Linear Technology LTC1174CN8-5, LTC1174CN8-3.3, LTC1174CN8, LTC1174IS8, LTC1174HVCS8-3.3 Datasheet

FEATURES

LOAD CURRENT (mA)

1

EFFICIENCY (%)

100

95

90

85

80

75

70

10 100

1174 TA02

200

VIN = 6V

V

IN

= 9V

L = 100µH V

OUT

= 5V

I

PGM

= 0V

■

High Efficiency: Up to 94%

■

Peak Inductor Current Independent of Inductor Value

■

Short-Circuit Protection

■

Optimized for 5V to –5V Applications

■

Wide VIN Range: 4V to 18.5V

■

Low Dropout Operation

■

Low-Battery Detector

■

Pin Selectable Current Limit

■

Internal 0.9Ω Power Switch: VIN = 9V

■

Only Four External Components Required

■

130µA Standby Current

■

Active Low Micropower Shutdown

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APPLICATIO S

■

Distributed Power Systems

■

Step-Down Converters

■

Inverting Converters

■

Memory Backup Supply

■

Portable Instruments

■

Battery-Powered Equipment

LTC1174

LTC1174-3.3/LTC1174-5

High Efficiency

Step-Down and Inverting

DC/DC Converter

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DESCRIPTIO

The LTC®1174 is a simple current mode DC/DC converter ideally suited for 9V to 5V, 5V to 3.3V or 5V to –5V operation. With an internal 0.9Ω switch (at a supply voltage of 9V), the LTC1174 requires only four external components to construct a complete high efficiency DC/DC converter.

Under a no load condition the LTC1174 draws only 130µA. In shutdown, it draws a mere 1µA making this converter ideal for current sensitive applications. In dropout, the internal P-channel MOSFET switch is turned on continuously allowing the user to maximize the life of the battery source.

The maximum inductor current of the LTC1174 family is pin selectable to either 340mA or 600mA, optimizing efficiency for a wide range of applications. Operation up to 200kHz permits the use of small surface mount inductors and capacitors.

For applications requiring higher output current or ultrahigh efficiency, see the LTC1148 data sheet.

and LTC are registered trademarks and LT is a trademark of Linear Technology Corporation.

TYPICAL APPLICATIO

High Efficiency Step-Down Converter

V

IN

9V

3 2

7

(3) AVX TPSD156K025

*

AVX TPSD107K010

**

†

COILTRONICS CTX100-4

LB LB I

PGM

V

SHUTDOWN

IN

OUT

LTC1174-5

GND

6

IN

4

8 1

V

OUT

5

SW

U

100µH

1N5818

LTC1174-5 Efficiency

15µF*

+

25V ×3

†

+

5V 175mA

100µF** 10V

1174 TA01

1

LTC1174 LTC1174-3.3/LTC1174-5

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ABSOLUTE AXI U RATI GS

(Note 1)

(Voltage Referred to GND Pin) Input Supply Voltage (Pin 6)

LTC1174........................................... –0.3V to 13.5V

LTC1174HV ...................................... –0.3V to 18.5V

Switch Current (Pin 5) .............................................. 1A Switch Voltage (Pin 5)

LTC1174................................................. VIN – 13.5V

LTC1174HV ............................................ VIN – 18.5V

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PACKAGE/ORDER I FOR ATIO

ORDER PART

NUMBER

LTC1174CN8

TOP VIEW

(VFB*)

V

OUT

1

LB

2

OUT

LB

3

IN

GND

4

N8 PACKAGE 8-LEAD PDIP

* ADJUSTABLE OUTPUT VERSION

T

= 125°C, θJA = 110°C/W

JMAX

SHUTDOWN

8

I

7

PGM

V

6

IN

SW

5

LTC1174CN8-3.3 LTC1174CN8-5 LTC1174IN8 LTC1174HVCN8 LTC1174HVCN8-3.3 LTC1174HVCN8-5

Operating Temperature Range

LTC1174CX ............................................ 0°C to 70°C

LTC1174IX ........................................ –40°C to 85°C

Junction Temperature (Note 2)............................ 125°C

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

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

ORDER PART

NUMBER

LTC1174CS8

TOP VIEW

V

(VFB*)

OUT

1

LB

2

OUT

LB

3

IN

GND

4

S8 PACKAGE

8-LEAD PLASTIC SO

* ADJUSTABLE OUTPUT VERSION

T

= 125°C, θJA = 150°C/W

JMAX

SHUTDOWN

8

I

7

PGM

V

6

IN

SW

5

LTC1174CS8-3.3 LTC1174CS8-5 LTC1174IS8 LTC1174HVCS8 LTC1174HVCS8-3.3 LTC1174HVCS8-5 LTC1174HVIS8

S8 PART MARKING

1174 117433 117450 1174I

1174HV 1174H3 1174H5 1174HI

Consult factor for Military grade parts.

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VIN = 9V, V

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

I V V

∆V

FB

OUT

Feedback Current LTC1174/LTC1174HV 1 µA Feedback Voltage LTC1174/LTC1174HV ● 1.20 1.25 1.30 V Regulated Output Voltage LTC1174-3.3/LTC1174HV-3.3 ● 3.14 3.30 3.46 V

LTC1174-5/LTC1174V-5

Output Voltage Line Regulation VIN = 6V to 12V, I

OUT

Output Voltage Load Regulation LTC1174-3.3 (Note 3)

20mA < I 20mA < I

LTC1174-5 (Note 3)

20mA < I 20mA < I

The ● denotes specifications which apply over the full operating

LOAD

< 175mA, I

LOAD

< 400mA, I

LOAD

< 175mA, I

LOAD

< 400mA, I

LOAD

= 100mA, I

PGM PGM

SHUTDOWN

PGM

= 0V –5 –70 mV = V

= VIN, I

= VIN (Note 3) 10 70 mV

IN

= 0V, unless otherwise noted.

PGM

● 4.75 5.00 5.25 V

–45 –70 mV

–50 –70 mV

2

LTC1174

LTC1174-3.3/LTC1174-5

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VIN = 9V, V

The ● denotes specifications which apply over the full operating

SHUTDOWN

= VIN, I

= 0V, unless otherwise noted.

PGM

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

I

Q

Input DC Supply Current (Note 4) Active Mode

LTC1174: 4V < V LTC1174HV: 4V < VIN < 16V, I

< 12V, I

IN

= 0V 450 600 µA

PGM

= 0V 450 600 µA

PGM

Sleep Mode LTC1174: 4V < V

< 12V 130 180 µA

IN

LTC1174HV: 4V < VIN < 16V 130 180 µA SHUTDOWN (Note 4)

= 0V, 4V < VIN < 12V 1 10 µA

SHUTDOWN

= 0V, 4V < VIN < 16V 2 25 µA

= 0.4V 1.0 1.2 1.5 mA

= 0.4V 0.6 0.8 1.5 mA

LBOUT

= 0V ● 0.54 0.60 0.78 A

OUT

= 0V ● 0.27 0.34 0.50 A

V

LBTRIP

I

LBIN

I

LBOUT

V

HYST

I

PEAK

R

ON

LTC1174: V

SHUTDOWN

LTC1174HV: V

Low-Battery Trip Point 1.25 1.4 V Current into Pin 3 0.5 µA Current Sunk by Pin 2 LTC1174: V

LBOUT

LTC1174HV: V Comparator Hysteresis LTC1174/LTC1174HV 7.5 15 30 mV Current Limit I

PGM

I

PGM

= VIN, V = 0V, V

OUT

ON Resistance of Switch LTC1174 ● 0.75 1.30 Ω

LTC1174HV ● 0.90 1.55 Ω

t V V I

I

OFF

IH IL

IH

IL

Switch Off-Time (Note 6) V

at Regulated Value 3 4 5 µs

OUT

SHUTDOWN Pin High Minimum Voltage at Pin 8 for Device to Be Active 1.2 V SHUTDOWN Pin Low Maximum Voltage at Pin 8 for Device to Be in Shutdown 0.75 V SHUTDOWN Pin Input Current LTC1174: V

LTC1174HV: V SHUTDOWN Pin Input Current 0 ≤ V

SHUTDOWN

= 12V 0.5 µA

SHUTDOWN

= 16V 2.0 µA

≤ 0.8V 0.5 µA

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at –40°C ≤ TA ≤ 85°C. LTC1174I and LTC1174HVI Only.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

FB

I

LBOUT

I

PEAK

t

OFF

R

ON

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

Note 2: T dissipation P

Feedback Voltage LTC1174I/LTC1174HVI ● 1.18 1.25 1.31 V Current Sunk by Pin 2 V

Current Limit I

Switch Off-Time (Note 6) V

= 0.4V (LTC1174I) ● 0.75 1.2 2.0 mA

LBOUT

V

= 0.4V (LTC1174HVI) ● 0.50 0.8 1.6 mA

LBOUT

= VIN, V

PGM

I

= 0V, V

PGM

I

= VIN, V

PGM

I

= 0V, V

PGM

at Regulated Value (LTC1174I) ● 2.0 4 6.0 µs

OUT

V

at Regulated Value (LTC1174HVI) ● 1.8 4 6.2 µs

OUT

= 0V (LTC1174I) ● 0.54 0.60 0.78 A

OUT

= 0V (LTC1174I) 0.34 A

OUT

= 0V (LTC1174HVI) ● 0.5 0.60 0.8 A

OUT

= 0V (LTC1174HVI) 0.34 A

OUT

Switch On Resistance LTC1174I/LTC1174HVI ● 0.9 1.7 Ω

Note 3: Guaranteed by design. Note 4: Dynamic supply current is higher due to the gate charge being

is calculated from the ambient temperature TA and power

J

according to the following formulas:

D

LTC1174CN8, LTC1174CN8-3.3, LTC1174CN8-5:

= TA + (PD × 110°C/W)

T

J

delivered at the switching frequency. Note 5: Current into Pin 6 only, measured without electrolytic input

capacitor. Note 6: The off-time is wafer-sort trimmed.

LTC1174CS8, LTC1174CS8-3.3, LTC1174CS8-5:

= TA + (PD × 150°C/W)

T

J

3

LTC1174 LTC1174-3.3/LTC1174-5

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TYPICAL PERFOR A CE CHARACTERISTICS

Efficiency vs Load Current Efficiency vs Load Current Efficiency vs Load Current

100

95

90

85

EFFICIENCY (%)

80

75

70

1

100

90

80

70

EFFICIENCY (%)

60

50

1

VIN = 6V

= 9V

V

IN

10 100

LOAD CURRENT (mA)

VIN = 5V

VIN = 9V

10 100

LOAD CURRENT (mA)

L = 50µH V

= 5V

OUT

= 0V

I

PGM

COIL = CTX50-4

1174 G01

L = 50µH V

= 3.3V

OUT

= 0V

I

PGM

COIL = CTX50-4

1174 G04

200

300

95

90

85

EFFICIENCY (%)

80

75

70

1

100

90

80

70

EFFICIENCY (%)

60

50

1

VIN = 6V

VIN = 9V

L = 50µH V

OUT

I

PGM

COIL = CTX50-4

10 100

LOAD CURRENT (mA)

VIN = 5V

VIN = 9V

L = 100µH V

OUT

I

PGM

COIL = CTX100-4

10 100

LOAD CURRENT (mA)

= 5V

= V

= 3.3V = V

IN

1174 G02

1174 G06

400

500

95

90

85

EFFICIENCY (%)

80

75

70

1

Efficiency vs Load CurrentEfficiency vs Load Current Efficiency vs Load Current

100

90

80

70

EFFICIENCY (%)

60

50

1

VIN = 6V

VIN = 9V

L = 100µH V

OUT

I

PGM

COIL = CTX100-4

10 100

LOAD CURRENT (mA)

VIN = 5V

VIN = 9V

L = 100µH V

OUT

I

PGM

COIL = CTX100-4

10 100

LOAD CURRENT (mA)

= 5V = V

= 3.3V = V

IN

500

1174 G03

500

1174 G06

Line Regulation

6

I

= 100mA

LOAD

4

= 0V

I

PGM

2 0

–2

(mV)

–4

OUT

–6

∆V

–8 –10 –12 –14

0

Kool Mµ is a registered trademark of Magnetics, Inc.

4

2

INPUT VOLTAGE (V)

8

6

10

12

4

1174 G07

Switch Leakage Current vs Temperature Efficiency vs Input Voltage

180

VIN = 13.5V

160

140

120

100

80

60

LEAKAGE CURRENT (nA)

40

20

14

0

40

20 60

TEMPERATURE (°C)

100

80

1174 G08

95

94

93

92

91

90

EFFICIENCY (%)

V

89

OUT

I

PGM

I

88

LOAD

CORE = CTX (Kool Mµ

87

5

68

L = 50µH

= 5V

= 0V

= 75mA

7

INPUT VOLTAGE (V)

L = 100µH

®

)

9

10 11 13

14

12

1174 G09

LTC1174-3.3/LTC1174-5

INPUT VOLTAGE (V)

0

SUPPLY CURRENT (µA)

500 450 400 350 300 250 200 150 100

50

0

4

8

10

1174 G12

2

6

12

14

ACTIVE MODE

I

PGM

= V

IN

SLEEP MODE

I

PGM

= 0V

TA = 25°C

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC1174

Efficiency vs Input Voltage

95

94

93

92

I

= 300mA

LOAD

= V

I

PGM

EFFICIENCY (%)

91

90

89

68

5

IN

7

9

INPUT VOLTAGE (V)

Operating Frequency vs VIN – V

2.0 V

1.5

1.0

0.5

NORMALIZED FREQUENCY

0

OUT

= 5V

TA = 25°C

3

2

1

(VIN – V

4

OUT

V

= 5V

OUT

L = 100µH COIL = CTX100-4

I

= 100mA

LOAD

= 0V

I

PGM

12

10 14

11

TA = 70°C

57

6

) VOLTAGE (V)

13

1174 G10

8

1174 G13

Supply Current in Shutdown

1.8 SHUTDOWN = 0V

1.6 T

= 25°C

A

CURRENT INTO PIN 6 ONLY

1.4

1.2

1.0

0.8

0.6

SUPPLY CURRENT (µA)

0.4

0.2

0

2

6

414

INPUT VOLTAGE (V)

8

10 12

1174 G11

DC Supply Current

Switch Resistance vs Input Voltage

1.7

1.6

1.5

1.4

1.3

(Ω)

1.2

(ON)

1.1

RDS

1.0

0.9

0.8

9

0.7

4

LTC1174

6

8

INPUT VOLTAGE (V)

LTC1174HV

10

12

TA = 25°C

14 16 18 20

1174 G14

Off-Time vs Output Voltage

50

40

30

20

OFF-TIME (µs)

10

0

LTC1174-3.3

LTC1174HV-3.3

0

LTC1174-5 LTC1174HV-5

1

2

OUTPUT VOLTAGE (V)

3

4

5

1174 G15

U

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PI FU CTIO S

V

(VFB) (Pin 1): For the LTC1174, this pin connects to the

OUT

main voltage comparator’s input. On the LTC1174-3.3 and LTC1174-5 this pin goes to an internal resistive divider which sets the output voltage.

LB

(Pin 2): Open Drain of an N-Channel Pull-Down. This

OUT

pin will sink current when Pin 3 (LBIN) goes below 1.25V. During shutdown the state of this pin is indeterminate.

LBIN (Pin 3): The “–” Input of the Low-Battery Voltage Comparator. The “+” input is connected to a reference voltage of 1.25V.

GND (Pin 4): Ground Pin.

SW (Pin 5): Drain of the P-Channel MOSFET Switch. Cathode

of Schottky diode must be closely connected to this pin. VIN (Pin 6): Input Supply Voltage. It must be decoupled

close to ground Pin 4.

I

(Pin 7): Selects the Current Limit of the P-Channel

PGM

Switch. With I with I

= 0V, the current trip value is reduced to 340mA.

PGM

= VIN, the current trip point is 600mA and

PGM

SHUTDOWN (Pin 8): Pulling this pin to ground keeps the internal switch off and puts the LTC1174 in micropower shutdown.

5

LTC1174 LTC1174-3.3/LTC1174-5

U

W

FU CTIO AL DIAGRA

+

A5

–

A4

+

V

TH1

–

+

gmV

V

TH2

C

FB

LB

2

OUT

T

A3

(Pin 1 connection shown for LTC1174-3.3 and LTC1174-5, changes create LTC1174)

V

IN

6

V

LIM2

I

PGM

7

R

SENSE

0.1Ω

SLEEP

V

LIM1

+

A2

–

RESET

SET

LB

IN

3

1.25V

REFERENCE

SHUTDOWN

Q

)

V

OUT (VFB

1

5

×

SW

R1*

V

FB

–

A1

8

+

31.5k

GND

4

* R1 = 51k FOR LTC1174-3.3 R1 = 93.5k FOR LTC1174-5

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OPERATIO

The LTC1174 uses a constant off-time architecture to switch its internal P-channel power MOSFET. The off-time is set by an internal timing capacitor and the operating frequency is a function of VIN.

The output voltage is set by an internal resistive divider (LTC1174-3.3 and LTC1174-5) or an external divider returned to VFB Pin 1 (LTC1174). A voltage comparator A1 compares the divided output voltage to a reference voltage of 1.25V.

To optimize efficiency, the LTC1174 automatically switches between continuous and Burst ModeTM operation. The voltage comparator is the primary control element when the device is in Burst Mode operation, while the current comparator controls the output voltage in continuous mode.

During the switch“ON” time, switch current flows through the 0.1Ω sense resistor. When this current reaches the threshold of the current comparator A2, its output signal will change state, setting the flip-flop and turning the switch off. Burst Mode is a trademark of Linear Technology Corporation.

(Refer to Functional Diagram)

The timing capacitor, CT, begins to discharge until its voltage goes below V

. Comparator A4 will then trip,

TH1

which resets the flip-flop and causes the switch to turn on again. Also, the timing capacitor is recharged. The inductor current will again ramp up until the current comparator A2 trips. The cycle then repeats.

When the load is relatively light, the LTC1174 automatically goes into Burst Mode operation. The current mode loop is interrupted when the output voltage reaches the desired regulated value. The hysteretic voltage comparator A1 trips when V

is above the desired output voltage, shutting off

OUT

the switch and causing the timing capacitor to discharge. This capacitor discharges past V below V

. Comparator A5 then trips and a sleep signal is

TH2

until its voltage drops

TH1

generated. In sleep mode, the LTC1174 is in standby and the load

current is supplied by the output capacitor. All unused

1174 BD

6