LT3837EFE#TRPBF Linear Technology, LT3837EFE#TRPBF Datasheet

IC CNTRLR SYNC ISO 16TSSOP

LT3837EFE#TRPBF

Manufacturer Part Number
LT3837EFE#TRPBF
Description
IC CNTRLR SYNC ISO 16TSSOP
Manufacturer
Linear Technology
Type
Flybackr
Datasheet

Specifications of LT3837EFE#TRPBF

Internal Switch(s)
No
Synchronous Rectifier
Yes
Number Of Outputs
1
Frequency - Switching
50kHz ~ 250kHz
Voltage - Input
4.5 ~ 20 V
Operating Temperature
-40°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
16-TSSOP Exposed Pad, 16-eTSSOP, 16-HTSSOP
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Current - Output
-
Voltage - Output
-
Power - Output
-

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Quantity
Price
Company:
Part Number:
LT3837EFE#TRPBFLT3837EFE
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Quantity:
20 000
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Part Number:
LT3837EFE#TRPBFLT3837EFE#PBF
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Manufacturer:
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Quantity:
20 000
Company:
Part Number:
LT3837EFE#TRPBF
Manufacturer:
LINEAR/凌特
Quantity:
20 000
FEATURES
APPLICATIONS
n
n
n
n
n
n
n
n
n
n
n
n
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.
Protected by U.S. Patents including 6498466, 5841643.
TYPICAL APPLICATION
2N3906
Senses Output Voltage Directly from Primary Side
Winding—No Optoisolator Required
Synchronous Driver for High Effi ciency
Supply Voltage Range 4.5V to 20V
Accurate Regulation Without User Trims
Programmable Switching Frequency from
50kHz to 250kHz
Synchronizable
Load Compensation
Undervoltage Lockout
Available in a Thermally Enhanced 16-Lead
TSSOP Package
Isolated Medium Power (10W to 60W) Supplies
Instrumentation Power Supplies
Isolated Medical Supplies
22.1k
3k
20k
BAS16
22μF
3.3nF
1.37k
150k
1nF
9V –18V to 3.3V at 10A Isolated Converter
100k
47pF
12k
0.1μF
FB
V
OSC
SFST
t
ENDLY
PGDLY
R
C
ON
C
CMP
CMP
LT3837
GND
V
CC
SENSE
SENSE
UVLO
PG
SG
+
330Ω
86.6k
15k
Si7852DP
8mΩ
0.1μF
10Ω
2.2nF
Si7336ADP
10μF
2.2nF
V
IN
Synchronous Flyback Controller
B0540W
10k
3837 TA01a
47μF 3
10Ω
FMMT618
FMMT718
100nH
BAT54
15Ω
OUTPUT 3.3V/10A
DESCRIPTION
The LT
designed for medium power fl yback topologies. A typical
application is 10W to 60W with the part powered from a
DC supply.
The LT3837 is a current mode controller that regulates an
output voltage based on sensing the secondary voltage
via a transformer winding during fl yback. This allows for
tight output regulation without the use of an optoisolator,
improving dynamic response and reliability. Synchronous
rectifi cation increases converter effi ciency and improves
output cross regulation in multiple output converters.
The LT3837 operates in forced continuous conduction
mode which improves cross regulation in multiple winding
applications. Switching frequency is user programmable
and can be externally synchronized. The part also has load
compensation, undervoltage lockout and soft-start circuitry.
The LT3837 is available in a thermally enhanced 16-pin
TSSOP package.
220μF
1μF
®
3837 is an isolated switching regulator controller
Isolated No-Opto
3.60
3.50
3.40
3.30
3.20
3.10
3.00
90
86
82
78
76
88
84
80
Regulation vs Load Current
2
2
Effi ciency vs Load Current
3
3
4
4
9V
LOAD CURRENT (A)
LOAD CURRENT (A)
IN
5
5
18V
9V
6
6
IN
IN
7
7
8
8
18V
LT3837
IN
3837 TA01b
3837 TA01c
9
9
10
10
3837fc
1

Related parts for LT3837EFE#TRPBF

LT3837EFE#TRPBF Summary of contents

Page 1

... Instrumentation Power Supplies n Isolated Medical Supplies 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. Protected by U.S. Patents including 6498466, 5841643. TYPICAL APPLICATION 9V –18V to 3.3V at 10A Isolated Converter 22 ...

Page 2

... Storage Temperature Range .................. –65°C to 150°C Lead Temperature (Soldering, 10 sec)................... 300°C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL LT3837EFE#PBF LT3837EFE#TRPBF LT3837IFE#PBF LT3837IFE#TRPBF LEAD BASED FINISH TAPE AND REEL LT3837EFE LT3837EFE#TR Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. ...

Page 3

ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are 27.4k 90k, unless otherwise specifi ed. PGDLY ENDLY PARAMETER Feedback Amplifi er Voltage Gain Soft-Start Charging Current Soft-Start Discharge Current Control Pin Threshold ( Gate ...

Page 4

LT3837 TYPICAL PERFORMANCE CHARACTERISTICS V Shutdown Current CC vs Temperature UVLO 14V – 100 –25 0 TEMPERATURE (°C) 3837 G01 SENSE ...

Page 5

TYPICAL PERFORMANCE CHARACTERISTICS Feedback Amplifi er Source and Sink Current vs Temperature 70 SOURCE CURRENT SINK CURRENT 1. – 100 –25 0 TEMPERATURE (°C) ...

Page 6

LT3837 TYPICAL PERFORMANCE CHARACTERISTICS PG Delay Time vs Temperature 300 250 R PGDLY 200 150 R PGDLY 100 50 0 –50 – TEMPERATURE (°C) PIN FUNCTIONS SG (Pin 1): Synchronous gate drive output. This pin pro- vides an ...

Page 7

PIN FUNCTIONS V (Pin 9): Pin used for frequency compensation for the C switcher control loop the output of the feedback amplifi er and the input to the current comparator. Switcher frequency compensation components are normally placed on ...

Page 8

LT3837 BLOCK DIAGRAM 1.237V REFERENCE ( DISABLE + 0.8V – UVLO 10 OSC 7 OSCILLATOR SYNC PGDLY 15 ENDLY 4 8 CLAMPS 0.7 + 1.3 – 1.25V 3V INTERNAL REGULATOR S ...

Page 9

FLYBACK FEEDBACK AMPLIFIER LT3837 FEEDBACK AMP 1.237V – + COLLAPSE DETECT ENABLE TIMING DIAGRAM PRIMARY SIDE MOSFET DRAIN VOLTAGE PG VOLTAGE SG VOLTAGE V FLBK – ...

Page 10

LT3837 OPERATION The LT3837 is a current mode switcher controller IC designed specifi cally for use in an isolated fl yback topology employing synchronous rectifi cation. The LT3837 operation is similar to traditional current mode switchers. The major difference is ...

Page 11

OPERATION Minimum Output Switch On-Time (t The LT3837 affects output voltage regulation via fl yback pulse action. If the output switch is not turned on, there is no fl yback pulse and output voltage information is not available. This causes ...

Page 12

LT3837 OPERATION LOAD COMP – CMP CMP Figure 1. Load Compensation Diagram Figure 1 shows the block diagram of the load compensa- tion ...

Page 13

APPLICATIONS INFORMATION Primary Winding Feedback The previous work was developed using a separate wind- ing for voltage feedback possible to use the primary winding as the feedback winding as well. This can simplify the design of the transformer. ...

Page 14

LT3837 APPLICATIONS INFORMATION ratio of between the two windings. Also keep the secondary MOSFET R small to improve cross regulation. DS(ON) Leakage Inductance Transformer leakage inductance (on either the primary or secondary) causes a spike after the primary side switch ...

Page 15

APPLICATIONS INFORMATION tight coupling usually increases primary-to-secondary capacitance and limits the primary-to-secondary break- down voltage isn’t always practical. Primary Inductance The transformer primary inductance the peak-to-peak ripple current ratio (X) in the trans- former relative to ...

Page 16

LT3837 APPLICATIONS INFORMATION Setting Feedback Resistive Divider Use the equation developed in the Operation section for the feedback divider recommended that the Thevenin impedance of the resistors on the FB Pin is roughly 3k for bias current cancellation ...

Page 17

APPLICATIONS INFORMATION 5. Verify this result by connecting a resistor of this value from the R pin to ground. CMP 6. Disconnect the ground short to C requisite 0.1μF fi lter capacitor to ground. Measure the output impedance R = ...

Page 18

LT3837 APPLICATIONS INFORMATION Enable Delay Time (ENDLY) Enable delay time provides a programmable delay between turn-off of the primary gate drive node and the subsequent enabling of the feedback amplifi er. As discussed earlier, this delay allows the feedback amplifi ...

Page 19

APPLICATIONS INFORMATION dropping the voltage on UVLO. In this manner, hysteresis is produced. Referring to Figure 4, the voltage hysteresis at V equal to the change in bias current times R procedure is to select the desired V hysteresis, V ...

Page 20

LT3837 APPLICATIONS INFORMATION Minimum Load Considerations At light loads, the LT3837 derived regulator goes into forced continuous conduction mode. The primary side switch always turns on for a short time as set by the t resistor. If this produces more ...

Page 21

APPLICATIONS INFORMATION If the output load current is relatively constant, the feedback resistive divider is used to compensate for these losses. Otherwise, use the LT3837 load compensation circuitry (see Load Compensation). If multiple output windings are used, the fl yback ...

Page 22

LT3837 APPLICATIONS INFORMATION With C determined, calculate the primary-side power MILLER MOSFET power dissipation δ • R DPRI RMS PRI ( ) ...

Page 23

... LTC SwitcherCAD™ terrifi c free circuit simulation tool that is available at www.linear.com. Final optimization of output ripple must be done on a dedicated PC board. Parasitic inductance due to poor layout can signifi cantly impact ripple. Refer to the PC Board Layout section for more details. SwitcherCAD is a trademark of Linear Technology Corporation. LT3837 ( ) ...

Page 24

LT3837 APPLICATIONS INFORMATION IC Thermal Considerations Take care to ensure that the LT3837 junction temperature does not exceed 125°C. Power is computed from the aver- age supply current, the sum of quiescent supply current (I in the specifi cations) plus ...

Page 25

APPLICATIONS INFORMATION VCC LT3825 GND LT3825 CC SG GND TYPICAL APPLICATION 36V 10k MMBT3904 10μF 0.1μF 7.5V 100k 1% 29. UVLO PGDLY 3.01k 17.4k t SYNC ON 1% ...

Page 26

LT3837 PACKAGE DESCRIPTION 6.60 ±0.10 4.50 ±0.10 SEE NOTE 4 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 (.0035 – .0079) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE ...

Page 27

... Text Change to Applications Information Changes to Related Parts 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. LT3837 ...

Page 28

... Limited Only by External Components, Ideal for 24V Nominal IN OUT Input Voltage 2.5V ≤ V ≤ 32V, Current Mode Control, 200kHz to 2.5MHz, IN 3mm × 3mm DFN-8, MSOP-8E and ThinSOT are trademarks of Linear Technology Corporation. SENSE www.linear.com ● ® ≤ 36V, Burst Mode Operation IN 3837fc LT 1209 REV C • ...

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