Linear Technology LTC1147L, LTC1147-5, LTC1147-3.3 Datasheet

FEATURES

■

Very High Efficiency: Over 95% Possible

■

Wide VIN Range: 3.5V* to 16V

■

Current Mode Operation for Excellent Line and Load
Transient Response

■

High Efficiency Maintained Over Three Decades of
Output Current

■

Low 160µA Standby Current at Light Loads

■

Logic Controlled Micropower Shutdown: IQ < 20µA

■

Short-Circuit Protection

■

Very Low Dropout Operation: 100% Duty Cycle

■

High Efficiency in a Small Amount of Board Space

■

Output Can Be Externally Held High in Shutdown

■

Available in 8-Pin SO Package

LTC1147-3.3

LTC1147-5/LTC1147L

High Efficiency Step-Down

Switching Regulator Controllers

U

DESCRIPTIO

The LTC®1147 series are step-down switching regulator
controllers featuring automatic Burst ModeTM operation to
maintain high efficiencies at low output currents. These
devices drive an external P-channel power MOSFET at
switching frequencies exceeding 400kHz using a constant
off-time current mode architecture providing constant
ripple current in the inductor.

The operating current level is user-programmable via an
external current sense resistor. Wide input supply range
allows operation from 3.5V* to 14V (16V maximum).
Constant off-time architecture provides low dropout regu­lation limited by only the R
and resistance of the inductor and current sense resistor.

of the external MOSFET

DS(ON)

U

APPLICATIO S

■

Notebook and Palmtop Computers

■

Portable Instruments

■

Battery-Operated Digital Devices

■

Cellular Telephones

■

DC Power Distribution Systems

■

GPS Systems

A

PPLICATITYPICAL

V

(5.2V TO 14V)

IN

+

1µF

0V = NORMAL

>1.5V = SHUTDOWN

RC
1k

CC
3300pF

CT
470pF

Figure 1. High Efficiency Step-Down Converter

SHDN

I

TH

C

T

V

IN

PDRIVE

LTC1147-5

SENSE
SENSE

GND

+

–

O

U

P-CHANNEL
Si4431DY

1000pF

D1
MBRD330

The LTC1147 series incorporates automatic power saving
Burst Mode operation to reduce switching losses when
load currents drop below the level required for continuous
operation. Standby power is reduced to only 2mW at
VIN = 10V (at I
operation are typically 0mA to 300mA.

For applications where even higher efficiency is required,
refer to the LTC1148 data sheet and Application Note 54.

Burst Mode is a trademark of Linear Technology Corporation.
*LTC1147L and LTC1147L-3.3 only.

+

CIN
100µF

L*

R

**

50µH

*

COILTRONICS CTX50-2-MP

**

KRL SL-1-C1-0R050J

SENSE

0.05Ω

+

= 0). Load currents in Burst Mode

OUT

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

LTC1147-5 Efficiency

100

95

VIN = 6V

V

OUT

5V/2A

C

OUT

390µF

LT1147 • F01





90

85

EFFICIENCY (%)

80

75

70

0.001

VIN = 10V

0.01 0.1 1
LOAD CURRENT (A)

LT1147 • TA01

1

LTC1147-3.3
LTC1147-5/LTC1147L

WW

W

U

ABSOLUTE AXI U RATI GS

Input Supply Voltage (Pin 1)..................... 16V to –0.3V

Continuous Output Current (Pin 8)...................... 50mA

Sense Voltages (Pins 4, 5)

VIN ≥ 12.7V ...........................................13V to –0.3V

VIN < 12.7V............................... (VIN + 0.3V) to –0.3V

UUW

PACKAGE/ORDER I FOR A TIO

TOP VIEW

V



1

IN



C

2

T



I

3

TH

–

SENSE

4

N8 PACKAGE

8-LEAD PLASTIC DIP

* ADJUSTABLE OUTPUT VERSION

T

= 125°C, θ

JMAX

= 125°C, θ

T

JMAX

8-LEAD PLASTIC SO

= 110°C/W (N)

JA

= 150°C/W (S)

JA

PDRIVE

8

GND

7

SHDN


6

(V

FB

SENSE

5



S8 PACKAGE

LTC1147CN8-3.3
LTC1147CN8-5

*)

+

LTC1147CS8-3.3
LTC1147CS8-5
LTC1147IS8-3.3

Operating Ambient Temperature Range

LTC1147C................................................0°C to 70°C

LTC1147I.............................................–40°C to 85°C

Extended Commercial

Temperature Range (Note 4) ................. –40°C to 85°C

Junction Temperature (Note 1)............................ 125°C

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

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

ORDER PART NUMBER S8 PART MARKING

LTC1147LCS8
LTC1147LCS8-3.3
LTC1147LIS8

11473
11475
1147L
1147L3
1147LI
1147I3

Consult factory for Military grade parts.

ELECTRICAL CHARACTERISTICS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V
I
V

∆V

I

6

6

OUT

OUT

Q

Feedback Voltage (LTC1147L) VIN = 9V ● 1.21 1.25 1.29 V
Feedback Current (LTC1147L) ● 0.2 1 µA
Regulated Output Voltage VIN = 9V

LTC1147-3.3, LTC1147L-3.3 I

LTC1147-5 I
Output Voltage Line Regulation VIN = 7V to 12V, I
Output Voltage Load Regulation

LTC1147-3.3, LTC1147L-3.3 5mA < I

LTC1147-5 5mA < I
Burst Mode Output Ripple I
Input DC Supply Current (Note 2) (Note 5)

LTC1147 Series

Normal Mode 4V < VIN < 12V 1.6 2.1 mA
Sleep Mode 4V < V
Sleep Mode (LTC1147-5) 5V < V
Shutdown V

LTC1147L Series

Normal Mode 3.5V < VIN < 12V 1.6 2.1 mA
Sleep Mode 3.5V < V
Shutdown (LTC1147L-3.3) V

TA = 25°C, VIN = 10V, V

= 700mA ● 3.23 3.33 3.43 V

LOAD

= 700mA ● 4.90 5.05 5.20 V

LOAD

= 50mA –40 0 40 mV

LOAD

< 2A ● 40 65 mV

LOAD

< 2A ● 60 100 mV

LOAD

= 0A 50 mV

LOAD

< 12V 160 230 µA

IN

< 12V 160 230 µA

IN

= 2.1V, 4V < VIN < 12V 10 20 µA

SHDN

< 12V 160 230 µA

IN

= 2.1V, 3.5V < VIN < 12V 10 20 µA

SHDN

= 0V, unless otherwise noted.

SHDN

P-P

2

LTC1147-3.3

LTC1147-5/LTC1147L

ELECTRICAL CHARACTERISTICS

TA = 25°C, VIN = 10V, V

= 0V, unless otherwise noted.

SHDN

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V5 – V

V

6

Current Sense Threshold Voltage (Note 6)

4

LTC1147-3.3, LTC1147L-3.3 V

LTC1147–5 V

LTC1147L V

SHDN Pin Threshold

SENSE

V

SENSE
SENSE

V

SENSE
SENSE

V

SENSE

–

= V

+ 100mV (Forced) 25 mV

OUT

–

= V

– 100mV (Forced) 130 150 170 mV

OUT

–

= V

+ 100mV (Forced) 25 mV

OUT

–

= V

– 100mV (Forced) 130 150 170 mV

OUT

–

= 5V, V6 = V

–

= 5V, V6 = V

/4 + 25mV (Forced) 25 mV

OUT

/4 – 25mV (Forced) 130 150 170 mV

OUT

LTC1147-3.3/LTC1147-5/LTC1147L-3.3 0.5 0.8 2 V

I

6

I

2

t

OFF

tr, t

f

SHDN Pin Input Current

LTC1147-3.3/LTC1147-5/LTC1147L-3.3 0V < V
CT Pin Discharge Current V

OUT

V

OUT

Off-Time (Note 3) CT = 390pF, I

< 8V, VIN = 16V 1.2 5 µA

SHDN

in Regulation, V

SENSE

–

= V

OUT

50 70 90 µA

= 0V 2 10 µA

= 700mA 4 5 6 µs

LOAD

Driver Output Transition Times CL = 3000pF (Pin 8), VIN = 6V 100 200 ns

–40°C ≤ TA ≤ 85°C (Note 4), VIN = 10V, unless otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

6

V

OUT

I

Q

V5 – V

V

6

t

OFF

The ● denotes specifications which apply over the full specified
temperature range.

Note 1: T
dissipation P

LTC1147CN8-3.3/LTC1147CN8-5: T
LTC1147LIS/LTC1147IS8/LTC1147LCS/
LTC1147CS8-3.3/LTC1147CS8-5: T

Note 2: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.

Feedback Voltage (LTC1147L) VIN = 9V ● 1.20 1.25 1.30 V
Regulated Output Voltage VIN = 9V

LTC1147-3.3/LTC1147L-3.3 I

LTC1147-5 I

= 700mA ● 3.17 3.33 3.43 V

LOAD

= 700mA ● 4.85 5.05 5.20 V

LOAD

Input DC Supply Current (Note 2) (Note 5)

LTC1147 Series

Normal Mode 4V < V
Sleep Mode 4V < V
Sleep Mode (LTC1147-5) 5V < V
Shutdown V

< 12V 1.6 2.4 mA

IN

< 12V 160 260 µA

IN

< 12V 160 260 µA

IN

= 2.1V, 4V < VIN < 12V 10 22 µA

SHDN

LTC1147L Series

Normal Mode 3.5V < VIN < 12V 1.6 2.4 mA
Sleep Mode 3.5V < V
Shutdown (LTC1147L-3.3) V

Current Sense Threshold Voltage (Note 6)

4

LTC1147-3.3 V

LTC1147-5 V

LTC1147L V

V
V
V

< 12V 160 260 µA

IN

= 2.1V, 3.5V < VIN < 12V 10 22 µA

SHDN

–

= V

SENSE
SENSE
SENSE
SENSE
SENSE
SENSE

+ 100mV (Forced) 25 mV

OUT

–

= V

– 100mV (Forced) ● 125 150 185 mV

OUT

–

= V

+ 100mV (Forced) 25 mV

OUT

–

= V

– 100mV (Forced) ● 125 150 185 mV

OUT

–

= 5V, 6V = V

–

= 5V, 6V = V

/4 + 25mV (Forced) 25 mV

OUT

/4 – 25mV (Forced) 125 150 185 mV

OUT

SHDN Pin Threshold

LTC1147-3.3/LTC1147-5/LTC1147L-3.3 0V < V
Off-Time (Note 3) CT = 390pF, I

< 8V, VIN = 16V 0.5 0.8 2 V

SHDN

= 700mA 3.8 5 6.5 µs

LOAD

Note 3: In applications where R

is placed at ground potential, the off-

SENSE

time increases approximately 40%.

is calculated from the ambient temperature TA and power

J

according to the following formulas:

D

= TA + (PD)(110°C/W)

J

Note 4: The LTC1147C is guaranteed to meet specified performance from
0°C to 70°C and is designed, characterized and expected to meet these
extended temperature limits, but is not tested at –40°C and 85°C. The
LTC1147I is guaranteed to meet the extended temperature limits.

= TA + (PD)(150°C/W)

J

Note 5: The LTC1147L/LTC1147L-3.3 allow operation to V
Note 6: The LTC1147L is tested with external feedback resistors resulting

in a nominal output voltage of 2.5V.

= 3.5V.

IN

3

LTC1147-3.3

LOAD CURRENT (A)

0

–100

∆V

OUT

(mV)

–80

–60

–40

–20

0

20

0.5 1.0 1.5 2.0

LTC1147 • G03

2.5

FIGURE 1 CIRCUIT
R

SENSE

= 0.05Ω

VIN = 6V


VIN = 12V



TEMPERATURE (°C)

0

0

SENSE VOLTAGE (mV)

25

50

75

175

125

20

40

150

100

60

80

100

MAXIMUM

THRESHOLD

MINIMUM

THRESHOLD

LTC1147 • G09

LTC1147-5/LTC1147L

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Efficiency vs Input Voltage Line Regulation Load Regulation

100

FIGURE 1 CIRCUIT

98
96
94

92

90
88

EFFICIENCY (%)

86
84
82

80

0

I

LOAD

4

8

INPUT VOLTAGE (V)

I

LOAD

= 100mA

12

= 1A

16

LTC1147 • G01

(mV)

OUT

∆V

–10
–20
–30
–40

40
30
20
10

0

0

FIGURE 1 CIRCUIT

= 1A

I

LOAD

4

INPUT VOLTAGE (V)

812

LTC1147 • G02

16

2.1

1.8

1.5

1.2

0.9

0.6

SUPPLY CURRENT (mA)

0.3

0

14

12

10

8

6

GATE CHARGE CURRENT (mA)

0

DC Supply Current Supply Current in Shutdown

NOT INCLUDING
GATE CHARGE CURRENT

ACTIVE MODE

SLEEP MODE

26

0

8 10 12 14 16 18

4

INPUT VOLTAGE (V)

Gate Charge Supply Current

QP = 50nC

4

2

20

OPERATING FREQUENCY (kHz)

80

QP = 29nC

140

200

LTC1147 • G04

260

LTC1147 • G07

20

V

18

(NOT AVAILABLE ON LTC1147L)

16
14
12
10

8
6

SUPPLY CURRENT (µA)

4

2

0

0

= 2V

SHUTDOWN

26

4

INPUT VOLTAGE (V)

Off-Time vs V

80
70
60
50
40
30

OFF-TIME (µs)

20
10

LTC1147-3.3

0

0

1

OUTPUT VOLTAGE (V)

10 18

12

8

OUT

V

SENSE

LTC1147-5

23

14

16

LTC1147 • G05

–

= V

4

LTC1147 • G08

OUT

Operating Frequency
vs (VIN – V

1.6
V

= 5V

OUT

1.4

1.2

1.0

0.8

0.6

0.4

NORMALIZED FREQUENCY

0.2

0

0

2

OUT

4

(VIN – V

)

6

) VOLTAGE (V)

OUT

0°C

25°C

8

70°C


10 12

LTC1148 • G06

Current Sense Threshold Voltage

5

4

UUU

PI FU CTIO S

V

(Pin 1): Main Supply Pin. Must be closely decoupled

IN

to ground Pin 7.
CT (Pin 2): External capacitor CT from Pin 2 to ground sets

the operating frequency. The actual frequency is also
dependent upon the input voltage.

ITH (Pin 3): Gain Amplifier Decoupling Point. The current
comparator threshold increases with the Pin 3 voltage.

SENSE– (Pin 4): Connects to internal resistive divider
which sets the output voltage. Pin 4 is also the (–) input for
the current comparator.

SENSE+ (Pin 5): The (+) input to the current comparator.
A built-in offset between Pins 4 and 5 in conjunction with
R

sets the current trip threshold.

SENSE

LTC1147-3.3

LTC1147-5/LTC1147L

SHDN/VFB (Pin 6): When grounded, the fixed output
versions of the LTC1147 family operate normally. Pulling
Pin 6 high holds the P-channel MOSFET off and puts the
LTC1147 in micropower shutdown mode. Requires CMOS
logic signal with tr, tf < 1µ s. Do not leave this pin floating.
On the LTC1147L this pin serves as the feedback pin from
an external resistive divider used to set the output voltage.

GND (Pin 7): Two independent ground lines must be
routed separately to: 1) the (–) terminal of C
cathode of the Schottky diode and (–) terminal of CIN.

PDRIVE (Pin 8): High current drive for the P-channel
MOSFET. Voltage swing at this pin is from VIN to ground.

, and 2) the

OUT

UUW

FU CTIO AL DIAGRA

SLEEP

Q

+

S

–

V

V

TH2

2

C

T

TH1

–

+

Pin 6 Connection Shown For LTC1147-3.3 and LTC1147-5; Changes Create LTC1147L.

1

8

7

V

IN

PDRIVE

GND

+

SENSE



5

V

FB

6

–

V

+

SENSE

4

–

–

R
S

T

OFF-TIME
CONTROL

V

IN

SENSE

–

C

I

TH

25mV TO 150mV

+

–

3

+

13k

SHDN

V

–

G

+

6

REFERENCE

OS

1.25V
100k

LTC1147 • FD

5pF

5