lt1144

7/28/2019 LT1144

1/81

LTC1144

Switched-CapacitorWide Input RangeVoltage Converter

with Shutdown

UA

OPPLICATITYPICAL

Output Voltage vs Load Current, V + = 15V

SFEATURE DU

ESCRIPTIO

s Wide Operating Supply Voltage Range: 2V to 18Vs Boost Pin (Pin 1) for Higher Switching Frequencys Simple Conversion of 15V to 15V Supplys Low Output Resistance: 120 Maximums Power Shutdown to 8A with SHDN Pins Open Circuit Voltage Conversion Efficiency:

99.9% Typicals Power Conversion Efficiency: 93% Typicals Easy to Use

The LTC1144 is a monolithic CMOS switched-capacitorvoltage converter. It performs supply voltage conversionfrom positive to negative from an input range of 2V to 18V,resulting in complementary output voltages of 2V to18V. Only two noncritical external capacitors are neededfor the charge pump and charge reservoir functions.

The converter has an internal oscillator that can beoverdriven by an external clock or slowed down whenconnected to a capacitor. The oscillator runs at a 10kHzfrequency when unloaded. A higher frequency outside theaudio band can also be obtained if the Boost Pin is tied toV +. The SHDN pin reduces supply current to 8A and canbe used to save power when the converter is not in use.

The LTC1144 contains an internal oscillator, divide-by-two, voltage level shifter, and four power MOSFETs. Aspecial logic circuit will prevent the power N-channelswitch substrate from turning on.

USAO

PPLICATI

s Conversion of 15V to 15V Suppliess Inexpensive Negative Suppliess Data Acquisition Systemss High Voltage Upgrade to LTC1044 or 7660s Voltage Division and Multiplicationss Automotive Applicationss Battery Systems with Wall Adapter/Charger

LOAD CURRENT (mA)

0 10

OUTPUTVOLTAGE(V)

15

14

13

12

11

1040

1144 TA02

20 30 50

ROUT = 56TA = 25C

1

2

34

8

7

65

BOOST

CAP+

GND

CAP

V+

OSC

SHDN

VOUT

+

+

10F

15V OUTPUT

15V INPUT

LTC1144

10F

1144 TA01

Generating 15V from 15V

7/28/2019 LT1144

2/82

LTC1144

WU UPACKAGE/ORDER I FOR ATIOA

UG

WA

WU

WARBSOLUTE XI TI S

(Note 1)

Supply Voltage (V +) (Transient) .............................. 20VSupply Voltage (V+) (Operating) ............................. 18V

Input Voltage on Pins 1, 6, 7(Note 2) ............................ 0.3V < VIN < (V

+) + 0.3VOutput Short-Circuit Duration

V + 10V .................................................... IndefiniteV + 15V ........................................................ 30 secV + 20V ............................................. Not Protected

Power Dissipation ............................................. 500mWOperating Temperature Range

LTC1144C................................................ 0C to 70CLTC1144I ............................................ 40C to 85C

Storage Temperature Range ................. 65C to 150CLead Temperature (Soldering, 10 sec) .................. 300C

TOP VIEW

1

2

3

4

8

7

6

5

BOOST

CAP+

GND

CAP

V+

OSC

SHDN

VOUT

S8 PACKAGE8-LEAD PLASTIC SOIC

T JMAX = 110C, JA = 130C/W

1

2

3

4

8

7

6

5

TOP VIEW

BOOST

CAP+

GND

CAP

V+

OSC

SHDN

VOUT

N8 PACKAGE8-LEAD PLASTIC DIP

T JMAX = 110C, JA = 100C/W

S8 PART MARKING

11441144I

LTC1144CS8LTC1144IS8

LTC1144CN8LTC1144IN8

ORDER PARTNUMBER

Consult factory for Military grade parts.

The q denotes specifications which apply over the full operatingtemperature range; all other limits and typicals at TA = 25C.Note 1: Absolute maximum ratings are those values beyond which the lifeof a device may be impaired.

Note 2: Connecting any input terminal to voltages greater than V + or less

than ground may cause destructive latch-up. It is recommended that no

inputs from sources operating from external supplies be applied prior topower-up of the LTC1144.

Note 3: fOSC is tested with COSC = 100pF to minimize the effects of testfixture capacitance loading. The 0pF frequency is correlated to this 100pFtest point, and is intended to simulate the capacitance at pin 7 when the

device is plugged into a test socket and no external capacitor is used.

LTC1144C LTC1144ISYMBOL PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS

Supply Voltage Range RL = 10k q 2 18 2 18 V

IS Supply Current RL = , Pins 1, 6 No Connection, 1.1 1.1 mAfOSC = 10kHz q 1.3 1.6 mA

SHDN = 0V, RL = , Pins 1, 7 q 0.008 0.03 0.008 0.035 mANo Connection

V + = 5V, RL = , Pins 1, 6 0.10 0.10 mANo Connection, fOSC = 4kHz q 0.13 0.15 mA

V + = 5V, SHDN = 0V, RL = , q 0.002 0.015 0.002 0.018 mAPins 1, 7 No Connection

ROUT Output Resistance V+ = 15V, IL = 20mA at 10kHz 56 100 56 100

q 120 140 V + = 5V, IL = 3mA at 4kHz q 90 250 90 300

fOSC Oscillator Frequency V+ = 15V (Note 3) 10 10 kHz

V + = 5V 4 4 kHz

Power Efficiency RL = 2k at 10kHz q 90 93 90 93 %

Voltage Conversion Efficiency RL = q 97.0 99.9 97.0 99.9 %Oscillator Sink or Source Current V + = 5V (VOSC = 0V to 5V) 0.5 0.5 A

V + = 15V (VOSC = 0V to 15V) 4 4 A

ELECTRICAL C CHARA TERISTICSV+ = 15V, COSC = 0pF, TA = 25C, Test Circuit Figure 1, unless otherwise noted.

7/28/2019 LT1144

3/83

LTC1144

TYPICAL PERFORMANCE CHARACTERISTICSUW

SUPPLY VOLTAGE (V)

2

OSCILLATORFREQUENCY(kHz)

10

100

1000

6 10 144 8 12 16 18

LTC1144 TPC03

1

TA = 25CCOSC = 0

BOOST = V+

BOOST = OPEN OR GROUND

Oscillator Frequencyvs Supply Voltage

Output Resistancevs Supply Voltage

SUPPLY VOLTAGE (V)

20

OUTPUTRESISTANCE()

50

100

150

200

6 10 14 18

LTC1144 TPC01

250

300

4 8 12 16

TA = 25C

TEMPERATURE (C)

55

OUTPUTRESISTANCE()

100

120

140

25 75

LTC1144 TPC02

80

60

25 0 50 100 125

40

20

V+ = 5VIL = 3mA

V+ = 15VIL = 20mA

Output Resistance vs Temperature

Oscillator Frequencyvs Temperature Output Voltage vs Load Current

Oscillator Frequency as aFunction of COSC

EXTERNAL CAPACITANCE (PIN 7 TO GND), COSC (pF)

1

OSCILLATORFREQUENCY(kHz)

1

10

10000

LTC1144 TPC04

0.1

0.0110 100 1000

1000

100

TA = 25CV+ = 15V


BOOST = V+

LOAD CURRENT (mA)

015

OUTPUTVOLTAGE(V)

10

5

0

10 20 30 40

LTC1144 TPC06

50 60

TA = 25CV+ = 15VC1 = C2 = 10FBOOST = OPEN

ROUT = 56

TEMPERATURE (C)

55 25

OSCILLATORF

REQUENCY

(kHz)

10

100

1000

0 25 50 75 100 125

LTC1144 TPC05

1

BOOST = V+


TA = 25CV+ = 15V

Power Conversion Efficiency andSupply Current vs Load Current

LOAD CURRENT (mA)

05

OUTPUTVOLT

AGE(V)

4

3

2

1

0

5 10 15 20

LTC1144 TPC07

25 30

TA = 25CV+ = 5VC1 = C2 = 10FBOOST = OPEN

ROUT = 90

Output Voltage vs Load CurrentSupply Current as a Function ofOscillator Frequency

OSCILLATOR FREQUENCY (kHz)

0.01

SUPPLY

CURRENT

(A)

100

1000

100

LTC1144 TPC08

10

10.1 1 10

10000TA = 25CC1 = C2 = 10F

V+ = 15V

V+ = 5V

LOAD CURRENT (mA)

0

POWERCONVERSION

EFFICIENCY(%)

SUPPLY

CURRENT(mA)

60

80

100

40

LTC1144 TPC09

40

20

0

60

80

100

40

20

010 20 30 50

PEFF

IS

TA = 25CV+ = 15VC1 = C2 = 10FBOOST = OPEN(SEE TEST CIRCUIT)

7/28/2019 LT1144

4/84

LTC1144

TYPICAL PERFORMANCE CHARACTERISTICSUW

Power Conversion Efficiency andSupply Current vs Load Current


0.10

OUTPUTRESISTANCE()

2000

3000

1 10 100

LTC1144 TPC12

1000

1F10F

100F

TA = 25CV+ = 15V


0.170

POWERCONVERSIONEFFICIENCY(%)

90

95

100

1 10 100

LTC1144 TPC11

85

80

75

TA = 25C, V+ = 15VBOOST = OPEN

IL = 20mA

IL = 3mA

1F

1F

10F

10F

100F

100F

Power Conversion Efficiencyvs Oscillator Frequency

Output Resistancevs Oscillator Frequency

Output Voltage vs Load Current

LOAD CURRENT (mA)

10OUTPUTVOLTAGE(V)

5

0

0.001 0.1 1 100

LTC1144 TPC15

150.01 10

V+ = 15VTA = 25CC1 = C2 BOOST = 15V

0.1F

0.1F 1F

1F

10F10F

BOOST = OPEN

Output Voltage vs Load Current

LOAD CURRENT (mA)

4

OUTPUTVOLTAGE(V)

3

2

1

0

0.001 0.1 1 100

LTC1144 G14

50.01 10

0.1F

0.1F 10F

10F

1F1F

V+ = 5VTA = 25CC1 = C2 BOOST = 5V

BOOST = OPEN

LOAD CURRENT (mA)

0.010

RIPPLEVOLTAGE(mV)

500

1000

1F

1F

1500

0.1 1

LTC1144 TPC13

10 100

0.1F

10F

10F

V+ = 5VTA = 25CC1 = C2 BOOST = 5V

BOOST = OPEN

0.1F

Ripple Voltage vs Load Current

PI FU CTIO SU UU

Boost (Pin 1): This pin will raise the oscillator frequencyby a factor of 10 if tied high.

CAP+ (Pin 2): Positive Terminal for Pump Capacitor.

GND (Pin 3): Ground Reference.

CAP (Pin 4): Negative Terminal for Pump Capacitor.

VOUT (Pin 5): Output of the Converter.

SHDN (Pin 6): Shutdown Pin. Tie to V + pin or leave floatingfor normal operation. Tie to ground when in shutdownmode.

OSC (Pin 7):Oscillator Input Pin. This pin can be overdrivenwith an external clock or can be slowed down by connect-ing an external capacitor between this pin and ground.

V + (Pin 8): Input Voltage.

LOAD CURRENT (mA)

0

POWERCONVERSIONEFFICIENCY(%)

SUPPLYCURRENT(mA)

60

80

100

16

LTC1144 TPC10

40

20

0

30

40

50

20

10

04 8 12 20

PEFF

ISTA = 25CV+ = 5VC1 = C2 = 10FBOOST = OPEN(SEE TEST CIRCUIT)

7/28/2019 LT1144

5/85

LTC1144

TEST CIRCUITS

Figure 1.

1

2

3

4

8

7

6

5

+

+

C110F

C210F

IS

VOUT

V+

15V

ILRL

EXTERNAL

OSCILLATOR

COSC

1144 F01

LTC1144

USAO

PPLICATIWU U

I FOR ATIO

Theory of Operation

To understand the theory of operation of the LTC1144, areview of a basic switched-capacitor building block ishelpful.

In Figure 2, when the switch is in the left position, capacitorC1 will charge to voltage V1. The total charge on C1 will beq1 = C1V1. The switch then moves to the right, discharg-ing C1 to voltage V2. After this discharge time, the chargeon C1 is q2 = C1V2. Note that charge has been transferredfrom the source V1 to the output V2. The amount of chargetransferred is:

q = q1 q2 = C1(V1 V2)V2

RL

C2C1

V1

f

1144 F02

Figure 2. Switched-Capacitor Building Block

If the switch is cycled f times per second, the chargetransfer per unit time (i.e., current) is:

I = f q = f C1(V1 V2)

Rewriting in terms of voltage and impedance equivalence,

IV V

f C

V V

REQUIV

=

= 1 21

1

1 2

A new variable REQUIV has been defined such that REQUIV= 1/(f C1). Thus, the equivalent circuit for the switched-capacitor network is as shown in Figure 3.

Figure 3. Switched-Capacitor Equivalent Circuit

V2

RL

REQUIV

C2

V1

1144 F03REQUIV =1

f C1

Examination of Figure 4 shows that the LTC1144 has thesame switching action as the basic switched-capacitorbuilding block. With the addition of finite switch on-resistance and output voltage ripple, the simple theory,

although not exact, provides an intuitive feel for how thedevice works.

For example, if you examine power conversion efficiencyas a function of frequency (see Figure 5), this simpletheory will explain how the LTC1144 behaves. The loss,

Figure 4. LTC1144 Switched-CapacitorVoltage Converter Block Diagram

SHDN(6)

OSC(7)

10X

(1)

BOOST

1144 F04

OSC 2

V+(8) SW1 SW2

CAP+

(2)

CAP(4)

GND(3)

VOUT(5)

C2

C1

+

+

7/28/2019 LT1144

6/86

LTC1144

and hence the efficiency, is set by the output impedance.As frequency is decreased, the output impedance willeventually be dominated by the 1/(f C1) term and powerefficiency will drop.

Note also that power efficiency decreases as frequencygoes up. This is caused by internal switching losses whichoccur due to some finite charge being lost on eachswitching cycle. This charge loss per unit cycle, whenmultiplied by the switching frequency, becomes a currentloss. At high frequency this loss becomes significant andthe power efficiency starts to decrease.

USAO

PPLICATIWU U

I FOR ATIO


0.1

POWERCONVERSIONEFFICIENCY

(%)

OUTPUTRESISTANCE()

100

95

90

85

80

75

70

600

500

400

300

200

100

01 10 100

1144 F05

V+ = 15V, C1 = C2 = 10FIL = 20mA, TA = 25C

POWERCONVERSIONEFFICIENCY

OUTPUTRESISTANCE

Figure 5. Power Conversion Efficiency and OutputResistance vs Oscillator Frequency

SHDN (Pin 6)

The LTC1144 has a SHDN pin that will disable the internaloscillator when it is pulled low. The supply current will alsodrop to 8A.

OSC (Pin 7) and Boost (Pin 1)

The switching frequency can be raised, lowered or drivenfrom an external source. Figure 6 shows a functional

diagram of the oscillator circuit.

By connecting the boost pin (pin 1) to V +, the charge anddischarge current is increased, and hence the frequency isincreased by approximately 10 times. Increasing the fre-quency will decrease output impedance and ripple forhigher load currents.

Loading pin 7 with more capacitance will lower the fre-quency. Using the boost (pin 1) in conjunction with exter-

nal capacitance on pin 7 allows user selection of thefrequency over a wide range.

Driving the LTC1144 from an external frequency sourcecan be easily achieved by driving pin 7 and leaving theboost pin open as shown in Figure 7. The output currentfrom pin 7 is small, typically 4A, so a logic gate is capableof driving this current. The choice of using a CMOS logicgate is best because it can operate over a wide supplyvoltage range (3V to 15V) and has enough voltage swing

to drive the internal Schmitt trigger shown in Figure 6. For5V applications, a TTL logic gate can be used by simplyadding an external pull-up resistor (see Figure 7).

Capacitor Selection

External capacitors C1 and C2 are not critical. Matching isnot required, nor do they have to be high quality or tighttolerance. Aluminum or tantalum electrolytics are excellentchoices, with cost and size being the only consideration.

Figure 6. Oscillator

OSC(7)

SCHMITTTRIGGER

BOOST(1)

1144 F06

9I

9I

I

I

V+

GND(3)

20pF

1

2

3

4

8

7

6

5

+

+

C1

OSC INPUT

NC

REQUIRED FORTTL LOGIC

C2

100k

(V +)

V+

1144 F07

LTC1144

Figure 7. External Clocking

7/28/2019 LT1144

7/87

LTC1144

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 represen-tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

USAO

PPLICATITYPICAL

Negative Voltage Converter

Figure 8 shows a typical connection which will provide a

negative supply from an available positive supply. Thiscircuit operates over full temperature and power supplyranges without the need of any external diodes.

The output voltage (pin 5) characteristics of the circuit arethose of a nearly ideal voltage source in series with a 56resistor. The 56 output impedance is composed of twoterms: 1) the equivalent switched capacitor resistance(see Theory of Operation), and 2) a term related to the on-resistance of the MOS switches.

Figure 9. Voltage Doubler

1

2

3

4

8

7

6

5

++

+

+

V IN2V TO 18V

VOUT = 2(VIN 1)

10F 10F

Vd

1N4148V

d

1N4148

1144 F09

LTC1144

Ultra-Precision Voltage Divider

An ultra-precision voltage divider is shown in Figure 10. Toachieve the 0.0002% accuracy indicated, the load currentshould be kept below 100nA. However, with a slight loss

in accuracy, the load current can be increased.

At an oscillator frequency of 10kHz and C1 = 10F, the firstterm is:

Rf C

EQUIV

OSC

=( )

=

=

1

2 1

1

5 10 10 10

203 6/

Notice that the above equation for REQUIV is nota capaci-tive reactance equation (XC = 1/C) and does not containa 2 term.

The exact expression for output impedance is extremelycomplex, but the dominant effect of the capacitor is clearlyshown in Figure 5. For C1 = C2 = 10F, the outputimpedance goes from 56 at fOSC = 10kHz to 250 atfOSC= 1kHz. As the 1/(fC) term becomes large comparedto the switch on-resistance term, the output resistance isdetermined by 1/(f C) only.

Voltage Doubling

Figure 9 shows a two-diode capacitive voltage doubler.With a 15V input, the output is 29.45V with no load and28.18V with a 10mA load.

Figure 8. Negative Voltage Converter

1

2

3

4

8

7

6

5

+

+10F

10F

V+2V TO 18V

VOUT = V+

TMIN TA TMAX1144 F08

LTC11441

2

3

4

8

7

6

5

+

+C210F

C110F

V+4V TO 36V

1144 F10

LTC1144

0.002%

TMIN TA TMAXIL 100nA

V+2

Figure 10. Ultra-Precision Voltage Divider

Battery Splitter

A common need in many systems is to obtain (+) and ()supplies from a single battery or single power supplysystem. Where current requirements are small, the circuitshown in Figure 11 is a simple solution. It providessymmetrical output voltages, both equal to one half theinput voltage. The output voltages are both referenced topin 3 (output common).

1

2

3

4

8

7

6

5

+

+

C210F

C110F

OUTPUTCOMMON

VB/2

9V

VB/29V

1144 F11

LTC1144VB

18V

+

Figure 11. Battery Splitter

7/28/2019 LT1144

8/88

LTC1144

USAO

PPLICATITYPICAL

Linear Technology Corporation1630 McCarthy Blvd., Milpitas, CA 95035-7487(408) 432 1900 q FAX: (408) 434 0507 q TELEX: 499 3977

LT/GP 0494 10K PRINTED IN USA

Regulated 5V Output Voltage

Figure 12 shows a regulated 5V output with a 9V input.

With a 0mA to 5mA load current, the ROUT is below 20.Paralleling for Lower Output Resistance

Additional flexibility of the LTC1144 is shown in Figure 13.Two LTC1144s are connected in parallel to provide a lowereffective output resistance. However, if the output resis-tance is dominated by 1/(f C1), increasing the capacitorsize (C1) or increasing the frequency will be of morebenefit than the paralleling circuit shown.

Figure 12. A Regulated 5V Supply

1

2

3

4

8

7

6

5

+

+

1F

100F

5V

9V

36k

300k

1144 F12

LTC1144

2N2369

Figure 13. Paralleling for Lower Output Resistance

VOUT = (V+)

V+

C110F

C220F

1144 F13

1

2

3

4

8

7

6

5

LTC1144+

+

C110F

1/4 CD4077*

* THE EXCLUSIVE NOR GATESYNCHRONIZES BOTH LTC1144sTO MINIMIZE RIPPLE

1

2

3

4

8

7

6

5

LTC1144+

PACKAGE DESCRIPTIONU

Dimemsions in inches (millimeters) unless otherwise noted.

0.009 0.015

(0.229 0.381)

0.300 0.320

(7.620 8.128)

0.325+0.0250.015

+0.635

0.381

8.255

( )

0.045 0.015

(1.143 0.381)

0.100 0.010(2.540 0.254)

0.065

(1.651)

TYP

0.045 0.065

(1.143 1.651)

0.130 0.005

(3.302 0.127)

0.020

(0.508)MIN

0.018 0.003(0.457 0.076)

0.125

(3.175)MIN

1 2 3 4

8 7 6 5

0.250 0.010

(6.350 0.254)

0.400

(10.160)MAX

0.016 0.050

0.406 1.270

0.010 0.020

(0.254 0.508) 45

0 8 TYP0.008 0.010

(0.203 0.254)

0.053 0.069

(1.346 1.752)

0.014 0.019

(0.355 0.483)

0.004 0.010

(0.101 0.254)

0.050

(1.270)

BSC

1 2 3 4

0.150 0.157

(3.810 3.988)

8 7 6 5

0.189 0.197

(4.801 5.004)

0.228 0.244

(5.791 6.197)

*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.

MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm).

S8 Package8-Lead Plastic SOIC

N8 Package8-Lead Plastic DIP

lt1144

Documents