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

U

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

U

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

WWWU

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

UU

W

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

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

PGM
PGM

SHUTDOWN

PGM

= 0V –5 –70 mV
= V

= 0V –5 –70 mV
= V

= VIN, I

= VIN (Note 3) 10 70 mV

IN

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

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

UW

TYPICAL PERFOR A CE CHARACTERISTICS

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

100

100

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

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

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

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

0

OUT

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

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

UU

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

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

U

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

OPERATIO

LOAD CURRENT (mA)

1

EFFICIENCY (%)

10 100 500

100

90

80

70

60

50

VIN = 5V
V

OUT

= 3.3V

I

PGM

= V

IN

CTX50-4

CTX50-4P

1174 F01

LOAD CURRENT (mA)

1

EFFICIENCY (%)

10 100 500

100

90

80

70

60

50

VIN = 5V
V

OUT

= 3.3V

I

PGM

= V

IN

CTX100-4

CTX100-4P

LTC1174

LTC1174-3.3/LTC1174-5

U

(Refer to Functional Diagram)

circuitry is shut off, reducing quiescent current from

0.45mA to 0.13mA. When the output capacitor discharges
by the amount of the hysteresis of the comparator A1, the
P-channel switch turns on again and the process repeats
itself.

Operating Frequency and Inductor

Since the LTC1174 utilizes a constant off-time architecture,
its operating frequency is dependent on the value of VIN. The
frequency of operation can be expressed as:

VV

−



1

f

=

t

OFF

IN OUT



VV



IN D



Hz

()



+



WUUU

APPLICATIO S I FOR ATIO

Inductor Core Selection

With the value of L selected, the type of inductor must be
chosen. Basically there are two kinds of losses in an
inductor, core and copper

where t

= 4µs and VD is the voltage drop across the diode.

OFF

Note that the operating frequency is a function of the input
and ouput voltage.

Although the size of the inductor does not affect the fre­quency, it does affect the ripple current. The peak-to-peak
ripple current is given by:

VV

I

RIPPLE



−

=

410

6

•





+

OUT D

L



A

()





−

PP

By choosing a smaller inductor, a low ESR output filter
capacitor has to be used (see CIN and C

). Moreover, core

OUT

loss will also increase (see Inductor Core Selection section)
due to higher ripple current.

Core losses are dependent on the peak-to-peak ripple
current and the core material. However it is independent of
the physical size of the core. By increasing the inductance
the inductor’s peak-to-peak ripple current will decrease,
therefore reducing core loss. Utilizing low core loss mate­rial, such as molypermalloy or Kool Mµ will allow users to
concentrate on reducing copper loss and preventing satu­ration. Figure 1 shows the effect of different core material on
the efficiency of the LTC1174. The CTX core is Kool Mµ and
the CTXP core is powdered iron (material 52).

Although higher inductance reduces core loss, it increases
copper loss as it requires more windings. When space is not
a premium larger gauge wire can be used to reduce the wire
resistance. This also prevents excessive heat dissipation.

C

IN

In continuous mode the source current of the P-channel
MOSFET is a square wave of duty cycle V

OUT/VIN

. To prevent

large voltage transients, a low ESR input capacitor sized for

Figure 1. Efficiency Using Different Types of
Inductor Core Material

7

LTC1174

V

R
R

LBTRIP

=+











125 1

4

3

.

LTC1174-3.3/LTC1174-5

WUUU

APPLICATIO S I FOR ATIO

the maximum RMS current must be used. The CIN RMS
current is given by:

12/

A

()

RMS

, where I

OUT

RMS

=

I

RMS

IVVV

[]

OUT OUT IN OUT

≈

−

()

V

IN

This formula has a maximum at VIN = 2V
I

/ 2. This simple worst case is commonly used for design

OUT

because even significant deviations do not offer much relief.
Note that ripple current directly affects capacitor’s lifetime.
DO NOT UNDERSPECIFY THIS COMPONENT. An additional

0.1µF ceramic capacitor is also required on VIN for high
frequency decoupling.

C

OUT

To avoid overheating, the output capacitor must be sized to
handle the ripple current generated by the inductor. The
worst case RMS ripple current in the output capacitor is
given by:

I

PEAK

I

≈

RMS

=2170

or 300mA

A

()

RMS

mA

the diode conducts only a small fraction of the time. The
most stressful condition for the diode is when the output is
short-circuited. Under this condition the diode must safely
handle I

at close to 100% duty cycle. A fast switching diode

PEAK

must also be used to optimize efficiency. Schottky diodes are
a good choice for low forward drop and fast switching times.
Most LTC1174 circuits will be well served by either a 1N5818,
a MBRS140T3 or a MBR0520L Schottky diode.

Short-Circuit Protection

The LTC1174 is protected from output short by its internal
current limit. Depending on the condition of I

PGM

pin, the
limit is either set to 340mA or 600mA. In addition, the off­time of the switch is increased to allow the inductor’s
current to decay far enough to prevent any current build-up
(see Figure 2).

I

= V

PGM

IN

I

= 0

PGM

Although the output voltage ripple is determined by the
hysteresis of the voltage comparator, ESR of the output
capacitor is also a concern. Too high of an ESR will create
a higher ripple output voltage and at the same time cause the
LTC1174 to sleep less often. This will affect the efficiency of
the LTC1174. For a given technology, ESR is a direct
function of the volume of the capacitor. Several small-sized
capacitors can also be paralleled to obtain the same ESR as
one large can. Manufacturers such as Nichicon, Chemicon
and Sprague should be considered for high performance
capacitors. The OS-CON semiconductor dielectric capaci­tor available from Sanyo has the lowest ESR for its size, at
a higher price.

Catch Diode Selection

The catch diode carries load current during the off-time. The
average diode current is therefore dependent on the
P-channel switch duty cycle. At high input voltages the
diode conducts most of the time. As VIN approaches V

OUT

GND

L = 100µH
V

= 13.5V

IN

Figure 2. Inductor's Current with Output Shorted

20µs/DIV

1174 F02

Low-Battery Detector

The low-battery indicator senses the input voltage through
an external resistive divider. This divided voltage connects
to the “–” input of a voltage comparator (Pin 3) which is
compared with a 1.25V reference voltage. With the current
going into Pin 3 being negligible, the following expression
is used for setting the trip limit:

When the LTC1174 is shut down, the low-battery detector
is inactive.

8

WUUU

APPLICATIO S I FOR ATIO

LTC1174

LTC1174-3.3/LTC1174-5

V

IN

R4

R3

LTC1174

3

–
+

1.25V
REFERENCE

1174 F03

Figure 3. Low-Battery Comparator

LTC1174 Adjustable/Low Noise Applications

The LTC1174 develops a 1.25V reference voltage between
the feedback (Pin 1) terminal and ground (see Figure 4). By
selecting resistor R1, a constant current is caused to flow
through R1 and R2 to set the overall output voltage. The
regulated output voltage is determined by:

V

=+

1251

OUT

.











1

R

2

R

For most applications, a 30k resistor is suggested for R1.
To prevent stray pickup, a 100pF capacitor is suggested
across R1 located close to the LTC1174. Alternatively, a
capacitor across R2 can be used to increase the switching
frequency for low noise operation.

V

OUT

LTC1174 V

ADJUSTABLE APPLICATIONS

*

LOW NOISE APPLICATIONS

**

6.8nF**

1

FB

100pF*

R2

R1

1174 F04

Figure 4. LTC1174 Adjustable Configuration

Inverting Applications

The LTC1174 can easily be set up for a negative output
voltage. If –5V is desired, the LTC1174-5 is ideal for this
application as it requires the least components. Figure 5
shows the schematic for this application. Note that the
output voltage is now taken off the GND pin. Therefore,
the maximum input voltage is now determined by the

INPUT VOLTAGE

4V TO 12V

47µF*

V

LB

IN

LB

OUT

I

PGM

LTC1174HV-5

IN

SHUTDOWN

GND

3

2

7

AVX TPSD476K016

*

COILTRONICS CTX50-4

**

6

8

1

V

OUT

5

SW

4

50µH**

MBRS140T3

0.1µF

+

16V
×2

+

47µF*
16V
×2

V

OUT

–5V
45mA

1174 F05

Figure 5. Positive-to-Negative 5V Converter

difference between the absolute maximum voltage rating
and the output voltage. A maximum of 12V is specified in
Figure 5, giving the circuit a 1.5V of headroom for VIN. Note
that the circuit can operate from a minimum of 4V, making
it ideal for a 4 NiCad cell application. For a higher output
current circuit, please refer to the Typical Applications
section.

Absolute Maximum Ratings and Latchup Prevention

The absolute maximum ratings specify that SW (Pin 5) can
never exceed VIN (Pin 6) by more than 0.3V. Normally this
situation should never occur. It could, however, if the
output is held up while the supply is pulled down. A con­dition where this could potentially occur is when a battery
is supplying power to an LTC1174/LTC1174-3.3/
LTC1174-5 regulator and also to one or more loads in
parallel with the the regulator’s VIN. If the battery is dis­connected while the LTC1174/LTC1174-3.3/LTC1174-5
regulator is supplying a light load and one of the parallel
circuits is a heavy load, the input capacitor of the LTC1174/
LTC1174-3.3/LTC1174-5 regulator could be pulled down
faster than the output capacitor, causing the absolute
maximum ratings to be exceeded. The result is often a
latchup which can be destructive if V

is reapplied. Bat-

IN

tery disconnect is possible as a result of mechanical stress,
bad battery contacts or use of a lithium-ion battery with
a built-in internal disconnect. The user needs to assess
his/her application to determine whether this situation
could occur. If so, additional protection is necessary.

9

LTC1174
LTC1174-3.3/LTC1174-5

WUUU

APPLICATIO S I FOR ATIO

Prevention against latchup can be accomplished by sim­ply connecting a Schottky diode across the SW and V

IN

pins as shown in Figure 6. The diode will normally be
reverse biased unless VIN is pulled below V
time the diode will clamp the (V

– VIN) potential to less

OUT

at which

OUT

than the 0.6V required for latchup. Note that a low leakage
Schottky should be used to minimize the effect on no-load
supply current. Schottky diodes such as MBR0530, BAS85
and BAT84 work well. Another more serious effect of the
protection diode leakage is that at no load with nothing to
provide a sink for this leakage current, the output voltage
can potentially float above the maximum allowable toler­ance. To prevent this from occuring, a resistor must be
connected between V

and ground with a value low

OUT

enough to sink the maximum possible leakage current.

LATCHUP
PROTECTION
SCHOTTKY

V

IN

LTC1174

LTC1174-3.3

LTC1174-5

SW

V

OUT

+

1174 F06

Board Layout Checklist

When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC1174. These items are also illustrated graphically in
the layout diagram in Figure 7. Check the following in your
layout:

1. Is the Schottky catch diode

closely

connected between

ground (Pin 4) and switch (Pin 5)?

2. Is the “+” plate of CIN

closely

connected to VIN (Pin 6)?
This capacitor provides the AC current to the internal
P-channel MOSFET.

3. Is the 0.1µF VIN decoupling capacitor

closely

conected
between VIN (Pin 6) and ground (Pin 4)? This capacitor
carries the high frequency peak currents.

4. Is the SHUTDOWN (Pin 8) actively pulled to VIN during
normal operation? The SHUTDOWN pin is high imped­ance and must not be allowed to float.

5. Is the I
I

PGM

(Pin 7) pulled either to VIN or ground? The

PGM

pin is high impedance and must not be allowed

to float.

Figure 6. Preventing Absolute Maximum
Ratings from Being Exceeded

OUTPUT DIVIDER

REQUIRED WITH

ADJUSTABLE

VERSION ONLY

R2

Figure 7. LTC1174 Layout Diagram (See Board Layout Checklist)

I

PGM

V

SW

8

7

6

IN

54

0.1µF

D

+

C

IN

C

OUT

V

IN

L

+

V

OUT

1174 F07

1

V

OUT

SHUTDOWN

(VFB)

2

LB

OUT

3

R1

LB

IN

LTC1174

GND

BOLD LINES INDICATE

HIGH CURRENT PATH

10

WUUU

APPLICATIO S I FOR ATIO

LTC1174

LTC1174-3.3/LTC1174-5

DESIGN EXAMPLE

As a design example, assume VIN = 9V (nominal), V
5V, and I
for this application, with I

= 350mA maximum. The LTC1174-5 is used

OUT

(Pin 7) connected to VIN. The

PGM

OUT

=

minmum value of L is determined by assuming the
LTC1174-5 is operating in continuous mode.

I

PEAK

AVG CURRENT

I

V

INDUCTOR CURRENT

TIME

Figure 8. Continuous Inductor Current

With I

= 350mA and I

OUT

PEAK

= 0.6A (I

0.1A.The peak-to-peak ripple inductor current, I

= I

=

= 350mA

= VIN), IV =

PGM

OUT

I

+ I

PEAK

2

1174 F08

RIPPLE

V

, is

0.5A and is also equal to:

VV

I

RIPPLE



−

=

410

6

•





+

OUT D

L



A

()





−

PP

Solving for L in the above equation and with VD = 0.6V,
L = 44.8µH. The next higher standard value of L is 50µH
(example: Coiltronics CTX50-4). The operating frequency,
neglecting voltage across diode VD is:

V

.•

kHz

5





f

≈−

2 5 10 1

=

111



With the value of L determined, the requirements for C
and C

are calculated. For CIN, its RMS current rating

OUT

OUT

V

IN






IN

should be at least:

/

A

()

RMS

I

RMS

IVVV

[]

OUT OUT IN OUT

=

mA

=12174

−

()

V

IN

For C

, the RMS current rating should be at least:

OUT

I

PEAK

I

RMS

≈

=2300

A

()

RMS

mA

Now allow VIN to drop to 6V. At this minimum input voltage
the operating frequency will decrease. The new frequency
is 42kHz.

Table 1. Inductor Manufacturers

MANUFACTURER PART NUMBER

Coilcraft DT3316 Series
1102 Silver Lake Road
Cary, IL 60013
[phone]

Coiltronics Inc. Econo-Pac
6000 Park of Commerce Blvd. Octa-Pac
Boca Raton, FL 33487
[phone]

Gowanda Electronics Corporation GA10 Series
1 Industrial Place
Gowanda, NY 14070
[phone]

Sumida Electric Co. Ltd. CD 54 Series
637 E. Golf Road, Suite 209 CD 75 Series
Arlington Heights, IL 60005
[phone]/7

Table 2. Capacitor Manufacturers

MANUFACTURER PART NUMBER

AVX Corporation TPS Series
P.O. Box 887 TAJ Series
Myrtle Beach, SC 29578
[phone]

Nichicon America Corporation PL Series
927 East State Parkway
Schaberg, IL 60173
[phone]

Sanyo Video Components OS-CON Series
2001 Sanyo Avenue
San Diego, CA 92173
[phone]

Attn: Sales Dept.

11

LTC1174
LTC1174-3.3/LTC1174-5

U

TYPICAL APPLICATIO S

6V to 5V Step-Down Regulator with Low-Battery Detection

LOW-BATTERY INDICATOR

*

IS SET TO TRIP AT V
AVX TPSD476K016

**

= MBRS140T3 (SURFACE MOUNT)

D1

1N5818

†

L1 SELECTION

MANUFACTURER

COILTRONICS
SUMIDA
GOWANDA

= 5.5V

IN

PART NO.

CTX100-4
CD75-101
GA10-103K

TYPE

SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE

BATTERY

INDICATOR

162k

47.5k

*LOW-

4.7k

INPUT VOLTAGE

7

I

PGM

2

LB

OUT

3

LB

IN

6V

6

V

IN

SHUTDOWN

LTC1174-5

GND

4

+

1174 TA03

47µF**
16V
×2

V

OUT

5V

47µF**
16V
×2

365mA

+

0.1µF

8

1

V

OUT

5

SW

†

L1

100µH

D1

INPUT VOLTAGE

4V TO 12.5V

AVX TPSD226K025

*

AVX TPSD476K016

**

†

COILTRONICS CTX50-4

High Efficiency 3.3V Regulator

+

22µF*
25V
×3

50µH

1N5818

7

3

2

I

PGM

LB

IN

LTC1174-3.3

LB

OUT

6

V

IN

SHUTDOWN

V

GND

4

OUT

SW

8

1

5

†

1174 TA04

0.1µF

V

OUT

3.3V
425mA

47µF**

+

16V
×2

12

TYPICAL APPLICATIO S

INPUT VOLTAGE

4V TO 12.5V

AVX TPSD226K025

*

AVX TPSD105K010

**

†

COILTRONICS CTX50-4

U

LTC1174

LTC1174-3.3/LTC1174-5

Low Noise 3V Regulator

+

50µH

1N5818

22µF*
25V
×3

†

0.1µF

6.8nF

100µF**

+

10V
×2

1174 TA05

42k

30k

V

OUT

3V
450mA

6

V

PGM

LB

IN

SHUTDOWN

IN

LTC1174

OUT

GND

4

7

I

3

2

LB

V

SW

8

1

FB

5

*

LOW-BATTERY INDICATOR
IS SET TO TRIP AT V
AVX TPSD106K035

**

AVX TPSD105K010

***

= MBRS130LT3 (SURFACE MOUNT)

D1

1N5818

†

L1 SELECTION

MANUFACTURER

COILTRONICS
COILCRAFT
SUMIDA
GOWANDA

= 4.4V

IN

PART NO.

CTX50-3
DT3316-473
CD54-470
GA10-472K

VIN(V)

I

OUT MAX

4

110

6

140

8

10

12.5

TYPE

SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE

170
200
235

Positive-to-Negative (–5V) Converter

INPUT VOLTAGE

4V TO 12.5V

(mA)

4.7K

BATTERY

INDICATOR

280k

43k

*LOW-

7

2

3

I

PGM

LB

OUT

LTC1174HV-5

LB

IN

6

V

IN

SHUTDOWN

V

GND

4

OUT

SW

+

10µF**

+

35V
×2

100µF***
10V

1174 TA06

V

OUT

–5V

0.1µF

8

1

5

†

L1

50µH

D1

13

LTC1174
LTC1174-3.3/LTC1174-5

U

TYPICAL APPLICATIO S

Positive-to-Negative (– 3.3V) Converter

LOW-BATTERY INDICATOR

*

IS SET TO TRIP AT V
AVX TPSD336K020

**

AVX TPSD105K010

***

= MBRS140T3 (SURFACE MOUNT)

D1

1N5818

†

L1 SELECTION

MANUFACTURER

COILTRONICS
COILCRAFT
SUMIDA
GOWANDA

= 4.4V

IN

PART NO.

CTX50-3
DT3316-473
CD54-470
GA10-472K

I

VIN(V)

OUT MAX

175

4

205

5

230

6

255

7

TYPE

SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE

(mA)

BATTERY

INDICATOR

220k

43k

*LOW-

4.7K

INPUT VOLTAGE

7

I

PGM

2

LB

OUT

LTC1174HV-3.3

3

LB

IN

4V TO 13.5V

6

V

IN

SHUTDOWN

GND

4

+

33µF**

+

20V
×2

100µF***
10V
×2

1174 TA07

V

OUT

–3.3V
210mA

0.1µF

8

1

V

OUT

5

SW

†

L1

50µH

D1

AVX TPSD336K020

*

= MBRS140T3 (SURFACE MOUNT)

D1

1N5818

†

L1 SELECTION

MANUFACTURER

COILTRONICS
COILCRAFT
SUMIDA
GOWANDA

PART NO.

CTX50-3
DT3316-473
CD54-470
GA10-472K

TYPE

SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE

Negative Boost Converter

7

I

PGM

2

LB

3

33µF*

+

16V
×2

LB

V
SHUTDOWN

OUT

LTC1174-3.3

IN

GND

6

IN

4

8

1

V

OUT

5

SW

D1

INPUT VOLTAGE

–5V

L1
50µH

310k

+

1174 TA08

33µF*
20V
×2

V
–9V
175mA

OUT

0.1µF

50k

†

0.1µF

14

TYPICAL APPLICATIO S

INPUT

VOLTAGE

6V TO 12.5V

SANYO OS-CON

*

AVX TPSD476K016

**

= MBRS140T3 (SURFACE MOUNT)

D1

†

L1 SELECTION

MANUFACTURER

COILTRONICS
COILCRAFT
SUMIDA
GOWANDA

††

USE 1% METAL FILM RESISTORS

1N5818

PART NO.

CTX50-3
DT3316-473
CD54-470
GA10-472K

TYPE

SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE

U

LTC1174

LTC1174-3.3/LTC1174-5

9V to 5V Pre-Post Regulator

+

6

V

LB

LB

I

PGM

IN

OUT

IN

SHUTDOWN

LTC1174

GND

4

V

SW

8

1

FB

5

L1

50µH

D1

3

2

7

100µF*
16V

†

+

47µF**
16V, ×2

100pF

0.1µF

110k

30.1k

V

8

V

OUT

0.1µF

IN

LT®1121-5

5

SHUTDOWN

GND

3

1174 TA09

††

††

1

+

OUT

5V
150mA

1µF
SOLID
TANTALUM

VIN(V)

4
5
6
7
8

9
10
11
12

AVX TAJE106K050

*

AVX TPSD476K016

**

= MBRS140T3 (SURFACE MOUNT)

D1

1N5818

†

L1 SELECTION

MANUFACTURER

COILTRONICS
COILCRAFT
SUMIDA
GOWANDA

††

USE 1% METAL FILM RESISTORS

I

OUT MAX

(mA)

20
25
30
35
43
50
55
60
65

PART NO.

CTX100-3
DT3316-104
CD75-101
GA10-103K

VOLTAGE

4V TO 12.5V

TYPE

SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE

INPUT

LCD Display Power Supply

††

1174 TA10

56.2k

50k

998k

+

††

††

10µF*
50V
×4

V

OUT

–24V
50mA AT

= 9V

V

IN

6

V

LB

I

LB

PGM

IN

OUT

IN

SHUTDOWN

LTC1174

GND

4

3

7

2

+

47µF**
16V
×2

0.1µF

V

SW

8

1

FB

5

1N914

0.1µF

2N2222

2N5210

Si9435

D1

†

L1
100µH

15

LTC1174
LTC1174-3.3/LTC1174-5

U

TYPICAL APPLICATIO S

INPUT VOLTAGE

4V TO 12.5V

SANYO OS-CON

*

WIMA MKS2

**

†

COILTRONICS CTX100-4

V

(V)

I

IN

OUT MAX

4
6

8
10
12
13

L1B

CTX100-4

4

75
100
125
145
160
180

23

1

(mA)

7

3

2

L1A

I

PGM

LB

IN

LTC1174HV-5

LB

OUT

V

GND

9V to 5V, –5V Outputs

6

IN

SHUTDOWN

4

8

1

V

OUT

5

SW

MBRS140T3

L1B
100µH

+

†

+

1174 TA11

100µF*
20V

V

OUT

5V
135mA AT

= 9V

V

IN

100µF*
16V

–V

OUT

–5V
135mA AT

= 9V

V

IN

0.1µF0.1µF

3.3µF**

L1A

†

+

100µH

MBRS140T3

100µF*
16V

*

AVX TAJD226K035

**

WIMA MKS2

†

COILTRONICS CTX100-4

††

USE 1% METAL FILM RESISTORS

(V)

V

IN

4
5
6
7
8

9
10
11
12

I

OUT MAX

(mA)

20
25
35
45
50
55
62
67
73

INPUT VOLTAGE

4V TO 12.5V

7

I

PGM

3

LB

IN

2

LB

OUT

6

V

IN

SHUTDOWN

LTC1174

GND

4

9V to 12V, –12V Outputs

0.1µF

8

1

V

FB

SW

Si9430DY

5

1N914

+

22µF*
35V
×3

3.3µF**

4

L1B
100µH

3

MBRS140T3

†

MBRS140T3

+

1

L1A

100µH

22µF*
35V
×2

L1B

23

CTX100-4

4

†

2

+

22µF*
35V
×2

L1A

1

V

OUT

12V
55mA AT

††

301k

34k

††

1174 TA12

= 9V

V

IN

–V

OUT

–12V
55mA AT

= 9V

V

IN

16

TYPICAL APPLICATIO S

INPUT

VOLTAGE

6V TO 12.5V

TPO610L

0.1µF

100µF*

20V

+

U

Automatic Current Selection

100k

2

7

3

100k

LB

I

LB

PGM

OUT

LTC1174-5

IN

V

IN

SHUTDOWN

GND

LTC1174

LTC1174-3.3/LTC1174-5

6

8

1

V

OUT

5

SW

4

50µH

1N5818

†

+

100µF*
16V

100k

36.5k

V

OUT

5V
0mA TO
320mA

SANYO OS-CON CAPACITOR

*

†

COILTRONICS CTX50-4

SANYO OS-CON

*

WIMA MKS2

**

†

COILTRONICS CTX100-4

23

L1B

CTX100-4

4

1

L1A

Buck-Boost Converter

INPUT VOLTAGE

4V TO 12V

6

V

I

PGM

LB

IN

LTC1174HV-5

LB

OUT

IN

SHUTDOWN

GND

4

7

3

2

1174 TA13

+

0.1µF

8

1

V

OUT

SW

5

4

3

†

L2A
100µH

3.3µF**

100µF*
20V

1

L1A

100µH

1N5818

†

1174 TA14

V

OUT

2

5V
160mA

+

100µF*
16V

17

LTC1174
LTC1174-3.3/LTC1174-5

U

PACKAGE DESCRIPTIO

Dimensions in inches (millimeters) unless otherwise noted.

N8 Package

8-Lead PDIP (Narrow 0.300)

(LTC DWG # 05-08-1510)

876

0.255 ± 0.015*
(6.477 ± 0.381)

0.400*

(10.160)

MAX

5

12

0.300 – 0.325

(7.620 – 8.255)

0.065

(1.651)

0.009 – 0.015

(0.229 – 0.381)

+0.035

0.325

–0.015
+0.889

8.255

()

–0.381

*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)

TYP

0.045 – 0.065

(1.143 – 1.651)

0.100
(2.54)

BSC

3

4

0.130 ± 0.005

(3.302 ± 0.127)

0.125

(3.175)

MIN

0.018 ± 0.003

(0.457 ± 0.076)

0.020

(0.508)

MIN

N8 1098

18

PACKAGE DESCRIPTIO

LTC1174-3.3/LTC1174-5

U

Dimensions in inches (millimeters) unless otherwise noted.

S8 Package

8-Lead Plastic Small Outline (Narrow 0.150)

(LTC DWG # 05-08-1610)

0.189 – 0.197*
(4.801 – 5.004)

7

8

5

6

LTC1174

0.228 – 0.244

(5.791 – 6.197)

0.010 – 0.020

(0.254 – 0.508)

0.008 – 0.010

(0.203 – 0.254)

*

DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

**

DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

×

°

45

0.016 – 0.050

(0.406 – 1.270)

0°– 8° TYP

0.053 – 0.069

(1.346 – 1.752)

0.014 – 0.019

(0.355 – 0.483)

TYP

0.150 – 0.157**
(3.810 – 3.988)

1

3

2

4

0.004 – 0.010

(0.101 – 0.254)

0.050

(1.270)

BSC

SO8 1298

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen­tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

19

LTC1174
LTC1174-3.3/LTC1174-5

U

TYPICAL APPLICATIO

Battery Charger

INPUT VOLTAGE

8V TO 12.5V

*

AVX TAJD226K020

**

AVX TAJD107K010

D1,D2

= MBRS140T3
(SURFACE MOUNT)
1N5818

†

L1 SELECTION

MANUFACTURER

COILTRONICS
COILCRAFT
SUMIDA
GOWANDA

PART NO.

CTX50-2P
DT3316-473
CD54-470
GA10-472K

VIN(V)

I

OUT MAX

8

9
10
11
12

TYPE

SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE

320
325
330
335
335

(mA)

+

6

V

PGM

IN

SHUTDOWN

IN

LTC1174

OUT

GND

4

7

I

3

LB

2

LB

V

SW

8

1

FB

5

D1

L1

50µH

0.1µF

†

150k

33k

22µF*
20V
×2

+

1174 TA15

D2

100µF**
10V

TO

V

OUT

4 NiCAD BATTERY

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Linear Technology Corporation

20

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

●

www.linear-tech.com

Output Ripple, SOT-23 Package

P-P

= 5V to 1.25V

OUT

1174fd LT/TP 0800 2K REV D • PRINTED IN USA

 LINEAR TE CHNOLOGY CORPORATION 1994