

Input High Threshold Voltage

Input Low Threshold Voltage

V

Note 1:

Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 2:

The LTC3874 is tested under pulsed load conditions such that

T

J

≈ T

A

. The LTC3874E is guaranteed to meet performance specifications

from 0°C to 85°C. Specifications over the –40°C to 125°C operating

junction temperature range are assured by design, characterization and

correlation with statistical process controls. The LTC3874I is guaranteed

over the –40°C to 125°C operating junction temperature range. High

junction temperatures degrade operating lifetimes; operating lifetime

is derated for junction temperatures greater than 125°C. Note that the

maximum ambient temperature consistent with these specifications is

determined by specific operating conditions in conjunction with board

layout, the rated package thermal impedance and other environmental

factors. T

J

is calculated from the ambient temperature T

A

and power

dissipation P

D

according to the following formula:

T

J

= T

A

+ (P

D

• 43˚C/W)

Note 3:

Output voltage is set and controlled by master controller in

multiphase operations.

Note 4:

Dynamic supply current is higher due to the gate charge being

delivered at the switching frequency. See Application Information.

Note 5:

Rise and fall times are measured using 10% and 90% levels. Delay

times are measured using 50% levels.

Note 6:

The minimum on-time condition corresponds to an inductor

peak-to-peak ripple current ≥ 40% of I

MAX

(see Minimum On-Time

Considerations in the Applications Information section).

Note 7:

EXTV

CC

is enabled only if V

IN

is higher than 7V.

4

3874fb

For more information

www.linear.com/LTC3874

LTC3874

TYPICAL PERFORMANCE CHARACTERISTICS

Efficiency vs Output Current

and Mode

100

90

80

EFFICIENCY (%)

70

60

50

40

30

20

10

0

0.1

1

10

LOAD CURRENT (A)

100

3874 G01

(T

A

= 25°C unless otherwise specified)

Dual Phase Efficiency and Power

Loss vs Output Current

100

95

V

IN

= 12V

V

OUT

= 1.8V

CCM

EFFICIENCY

14

12

10

8

85

POWER LOSS

80

75

70

0.32m

1.5m

0.32m

1.5m

0

10

20

30

40

LOAD CURRENT (A)

50

6

4

2

0

60

POWER LOSS (W)

Efficiency vs Output Current

and Mode

100

90

80

DCM

EFFICIENCY (%)

90

DCM

CCM

V

IN

= 12V

V

OUT

= 1.2V

70

60

50

40

30

20

10

0

0.1

CCM

V

IN

= 12V

V

OUT

= 1.8V

1

10

LOAD CURRENT (A)

100

3874 G02

3874 G03

Load Step (Forced Continuous

Mode) 3-Phase with Master

Controller LTC3866

I

L(MASTER)

20A/DIV

I

L(SLAVE1)

20A/DIV

I

L(SLAVE0)

20A/DIV

V

OUT

200mV/DIV

AC-COUPLED

V

IN

= 12V

V

OUT

= 1.2V

I

LOAD

5A TO 50A

I

L(MASTER)

20A/DIV

I

L(SLAVE1)

20A/DIV

I

L(SLAVE0)

20A/DIV

V

OUT

200mV/DIV

AC-Coupled

Load Step (Discontinuous

Conduction Mode) 3-Phase with

Master Controller LTC3866

50µs/DIV

3874 G04

V

IN

= 12V

V

OUT

= 1.2V

I

LOAD

5A TO 50A

50µs/DIV

3874 G05

Inductor Current at Light Load

FORCED

CONTINUOUS

MODE

5A/DIV

DISCONTINUOUS

CONDUCTION

MODE

5A/DIV

V

IN

= 12V

V

OUT

= 1.2V

I

LOAD

= 2A

1µs/DIV

RUN

5V/DIV

OV

V

OUT

1V/DIV

OV

3874 G06

Start-Up Into a Pre-Biased Output

with Master Controller LTC3875

V

IN

= 12V

V

OUT

= 1.0V

20ms/DIV

3874 G06a

3874fb

For more information

www.linear.com/LTC3874

5

Parameter Name	Attribute value
EU restricts the use of certain hazardous substances	Compliant
ECCN (US)	EAR99
Part Status	Active
HTS	8542.39.00.01
Number of Outputs	1
Topology	Step Down
Output Voltage (V)	5.5(Max)
Minimum Input Voltage (V)	4.5
Maximum Input Voltage (V)	38
Operating Supply Voltage (V)	4.5 to 38
Typical Switching Frequency (kHz)	500
Minimum Operating Temperature (°C)	-40
Maximum Operating Temperature (°C)	125
Supplier Temperature Grade	Extended
Packaging	Tape and Reel
Supplier Package	QFN EP
Pin Count	28
Standard Package Name	QFN
Mounting	Surface Mount
Package Height	0.75(Max)
Package Length	5
Package Width	4
PCB changed	28
Lead Shape	No Lead

	LTC3874EUFD#TRPBF	LTC3874EUFD#PBF	LTC3874IUFD#PBF	LTC3874IUFD#TRPBF
Description	DC/DC Cntrlr Single-OUT Step Down 28-Pin QFN EP T/R	DC/DC Cntrlr Single-OUT Step Down 28-Pin QFN EP Tube	DC/DC Cntrlr Single-OUT Step Down 28-Pin QFN EP Tube	DC/DC Cntrlr Single-OUT Step Down 28-Pin QFN EP T/R
EU restricts the use of certain hazardous substances	Compliant	Compliant	Compliant	Compliant
ECCN (US)	EAR99	EAR99	EAR99	EAR99
Part Status	Active	Active	Active	Active
HTS	8542.39.00.01	8542.39.00.01	8542.39.00.01	8542.39.00.01
Number of Outputs	1	1	1	1
Topology	Step Down	Step Down	Step Down	Step Down
Output Voltage (V)	5.5(Max)	5.5(Max)	5.5(Max)	5.5(Max)
Minimum Input Voltage (V)	4.5	4.5	4.5	4.5
Maximum Input Voltage (V)	38	38	38	38
Operating Supply Voltage (V)	4.5 to 38	4.5 to 38	4.5 to 38	4.5 to 38
Typical Switching Frequency (kHz)	500	500	500	500
Minimum Operating Temperature (°C)	-40	-40	-40	-40
Maximum Operating Temperature (°C)	125	125	125	125
Supplier Temperature Grade	Extended	Extended	Industrial	Industrial
Packaging	Tape and Reel	Tube	Tube	Tape and Reel
Supplier Package	QFN EP	QFN EP	QFN EP	QFN EP
Pin Count	28	28	28	28
Standard Package Name	QFN	QFN	QFN	QFN
Mounting	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package Height	0.75(Max)	0.75(Max)	0.75(Max)	0.75(Max)
Package Length	5	5	5	5
Package Width	4	4	4	4
PCB changed	28	28	28	28
Lead Shape	No Lead	No Lead	No Lead	No Lead

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