LTC3726IGN#TRPBF_技术文档

LTC3900

Synchronous Rectiﬁer Driver

for Forward Converters

FeaTures

DescripTion

The LTC^®3900 is a secondary-side synchronous recti-

ﬁer driver designed to be used in isolated forward con-

verter power supplies. The chip drives N-channel rectiﬁer

MOSFETs and accepts pulse sychronization from the

primary-side controller via a pulse transformer.

n

N-Channel Synchronous Rectiﬁer MOSFET Driver

n

Programmable Timeout Protection

n

Reverse Inductor Current Protection

n

Pulse Transformer Synchronization

n

Wide V Supply Range: 4.5V to 11V

CC

n

15ns Rise/Fall Times at V = 5V, C = 4700pF

CC

L

TheLTC3900incorporatesafullrangeofprotectionforthe

external MOSFETs. A programmable timeout function is

included that disables both drivers when the synchroniza-

tion signal is missing or incorrect. Additionally, the chip

sensestheoutputinductorcurrentthroughthedrain-source

resistance of the catch MOSFET, shutting off the MOSFET

if the inductor current reverses. The LTC3900 also shuts

off the drivers if the supply voltage is too low.

Undervoltage Lockout

Small SO-8 Package

applicaTions

n

48V Input Isolated DC/DC Converters

Isolated Telecom Power Supplies

High Voltage Distributed Power

Step-Down Converters

Industrial Control System Power Supplies

Automotive and Heavy Equipment

n

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

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

owners.

n

Typical applicaTion

ISOLATION

BARRIER

L0

Z

V

3.3V

40A

OUT

V

IN

36V TO 72V

+

D3

C

OUT

Q

Efﬁciency

T1

C

R

Z

95

90

85

80

75

70

65

GATE

OUT

V

= 3.3V

OUT

REG

R

Q1

CS2

R

B

R

CS1

D

= 36V

Z

IN

Q3

+

CS

V

= 72V

IN

OC

CG

Q4

470Ω

V

IN

= 48V

V

CC

I

SENSE

–

CS

R

TMR

R

CS3

LTC3900

10mΩ

LT1952

C

TIMER

VCC

FG

C

SG

C

TMR

S

OUT

SYNC

GND

COMP

GND

T2

R

SG

SYNC

270Ω

25 30

LOAD CURRENT (A)

0

5

10 15 20

35 40

R1

OPTO

V

IN

3900 F10b

LT4430

COMP

GND

OC

OCI

FB

R2

3900 F01

Figure 1. Simpliﬁed Isolated Synchronous Forward Converter

3900fb

1

LTC3900

absoluTe MaxiMuM raTings

pin conFiguraTion

(Note 1)

Supply Voltage

TOP VIEW

+

V ........................................................................12V

CC

CS

1

2

3

4

8

7

6

5

SYNC

TIMER

GND

FG

Input Voltage

–

CS , TIMER .............................. –0.3V to (V +0.3V)

CC

CG

SYNC ...................................................... –12V to 12V

V

CC

Input Current

S8 PACKAGE

8-LEAD PLASTIC SO

= 150°C, θ = 130°C/W

+

CS ....................................................................15mA

T

JMAX

Operating Junction Temperature Range (Note 2)

JA

LTC3900E........................................... –40°C to 125°C

LTC3900I............................................ –40°C to 125°C

LTC3900H .......................................... –40°C to 150°C

LTC3900MP ....................................... –55°C to 150°C

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

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

orDer inForMaTion

LEAD FREE FINISH

LTC3900ES8#PBF

LTC3900IS8#PBF

LTC3900HS8#PBF

LTC3900MPS8#PBF

LEAD BASED FINISH

LTC3900ES8

TAPE AND REEL

PART MARKING*

PACKAGE DESCRIPTION

TEMPERATURE RANGE

–40°C to 125°C

LTC3900ES8#TRPBF

LTC3900IS8#TRPBF

LTC3900HS8#TRPBF

LTC3900MPS8#TRPBF

TAPE AND REEL

3900

8-Lead Plastic Small Outline

PACKAGE DESCRIPTION

3900

–40°C to 125°C

3900

–40°C to 150°C

3900

–55°C to 150°C

PART MARKING*

3900

TEMPERATURE RANGE

–40°C to 125°C

LTC3900ES8#TR

8-Lead Plastic Small Outline

LTC3900IS8

LTC3900IS8#TR

3900

–40°C to 125°C

LTC3900HS8

LTC3900HS8#TR

LTC3900MPS8#TR

3900

–40°C to 150°C

LTC3900MPS8

3900

–55°C to 150°C

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

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/

elecTrical characTerisTics ^Thel denotes the speciﬁcations which apply over the speciﬁed operating

junction temperature range, otherwise speciﬁcations are at T_A= 25°C. V_CC= 5V unless otherwise speciﬁed. (Notes 2, 3)

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

11

UNITS

l

V

Supply Voltage Range

4.5

5

V

CC

V

Undervoltage Lockout Threshold

Undervoltage Lockout Hysteresis

Rising Edge

Rising Edge to Falling Edge

4.1

0.5

4.5

V

UVLO

CC

l

I

V

Supply Current

V

= 0V

0.5

7

1

15

mA

VCC

CC

SYNC

f

= 100kHz, C = C = 4700pF (Note 4)

FG

CG

Timer

l

V

Timer Threshold Voltage

Timer Input Current

–10%

V

/5

10%

–10

V

TMR

CC

I

V

= 0V

–6

µA

TMR

3900fb

2

LTC3900

elecTrical characTerisTics ^Thel denotes the speciﬁcations which apply over the speciﬁed operating

junction temperature range, otherwise speciﬁcations are at T_A= 25°C. V_CC= 5V unless otherwise speciﬁed. (Notes 2, 3)

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

40

MAX

UNITS

l

t

Timer Discharge Time

Timer Pin Clamp Voltage

C

= 1000pF, R

TMR

= 4.7k

120

ns

V

TMRDIS

TMR

V

= 1000pF, R

2.5

TMRMAX

TMR

Current Sense

+

l

I

+

–

CS Input Current

V

+ = 0V

1

µA

V

CS

–

CS Input Current

– = 0V

+

V

CS Pin Clamp Voltage

I

IN

= 5mA, V = –5V

SYNC

11

CSMAX

CS

Current Sense Threshold Voltage

V

– = 0V

7.5

3

1

10.5

13.5

18

20

mV

CS

l

LTC3900E/LTC3900I (Note 5)

LTC3900H/LTC3900MP (Note 5)

SYNC Input

l

I

SYNC Input Current

V

= 10V

SYNC

1

10

µA

SYNC

V

SYNC Input Positive Threshold

SYNC Positive Input Hysteresis

1.0

1.4

0.2

1.8

V

SYNCP

(Note 6)

l

V

SYNC Input Negative Threshold

SYNC Negative Input Hysteresis

–1.8

–1.4

0.2

–1.0

V

SYNCN

Driver Output

R

Driver Pull-Up Resistance

Driver Pull-Down Resistance

Driver Peak Output Current

I

= –100mA

OUT

0.9

2

1.2

1.6

2.0

Ω

ONH

l

LTC3900E/LTC3900I

LTC3900H/LTC3900MP

R

I

= 100mA

1.2

1.6

2.0

Ω

ONL

OUT

l

LTC3900E/LTC3900I

LTC3900H/LTC3900MP

I

PK

(Note 6)

A

Switching Characteristics (Note 7)

t

SYNC Input to Driver Output Delay

C

= C = 4700pF, V

SYNC

=

5V

d

FG

CG

l

LTC3900E/LTC3900I

LTC3900H/LTC3900MP

60

15

120

150

ns

l

t

Minimum SYNC Pulse Width

Driver Rise/Fall Time

V

C

=

5V

75

ns

SYNC

FG

t , t

= C = 4700pF, V

r

f

CG

SYNC

calculated from the ambient temperature (T , in °C) and power dissipation

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 device

reliability and lifetime.

A

(P , in watts) according to the formula:

D

T = T + (P • θ ), where θ (in °C/W) is the package thermal

J

A

D

JA

impedance.

Note 2: The LTC3900 is tested under pulsed load conditions such that

Note 3: All currents into device pins are positive; all currents out of device

pins are negative. All voltages are referenced to ground unless otherwise

speciﬁed.

Note 4: Supply current in normal operation is dominated by the current

needed to charge and discharge the external MOSFET gates. This current

will vary with supply voltage, switching frequency and the external

MOSFETs used.

T

≈

T . The LTC3900E is guaranteed to meet performance speciﬁcations

J

A

from 0°C to 85°C operating 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 LTC3900I is guaranteed over the –40°C to 125°C operating

junction temperature range. The LTC3900H is guaranteed over the full

–40°C to 150°C operating junction temperature range. The LTC3900MP

is guaranteed and tested over the full –55°C to 150°C operating junction

temperature range. High junction temperatures degrade operating

lifetimes; operating lifetime is derated for junction temperatures greater

than 125°C. Note that the maximum ambient temperature consistent

with these speciﬁcations is determined by speciﬁc operating conditions

in conjunction with board layout, the rated package thermal impedance

Note 5: The current sense comparator threshold has a 0.33%/°C

temperature coefﬁcient (TC) to match the TC of the external MOSFET

R

DS(ON)

.

Note 6: Guaranteed by design, not subject to test.

Note 7: Rise and fall times are measured using 10% and 90% levels. Delay

times are measured from 1.4V at SYNC input to 20%/80% levels at the

driver output.

and other environmental factors. The junction temperature (T , in °C) is

J

3900fb

3

LTC3900

Typical perForMance characTerisTics

Timeout vs V_CC

Timeout vs Temperature

Timeout vs R_TMR

5.25

5.20

5.15

5.10

5.05

5.00

4.95

4.90

4.85

4.80

4.75

5.25

5.20

5.15

5.10

5.05

5.00

4.95

4.90

4.85

4.80

4.75

10

9

8

7

6

5

4

3

2

1

0

T

= 25°C

V

= 5V

T

= 25°C

A

CC

A

R

= 51k

R

= 51k

V

= 5V

CC

TMR

C

= 470pF

C

= 470pF

C

= 470pF

TMR

4

6

7

8

9

10

11

–75 –50

0

25 50 75 100 125 150

5

–25

0

10 20 30 40 50 60 70 80 90 100

V

(V)

TEMPERATURE (°C)

R

(kΩ)

CC

TMR

3900 G01

3900 G02

3900 G03

Current Sense Threshold vs

Temperature

V_CS(MAX)Clamp Voltage vs CS⁺

Input Current

SYNC Positive Threshold vs

Temperature

18

17

16

15

14

13

12

11

10

1.8

T

= 25°C

V

= 5V, 11V

17

15

13

11

9

A

CC

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

V

CC

= 11V

V

CC

= 5V

7

5

3

–25

0

25 50 75

125 150

25

–75 –50

100

0

5

10

15

CS INPUT CURRENT (mA)

20

30

–25

0

25 50 75

125 150

–75 –50

100

+

TEMPERATURE (°C)

3900 G04

3900 G05

3900 G06

SYNC Negative Threshold vs

Temperature

Propagation Delay vs

Temperature

Propagation Delay vs V_CC

–1.0

–1.1

–1.2

–1.3

–1.4

–1.5

–1.6

–1.7

–1.8

120

110

100

90

120

110

100

90

V

= 5V, 11V

T

= 25°C

LOAD

V

C

= 5V

CC

A

CC

LOAD

C

= 4.7nF

80

70

SYNC TO FG

60

SYNC TO FG

SYNC TO CG

50

SYNC TO CG

40

–25

0

25 50 75

125 150

4

5

6

7

8

9

10

11

–75 –50

100

–25

0

25 50 75

100

125 150

–75 –50

TEMPERATURE (°C)

V

(V)

CC

TEMPERATURE (°C)

3900 G07

3900 G08

3900 G09

3900fb

4

LTC3900

Typical perForMance characTerisTics

Propagation Delay vs C_LOAD

Rise/Fall Time vs V_CC

Rise/Fall Time vs Temperature

50

45

40

35

30

25

20

15

10

5

50

45

40

35

30

25

20

15

10

5

120

110

100

90

V

C

= 5V

T

= 25°C

= 5V

T

= 25°C

LOAD

CC

LOAD

A

CC

A

= 4.7nF

V

C

= 4.7nF

80

70

RISE TIME

SYNC TO FG

RISE TIME

60

FALL TIME

SYNC TO CG

FALL TIME

50

0

40

0

5

6

7

8

9

11

–25

0

25 50 75 125 150

100

4

10

–75 –50

1

2

3

4

5

6

7

8

9

10

TEMPERATURE (°C)

V

CC

(V)

C

LOAD

(nF)

3900 G11

3900 G10

3900 G12

Undervoltage Lockout Threshold

Voltage vs Temperature

Rise/Fall Time vs Load

Capacitance

50

45

40

35

30

25

20

15

10

5

T

= 25°C

CC

4.4

A

V

= 5V

4.2

4.0

3.8

3.6

3.4

3.2

3.0

RISING EDGE

RISE TIME

FALLING EDGE

FALL TIME

0

–25

0

25 50 75

125 150

100

–75 –50

0

1

2

3

4

5

6

7

8

9

10

TEMPERATURE (°C)

C

LOAD

(nF)

3900 G13

3900 G14

V_CCSupply Current vs

Temperature

V_CCSupply Current vs Load

Capacitance

20

18

16

14

12

10

8

30

25

20

15

10

5

C

= 4.7nF

T

f

= 25°C

SYNC

LOAD

A

= 100kHz

V

= 11V

CC

V

= 11V

CC

V

= 5V

CC

8

V

= 5V

CC

6

4

0

–25

0

25 50 75

125 150

–75 –50

100

0

1

2

3

4

5

6

7

9

10

TEMPERATURE (°C)

C

(nF)

LOAD

3900 G15

3900 G16

3900fb

5

LTC3900

pin FuncTions

+

–

CS , CS (Pin 1, 2): Current Sense Differential Input.

GND (Pin 6): The V bypass capacitor should be con-

CC

+

Connect CS through a series resistor to the drain of the

nected directly to this GND pin.

–

external catch MOSFET, Q4. Connect CS to the source.

TIMER(Pin7):TimerInput. Connectthispintoanexternal

R-C network to program the timeout period. The LTC3900

resets the timer at every negative transition of the SYNC

input. If the SYNC signal is missing or incorrect, the

LTC3900 pulls both CG and FG low once the TIMER pin

goes above the timeout threshold. See the Timer section

for more details on programming the timeout period.

The LTC3900 monitors the CS inputs 250ns after CG goes

high. If the inductor current reverses and ﬂows into the

+

–

MOSFET causing CS to rise above CS by more than

10.5mV, the LTC3900 pulls CG low. See the Current Sense

section for more details on choosing the resistance value

for R

to R

.

CS1

CS3

CG (Pin 3): Catch MOSFET Gate Driver. This pin drives the

gate of the external N-channel catch MOSFET, Q4.

SYNC (Pin 8): Driver Synchronization Input. This input

is signal edge sensitive. A negative voltage slew at SYNC

forces FG to pull high and CG to pull low. A positive volt-

age slew at SYNC forces FG to pull low and CG to pull

high. The SYNC input can accept both pulse or square

wave signals.

V

CC

(Pin 4): Main Supply Input. This pin powers the driv-

ers and the rest of the internal circuitry. Bypass this pin

to GND using a 4.7µF ceramic capacitor in close proximity

to the LTC3900.

FG (Pin 5): Forward MOSFET Gate Driver. This pin drives

the gate of the external N-channel forward MOSFET, Q3.

block DiagraM

+

SYNC

+

S

V

CC

4

+1.4V

–1.4V

–

SYNC

–

S

SYNC

8

SYNC

AND

DRIVER

LOGIC

5

3

FG

+

CS

1

2

IS

–

CS

+

–

DISABLE

DRIVER

10.5mV

Z

CS

11V

CG

TIMER

RESET

UVLO

TMR

TIMER

7

R1

180k

R2

45k

Z

TMR

0.5 • V

CC

M

TMR

3900 BD

6

GND

3900fb

6

LTC3900

applicaTions inForMaTion

Overview

load through Q3, T1 and L . In the next period, Q1 turns

O

off, SG goes low and T2 generates a positive pulse at the

LTC3900 SYNC input. The LTC3900 forces FG to turn off

and CG to turn on, Q4 conducts. Current continues to

In a typical forward converter topology, a power trans-

former is used to provide the functions of input/output

isolation and voltage step-down to achieve the required

low output voltage. Schottky diodes are often used on

the secondary-side to provide rectiﬁcation. Schottky

diodes, though easy to use, result in a loss of efﬁciency

due to relatively high voltage drops. To improve efﬁciency,

synchronousoutputrectiﬁersutilizingN-channelMOSFETs

can be used instead of Schottky diodes. The LTC3900

provides all of the necessary functions required to drive

the synchronous rectiﬁer MOSFETs.

ﬂow to the load through Q4 and L . Figure 2 shows the

O

LTC3900 synchronization waveforms.

External MOSFET Protection

Aprogrammabletimerandadifferentialinputcurrentsense

comparator are included in the LTC3900 for protection

of the external MOSFET during power down and Burst

Mode^®operation. The chip also shuts off the MOSFETs

if V < 4.1V.

CC

Figure1showsasimpliﬁedforwardconverterapplication.

T1 is the power transformer; Q1 is the primary-side power

transistor driven by the primary controller, LT1952 output

(OUT).ThepulsetransformerT2providessynchronization

Whentheprimarycontrollerispoweringdown,theprimary

controller shuts down ﬁrst and the LTC3900 continues to

operate for a while by drawing power from the V

bypass

CC

andisdrivenbyLT1952synchronizationsignal,S orSG

cap, C . The SG signal stops switching and there is no

OUT

VCC

fromtheprimarycontroller. Q3andQ4aresecondary-side

synchronous switches driven by the LTC3900’s FG and CG

SYNC pulse to the LTC3900. The LTC3900 keeps one of

the drivers turned on depending on the polarity of the

last SYNC pulse. If the last SYNC pulse is positive, CG

will remain high and the catch MOSFET, Q4 will stay on.

The inductor current will start falling down to zero and

continue going in the negative direction due to the voltage

thatisstillpresentacrosstheoutputcapacitor(thecurrent

output. Inductor L and capacitor C

form the output

O

OUT

ﬁlter to provide a steady DC output voltage for the load.

Also shown in Figure 1 is the feedback path from V

OUT

throughtheoptocouplerdriverLT4430andanoptocoupler,

back to the primary controller to regulate V

.

OUT

now ﬂows from C

back to L ). If Q4 is turned off while

OUT

O

Each full cycle of the forward converter operation con-

sists of two periods. In the ﬁrst period, Q1 turns on and

the primary-side delivers power to the load through T1.

SG goes high and T2 generates a negative pulse at the

LTC3900 SYNC input. The LTC3900 forces FG to turn on

and CG to turn off, Q3 conducts. Current ﬂows to the

the inductor current is negative, the inductor current will

produce high voltage across Q4, resulting in a MOSFET

avalanche. Depending on the amount of energy stored in

the inductor, this avalanche energy may damage Q4.

GATE

(OUT)

SG

OUT

(S

)

SYNC

FG

CG

3900 F02

Figure 2. Synchronization Waveforms

3900fb

7

LTC3900

applicaTions inForMaTion

ThetimercircuitandcurrentsensecomparatorinLTC3900

are used to prevent reverse current buildup in the output

inductor.

designed to be of the same magnitude (1.4V typical) but

opposite in polarity. In some situations, for example dur-

ing power up or power down, the SYNC pulse magnitude

may be low, slightly higher or lower than the threshold of

the comparators. This can cause only one of the SYNC

comparators to trip. This also appears as incorrect SYNC

pulse and the timer will not reset.

Timer

Figure 3 shows the LTC3900 timer internal and external

circuits. The timer operates by using an external R-C

charging network to program the time-out period. On

every negative transition at the SYNC input, the chip

generates a 200ns pulse to reset the timer cap. If the

SYNC signal is missing or incorrect, allowing the timer

cap voltage to go high, it shuts off both drivers once the

voltage reaches the time-out threshold. Figure 4 shows

the timer waveforms.

The timeout period is determined by the external R

TMR

and C

values and is independent of the V voltage.

TMR

CC

This is achieved by making the timeout threshold a ratio

of V . The ratio is 0.2x, set internally by R1 and R2 (see

CC

Figure 3). The timeout period should be programmed to

be around one period of the primary switching frequency

using the following formula:

TIMEOUT = 0.2 • R

• C

+ 0.27E-6

TMR

A typical forward converter cycle always turns on Q3

and Q4 alternately and the SYNC input should alternate

between positive and negative pulses. The LTC3900 timer

also includes sequential logic to monitor the SYNC input

sequence. If after one negative pulse, the SYNC compara-

tor receives another negative pulse, the LTC3900 will not

reset the timer cap. If no positive SYNC pulse appears,

both drivers are shut off once the timer times out. Once

positive pulses reappear the timer resets and the drivers

start switching again. This is to protect the external com-

ponents in situations where only negative SYNC pulse is

present and FG output remains high. Figure 5 shows the

timer waveforms with incorrect SYNC pulses.

To reduce error in the timeout setting due to the discharge

time, select C between 100pF and 1000pF. Start with a

TMR

C

around 470pF and then calculate the required R

.

TMR

shouldbeplacedascloseaspossibletotheLTC3900

, the TIMER pin

TMR

with minimum PCB trace between C

TMR

and GND. This is to reduce any ringing caused by the PCB

trace inductance when C

introduce error to the timeout setting.

discharges. This ringing may

TMR

The timer input also includes a current sinking clamp

circuit (Z

in Figure 3) that clamps this pin to about

TMR

0.5 • V if there is missing SYNC/timer reset pulse. This

CC

clamp circuit prevents the timer cap from getting fully

charged up to the rail, which results in a longer discharge

+

TheLTC3900hastwoseparateSYNCcomparators(S and

–

S intheBlockDiagram)todetectthepositiveandnegative

pulses. The threshold voltages of both comparators are

SG

SYNC

V

CC

LAST

PULSE

R2

R1

4

7

FG

R

TMR

TIMEOUT

CG

TIMER RESET

(INTERNAL)

TIMER

RESET

Z

TMR

C

TMR

3900 F03

TIMER

TIMEOUT

THRESHOLD

3900 F04

Figure 3. Timer Circuit

Figure 4. Timer Waveforms

3900fb

8

LTC3900

applicaTions inForMaTion

time. The current sinking capability of the circuit is around

1mA. The timeout function can be disabled by connecting

the timer pin to GND.

10.5mV to prevent tripping under light load conditions.

If the product of the inductor negative peak current and

MOSFET R

is higher than 10.5mV, the LTC3900 will

DS(ON)

operate in discontinuous current mode. Figure 6 shows

the LTC3900 operating in discontinuous current mode;

the CG output goes low before the next negative SYNC

pulse, as soon as the inductor current becomes negative.

Discontinuous current mode is sometimes undesirable.

Current Sense

The differential input current sense comparator is used

for sensing the voltage across the drain-to-source termi-

+

–

nals of Q4 through the CS and CS pins. If the inductor

+

To disable discontinuous current mode operation, add a

current reverses into the Q4 causing CS to rise above

+

–

resistor divider, R

and R

at the CS pin to increase

CS1

CS2

CS by more than 10.5mV, the LTC3900 pulls CG low. This

the 10.5mV threshold so that the LTC3900 operates in

continuous mode at no load.

comparator is used to prevent inductor reverse current

buildupduringpowerdownorBurstModeoperation,which

may cause damage to the MOSFET. The 10.5mV input

threshold has a positive temperature coefﬁcient, which

+

The LTC3900 CS pin has an internal current sinking

clamp circuit (Z in the Block Diagram) that clamps the

CS

closely matches the TC of the external MOSFET R

.

DS(ON)

pin to 11V. The clamp circuit is to be used together with

+

The current sense comparator is only active 250ns after

CG goes high; this is to avoid any ringing immediately

after Q4 is switched on.

the external series resistor, R

to protect the CS pin

CS1

from high Q4 drain voltage in the power transfer cycle.

During the power transfer cycle, Q4 is off, the drain volt-

age of Q4 is determined by the primary input voltage and

the transformer turns ratio. This voltage can be high and

Under light load conditions, if the inductor average cur-

rent is less than half of its peak-to-peak ripple current,

the inductor current will reverse into Q4 during a portion

of the switching cycle, forcing CS to rise above CS .

The current sense comparator input threshold is set at

+

may damage the LTC3900 if CS is connected directly to

+

–

the drain of Q4. The current sinking capability of the clamp

circuit is 5mA minimum.

TIMER DO NOT RESET

AT SECOND NEGATIVE

SYNC PULSE

SG

MISSING/LOW

POSITIVE

SYNC PULSE

TIMER RESET AFTER

RECEIVING POSITIVE

SYNC PULSE

SYNC

FG

CG

TIMER RESET

(INTERNAL)

INDUCTOR

CURRENT

TIMEOUT

0A

CURRENT SENSE

COMPARATOR TRIP

3900 F06a

TIMEOUT

THRESHOLD

TIMER

Figure 6a. Discontinuous Current Mode Operation at No Load

3900 F05

Figure 5. Timer Waveforms with Incorrect SYNC Pulses

3900fb

9

LTC3900

applicaTions inForMaTion

The value of the resistors, R , R

and R , should

To minimize this delay and error, do not use resistance

value higher than required and make the PCB trace from

CS1 CS2

CS3

be calculated using the following formulas to meet both

the threshold and clamp voltage requirements:

+

–

the resistors to the LTC3900 CS /CS pins as short as

possible. Add a series resistor, R

with value equal to

CS3

k = 48 • I

• R

–1

RIPPLE

DS(ON)

–

parallel sum of R and R to the CS pin and connect

CS1

CS2

R

CS2

R

CS1

R

CS3

= {200 • V

• (N /N ) –2200 • (1 + k)} /k

the other end of R

directly to the source of Q4.

IN(MAX)

S

P

CS3

= k • R

CS2

SYNC Input

= {R

• R } / {R

+ R

}

CS1

CS2

CS1

CS2

Figure 7 shows the external circuit for the LTC3900 SYNC

input. With a selected type of pulse transformers, the

If k = 0 or less than zero, R is not needed and R

CS2

CS1

= R = {V

• (N /N ) – 11V} / 5mA

values of the C and R

should be adjusted to obtain

CS3

IN(MAX)

S P

SG

SYNC

an optimum SYNC pulse amplitude and width. A bigger

where:

capacitor, C , generates a higher and wider SYNC pulse.

SG

I

= Inductor peak-to-peak ripple current

RIPPLE

Thepeakofthispulseshouldbemuchhigherthanthetypi-

cal LTC3900 SYNC threshold of 1.4V. Amplitudes greater

than 5V will help to speed up the SYNC comparator and

reduce the SYNC to drivers propagation delay. The pulse

width should be wider than 75ns. Overshoot during the

pulse transformer reset interval must be minimized and

kept below the minimum SYNC threshold of 1V. The

amount of overshoot can be reduced by having a smaller

R

DS(ON)

= On-resistance of Q4 at I /2

RIPPLE

V

= Primary side main supply maximum input

IN(MAX)

voltage

N /N = Power transformer T1, turn ratio

S

P

If the LTC3900 still operates in discontinuous mode with

the calculated resistance value, increase the value of R

CS1

R

.

SYNC

toraisethethreshold. TheresistorsR andR andthe

CS1

CS2

+

CS pins input capacitance plus the PCB trace capacitance

form an R-C delay; this slows down the response time

+

C

SG

220pF

of the comparator. The resistors and CS input leakage

PRIMARY

CONTROLLER

SG

T2

LTC3900

SYNC

currents also create an input offset error.

R

SYNC

470Ω

(S

)

OUT

T2: COILCRAFT Q4470B

OR PULSE P0926

3900 F07

SYNC

Figure 7. SYNC Input Circuit

FG

CG

INDUCTOR

CURRENT

0A

ADJUSTED CURRENT

SENSE THRESHOLD

3900 F06b

Figure 6b. Continuous Current Mode Operation

with Adjusted Current Sense Threshold

3900fb

10

LTC3900

applicaTions inForMaTion

An alternative method of generating the SYNC pulse is

shown in Figure 8. This circuit produces square SYNC

pulses with amplitude dependent on the logic supply

voltage. The SYNC pulse width can be adjusted with R1

and C1 without affecting the pulse amplitude.

derived from the power transformer T1, the LTC3900 will

initially remain off. During that period (V < 4.1V), the

CC

output rectiﬁer MOSFETs Q3 and Q4 will remain off and

the MOSFETs body diodes will conduct. The MOSFETs

may experience very high power dissipation due to a high

voltage drop in the body diodes. To prevent MOSFET dam-

Fornonisolatedapplications,theSYNCinputcanbedriven

directly by a bipolar square pulse. To reduce the propa-

gation delay, make the positive and negative magnitude

of the square wave much greater than the 1.4V SYNC

threshold.

age, V voltage greater than 4.1V should be provided

CC

quickly. The V supply circuit shown in Figure 9 will pro-

CC

vide power for the LTC3900 within the ﬁrst few switching

pulses of the primary controller, preventing overheating

of the MOSFETs.

V

Regulator

CC

MOSFET Selection

The V supply for the LTC3900 can be generated by peak

CC

TherequiredMOSFETR

on allowable power dissipation and maximum required

output current.

shouldbedeterminedbased

DS(ON)

rectifying the transformer secondary winding as shown

in Figure 9. The Zener diode D sets the output voltage to

Z

(V – 0.7V). A resistor, R (on the order of a few hundred

Z

B

Thebodydiodesconductduringthepower-upphase,when

ohms), in series with the base of Q

may be required

REG

the LTC3900 V supply is ramping up. The CG and FG

CC

to surpress high frequency oscillations depending on

’s selection.

signals stay low and the inductor current ﬂows through

the body diodes. The body diodes must be able to handle

Q

REG

The LTC3900 has an UVLO detector that pulls the drivers

the load current during start-up until V reaches 4.1V.

CC

output low if V < 4.1V. The UVLO detector has 0.5V of

CC

The LTC3900 drivers dissipate power when switching

MOSFETs. The power dissipation increases with switch-

hysteresis to prevent chattering.

In a typical forward converter, the secondary-side circuits

have no power until the primary-side controller starts

operating. Since the power for biasing the LTC3900 is

ing frequency, V and size of the MOSFETs. To calculate

CC

D3

MBR0540

T1

SECONDARY

WINDING

74HC14

PRIMARY

CONTROLLER

74HC132

SG

R

Z

2k

R

0.1µF

B

R1

470Ω

T2

LTC3900

SYNC

10Ω

Q

REG

BCX55

R

74HC14

SYNC

470Ω

C1

V

D

CC

Z

220pF

7.5V

C

VCC

4.7µF

3900 F09

SYNC

SG

3900 F08

Figure 9. V_CCRegulator

Figure 8. Symmetrical SYNC Drive

3900fb

11

LTC3900

applicaTions inForMaTion

the driver dissipation, the total gate charge Q is used.

2. Connect the two MOSFET drain terminals directly to

the transformer. The two MOSFET sources should be as

close together as possible.

G

This parameter is found on the MOSFET manufacturers

data sheet.

The power dissipated in each LTC3900 MOSFET driver

is:

3. Keep the timer, SYNC and V regulator circuit away

CC

from the high current path of Q3, Q4 and T1.

P

= Q • V • f

4. Place the timer capacitor, C

, as close as possible

TMR

DRIVER

G

CC SW

to the LTC3900.

where f is the switching frequency of the converter.

SW

5. Keep the PCB trace from the resistors R , R

and

CS1 CS2

+

–

PC Board Layout Checklist

R

CS3

to the LTC3900 CS /CS pins as short as possible.

Connecttheotherendsoftheresistorsdirectlytothedrain

and source of the MOSFET, Q4.

When laying out the printed circuit board, the following

checklist should be used to ensure proper operation of

the LTC3900 for your layout:

1.Connectthe4.7µFbypasscapacitorascloseaspossible

to the V and GND pins.

CC

Typical applicaTions

36V to 72V, 3.3V at 40A Synchronous Forward Converter

V

B1

PA0912.002

L1

47k

82k

• •

+V

IN

36V TO 72V

V

OUT

3.3V, 40A

BAS516

0.1µF

BCX55

12V

C

OUT

Q2

PH3230

2x

Q3

PH3230

2x

100µF

3x

18V

10k

2.2µF

LTC3900

•

5

6

3

1

FG

CG

+

370k

7

10k

GND

CS

13.2k

27k

14

15

8

V

B1

1µF

Si7846

SD_V

SEC

OUT

4

8

2

7

–

115k

V

CC

CS

3

9

5

R

OSC

V

IN

BAT760

SYNC TIMER

8V

BIAS

BLANK

GND

1nF

13

12

11

10

16

15k

0.22µF

0.1µF

SS_MAXDC

PGND

59k

10k

33k

39k

0.010R

LT1952 DELAY

= 2.5V OC

1nF

8V

BIAS

6

1

2

V

R

470Ω

560R

220pF

COMP

I

SENSE

• •

Q4470-B

FB = 1.23V

SOUT

R22

270Ω

22k

2.2k

V

B1

NEC

C16

10pF

PS2701

L1: PA0713, PULSE ENGINEERING

ALL CAPACITORS X7R, CERAMIC, TDK

8V BIAS

R24

27.4k

1%

1

6

C15

R23

3.3k

C13

1µF

V

OPTO

IN

6.8nF

LT4430

5

4

2

GND

OC

COMP

FB

C14

33nF

3

R25

6.04k

1%

3900 TA01

3900fb

12

LTC3900

Typical applicaTions

36V to 72V Input to 12V and 24V (or 12V), 2A Output Converter in 1/8th Brick Footprint

V

IN

36V TO 72V

V

L1A

U1

L1: DRQ127-220

0.1µF

7

9

V

24V

2A

OUT2

•

BCX56

82k

1.5mH

2

•

Q2

Q3

0.1µF

10k

2.2µF

PDZ10B

BAS516

1

3

F

C

G

+

150µF

BAS516

10k

V

IN

16V

L1B

4

8

V

12V

2A

OUT1

V

•

Si7462

V

FB

LT1952-1

COMP

22k

33k

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

47k

S

OUT

Q4

Q5

10

BC857BF

FB = 1.23V

V

U1

IN

115k

1.2k

T1

PA1577

F

C

G

R

OUT

PGND

DELAY

OC

1µF

OSC

33µF

16V

SYNC

100pF

145k

0.030R

0.1µF

MAXDC

V

= 2.5V

R

680Ω

LTC3900

+

SD

GND

I

10k

SENSE

1

8

7

6

5

13.3k

CS

SYNC

BLANK

2

–

220pF

CS

TIMER

GND

FG

82k

470pF

560R

0.47µF

3

V

AUX

•

CG

S

OUT

CG

340k

4

FG

V

CC

OUT1

•

V

22k

56k

IN

BCX55

38.3k

1k

PE-68386

1µF

PDZ7.5B

Q2, Q3, Q4, Q5 = Si7850

PS2801-1

LT4430

OPTO

GND COMP

OC FB

470R

1

2

3

6

5

4

V

U1

V

AUX

V

CC

3.92k

5.23k

15nF

100k

V

FB

BAS516

V

OUT1

1µF

3900 TA02

33pF

The LTC3900 can drive multiple synchronous output

rectiﬁers. The 12V and 24V or 12V output converter

has good cross regulation due to low voltage drops in

the output MOSFETs. Other combinations like 3.3V and

–5V or 1.5V and 5V can be easily achieved by changing

the transformer turns ratio.

3900fb

13

LTC3900

Typical applicaTions

18V to 40V Input to 14V at 14A Output Converter in 1/4 Brick Footprint

PZTA42

V

IN

18V TO 40V

V

U1

22k

PA1494.362

33µF

1.5mH

V

14V

14A

OUT1

2, 3

1

•

6.8µF

×4

+

150µF

PXE

PDZ10B

BAS516

HAT2266

4, 5

FG

6

7

V

IN

CG

40R2-4421.003

11

LTC4441

1

2

3

4

5

10

9

BAS521

82k

10k

PGND OUT

HAT2266

×2

680µH

0.1µF

V

AUX

332k

0.1µF

220pF

BL

R

DRV

CC

8

Si3459

V

LTC3900

47k

V

U1

BL

IN

BAS516

1

8

7

6

5

7

0.004R

+

CS

SYNC

SGND

IN

FB

255R

57.6k

BAS516

10k

2

3

4

6

2.2µF

–

220pF

TIMER

GND

FG

EN

PGND

470pF

560R

255R

10k

•

V

0.22µF

GATE

R

CG

S

OUT

FG

V

CC

•

GATE

BCX55

V

AUX

1k

V

FB

1µF

LT1952-1

COMP

PE-68386

22k

33k

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

V

U1

S

OUT

PDZ7.5B

BAS516

FB = 1.23V

V

BC857BF

IN

115k

R

OUT

PGND

DELAY

OC

4.7µF

OSC

SYNC

158k

2K

0.47µF

220R

15nF

MAXDC

0.1µF

PS2801-1

LT4430

V OPTO

270R

1

2

3

6

V

R

= 2.5V

V

AUX

CC

GND COMP

OC FB

5

4

1.96k

82.5k

SD

GND

I

V

SENSE

FB

13.3k

165k

BLANK

V

OUT1

1µF

1.2k

82k

2.2nF

1µF

3.65k

22k

158k

3900 TA03a

33pF

V

IN

V

R

By Using Active Reset and 60V MOSFETs Converter is Achieving 94% to 95%

Efﬁciency with Only Four MOSFETs.

96

94

92

90

88

86

84

V

= 24V

IN

OUT

= 14V

82

0

2

4

6

8

10

12 14

I

(A)

OUT

3900 TA03b

3900fb

14

LTC3900

Typical applicaTions

36V to 72V Input to 12V, 14A Output Converter in 1/8th Brick Footprint

T1

V

L2

1.5mH

L1

3µH

U1

PA0423

V

12V

14A

OUT

PZTA42

7

1

6

2

5

•

33µF

PDZ10B

BAS516

2.2µF

47k

10k

HAT2244

10

82k

V

IN

36V TO 72V

•

LTC3900

CG

560R

5

8

6

7

3

1

2

4

FB

+

370k

SYNC

GND

TIMER

CS

Si7430

2k

10k

–

LT1952-1

13.3k

133k

82k

470pF

38.3k

7

3

9

5

14

11

10

15

8

1nF

SD/V

SEC

OUT

OC

V

CC

R

OSC

1µF

PDZ7.5

PE-68386

BLANK

SS

I

SENSE

1µF

158k

0.1µF

1k

•

BCX55

V

0.010

IN

U1

22k

GND

4.7µF

3900 TA04a

6

1

2

13

12

16

V

PGND

R

20k

75k

COMP

FB

DELAY

12.4k

220pF

47nF

S

OUT

97.6k

V

U1

L1: PULSE PA1393.302

L2: COILCRAFT DO1607B-155

ALL CERAMIC CAPS ARE X5R OR X7R

The Efﬁciency of 12V Output Converter is Over 95% at 8A Output.

96

94

92

90

88

86

84

V

= 48V

IN

OUT

= 12V

82

8

12

14

0

2

4

6

10

I

(A)

OUT

3900 TA04b

3900fb

15

LTC3900

Typical applicaTions

18V to 72V Input to 12V at 13A Active Reset Converter Fits in 1/8th Brick Size

PZTA42

V

IN

18V TO 72V

V

U1

33k

40R2-4444.004

V

R2

1.5mH

PA2050.103

V

12V

13A

OUT

7

1

•

+

2.2µF

×3

10V

BAS516

330µF

HAT2169

FG

HAT2173

×2

10

6

2

33µF

•

V

IN

CG

V

5

0.22µF

U1

BAS521

33nF

1, 6

2, 4

BAS516

57Ω

680µH

3

5

HAT2173

×2

Si2325

LTC4440

0.006Ω

1k

0.1µF

BCX55

220pF

237Ω

22k

GATE

7.5V

V

FB

LT1952-1

10k

LTC3900

220pF

BAS516

22k

33k

10k

1

16

1

2

3

4

8

7

6

5

+

COMP

S

OUT

CS

SYNC

TIMER

GND

GATE

2

3

4

5

6

7

8

15

14

13

12

11

10

9

–

FB = 1.23V

V

IN

V

U1

560R

•

BC857

174k

1µF

•

R

OUT

PGND

DELAY

OC

4.7µF

137k

OSC

CG

PE-68386

SYNC

V

FG

CC

1µF

39.2K

MAXDC

0.1µF

13.3k

470pF

V

= 2.5V

R

PS2801-1

LT4430

47k

470R

1k

1

2

3

6

5

4

SD

GND

I

V

OPTO

GND COMP

OC FB

SENSE

CC

7.87k

10nF

BLANK

V

FB

22k

348k

189k

332k

BAS516

V

OUT

1.2k

1µF

V

R2

V

B

18.2k

3900 TA05a

2.2nF

10pF

The High Efﬁciency of Converter is Achieved by Precise MOSFET Timing Provided

by LT1952 and LTC3900 Controllers.

96

94

92

90

88

86

84

82

80

24V

48V

IN

0

2

4

6

8

10

12

14

I

(A)

OUT

3900 TA05b

3900fb

16

LTC3900

Typical applicaTions

Synchronous Forward Converter With Pulse Skip Mode

PZTA42

V

IN

36V TO 72V

V

U1

82k

1.5mH

PA1671

V

3.3V

30A

OUT

7

1

•

+

2.2µF

PDZ10B

BAS516

HA2165

10

6

2

100µF

470µF

V

IN

FG

CG

10nF

5

2.2R

10k

Si7430

T1

PA0369

V

AUX

1.5nF

B0540W

R_DCM

3.3M

+

*

0.02µF

10k

38.3k

0.015R

B0540W

0.22µF

1

2

3

4

8

7

6

5

CS

SYNC

TIMER

GND

10k

–

220pF

470pF

560R

V

CG

V

S

OUT

FB

LT1952-1

COMP

FB = 1.23V

22k

BC857

33k

•

V

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

U1

FG

CC

S

OUT

•

LTC3900

BCX55

1k

V

IN

1µF

115k

PE-68386

R

OUT

PGND

DELAY

OC

1µF

OSC

PDZ7.5B

SYNC

0.47µF

133k

910Ω

82k

MAXDC

PS2801-1

LT4430

OPTO

GND COMP

OC FB

0.1µF

13.3k

270R

1

2

3

6

5

4

V

= 2.5V

R

V

CC

1.96k

18.2k

SD

GND

I

15nF

82.5k

V

FB

SENSE

BAS516

BLANK

V

OUT

1.2k

22.1k

158k

1µF

442k

47pF

3900 TA06a

V

IN

*CONVERTERS THAT USE THE LTC3900 CAN BE FORCED TO OPERATE IN DISCONTINUOUS CURRENT MODE

AT LIGHT LOADS BY OFFSETTING THE CURRENT SENSE INPUT WITH R_DCM RESISTOR.

The Discontinuous Current Mode (DCM) Operation of Circuit is About 10% More Efﬁcient

with 1A-2A Loads. The No Load Input Current is 15mA in DCM Versus 90mA in CCM.

95

85

75

65

V

= 48V

IN

OUT

= 3.3V

55

45

CONTINUOUS

CURRENT MODE

DISCONTINUOUS

CURRENT MODE

35

0

5

10

15

(A)

20

25

30

I

OUT

3900 TA06b

3900fb

17

LTC3900

package DescripTion

S8 Package

8-Lead Plastic Small Outline (Narrow .150 Inch)

(Reference LTC DWG # 05-08-1610)

.189 – .197

(4.801 – 5.004)

NOTE 3

.045 .005

.160 .005

.050 BSC

7

5

8

6

.245

MIN

.150 – .157

(3.810 – 3.988)

NOTE 3

.228 – .244

(5.791 – 6.197)

.030 .005

TYP

RECOMMENDED SOLDER PAD LAYOUT

1

3

4

2

.010 – .020

(0.254 – 0.508)

× 45°

.053 – .069

(1.346 – 1.752)

.004 – .010

(0.101 – 0.254)

.008 – .010

(0.203 – 0.254)

NOTE:

1. DIMENSIONS IN

INCHES

(MILLIMETERS)

0°– 8° TYP

2. DRAWING NOT TO SCALE

3. THESE DIMENSIONS DO NOT INCLUDE

MOLD FLASH OR PROTRUSIONS.

MOLD FLASH OR PROTRUSIONS

SHALL NOT EXCEED .006" (0.15mm)

.016 – .050

(0.406 – 1.270)

.050

(1.270)

BSC

.014 – .019

(0.355 – 0.483)

TYP

SO8 0303

3900fb

18

LTC3900

revision hisTory ^{(Revision history begins at Rev B)}

REV

DATE DESCRIPTION

PAGE NUMBER

B

5/11 Added H- and MP-grade parts. Reﬂected throughout the data sheet.

1 to 20

3900fb

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.

19

LTC3900

Typical applicaTion

36V to 72V Input to 12V at 20A “No Optocoupler” Synchronous “Bus Converter”

L1

V

U1

2.4µH

V

PA0815.002

OUT

47k

82k

• •

12V, 10ꢀ,

20A MAX

V

IN

36V TO 72V

BAS516

0.1µF

BCX55

12V

C

OUT

33µF, 16V

X5R, TDK

×3

Si7370

×2

PH4840

18V

10k

×2

2.2µF, 100V

×2

LTC3900

•

5

6

3

1

FG

CG

+

PH21NQ15

370k

7

10k

×2

GND

CS

13.2k

27k

14

15

8

V

U1

1µF

SD_V

SEC

OUT

4

8

2

7

–

115k

V

CS

3

9

5

CC

R

OSC

V

IN

SYNC TIMER

BAT

760

8V

BIAS

BLANK

GND

1µF

C

T

13

12

11

10

16

R

T

0.47µF

0.1µF

SS_MAXDC

PGND

1nF

15k

59k

10k

39k

9mΩ

LT1952 DELAY

= 2.5V OC

1nF

8V

BIAS

6

1

2

V

R

470Ω

560Ω

220pF

COMP

I

SENSE

SOUT

L1: PULSE PA1494.242

ALL CAPACITORS ARE TDK, X5R CERAMIC

• •

FB = 1.23V

Q4470-B

3900 TA07a

LTC3900-Based Synchronous “Bus Converter” Efﬁciency vs Load Current

16

12

8

96.0

95.5

95.0

94.5

94.0

93.5

93.0

EFFICIENCY

POWER LOSS

V

= 48V

IN

OUT

= 12V

4

6

8

10 12 14 16 18 20

LOAD CURRENT (A)

3900 TA07b

relaTeD parTs

PART NUMBER

DESCRIPTION

COMMENTS

LT1952/LT1952-1 Synchronous Forward Converter Controllers

Ideal for Medium Power 24V or 48V Input Isolated Applications

LTC3901

Secondary Side Synchronous Driver for Push-Pull and Full

Bridge Converters

Similar to the LTC3900, Used in Full Bridge and Push-Pull

Converters

LT4430

LT1431

Secondary Side Optocoupler Driver

Programmable Reference

Optocoupler Driver with Precise Reference Voltage

Adjustable Shunt Voltage Regulator with 100mA Sink Capability

LTC3726/LTC3725 Synchronous No Opto Forward Converter Controller Chip Set Ideal for Medium Power 24V or 48V Input Isolated Applications

LTC3723-1/

LTC3723-2

Synchronous Push-Pull Controllers

High Efﬁciency with On-Chip MOSFET Drivers

LTC3721-1/

LTC3721-2

Nonsynchronous Push-Pull Controllers

Synchronous Phase Modulated Full Bridge Controllers

Minimizes External Components, On-Chip MOSFET Drivers

Ideal for High Power 24V or 48V Input Applications

LTC3722/

LTC3722-2

3900fb

LT 0511 REV B • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

20

●

 LINEAR TECHNOLOGY CORPORATION 2003

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


型号：	LTC3726IGN#TRPBF
厂家：	Linear
描述：	LTC3726 - Secondary-Side Synchronous Forward Controller; Package: SSOP; Pins: 16; Temperature Range: -40°C to 85°C 驱动器
文件：	总20页 (文件大小：268K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC3726IGN#TRPBF [Linear]

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