LT3999 [Linear]

Low Noise, 1A, 1MHz Push-Pull DC/DC Driver with Duty Cycle Control;


型号：	LT3999
厂家：	Linear
描述：	Low Noise, 1A, 1MHz Push-Pull DC/DC Driver with Duty Cycle Control
文件：	总16页 (文件大小：302K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LT3999

Low Noise, 1A, 1MHz

Push-Pull DC/DC Driver

with Duty Cycle Control

FEATURES

DESCRIPTION

The LT^®3999 is a monolithic, high voltage, high frequency

DC/DC transformer driver providing isolated power in a

Wide Input Operating Range: 2.7V to 36V

Dual 1A Switches with Programmable Current Limit

Programmable Switching Frequency: 50kHz to 1MHz small solution footprint.

Frequency Synchronization Up to 1MHz

The LT3999 has two 1A current limited power switches

∆V Compensation Using Duty Cycle Control

that switch out of phase. The duty cycle is programmable

to adjust the output voltage. The switching frequency is

programmed up to 1MHz and can be synchronized to an

external clock for more accurate placement of switcher

harmonics. The input operating range is programmed

withtheprecisionundervoltageandovervoltagelockouts.

The supply current is reduced to less than 1µA during

shutdown. A user-defined RC time constant provides an

adjustable soft-start capability by limiting the inrush cur-

rent at start-up.

Low Noise Topology

Programmable Input Over and Undervoltage Lockout

Cross Conduction Prevention Circuitry

Programmable Soft-Start

Low Shutdown Current: <1µA

10-Lead MSOP and DFN Packages

APPLICATIONS

Low Noise Isolated Supplies

Medical Instrument and Safety

The LT3999 is available in a 10-lead MSOP and 3mm ×

3mm DFN package with exposed pad.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

Distributed Power

Multiple Output Supplies

Positive-to-Negative Supplies

Noise Immunity in Data Acquisition, RS232

and RS485

TYPICAL APPLICATION

LT3999 Line Regulation with

Duty Cycle Control

12V to 12V, 10W Low Noise Isolated DC/DC Converter

12V

10µF

16V

15.3µH

OUT

12V

SYNC

SWA

SWB

•

0.8A

255k

10k

UVLO

10µF

16V

= 400mA

OUT

OVLO/DC

RDC

= 200mA

OUT

LT3999

15.8k

= 800mA

OUT

3999 TA01a

ILIM/SS

RBIAS

28k

GND

0.1µF 49.9k

500kHz

14 15

10 11 12 13

INPUT VOLTAGE (V)

16 17 18

3999 TA01b

3999fa

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LT3999

(Note 1)

ABSOLUTE MAXIMUM RATINGS

SWA, SWB................................................. –0.3V to 80V

OVLO/DC, SYNC ......................................... –0.3V to 8V

Operating Junction Temperature Range (Note 2)

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

Lead Temperature (Soldering, 10 sec)

V , UVLO .................................................. –0.3V to 60V

MSOP ...............................................................300°C

LT3999E ............................................ –40°C to 125°C

LT3999I ............................................. –40°C to 125°C

LT3999H............................................ –40°C to 150°C

LT3999MP......................................... –55°C to 150°C

PIN CONFIGURATION

TOP VIEW

SWA

10 SWB

SWA

10 SWB

RBIAS

ILIM/SS

RBIAS

ILIM/SS

GND

SYNC

RDC

SYNC

GND

UVLO

OVLO/DC

RDC

MSE PACKAGE

10-LEAD PLASTIC MSOP

DD PACKAGE

= 40°CW, θ = 10°CW

EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB

10-LEAD (3mm × 3mm) PLASTIC DFN

= 43°C/W, θ = 5.5°C/W

EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

LT3999EMSE#PBF

LT3999IMSE#PBF

LT3999HMSE#PBF

LT3999MPMSE#PBF

LT3999EDD#PBF

LT3999IDD#PBF

TAPE AND REEL

PART MARKING*

LTGKR

PACKAGE DESCRIPTION

TEMPERATURE RANGE

LT3999EMSE#TRPBF

LT3999IMSE#TRPBF

LT3999HMSE#TRPBF

LT3999MPMSE#TRPBF

LT3999EDD#TRPBF

LT3999IDD#TRPBF

10-Lead Plastic MSOP

–40°C to 125°C

–40°C to 150°C

–55°C to 150°C

–40°C to 125°C

LTGKR

10-Lead Plastic MSOP

LTGKR

10-Lead Plastic MSOP

LTGKR

10-Lead Plastic MSOP

LGKQ

10-Lead (3mm × 3mm) Plastic DFN

LGKQ

Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.

Consult LTC Marketing for information on nonstandard lead based finish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/

3999fa

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LT3999

ELECTRICAL CHARACTERISTICS ^Thel denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. V_IN= 15V

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Input Supply and Shutdown

Minimum Operating Voltage

Overvoltage Lockout

Supply Current

2.7

Internal, Rising

(Note 3)

4.3

0.1

1.25

125

μA

Shutdown Current

= 0.3V

UVLO

UVLO Threshold (Rising)

UVLO Hysteresis

1.15

1.35

UVLO Pin Current

= 1.25V

100

UVLO

OVLO/DC Threshold (Rising)

OVLO/DC Hysteresis

OVLO/DC Pin Current

Power Switches (SWA, SWB)

Switch Saturation Voltage

Switch Current Limit

Non Overlap Time

1.25

125

1.35

= 1.25V

100

1.7

OVLO/DC

= 1A

350

1.4

Internal Default

1.0

Switch Base Drive Current

Oscillator/Sync

= 1A

Switching Frequency

R = 316k

kHz

R = 49.9k

280

100

300

320

R = 12.1k

1000

Synchronization Frequency Range

SYNC Voltage Threshold

SYNC Pin Input Resistance

ILIM/SS

1000

kHz

1.5

200

kΩ

SWA and SWB Current Limit

ILIM/SS Pin Current

Duty Cycle

= 43.2k

0.4

0.5

0.6

ILIM/SS

μA

Switch Duty Cycle

OVLO/DC = 0.8V, R = 24.3k, R = 49.9k

OVLO/DC = 0.612V, R = 24.3k, R = 49.9k

OVLO/DC = 0.3V, R = 24.3k, R = 49.9k

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect the device

reliability and lifetime.

Note 3: Supply current specification does not include switch drive

currents. Actual supply currents will be higher.

Note 2: The LT3999E is guaranteed to meet performance specifications

from 0°C to 125°C junction temperature. Specifications over the –40°C

to 125°C operating junction temperature range are assured by design,

characterization, and correlation with statistical process controls. The

LT3999I Is guaranteed over the –40°C to 125°C operating junction

temperature range. The LT3999H is guaranteed over the full –40°C to

150°C operating junction temperature range. The LT3999MP is 100%

tested and guaranteed over the –55°C to 150°C junction temperature

range. High junction temperatures degrade operating lifetimes; operating

lifetime is derated for junction temperatures greater than 125°C.

3999fa

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LT3999

TYPICAL PERFORMANCE CHARACTERISTICS

_INShutdown Current

Switching Frequency

V_CESATvs Switch Current

2.5

400

375

350

325

300

275

250

225

200

400

350

300

250

200

150

100

2.0

1.5

1.0

0.5

50 75

TEMPERAURE (°C)

–50 –25

100 125 150

TEMPERATURE (°C)

400 500

600 700

–50 –25

75 100 125 150

100

800 9001000

200 300

SWITCH CURRENT (mA)

3999 G02

3999 G01

3999 G03

Switch V_CESAT

Switch Leakage Current

Switch Current Limit

2000

1800

1600

1400

1200

1000

800

600

3.0

2.5

2.0

1.5

1.0

0.5

SWITCH CURRENT = 1A

500

400

= OPEN

= 80.6k

ILIM/SS

300

200

100

= 43.2k

600

400

200

–50

100 125

150

75 100

–25

–50 –25

25 50

125 150

–50 –25

75 100 125 150

TEMPERATURE (°C)

3999 G06

3999 G04

3999 G05

UVLO Threshold Voltage

OVLO Threshold Voltage

1.40

1.35

1.30

1.25

1.20

1.15

1.10

1.05

1.00

0.95

0.90

1.40

1.35

1.30

1.25

1.20

1.15

1.10

1.05

1.00

0.95

0.90

OVLO RISING

UVLO RISING

OVLO FALLING

UVLO FALLING

–50

100 125

150

–25

–50

100 125

150

–25

TEMPERATURE (°C)

3999 G08

3999 G07

3999fa

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LT3999

TYPICAL PERFORMANCE CHARACTERISTICS

Soft-Start (ILIM/SS) Current

Switch Duty Cycle

75 100

–50

100 125

150

–50 –25

25 50

125 150

–25

TEMPERATURE (°C)

3999 G09

3999 G10

PIN FUNCTIONS

SWA, SWB (Pin 1, Pin 10): SWA and SWB pins are the

open-collector nodes of the power switches. These pins

drive the transformer and are connected to the outer ter-

minals of the center tapped transformer. Large currents

flowthroughthesepinssokeepPCBtracesshortandwide.

RDC (Pin 6): The RDC pin is the duty cycle control pin. A

resistor to ground sets the duty cycle. If unused leave the

pin floating or connect to the OVLO/DC pin.

RT (Pin 7): The RT pin sets the switching frequency of

the power switches.

RBIAS (Pin 2): The RBIAS pin sets the bias current of

the power switches (SWA and SWB). Connect the pin to

a 49.9k resistor to GND.

SYNC (Pin 8): The SYNC pin synchronizes the part to an

external clock. Set the internal oscillator frequency below

the external clock frequency. Synchronizing the clock to

an external reference is useful for creating more stable

positioning of the switcher voltage or current harmonics.

Connect the SYNC pin to ground if not used.

(Pin 3): The V pin is the main supply pin for the

switch driver and internal regulator. Short duration, high

current pulses are produced during the turn on and turn

off of the power switches. Connect a low ESR capacitor

of 4.7µF or greater.

ILIM/SS (Pin 9): The ILIM/SS pin sets a threshold level

for the cycle by cycle maximum switch current. Imple-

UVLO (Pin 4): The UVLO pin has a precision threshold

ment soft-start with a capacitor, C , placed on this pin to

with hysteresis to implement an accurate V undervolt-

ground. An internal current source charges the capacitor.

age lockout. The UVLO function disables switching and

The R , C time constant sets the soft-start time and

ILIM SS

sets the part into a low current shutdown mode. Connect

ramps the maximum switch current threshold at start-up.

the UVLO pin directly to V or to a resistor divider string.

If the ILIM/SS function is not used, float this pin and the

current limit will default to the internal limit.

OVLO/DC(Pin5):TheOVLO/DCpinhasaprecisionthresh-

old withhysteresistoimplementan accurateV overvolt-

GND (Pin 11): The ground pin is the exposed pad of the

package. Solder the exposed pad directly to the ground

plane.

age lockout. The OVLO function disables the switching.

Connect OVLO/DC pin to ground to disable the function

or to a resistor divider string to program the duty cycle.

3999fa

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LT3999

BLOCK DIAGRAM

OUT

•

SWA SWB

LINEAR

BANDGAP

REGULATOR

UVLO

–

INTERNAL

BIAS

–

RBIAS

SWITCH

CONTROL

OVLO/DC

BIAS

SWITCH A

SWITCH B

–

OSCILLATOR

–

DUTY CYCLE

CONTROL

SENSE

–

RDC

SYNC RT

GND ILIM/SS

3999 BD

ILIM

3999fa

For more information www.linear.com/LT3999

LT3999

OPERATION

Overview

Current Limit and Soft-Start

The LT3999 is a monolithic isolated push-pull DC trans-

former driver. It includes functions such as duty cycle

control, soft-start and protection features.

The LT3999 ILIM/SS pin programs the cycle-by-cycle

switch current limit and the soft-start time. A resistor on

the ILIM/SS pin sets the current limit. A capacitor on the

pininconjunctionwiththeresistorsetsthesoft-starttime.

Push-Pull Topology

When the programmed current limit is reached the switch

isimmediatelyturnedoffandremainsofffortheremainder

of the cycle. Leaving the ILIM/SS pin unconnected will

disable the programmable current limit and the LT3999

will default to its internal current limit.

In a push-pull topology, a pair of switches operating out

of phase generate a square wave voltage pulse on the

primary side of a center tapped transformer. The diodes

on the secondary side rectify the voltage and generate

the output voltage. This voltage is simply V times the

Thesoft-startfunctionrampsthemaximumswitchcurrent

over the programmed soft-start time. The purpose of the

soft-startistoreduceinrushcurrentfromtheinputsupply.

transformer turns ratio.

Duty Cycle Control

The LT3999 duty cycle control provides, to a degree, line

regulation. The duty cycle is programmed by a resistor

on the RDC pin and the OVLO/DC voltage. By making the

Other Features

The LT3999 protection features include overvoltage lock-

out (OVLO), undervoltage lockout (UVLO) and thermal

shutdown.

OVLO/DC voltage a function of V the duty cycle will

adjust with varying V thereby keeping V

constant.

OUT

The OVLO function is programmed with the OVLO/DC pin.

Switching is disabled during an OVLO event. An internal

ThisfeatureisusefulincaseswhereanLDOisusedtopost

regulate the output of the LT3999. By pseudo regulating

the output with the duty cycle control the power dissipa-

tion in the LDO is minimized.

overvoltage lockout on the V pin is also provided to

protect the LT3999.

The UVLO function is programmed with the UVLO pin.

Switching is disabled during a UVLO event. The UVLO

pin is also used to put the LT3999 into a low quiescent

shutdown state.

Leaving the RDC pin floating or connecting it to the OVLO/

DC pin disables the duty cycle function and the LT3999

operates at close to 50% duty cycle.

At a junction temperature above the operating tempera-

ture range the thermal shutdown function turns off both

switches.

3999fa

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LT3999

APPLICATIONS INFORMATION

Switching Frequency

Oscillator Sync

The LT3999 drives two output power switches out of

phase, thustheoscillatorfrequencyistwotimestheactual

switching frequency of each power switch. The choice

of switching frequency is a trade-off between power ef-

ficiency and the size of capacitive and inductive storage

components.

In applications where a more precise frequency is desired

toaccuratelyplacehighfrequencyharmonics, theLT3999

oscillator can be synchronized to an external clock. Set

the internal oscillator frequency 10% to 50% lower than

the external sync frequency. The switching frequency is

one-half the sync frequency.

Operating at low switching frequency reduces the switch-

inglosses(transientlosses)andconsequentlyimprovesthe

power converter efficiency. However, the lower switching

frequency requires greater inductance for a given amount

of ripple current, resulting in a larger design footprint and

higher cost.

Drive the SYNC pin with a 2V or greater square wave.

The rising edge of the sync square wave will initiate clock

discharge. If unused, connect the SYNC pin to ground.

Duty Cycle

To run the LT3999 at full duty cycle leave the RDC pin

unconnected.

TheLT3999switchingfrequencyissetintherangeof50kHz

to 1MHz. The value of R for a given operating frequency

Variations in V are, to a first order, compensated with

is chosen from Table 1 or from the following equation:

the LT3999 duty cycle control function. The duty cycle

function is implemented with a resistor divider on V

Table 1. Recommended 1% Standard Values

connected to the OVLO/DC pin and a resistor to ground

on the RDC pin. Use the following formula to calculate

the RDC resistor or duty cycle:

316kΩ

158kΩ

76.8kΩ

49.9kΩ

36.5kΩ

28kΩ

50kHz

100kHz

200kHz

300kHz

400kHz

500kHz

600kHz

700kHz

800kHz

900kHz

1000kHz

1.25•RDC

Duty Cycle DC =

(

)

R_B

V •

•R_T•4

R_A+R_B

22.6kΩ

19.1kΩ

16.2kΩ

14kΩ

R_B

R_A+R_B

1.25

V •

•R_T•DC•4

RDC=

12.1kΩ

where R and R are the resistors from the V to OVLO/

DC resistor divider and R is the frequency setting resis-





R kΩ =

–70ns •3.25•10¹⁰







(

)

tor. See Figure 1. Setting the OVLO/DC pin to be 0.612V

2•f



at the nominal V voltage yields good line regulation over

a wide input range.

The duty cycle refers to the duty cycle of the individual

switch. Normally each switch operates at close to 50%

duty cycle.

3999fa

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LT3999

APPLICATIONS INFORMATION

Soft-Start and Current Limit

The LT3999 soft-start ramps the peak switch current over

a time programmed by either a capacitor or a resistor and

capacitor on the ILIM/SS pin.

UVLO

OVLO/DC

UVLO

OVLO/DC

Whenprogrammingthesoft-starttimewithacapacitoronly

thesoft-starttimeiscalculatedwiththefollowingformula:

3999 F01

Figure 1. Precision UVLO and OVLO Resistor Divider

(ms) = C • 80

where C is in µF.

Resistors are chosen by first selecting R . Then calculate

R with the following formula:

Thecurrentlimitdefaultstotheinternallysetvaluebecause

there is no resistor on the pin.









V_TH

1.25V



–1

R_A=R_B



When programming the soft-start time with a resistor

and capacitor on the ILIM/SS pin the soft-start time is

calculated with the following formula:



where V is the V referred voltage at which the supply

is enabled (UVLO) or disabled (OVLO/DC).

τ = RC

Transformer Design

where 3τ will be 95% of the maximum current.

Table 3 lists recommended center tapped transformers

for a variety of input voltage, output voltage and power

combinations. These transformers will yield slightly high

output voltages so that they can accommodate an LDO

regulator on the output.

The cycle-by-cycle current limit of the LT3999 is set with

a resistor on the ILIM/SS pin. Use the following formula

to calculate the value of the resistor:

ILIM

(kΩ) = I • 86.4

LIM

OVLO/DC and UVLO

If your application is not listed, the LTC Applications group

is available to assist in the choice and/or the design of the

transformer. In the design/selection of the transformer

the following characteristics are critical and should be

considered:

The UVLO pin has a precision voltage threshold with

hysteresis to enable the LT3999. The pin is typically con-

nected to V through a resistor divider; however, it can

be directly connected to V .

Table 3. Recommended Center Tapped Transformers

The OVLO/DC pin has a precision voltage threshold with

hysteresis to disable the LT3999 switching operation. The

NOMINAL

INPUT

NOMINAL

OUTPUT

pin is typically connected to V through a resistor divider.

VOLTAGE (V) VOLTAGE (V) POWER (W)

PART NUMBER

Coilcraft PA6383

Coilcraft PA6381

The OVLO/DC pin can be directly connected to GND to

disable the function. It is possible to use two separate

resistor divider strings for OVLO/DC and UVLO pins or

combine them together and use one resistor divider string

to drive both pins. See Figure 1.

Cooper Bussmann

CTX02-19064

Coilcraft PA6384

Cooper Bussmann

CTX02-19061

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LT3999

APPLICATIONS INFORMATION

Turns Ratio

Winding Resistance

The turns ratio of the transformer determines the output

voltage. The following equation is used as a first pass to

calculate the turns ratio:

Resistance in either the primary or secondary winding

reduces overall efficiency and degrades load regulation.

If efficiency or load regulation is unsatisfactory, verify

that the voltage drops in the transformer windings are

not excessive.

N_S

V_OUT+V_F

N_P2 V – V

(

)

Capacitors

where V is the forward voltage of the output diode, V

In applications with full duty cycle operation, the input

supplycurrentisapproximatelyconstant. Therefore, large

input “hold-up type” capacitors are not necessary. A low

value (>4.7µF), low ESR ceramic will be adequate to filter

high frequency noise at the input. The output capacitors

supply energy to the output load only during switch

transitions. Therefore, large capacitance values are not

necessary on the output.

is the voltage drop across the internal switches (see the

Typical Performance curves) and DC is the duty cycle.

Sufficient margin should be added to the turns ratio to

account for voltage drops due to transformer winding

resistance.

Magnetizing Current

The magnetizing inductance of the transformer causes

a ripple current that is independent of load current. This

ripple current is calculated by:

Transformer winding capacitance between the isolated

primary and secondary has parasitic currents that can

cause noise on the grounds. Providing a high frequency,

low impedance path between the primary and secondary

gives the parasitic currents a local return path. A 2.2nF,

1kV ceramic capacitor is recommended.

V •DC

f_SW•L_M

∆I=

where∆IandL areprimaryripplecurrentandmagnetizing

Optional LC Filter

inductancereferredtotheprimarysideofthetransformer,

respectively. Increasing the transformer magnetizing in-

An optional LC filter, as shown on the Typical Application

on the first page of this data sheet, should be included if

ultralow noise and ripple are required. It is recommended

that the corner frequency of the filter should be set a

decade below the switching frequency so that the switch

noise is attenuated by a factor of 100. For example, if the

ductance,L ,reducestheripplecurrent.Theripplecurrent

formula shows the effect of the switching frequency on

the magnetizing inductance. Setting the LT3999 at high

switching frequency reduces the ripple current for the

same magnetizing inductance. Therefore, it is possible to

reduce the transformer turns and still achieve low ripple

current.Thishelpstoreducethepowerconverterfootprint

as well. The transformer magnetizing inductance should

be designed for the worst-case duty cycle and input line

voltage combination.

= 100kHz, then f

= 10kHz where:

OSC

CORNER

f_CORNER

2•π LC

Switching Diode Selection

A good rule of thumb is to set the primary current ripple

A fast recovery, surface mount diode such as a Schottky

is recommended. The proximity of the diodes to the

transformer outputs is important and should be as close

as possible with short, wide traces connecting them.

amplitude 10% to 30% of the average primary current, I :

P_OUT

I_P=

V •eff

where P

is the output power of the converter and eff

OUT

is the converter efficiency, typically around 85%.

3999fa

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LT3999

APPLICATIONS INFORMATION

Output Voltage Regulation

The junction temperature is computed as:

T = T

+ P • θ

The output voltage of the DC transformer topology is

unregulated. Variations in the input voltage will cause

the output voltage to vary because the output voltage is

a function of the input voltage and the transformer turn

ratio. Also, variations in the output load will cause the

output voltage to change because of circuit parasitics,

such as the transformer DC resistance and power switch

on resistance. If regulation is necessary, a post regulator

such as a linear regulator can be added to the output of

the supply. See the Typical Applications for examples of

adding a linear regulator.

AMB

where:

P = P

+ P

+ P and θ is the package

SW JA

VIN

VCESAT

thermal resistance.

Layout Consideration Check List

The following is a list of recommended layout consider-

ations:

• Locate the bypass capacitor on the V pin of the trans-

former close to the transformer.

Power Consideration

• Create a solid GND plane, preferably on layer two of

the PCB.

The current derived from the V pin and the SWA and

SWB switching currents are the sources of the LT3999

• Use short wide traces to connect to the transformer.

power dissipation. The power dissipation is the sum of:

• The transformer and PCB routing should be care-

fully designed to maximize the symmetry between two

switching half cycles.

1) The quiescent current and switch drive power

dissipation:





I_SW•DC

• SoldertheLT3999exposedpadtothePCB.Addmultiple

vias to connect the exposed pad to the GND plane.

_IN

_VIN= V



+4mA









More Help

where I is the average switch current.

AN70: “A Monolithic Switching Regulator with 100mV

Output Noise” contains much information concerning

applications and noise measurement techniques.

2) Theconductingpowerdissipationoftheswitchesduring

on state:

= V • I • 2DC

CESAT SW

VCESAT

where DC is the duty cycle and V

is the collector

CESAT

to emitter voltage drop during the switch saturation.

3) The dynamic power dissipation due to the switching

transitions:

= V • I • f

• (t + t )

IN SW OSC r f

where t and t are the rise and fall times.

3999fa

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LT3999

TYPICAL APPLICATIONS

30V to 12V, 10W Push-Pull DC Transformer

30V

10µF

50V

OPTIONAL

OUT

SYNC

12V

SWA

SWB

499k

•

10µF

16V

0.8A

OUT

UVLO

19.1k

OVLO/DC

LT3999

RDC

3999 TA02

ILIM/SS

RBIAS

D1, D2: DIODES INC. B260

L1: COILCRAFT M56132-153

T1: COOPER BUSSMANN CTX02-19062

GND

49.9k

0.1µF

BIAS

28k

500kHz

5V to 5V, 4W Low Part Count Push-Pull DC Transformer

47µF

10V

OUT

UVLO

SWA

SWB

•

10µF

10V

0.8A

OUT

SYNC

OVLO/DC

LT3999

RDC

3999 TA03

ILIM/SS

RBIAS

D1, D2: CENTRAL SEMI. CMSH1-20M

T1: COILCRAFT PA6383

GND

BIAS

12.1k

1MHz

49.9k

10V-15V to 12V, 200mA Isolated Switching Regulator

10V TO 15V

10µF

100V

OUT

715k

39µH

SHDN OUT

12V

10µF

25V

OUT1

SYNC

200mA

SWA

SWB

•

36.5k

LT3065

UVLO

10µF

50V

ADJ

180pF

OVLO/DC

REF/BYP

52.3k

10k

39µH

66.5k

0.01µF

39k

LT3999

–V

OUT

SHDN OUT

–12V

R6 200mA

10k

RDC

OUT2

10µF

25V

10µF

50V

ILIM

LT3090

ILIM/SS

RBIAS

SET

D1-D4: CENTRAL SEMI. CMSH1-200HE

L1, L2: COILCRAFT XFL3012-393MEG

T1: WÜRTH 750314781

R10

243k

GND

BIAS

12.1k

1MHz

13.3k

0.01µF 49.9k

3999 TA04

3999fa

For more information www.linear.com/LT3999

LT3999

PACKAGE DESCRIPTION

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

MSE Package

10-Lead Plastic MSOP, Exposed Die Pad

(Reference LTC DWG # 05-08-1664 Rev I)

BOTTOM VIEW OF

EXPOSED PAD OPTION

1.88

(.074)

1.88 ±0.102

(.074 ±.004)

0.889 ±0.127

(.035 ±.005)

0.29

REF

1.68

(.066)

0.05 REF

5.10

(.201)

MIN

1.68 ±0.102

3.20 – 3.45

DETAIL “B”

(.066 ±.004) (.126 – .136)

CORNER TAIL IS PART OF

THE LEADFRAME FEATURE.

FOR REFERENCE ONLY

DETAIL “B”

NO MEASUREMENT PURPOSE

0.50

(.0197)

BSC

0.305 ± 0.038

(.0120 ±.0015)

TYP

3.00 ±0.102

(.118 ±.004)

(NOTE 3)

0.497 ±0.076

(.0196 ±.003)

10 9

7 6

RECOMMENDED SOLDER PAD LAYOUT

REF

3.00 ±0.102

(.118 ±.004)

(NOTE 4)

4.90 ±0.152

(.193 ±.006)

DETAIL “A”

0.254

(.010)

0° – 6° TYP

4 5

GAUGE PLANE

0.53 ±0.152

(.021 ±.006)

0.86

(.034)

REF

1.10

(.043)

MAX

DETAIL “A”

0.18

(.007)

SEATING

PLANE

0.17 – 0.27

(.007 – .011)

TYP

0.1016 ±0.0508

(.004 ±.002)

0.50

(.0197)

BSC

MSOP (MSE) 0213 REV I

NOTE:

1. DIMENSIONS IN MILLIMETER/(INCH)

2. DRAWING NOT TO SCALE

3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.

MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.

INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX

6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD

SHALL NOT EXCEED 0.254mm (.010") PER SIDE.

3999fa

For more information www.linear.com/LT3999

LT3999

PACKAGE DESCRIPTION

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

DD Package

10-Lead Plastic DFN (3mm × 3mm)

(Reference LTC DWG # 05-08-1699 Rev C)

0.70 ±0.05

3.55 ±0.05

2.15 ±0.05 (2 SIDES)

1.65 ±0.05

PACKAGE

OUTLINE

0.25 ± 0.05

0.50

BSC

2.38 ±0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

R = 0.125

0.40 ± 0.10

TYP

3.00 ±0.10

(4 SIDES)

1.65 ± 0.10

(2 SIDES)

PIN 1 NOTCH

R = 0.20 OR

PIN 1

TOP MARK

(SEE NOTE 6)

0.35 × 45°

CHAMFER

(DD) DFN REV C 0310

0.25 ± 0.05

0.50 BSC

0.75 ±0.05

0.200 REF

2.38 ±0.10

(2 SIDES)

0.00 – 0.05

BOTTOM VIEW—EXPOSED PAD

NOTE:

1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).

CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE

TOP AND BOTTOM OF PACKAGE

3999fa

For more information www.linear.com/LT3999

LT3999

REVISION HISTORY

REV

DATE

DESCRIPTION

PAGE NUMBER

04/15 Corrected pin assignments

Revised schematics

13, 16

3999fa

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 representa-

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

For more information www.linear.com/LT3999

LT3999

TYPICAL APPLICATION

5V to 12V, 1W Low Power Push-Pull DC Transformer

10µF

D1A

OUT

10V

12V

SYNC

SWA

SWB

261k

•

2.2µF

16V

0.08A

OUT

UVLO

100k

OVLO/DC

LT3999

RDC

D1B

3999 TA05

ILIM/SS

RBIAS

D1, D2: VISHAY BAT54C

T1: COOPER BUSSMANN CTX02-19065R

12.1k

1MHz

GND

BIAS

49.9k

ILIM

40.3k

0.1µF

RELATED PARTS

PART NUMBER DESCRIPTION

COMMENTS

LT3439

LT1533

LT1683

LT1738

Slew Rate Controlled Ultralow Noise 1A Isolated DC/DC

Transformer Driver

V : 2.7V to 17.5V, I (Supply) = 12mA, I < 12mA, SO-16,

IN Q SD

Low Noise: <100mV , Independent Control of Switch Voltage

P-P

and Current Slew Rates

Slew Rate Controlled Ultralow Noise 1A Switching Regulator

Slew Rate Controlled Ultralow Noise Push-Pull Controller

Slew Rate Controlled Ultralow Noise DC/DC Controller

V : 2.7V to 23V, I (Supply) = 12mA, I < 12mA, SO-16,

IN Q SD

Low Noise: <100mV , Independent Control of Switch Voltage

P-P

and Current Slew Rates

V : 2.7V to 20V, I (Supply) = 25mA, I < 24mA, SSOP-20,

Low Noise: <200mV , Independent Control of Switch Voltage

P-P

and Current Slew Rates

V : 2.7V to 20V, I (Supply) = 12mA, I < 24mA, SSOP-20,

Greatly Reduced Conducted and Radiated EMI, Independent

Control of Switch Voltage and Current Slew Rates

3999fa

LT 0415 REV A • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

For more information www.linear.com/LT3999

●

 LINEAR TECHNOLOGY CORPORATION 2014

(408)432-1900 FAX: (408) 434-0507 www.linear.com/LT3999

LT3999 [Linear]

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