ANALOG DEVICES LTC 3411 EMS Datasheet

FEATURES

LTC3411

1.25A, 4MHz, Synchronous

Step-Down DC/DC Converter

U

DESCRIPTIO

■

Small 10-Lead MSOP or DFN Package

■

Uses Tiny Capacitors and Inductor

■

High Frequency Operation: Up to 4MHz

■

High Switch Current: 1.6A

■

Low R

■

High Efficiency: Up to 95%

■

Stable with Ceramic Capacitors

■

Current Mode Operation for Excellent Line

Internal Switches: 0.110Ω

DS(ON)

and Load Transient Response

■

Short-Circuit Protected

■

Low Dropout Operation: 100% Duty Cycle

■

Low Shutdown Current: IQ ≤ 1µA

■

Low Quiescent Current: 60µA

■

Output Voltages from 0.8V to 5V

■

Selectable Burst Mode® Operation

■

Sychronizable to External Clock

U

APPLICATIO S

■

Notebook Computers

■

Digital Cameras

■

Cellular Phones

■

Handheld Instruments

■

Board Mounted Power Supplies

The LTC®3411 is a constant frequency, synchronous,
step- down DC/DC converter. Intended for medium power
applications, it operates from a 2.63V to 5.5V input voltage
range and has a user configurable operating frequency up
to 4MHz, allowing the use of tiny, low cost capacitors and
inductors 2mm or less in height. The output voltage is
adjustable from 0.8V to 5V. Internal sychronous 0.11Ω
power switches with 1.6A peak current ratings provide
high efficiency. The LTC3411’s current mode architecture
and external compensation allow the transient response
to be optimized over a wide range of loads and output
capacitors.

The LTC3411 can be configured for automatic power
saving Burst Mode operation to reduce gate charge losses
when the load current drops below the level required for
continuous operation. For reduced noise and RF interfer­ence, the SYNC/MODE pin can be configured to skip
pulses or provide forced continuous operation.

To further maximize battery life, the P-channel MOSFET is
turned on continuously in dropout (100% duty cycle) with
a low quiescent current of 60µA. In shutdown, the device
draws <1µA.

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

Burst Mode is a registered trademark of Linear Technology Corporation.

TYPICAL APPLICATIO

2.63V TO 5.5V

SYNC/MODEV

IN

PGOOD

LTC3411

I

TH

SHDN/R

13k

1000pF

NOTE: IN DROPOUT, THE OUTPUT TRACKS
THE INPUT VOLTAGE
C1, C2: TAIYO YUDEN JMK325BJ226MM
L1: TOKO A914BYW-2R2M (D52LC SERIES)

324k

T

Figure 1. Step-Down 2.5V/1.25A Regulator

PV

IN

SV

IN

SW

V

FB

PGNDSGND

U

V

IN

L1

2.2µH

887k

412k

3411 F01

C1
22µF

V

2.5V/1.25A

C2
22µF

OUT

EFFICIENCY (%)

Efficiency vs Load Current

100

95

90

85

80

VIN = 3.3V

= 2.5V

V

OUT

75

f

= 1MHz

O

Burst Mode OPERATION

70

1 100 1000

10

LOAD CURRENT (mA)

3411 TA01

3411f

1

LTC3411

WW

W

ABSOLUTE AXI U RATI GS

PVIN, SV

Voltages .....................................–0.3V to 6V

IN

U

(Note 1)

VFB, ITH, SHDN/RT Voltages .......... –0.3V to (VIN + 0.3V)

SYNC/MODE Voltage .................... –0.3V to (VIN + 0.3V)

SW Voltage ................................... –0.3V to (VIN + 0.3V)

PGOOD Voltage ...........................................–0.3V to 6V

Operating Ambient Temperature Range

(Note 2) .................................................. – 40°C to 85°C

UUW

PACKAGE/ORDER I FOR ATIO

TOP VIEW

SHDN/R

SYNC/MODE

1

T

2
3

SGND

4

SW

5

PGND

10-LEAD (3mm × 3mm) PLASTIC DFN

T

JMAX

(EXPOSED PAD MUST BE SOLDERED TO PCB)

DD PACKAGE

= 125°C, θJA = 43°C/W, θJC = 3°C/W

10

9
8
7
6

I

TH

V

FB

PGOOD
SV

IN

PV

IN

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

ORDER PART

NUMBER

LTC3411EDD

DD PART MARKING

LADT

Junction Temperature (Notes 5, 8) ....................... 125°C

Storage Temperature Range

DD Package ...................................... –65°C to 125°C

MS Package .................................... –65°C to 150°C

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

ORDER PART

TOP VIEW

1

SHDN/R

SYNC/MODE

T

2

SGND

3

SW

4

PGND

5

MS PACKAGE

10-LEAD PLASTIC MSOP

T

= 125°C, θJA = 120°C/W, θJC = 10°C/W

JMAX

10
9
8
7
6

I

TH

V

FB

PGOOD
SV

IN

PV

IN

NUMBER

LTC3411EMS

MS PART MARKING

LTQT

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VIN = 3.3V, RT = 324k unless otherwise specified. (Note 2)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

IN

I

FB

V

FB

∆V

LINEREG

∆V

LOADREG

g

m(EA)

I

S

V

SHDN/RT

f

OSC

f

SYNC

I

LIM

R

DS(ON)

I

SW(LKG)

V

UVLO

Operating Voltage Range 2.625 5.5 V
Feedback Pin Input Current (Note 3) ±0.1 µA
Feedback Voltage (Note 3) ● 0.784 0.8 0.816 V
Reference Voltage Line Regulation VIN = 2.7V to 5V 0.04 0.2 %/V
Output Voltage Load Regulation ITH = 0.36, (Note 3) ● 0.02 0.2 %

I

= 0.84, (Note 3) ● –0.02 –0.2 %

TH

Error Amplifier Transconductance ITH Pin Load = ±5µA (Note 3) 800 µS
Input DC Supply Current (Note 4)

Active Mode V
Sleep Mode V
Shutdown V

= 0.75V, SYNC/MODE = 3.3V 240 350 µA

FB
SYNC/MODE
SHDN/RT

= 3.3V, VFB = 1V 62 100 µA

= 3.3V 0.1 1 µA

Shutdown Threshold High VIN – 0.6 VIN – 0.4 V
Active Oscillator Resistor 324k 1M Ω

Oscillator Frequency RT = 324k 0.85 1 1.15 MHz

(Note 7) 4 MHz
Synchronization Frequency (Note 7) 0.4 4 MHz
Peak Switch Current Limit ITH = 1.3 1.6 2 A
Top Switch On-Resistance (Note 6) VIN = 3.3V 0.11 0.15 Ω
Bottom Switch On-Resistance (Note 6) VIN = 3.3V 0.11 0.15 Ω
Switch Leakage Current VIN = 6V, V

= 0V, VFB = 0V 0.01 1 µA

ITH/RUN

Undervoltage Lockout Threshold VIN Ramping Down 2.375 2.5 2.625 V

3411f

2

LTC3411

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VIN = 3.3V, RT = 324k unless otherwise specified. (Note 2)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

PGOOD Power Good Threshold VFB Ramping Up, SHDN/RT = 1V 6.8 %

R

PGOOD

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

Note 2: The LTC3411E is guaranteed to meet specified performance from
0°C to 70°C. Specifications over the –40°C to 85°C operating ambient
termperature range are assured by design, characterization and correlation
with statistical process controls.

Note 3: The LTC3411 is tested in a feedback loop which servos V
midpoint for the error amplifier (V

Note 4: Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.

Power Good Pull-Down On-Resistance 118 200 Ω

= 0.6V).

ITH

The ● denotes the specifications which apply over the full operating

V

Ramping Down, SHDN/RT = 1V –7.6 %

FB

is calculated from the ambient TA and power dissipation P

J

LTC3411EDD: TJ = TA + (PD • 43°C/W)
LTC3411EMS: T

= TA + (PD • 120°C/W)

J

to the

FB

Note 5: T
according to the following formula:

Note 6: Switch on-resistance is guaranteed by correlation to wafer level
measurements.

Note 7: 4MHz operation is guaranteed by design but not production tested
and is subject to duty cycle limitations (see Applications Information).

Note 8: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.

D

UUU

PI FU CTIO S

SHDN/RT (Pin 1): Combination Shutdown and Timing
Resistor Pin. The oscillator frequency is programmed by
connecting a resistor from this pin to ground. Forcing this
pin to SVIN causes the device to be shut down. In shut­down all functions are disabled.

SYNC/MODE (Pin 2): Combination Mode Selection and
Oscillator Synchronization Pin. This pin controls the op­eration of the device. When tied to SVIN or SGND, Burst
Mode operation or pulse skipping mode is selected, re­spectively. If this pin is held at half of SVIN, the forced
continuous mode is selected. The oscillation frequency
can be syncronized to an external oscillator applied to this
pin. When synchronized to an external clock pulse skip
mode is selected.

SGND (Pin 3): The Signal Ground Pin. All small signal
components and compensation components should be
connected to this ground (see Board Layout Consider­ations).

SW (Pin 4): The Switch Node Connection to the Inductor.
This pin swings from PVIN to PGND.

PGND (Pin 5): Main Power Ground Pin. Connect to the
(–) terminal of C

, and (–) terminal of CIN.

OUT

PVIN (Pin 6): Main Supply Pin. Must be closely decoupled
to PGND.

SVIN (Pin 7): The Signal Power Pin. All active circuitry is
powered from this pin. Must be closely decoupled to
SGND. SVIN must be greater than or equal to PVIN.

PGOOD (Pin 8): The Power Good Pin. This common drain
logic output is pulled to SGND when the output voltage is
not within ±7.5% of regulation.

VFB (Pin 9): Receives the feedback voltage from the
external resistive divider across the output. Nominal volt­age for this pin is 0.8V.

ITH (Pin 10): Error Amplifier Compensation Point. The
current comparator threshold increases with this control
voltage. Nominal voltage range for this pin is 0V to 1.5V.

3411f

3

LTC3411

UUU

PI FU CTIO S

NOMINAL (V) ABSOLUTE MAX (V)

PIN NAME DESCRIPTION MIN TYP MAX MIN MAX

1 SHDN/R
2 SYNC/MODE Mode Select/Sychronization Pin 0 SV

Shutdown/Timing Resistor –0.3 0.8 SV

T

IN
IN

–0.3 SVIN + 0.3

–0.3 SVIN + 0.3
3 SGND Signal Ground 0
4 SW Switch Node 0 PV

IN

–0.3 PVIN + 0.3
5 PGND Main Power Ground 0
6PVINMain Power Supply –0.3 5.5 – 0.3 SVIN + 0.3
7SVINSignal Power Supply 2.5 5.5 –0.3 6
8 PGOOD Power Good Pin 0 SV

IN

–0.3 6
9VFBOutput Feedback Pin 0 0.8 1.0 – 0.3 SVIN + 0.3
10 I

TH

Error Amplifier Compensation and Run Pin 0 1.5 –0.3 SVIN + 0.3

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Burst Mode Operation Pulse Skipping Mode Forced Continuous Mode

V

OUT

10mV/

DIV

I

L1

100mA/

DIV

VIN = 3.3V 2µs/DIV 3411 G01.eps
V

= 2.5V

OUT

= 50mA

I

LOAD

CIRCUIT OF FIGURE 7

Efficiency vs Load Current

100

Burst Mode

OPERATION

95

90

85

PULSE SKIP FORCED CONTINUOUS

80

75

EFFICIENCY (%)

70

65

60

1 100 1000 10000

10

LOAD CURRENT (mA)

VIN = 3.3V

= 2.5V

V

OUT

CIRCUIT OF FIGURE 7

3411 G04

V

OUT

10mV/

DIV

I

L1

100mA/

DIV

= 3.3V 2µs/DIV 3411 G02.eps

V

IN

V

= 2.5V

OUT

= 50mA

I

LOAD

CIRCUIT OF FIGURE 7

Efficiency vs V

100

I

OUT

95

90

I

OUT

85

80

75

EFFICIENCY (%)

70

65

V

= 2.5V

OUT

CIRCUIT OF FIGURE 7

60

2.5 3.5 4.5 5.5

IN

= 400mA

= 1.25A

VIN (V)

3411 G05

V

OUT

10mV/

DIV

I

L1

100mA/

DIV

VIN = 3.3V 2µs/DIV 3411 G03.eps
V

= 2.5V

OUT

= 50mA

I

LOAD

CIRCUIT OF FIGURE 7

Load Step

V

OUT

100mV/

DIV

I

L1

0.5mA/
DIV

VIN = 3.3V 40µs/DIV 3411 G06.eps
V

= 2.5V

OUT

I

= 0.25mA TO 1.25A

LOAD

CIRCUIT OF FIGURE 7

4

3411f

2 3 4 5 6

VIN (V)

FREQUENCY VARIATION (%)

10

8
6
4
2

0
–2
–4
–6
–8

–10

3411 G09

V

OUT

= 1.8V

I

OUT

= 1.25A

T

A

= 25°C

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC3411

Load Regulation Line Regulation Frequency vs V

0.4

0.3

0.2
PULSE SKIP

0.1

0

CONTINUOUS

–0.1

ERROR (%)

OUT

–0.2

V

–0.3

–0.4

–0.5

1 10 100 1000 10000

FORCED

LOAD CURRENT (mA)

Burst Mode
OPERATION

VIN = 3.3V
V

= 2.5V

OUT

3411 G07

0.50
V

= 1.8V

OUT

0.45

= 25°C

T

A

0.40

0.35

0.30

0.25

ERROR (%)

0.20

OUT

V

0.15

0.10

0.05

0

2 3 4 5 6

I

OUT

= 1.25A

I

VIN (V)

OUT

= 400mA

3411 G08

Frequency Variation
vs Temperature

10

8
6
4
2

0
–2
–4

REFERENCE VARIATION (%)

–6
–8

–10

–50 –25 0 25 50 75 100 125

TEMPERATURE (°C)

3411 G10

Efficiency vs Frequency

100

95

EFFICIENCY (%)

90

85

0

12

FREQUENCY (MHz)

VIN = 3.3V

= 2.5V

V

OUT

= 500mA

I

OUT

T

= 25°C

A

34

3411 G11

R

120

TA = 25°C

115

110

(mΩ)

105

DS(ON)

R

100

95

90

2.5 3 3.5 4 4.5 5 5.5 6

DS(ON)

vs V

IN

SYNCHRONOUS SWITCH

MAIN SWITCH

VIN (V)

IN

3411 G12

3411f

5

LTC3411

BLOCK DIAGRA

W

V

PGOOD

IN

VOLTAGE

REFERENCE

SGND

SV

7

0.8V

+

9

FB

0.74V

–

ERROR
AMPLIFIER

+

–

I

TH

10

3

I

TH

LIMIT

BCLAMP

B

–

+

V

B

BURST
COMPARATOR
HYSTERESIS = 80mV

OSCILLATOR

PMOS CURRENT
COMPARATOR

+

–

SLOPE

COMPENSATION

PV

IN

6

4

SW

+

0.86V

–

8

LOGIC

NMOS

COMPARATOR

+

–

1

SHDN/R

–

5

REVERSE

COMPARATOR

2

SYNC/MODE

T

+

PGND

3411 BD

6

3411f