LT1931AES5_技术文档

LT1931/LT1931A

1.2MHz/2.2MHz Inverting

DC/DC Converters in ThinSOT

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FEATURES

DESCRIPTIO

The LT^®1931/LT1931A are the industry’s highest power

inverting SOT-23 current mode DC/DC converters. Both

parts include a 1A integrated switch allowing high current

outputs to be generated in a small footprint. The LT1931

switchesat1.2MHzwhiletheLT1931Aswitchesat2.2MHz.

These high speeds enable the use of tiny, low cost

capacitors and inductors 2mm or less in height. The

LT1931 is capable of generating –5V at 350mA or –12V

at 150mA from a 5V supply, while the LT1931A can

generate –5V at 300mA using significantly smaller induc-

tors. Both parts are easy pin-for-pin upgrades for higher

power LT1611 applications.

■

Fixed Frequency 1.2MHz/2.2MHz Operation

■

Very Low Noise: 1mV_P-POutput Ripple

■

–5V at 350mA from 5V Input

–12V at 150mA from 5V Input

■

Uses Small Surface Mount Components

■

Wide Input Range: 2.6V to 16V

■

Low Shutdown Current: <1µA

■

Low V_CESATSwitch: 400mV at 1A

Low Profile (1mm) ThinSOT^TMPackage

■

Pin-for-Pin Compatible with the LT1611

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APPLICATIO S

The LT1931/LT1931A operate in a dual inductor inverting

topology that filters both the input side and output side

current.Verylowoutputvoltagerippleapproaching1mV_P-P

canbeachievedwhenceramicoutputcapacitorsareused.

Fixed frequency switching ensures a clean output free

from low frequency noise typically present with charge

pumpsolutions.Thelowimpedanceoutputremainswithin

1% of nominal during large load steps. The 36V switch

allows V_INto V_OUTdifferential of up to 34V.

■

Disk Drive MR Head Bias

■

Digital Camera CCD Bias

■

LCD Bias

GaAs FET Bias

Local Low Noise/Low Impedance Negative Supply

■

The LT1931/LT1931A are available in the 5-lead ThinSOT

package.

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

ThinSOT is a trademark of Linear Technology Corporation.

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TYPICAL APPLICATIO

C2

1µF

Efficiency

L1A

L1B

10µH

V

IN

5V

100

95

D1

90

85

80

75

70

65

60

55

50

V

SW

OUT

IN

–5V

SHDN

350mA

R1

C4

220pF

LT1931

GND

29.4k

C1

4.7µF

C3

22µF

NFB

R2

10k

C1: TAIYO YUDEN X5R JMK212BJ475MG

C2: TAIYO YUDEN X5R LMK212BJ105MG

C3: TAIYO YUDEN X5R JMK325BJ226MM

D1: ON SEMICONDUCTOR MBR0520

L1: SUMIDA CLS62-100

1931 F01

0

100 150 200 250 300 350

LOAD CURRENT (mA)

50

1931 TA01

Figure 1. 5V to –5V, 350mA Inverting DC/DC Converter

1

LT1931/LT1931A

W W

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ABSOLUTE AXI U RATI GS

PACKAGE/ORDER I FOR ATIO

(Note 1)

V_INVoltage .............................................................. 16V

SW Voltage ................................................–0.4V to 36V

NFB Voltage ............................................................. –2V

Current Into NFB Pin............................................ ±1mA

SHDN Voltage .......................................................... 16V

Maximum Junction Temperature .......................... 125°C

Operating Temperature Range (Note 2) .. –40°C to 85°C

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

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

ORDER PART

NUMBER

TOP VIEW

SW 1

GND 2

NFB 3

5 V

IN

LT1931ES5

LT1931AES5

4 SHDN

S5 PART MARKING

S5 PACKAGE

5-LEAD PLASTIC SOT-23

LTRA

LTSP

T_JMAX= 125°C, θ_JA= 256°C/ W

Consult factory for parts specified with wider operating temperature ranges.

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are T_A= 25°C.

V_IN= 3V, V_SHDN= V_IN, unless otherwise noted. (Note 2)

LT1931

TYP

LT1931A

TYP

PARAMETER

CONDITIONS

MIN

MAX

2.6

MIN

MAX

2.6

UNITS

Minimum Operating Voltage

Maximum Operating Voltage

Feedback Voltage

2.45

V

16

–1.275 –1.255 –1.235 –1.275 –1.255 –1.235

V

●

–1.280

–1.230 –1.280

–1.230

NFB Pin Bias Current

V

= –1.255V

4

8

6

8

16

8

µA

mA

µA

NFB

Quiescent Current

= 2.4V, Not Switching

4.2

5.8

SHDN

Quiescent Current in Shutdown

Reference Line Regulation

Switching Frequency

= 0V, V = 3V

0.01

1.2

1

0.01

2.2

1

IN

2.6V ≤ V ≤ 16V

0.05

%/V

IN

1

0.85

1.4

1.6

1.8

1.6

2.6

2.9

MHz

●

Maximum Duty Cycle

Switch Current Limit

84

1

90

1.2

75

1

82

1.2

%

A

(Note 3)

2

600

1

2.5

600

1

Switch V

I

= 1A

= 5V

400

0.01

400

0.01

mV

µA

V

CESAT

SW

Switch Leakage Current

SHDN Input Voltage, High

SHDN Input Voltage, Low

SHDN Pin Bias Current

V

SW

2.4

0.5

V

SHDN

V

SHDN

= 3V

= 0V

16

0

32

0.1

35

0

70

0.1

µA

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

operating temperature range are assured by design, characterization and

correlation with statistical process controls.

Note 2: The LT1931E/LT1931AE are guaranteed to meet performance

specifications from 0°C to 70°C. Specifications over the –40°C to 85°C

Note 3: Current limit guaranteed by design and/or correlation to static test.

2

LT1931/LT1931A

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TYPICAL PERFOR A CE CHARACTERISTICS

Quiescent Current

Feedback Pin Voltage

Shutdown Pin Current

–1.28

–1.27

–1.26

–1.25

–1.24

–1.23

–1.22

7.0

6.5

6.0

5.5

90

80

70

60

50

40

30

20

10

0

NOT SWITCHING

T

= 25°C

A

LT1931A

LT1931

50

5.0

4.5

LT1931

4.0

3.5

3.0

–10

–50

0

25

50

75

100

–25

0

–50

75

100

25

0

1

3

4

5

6

2

TEMPERATURE (°C)

SHDN PIN VOLTAGE (V)

TEMPERATURE (°C)

1931 G02

1931 G01

1931 G03

Current Limit

Switch Saturation Voltage

Oscillator Frequency

0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

0.05

2.5

2.3

2.1

1.9

1.7

1.5

1.3

1.1

0.9

0.7

0.5

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

T

= 25°C

T

= 25°C

A

LT1931A

LT1931

0

–50

–25

25

50

75

100

0

50 60

0

0.2

0.4

0.6

1.2

10 20 30 40

70 80 90

0.8

1.0

TEMPERATURE (°C)

SWITCH CURRENT (A)

DUTY CYCLE (%)

1931 G06

1931 G04

1931 G05

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PI FU CTIO S

SW (Pin 1): Switch Pin. Connect inductor/diode here.

| V_OUT| –1.255

For LT1931A: R1=

Minimize trace area at this pin to keep EMI down.

1.255

+ 8 •10^–6

(

)

R2

GND (Pin 2): Ground. Tie directly to local ground plane.

SHDN(Pin4):ShutdownPin.Tieto2.4Vormoretoenable

NFB (Pin 3): Feedback Pin. Reference voltage is –1.255V.

Connect resistive divider tap here. Minimize trace area.

The NFB bias current flows out of the pin. Set R1 and R2

according to:

device. Ground to shut down.

V_IN(Pin 5): Input Supply Pin. Must be locally bypassed.

| V_OUT| –1.255

For LT1931: R1=

1.255

+ 4 •10^–6

(

)

R2

3

LT1931/LT1931A

W

BLOCK DIAGRA

V

IN

5

IN

R5

80k

R6

80k

1

SW

+

–

COMPARATOR

A2

–

+

A1

m

DRIVER

g

LATCH

S

Q3

R

Q

R

C

RAMP

Q1

Q2

Σ

GENERATOR

x10

C

+

–

C

V

OUT

R3

30k

0.01Ω

1.2MHz

OSCILLATOR

R1

C

PL

(EXTERNAL)

R4

150k

(OPTIONAL)

NFB

SHDN

4

SHUTDOWN

3

NFB

2

GND

R2

1931 BD

(EXTERNAL)

Figure 2

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OPERATIO

The LT1931 uses a constant frequency, current mode

control scheme to provide excellent line and load regula-

tion. Operation can be best understood by referring to the

Block Diagram in Figure 2. At the start of each oscillator

cycle, the SR latch is set, turning on the power switch Q3.

A voltage proportional to the switch current is added to a

stabilizing ramp and the resulting sum is fed into the

positive terminal of the PWM comparator A2. When this

voltageexceedsthelevelatthenegativeinputofA2,theSR

latch is reset, turning off the power switch. The level at the

negative input of A2 is set by the error amplifier (g_m) and

is simply an amplified version of the difference between

thefeedbackvoltageandthereferencevoltageof–1.255V.

In this manner, the error amplifier sets the correct peak

current level to keep the output in regulation. If the error

amplifier’s output increases, more current is taken from

the output; if it decreases, less current is taken. One

function not shown in Figure 2 is the current limit. The

switch current is constantly monitored and not allowed to

exceed the nominal value of 1.2A. If the switch current

reaches 1.2A, the SR latch is reset regardless of the state

of comparator A2. This current limit protects the power

switch as well as various external components connected

to the LT1931.

TheBlockDiagramfortheLT1931Aisidenticalexceptthat

theoscillatoris2.2MHzandresistorsR3toR6areone-half

the LT1931 values.

4

LT1931/LT1931A

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APPLICATIO S I FOR ATIO

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LT1931A AND LT1931 DIFFERENCES:

corelossesatfrequenciesabove1MHzaremuchlowerfor

ferrite cores than for powdered-iron units. When using

coupled inductors, choose one that can handle at least 1A

of current without saturating, and ensure that the inductor

has a low DCR (copper-wire resistance) to minimize I²R

powerlosses. Ifusinguncoupledinductors, eachinductor

need only handle one-half of the total switch current so

that 0.5A per inductor is sufficient. A 4.7µH to 15µH

coupled inductor or a 15µH to 22µH uncoupled inductor

will usually be the best choice for most LT1931 designs.

For the LT1931A, a 2.2µH to 4.7µH coupled inductor or a

3.3µH to 10µH uncoupled inductor will usually suffice. In

certain applications such as the “Charge Pump” inverting

DC/DC converter, only a single inductor is used. In this

case, the inductor must carry the entire 1A switch current.

Switching Frequency

The key difference between the LT1931A and LT1931 is

thefasterswitchingfrequencyoftheLT1931A.At2.2MHz,

the LT1931A switches at nearly twice the rate of the

LT1931. Care must be taken in deciding which part to use.

The high switching frequency of the LT1931A allows

smaller cheaper inductors and capacitors to be used in a

given application, but with a slight decrease in efficiency

and maximum output current when compared to the

LT1931. Generally, if efficiency and maximum output

current are critical, the LT1931 should be used. If applica-

tion size and cost are more important, the LT1931A will be

the better choice. In many applications, tiny inexpensive

chip inductors can be used with the LT1931A, reducing

solution cost.

Table 1. Recommended Inductors—LT1931

L

Size

PART

(µH) (L × W × H) mm

VENDOR

Duty Cycle

CLS62-100

CR43-150

CR43-220

10

15

22

6.8 × 6.6 × 2.5

4.5 × 4.0 × 3.2

Sumida

(847) 956-0666

www.sumida.com

The maximum duty cycle (DC) of the LT1931A is 75%

compared to 84% for the LT1931. The duty cycle for a

given application using the dual inductor inverting topol-

ogy is given by:

CTX10-1

CTX15-1

10

15

8.9 × 11.4 × 4.2

3.2 × 2.5 × 2.0

Coiltronics

(407) 241-7876

www. coiltronics.com

LQH3C100K24

LQH4C150K04

10

15

Murata

(404) 436-1300

www.murata.com

| V_OUT

|

DC =

| V | + | V_OUT

|

IN

Table 2. Recommended Inductors—LT1931A

Size

(µH) (L × W × H) mm

For a 5V to –5V application, the DC is 50% indicating that

the LT1931A can be used. A 5V to –16V application has a

DC of 76.2% making the LT1931 the right choice. The

LT1931A can still be used in applications where the DC, as

calculated above, is above 75%. However, the part must

beoperatedinthediscontinuousconductionmodesothat

the actual duty cycle is reduced.

L

PART

VENDOR

ELJPC3R3MF

ELJPC4R7MF

3.3

4.7

2.5 × 2.0 × 1.6

7.6 × 4.8 × 1.8

2.0 × 1.6 × 1.6

3.2 × 2.5 × 2.0

Panasonic

(408) 945-5660

www.panasonic.com

1

2

CLQ4D10-4R7

CLQ4D10-6R8

4.7

6.8

Sumida

(847) 956-0666

www.sumida.com

LB20164R7M

LB20163R3M

4.7

3.3

Taiyo Yuden

(408) 573-4150

www.t-yuden.com

INDUCTOR SELECTION

SeveralinductorsthatworkwellwiththeLT1931arelisted

in Table 1 and those for the LT1931A are listed in Table 2.

Besides these, there are many other inductors that can be

used. Consult each manufacturer for detailed information

and for their entire selection of related parts. Ferrite core

inductors should be used to obtain the best efficiency, as

LQH3C4R7K24

LQH4C100K24

4.7

10

Murata

(404) 436-1300

www.murata.com

1

Use drawing #5382-T039

Use drawing #5382-T041

2

5

LT1931/LT1931A

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APPLICATIO S I FOR ATIO

The inductors shown in Table 2 for use with the LT1931A

were chosen for their small size. For better efficiency, use

similar valued inductors with a larger volume. For in-

stance, the Sumida CR43 series, in values ranging from

3.3µH to 10µH, will give a LT1931A application a few

percentage points increase in efficiency.

zero to the system. For the tantalum and OS-CON capaci-

tors, this zero is located at a lower frequency due to the

higher value of the ESR, while the zero of a ceramic

capacitor is at a much higher frequency and can generally

be ignored.

A phase lead zero can be intentionally introduced by

placing a capacitor (C4) in parallel with the resistor (R1)

between V_OUTand V_NFBas shown in Figure 1. The

frequency of the zero is determined by the following

equation.

CAPACITOR SELECTION

Low ESR (equivalent series resistance) capacitors should

beusedattheoutputtominimizetheoutputripplevoltage.

Multilayer ceramic capacitors are an excellent choice, as

they have an extremely low ESR and are available in very

small packages. X5R dielectrics are preferred, followed by

X7R, as these materials retain their capacitance over wide

voltage and temperature ranges. A 10µF to 22µF output

capacitor is sufficient for most LT1931 applications while

a 4.7µF to 10µF capacitor will suffice for the LT1931A.

Solid tantalum or OS-CON capacitors can be used, but

they will occupy more board area than a ceramic and will

haveahigherESR. Alwaysuseacapacitorwithasufficient

voltage rating.

1

ƒ_Z=

2π •R1•C4

By choosing the appropriate values for the resistor and

capacitor, the zero frequency can be designed to improve

the phase margin of the overall converter. The typical

target value for the zero frequency is between 20kHz to

60kHz. Figure 3 shows the transient response of the

inverting converter from Figure 1 without the phase lead

capacitor C4. The phase margin is reduced as evidenced

by more ringing in both the output voltage and inductor

current. A 220pF capacitor for C4 results in better phase

margin, which is revealed in Figure 4 as a more damped

responseandlessovershoot. Figure5showsthetransient

response when a 22µF tantalum capacitor with no phase

lead capacitor is used on the output. The higher output

voltage ripple is revealed in the upper waveform as a

thicker line. The transient response is adequate which

implies that the ESR zero is improving the phase margin.

Ceramic capacitors also make a good choice for the input

decoupling capacitor, which should be placed as close as

possible to the LT1931/LT1931A. A 1µF to 4.7µF input

capacitorissufficientformostapplications.Table3shows

a list of several ceramic capacitor manufacturers. Consult

the manufacturers for detailed information on their entire

selection of ceramic parts.

Table 3. Ceramic Capacitor Manufacturers

Taiyo Yuden

(408) 573-4150

www.t-yuden.com

V_OUT

20mV/DIV

AC COUPLED

AVX

(803) 448-9411

www.avxcorp.com

Murata

(714) 852-2001

www.murata.com

I

_L1A+ I_L1B

0.5A/DIV

AC COUPLED

200mA

100mA

LOAD

CURRENT

ThedecisiontouseeitherlowESR(ceramic)capacitorsor

the higher ESR (tantalum or OS-CON) capacitors can

effect the stability of the overall system. The ESR of any

capacitor, along with the capacitance itself, contributes a

100µs/DIV

1931 F03

Figure 3. Transient Response of Inverting Converter

Without Phase Lead Capacitor

6

LT1931/LT1931A

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APPLICATIO S I FOR ATIO

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V_OUT

20mV/DIV

AC COUPLED

V_OUT

2V/DIV

I_L1A+ I_L1B

0.5A/DIV

AC COUPLED

I_IN

0.5A/DIV

AC COUPLED

200mA

100mA

LOAD

CURRENT

5V

0V

V_SHDN

100µs/DIV

1931 F04

500µs/DIV

1931 F06

Figure 4. Transient Response of Inverting Converter

with 220pF Phase Lead Capacitor

Figure 6. Start-Up Waveforms for 5V to –5V Application

(Figure 1). No Soft-Start Circuit. V_OUTReaches –5V in

500µs; Input Current Peaks at 800mA

V_OUT

0.1V/DIV

regulatortriestochargeuptheoutputcapacitorasquickly

as possible, which results in a large inrush current. Fig-

ure 6 shows a typical oscillograph of the start-up wave-

form for the application of Figure 1 starting into a load of

33Ω. The lower waveform shows SHDN being pulsed

from 0V to 5V. The middle waveform shows the input

current, which reaches as high as 0.8A. The total time

required for the output to reach its final value is approxi-

mately 500µs. For some applications, this initial inrush

current may not be acceptable. If a longer start-up time is

acceptable, a soft-start circuit consisting of R_SSand C_SS,

as shown in Figure 7, can be used to limit inrush current

to a lower value. Figure 8 shows the relevant waveforms

with R_SS= 15k and C_SS= 33nF. Input current, measured

atV_IN,islimitedtoapeakvalueof0.5Aasthetimerequired

to reach final value increases to 1ms. In Figure 9, C_SSis

AC COUPLED

I_L1A+ I_L1B

0.5A/DIV

AC COUPLED

200mA

100mA

LOAD

CURRENT

50µs/DIV

1931 F05

Figure 5. Transient Response of Inverting Converter with 22µF

Tantalum Output Capacitor and No Phase Lead Capacitor

START-UP/SOFT-START

For most LT1931/LT1931A applications, the start-up in-

rush current can be high. This is an inherent feature of

switching regulators in general since the feedback loop is

saturated due to V_OUTbeing far from its final value. The

C2

CURRENT

PROBE

L1A

10µH

L1B

1µF

10µH

V

IN

5V

D1

+

V

IN

SW

C1

4.7µF

V

OUT

–5V

R1

29.4k

C4

220pF

R

LT1931

SS

15k

C3

22µF

V

SS

SHDN

NFB

GND

R2

10k

D2

1N4148

C

SS

C1: TAIYO YUDEN X5R JMK212BJ475MG

C2: TAIYO YUDEN X5R LMK212BJ105MG

C3: TAIYO YUDEN XR5 JMK325BJ226MM

D1: ON SEMICONDUCTOR MBR0520

L1: SUMIDA CLS62-100

33nF/68nF

1931 F07

V

OUT

Figure 7. R_SSand C_SSat SHDN Pin Provide Soft-Start to LT1931 Inverting Converter

7

LT1931/LT1931A

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APPLICATIO S I FOR ATIO

DIODE SELECTION

V_OUT

2V/DIV

ASchottkydiodeisrecommendedforusewiththeLT1931/

LT1931A. The Motorola MBR0520 is a very good choice.

Wheretheinputtooutputvoltagedifferentialexceeds20V,

use the MBR0530 (a 30V diode). These diodes are rated to

handleanaverageforwardcurrentof0.5A. Inapplications

where the average forward current of the diode exceeds

0.5A, a Microsemi UPS5817 rated at 1A is recommended.

I_IN

0.5A/DIV

AC COUPLED

5V

0V

V_SS

200µs/DIV

1931 F08

Figure 8. R_SS= 15k, C_SS= 33nF; V_OUTReaches –5V in 1ms;

Input Current Peaks at 500mA

LAYOUT HINTS

The high-speed operation of the LT1931/LT1931A de-

mands careful attention to board layout. You will not get

advertised performance with careless layout. Figure 10

shows the recommended component placement. The

ground cut at the cathode of D1 is essential for low noise

operation.

V_OUT

2V/DIV

I_IN

0.5A/DIV

AC COUPLED

5V

0V

V_SS

500µs/DIV

1931 F09

Figure 9. R_SS= 15k, C_SS= 68nF; V_OUTReaches –5V in 1.6ms;

Input Current Peaks at 350mA

L1A

L1B

C2

C1

–V

+

OUT

increased to 68nF, resulting in a lower peak input current

of 350mA with a V_OUTramp time of 1.6ms. C_SSor R_SScan

be increased further for an even slower ramp, if desired.

Diode D2 serves to quickly discharge C_SSwhen V_SSis

driven low to shut down the device. D2 can be omitted,

resulting in a “soft-stop” slow discharge of the output

capacitor.

D1

V

IN

C3

+

1

2

3

5

4

SHUTDOWN

R2

R1

GND

1931 F10

Figure 10. Suggested Component Placement.

Note Cut in Ground Copper at D1’s Cathode

8

LT1931/LT1931A

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TYPICAL APPLICATIO S

5V to –12V Inverting Converter

Efficiency

100

95

90

85

80

75

70

65

60

55

50

C2

L1A

1µF

L1B

10µH

V

IN

5V

D1

V

SW

OUT

IN

–12V

SHDN

LT1931

150mA

R1

84.5k

C1

4.7µF

C3

10µF

NFB

GND

R2

10k

C1: TAIYO YUDEN X5R JMK212BJ475MG

C2: TAIYO YUDEN X5R TMK316BJ105ML

C3: TAIYO YUDEN X5R EMK325BJ106MM

D1: ON SEMICONDUCTOR MBR0520

L1: SUMIDA CLS62-100

1931 TA02

0

25

75

100

125

150

50

LOAD CURRENT (mA)

1931 TA03

5V to –5V Inverting Converter Using Uncoupled Inductors

C2

1µF

L1

10µH

L2

10µH

V

IN

5V

D1

V

SW

OUT

IN

–5V

SHDN

300mA

R1

29.4k

220pF

LT1931

C1

4.7µF

C3

22µF

NFB

GND

R2

10k

C1: TAIYO YUDEN X5R JMK212BJ475MG

C2: TAIYO YUDEN X5R LMK212BJ105MG

C3: TAIYO YUDEN X5R JMK212BJ226MM

D1: ON SEMICONDUCTOR MBR0520

L1, L2: MURATA LQH3C100K04

1931 TA04

2.2MHz, 5V to –5V Inverting Converter

Efficiency

C2

80

75

70

65

60

55

50

L1

L2

4.7µH

1µF

4.7µH

V

IN

5V

D1

V

IN

SW

OUT

–5V

SHDN

300mA

R1

C4

180pF

LT1931A

28.7k

C1

4.7µF

C3

4.7µF

NFB

GND

R2

10k

C1: TAIYO YUDEN X5R JMK212BJ475MG

C2: TAIYO YUDEN X5R LMK212BJ105MG

C3: TAIYO YUDEN X5R JMK212BJ475MG

D1: ON SEMICONDUCTOR MBR0520

L1, L2: MURATA LQH3C4R7M24

1931 TA05a

0

100 150 200 250 300 350

LOAD CURRENT (mA)

50

1931 TA05b

9

LT1931/LT1931A

TYPICAL APPLICATIO S

U

2.2MHz, 5V to –5V Converter Uses Tiny Chip Inductors

Efficiency

C2

1µF

80

75

L1

3.3µH

L2

3.3µH

V

IN

5V

D1

V

SW

70

65

OUT

IN

–5V

SHDN

200mA

R1

28.7k

C4

68pF

LT1931A

C1

2.2µF

C3

4.7µF

NFB

60

55

50

GND

R2

10k

C1: TAIYO YUDEN X5R JMK212BJ225MG

C2: TAIYO YUDEN X5R LMK212BJ105MG

C3: TAIYO YUDEN X5R JMK212BJ475MG

D1: ON SEMICONDUCTOR MBR0520

L1, L2: PANASONIC ELJPC3R3MF

1931 TA06a

0

50

100

150

200

250

LOAD CURRENT (mA)

1931 TA06b

SLIC Power Supply with –33V and –68V Outputs, Uses Soft-Start

L1

22µH

R1

1Ω

V

IN

12V

C2

C1

4.7µF

16V

1µF

V

SW

35V

IN

D1

R

SS

LT1931

3

2

1

COM

C4

15k

SHDN

NFB

V

SS

4.7µF

GND

35V

V

OUT1

–33V

R2

1k

R3

25.5k

C

SS

100mA*

68nF

C3

1µF

35V

C6

1000pF

R4

2.7k

D2

3

2

1

C5

4.7µF

35V

*TOTAL OUTPUT POWER NOT TO EXCEED 3.3W

C1 TO C5: X5R OR X7R

D1, D2: BAV99 OR EQUIVALENT

L1: SUMIDA CR43-220

V

OUT2

–66V

1931 TA08

48mA*

10

LT1931/LT1931A

U

TYPICAL APPLICATIO S

SLIC Power Supply with –21.6V and –65V Outputs, Uses Soft-Start

L1

10µH

R1

1Ω

V

IN

5V

C1

C2

1µF

35V

4.7µF

16V

V

SW

IN

D1

R

SS

3

2

1

LT1931

SHDN

COM

15k

C5

NFB

V

SS

4.7µF

GND

25V

V

OUT1

–21.6V

48mA*

R2

1k

R3

16.2k

C3

1µF

35V

C8

1000pF

C

R4

2.7k

SS

68nF

D2

D3

3

2

1

C6

4.7µF

25V

*TOTAL OUTPUT POWER NOT TO EXCEED 1.3W

C1 TO C7: X5R OR X7R

D1, D2: BAV99 OR EQUIVALENT

L1: SUMIDA CR43-100

C4

1µF

35V

3

2

1

C7

4.7µF

25V

V

OUT2

–65V

1931 TA09

20mA*

U

PACKAGE DESCRIPTIO

S5 Package

5-Lead Plastic SOT-23

(LTC DWG # 05-08-1633)

(LTC DWG # 05-08-1635)

2.80 – 3.10

(.110 – .118)

(NOTE 3)

.20

(.008)

A2

A

2.60 – 3.00

1.50 – 1.75

DATUM ‘A’

(.102 – .118) (.059 – .069)

(NOTE 3)

1.90

(.074)

REF

L

.09 – .20

(.004 – .008)

(NOTE 2)

A1

NOTE:

1. CONTROLLING DIMENSION: MILLIMETERS

MILLIMETERS

2. DIMENSIONS ARE IN

(INCHES)

SOT-23

PIN ONE

(Original)

(ThinSOT)

.90 – 1.45

1.00 MAX

(.039 MAX)

3. DRAWING NOT TO SCALE

4. DIMENSIONS ARE INCLUSIVE OF PLATING

5. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR

6. MOLD FLASH SHALL NOT EXCEED .254mm

7. PACKAGE EIAJ REFERENCE IS:

SC-74A (EIAJ) FOR ORIGINAL

JEDEL MO-193 FOR THIN

A

A1

A2

L

.95

(.037)

REF

(.035 – .057)

.00 – .15

.01 – .10

(.0004 – .004)

.25 – .50

(.00 – .006)

(.010 – .020)

S5 SOT-23 0501

.90 – 1.30

.80 – .90

(.031 – .035)

(5PLCS, NOTE 2)

(.035 – .051)

.35 – .55

.30 – .50 REF

(.014 – .021)

(.012 – .019 REF)

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-

tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.

11

LT1931/LT1931A

U

TYPICAL APPLICATIO

2.2MHz, 12V to –5V Converter Uses Low Profile Coupled Inductor

C2

0.1µF

L1A

4.7µH

L1B

4.7µH

V

IN

12V

D1

V

SW

OUT

IN

–5V

SHDN

450mA

R1

28.7k

LT1931A

C1

2.2µF

C3

4.7µF

NFB

GND

R2

10k

C1: TAIYO YUDEN Y5V EMK212F225ZG

C2: 0.1µF 25V X5R

1931 TA07a

C3: TAIYO YUDEN X5R JMK212BJ475MG

D1: ON SEMICONDUCTOR MBR0520

L1: SUMIDA CLQ4D10-4R7 DRAWING #5382-T039

Efficiency

80

75

70

65

60

55

50

0

100

200

300

400

500

LOAD CURRENT (mA)

1931 TA07b

RELATED PARTS

PART NUMBER

LT1307

DESCRIPTION

COMMENTS

Single Cell Micropower 600kHz PWM DC/DC Converter

3.3V at 75mA from One Cell, MSOP Package

1.5V Minimum, Precise Control of Peak Current Limit

3.3V at 200mA from Two Cells, 600kHz Fixed Frequency

3V at 30mA from 1V, 1.7MHz Fixed Frequency

–5V at 150mA from 5V Input. Tiny SOT-23 Package

5V at 200mA from 3.3V Input. Tiny SOT-23 Package

20V at 12mA from 2.5V. Tiny SOT-23 Package

–15V at 12mA from 2.5V. Tiny SOT-23 Package

5V at 450mA from 3.3V Input. Tiny SOT-23 Package

LT1316

Burst Mode^TMOperation DC/DC with Programmable Current Limit

2-Cell Micropower DC/DC with Low-Battery Detector

Single Cell Micropower DC/DC Converter

LT1317

LT1610

LT1611

Inverting 1.4MHz Switching Regulator in 5-Lead ThinSOT

1.4MHz Switching Regulator in 5-Lead ThinSOT

LT1613

LT1615

Micropower Constant Off-Time DC/DC Converter in 5-Lead ThinSOT

Micropower Inverting DC/DC Converter in 5-Lead ThinSOT

1.2MHz/2.2MHz, 1A Switching Regulators in 5-Lead ThinSOT

LT1617

LT1930/LT1930A

Burst Mode operation is a trademark of Linear Technology Corporation.

1931f LT/TP 0601 2K • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

12

●

(408)432-1900 FAX:(408)434-0507 www.linear-tech.com

LINEAR TECHNOLOGY CORPORATION 2000


型号：	LT1931AES5
厂家：	Linear
描述：	LT1931 - 1.2MHz/2.2MHz Inverting DC/DC Converters in ThinSOT; Package: SOT; Pins: 5; Temperature Range: -40°C to 85°C 开关光电二极管
文件：	总12页 (文件大小：207K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LT1931AES5 [Linear]

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