LTC3721-2 LINER [Linear Technology], LTC3721-2 Datasheet

no-image

LTC3721-2

Manufacturer Part Number
LTC3721-2
Description
Synchronous Rectifier Driver for Forward Converters
Manufacturer
LINER [Linear Technology]
Datasheet
1.LTC3721-2.pdf (20 pages)
FeaTures
n
n
n
n
n
n
n
n
applicaTions
n
n
n
n
n
Typical applicaTion
36V TO 72V
GND
N-Channel Synchronous Rectifier MOSFET Driver
Programmable Timeout Protection
Reverse Inductor Current Protection
Pulse Transformer Synchronization
Wide V
15ns Rise/Fall Times at V
Undervoltage Lockout
Small SO-8 Package
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
LT1952
GATE
OUT
COMP
I
V
SENSE
IN
S
OUT
OC
Figure 1. Simplified Isolated Synchronous Forward Converter
CC
470
SG
Supply Range: 4.5V to 11V
Q1
10m
OCI
C
SG
ISOLATION
BARRIER
T1
T2
Q3
CC
Q4
= 5V, C
R
SYNC
R
R
R
CS1
CS3
CS2
270
L
= 4700pF
CS
CG
CS
FG
SYNC
+
–
LTC3900
GND
D3
GND
TIMER
V
OC
IN
V
CC
LT4430
C
Z
L0
R
R
D
OPTO
COMP
FB
Z
TMR
C
Z
C
R
Synchronous Rectifier Driver
TMR
VCC
B
DescripTion
C
The LTC
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.
The LTC3900 incorporates a full range of protection for the
external MOSFETs. A programmable timeout function is
included that disables both drivers when the synchroniza-
tion signal is missing or incorrect. Additionally, the chip
senses the output inductor current through the drain-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.
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.
OUT
Q
REG
+
for Forward Converters
®
3900 F01
R1
R2
3900 is a secondary-side synchronous recti-
V
3.3V
40A
OUT
80
95
90
85
75
70
65
0
V
V
OUT
IN
= 36V
5
= 3.3V
10
LOAD CURRENT (A)
V
Efficiency
15
IN
V
= 48V
IN
20
= 72V
LTC3900
25
30
35
3900 F10b
40
3900fb
1

Related parts for LTC3721-2

Image
Part Number
Description
Manufacturer
Datasheet
Request R
LTC-3808
Part Number:
LTC-3808
Description:
(LTC-3000 Series) SEVEN-SEGMENT NUMERIC LED DISPLAY
Manufacturer:
LITE-ON Electronics
Datasheet:
LTC-3808.pdf (8 pages)
ltc-5623p-01j
Part Number:
ltc-5623p-01j
Description:
Led Display Seven-segment Single Digit Ltc-5623p-01j
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623P-01J.pdf (5 pages)
ltc-5623g-07
Part Number:
ltc-5623g-07
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623g-07
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623G-07.pdf (5 pages)
ltc-5623g-12
Part Number:
ltc-5623g-12
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623g-12
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623G-12.pdf (5 pages)
ltc-5623g-14
Part Number:
ltc-5623g-14
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623g-14
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623G-14.pdf (5 pages)
ltc-5623g-08
Part Number:
ltc-5623g-08
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623g-08
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623G-08.pdf (5 pages)
ltc-5623g-nb
Part Number:
ltc-5623g-nb
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623g-nb
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623G-NB.pdf (5 pages)
ltc-5623hr-05
Part Number:
ltc-5623hr-05
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623hr-05
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623HR-05.pdf (5 pages)
ltc-5623hr-01j
Part Number:
ltc-5623hr-01j
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623hr-01j
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623HR-01J.pdf (5 pages)
ltc-5623hr-09
Part Number:
ltc-5623hr-09
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623hr-09
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623HR-09.pdf (5 pages)
ltc-5623jg-j
Part Number:
ltc-5623jg-j
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623jg-j
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623JG-J.pdf (6 pages)
ltc-5623jg
Part Number:
ltc-5623jg
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623jg
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623JG.pdf (6 pages)
ltc-5623p-01
Part Number:
ltc-5623p-01
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623p-01
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623P-01.pdf (5 pages)
ltc-5623p-07
Part Number:
ltc-5623p-07
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623p-07
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623P-07.pdf (5 pages)
ltc-5623wc
Part Number:
ltc-5623wc
Description:
Led Display Seven-segment Quadruple Digits Ltc-5623wc
Manufacturer:
LiteOn Technology Corp.
Datasheet:
LTC-5623WC.pdf (5 pages)

LTC3721-2 Summary of contents

Page 1

FeaTures 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 n CC 15ns Rise/Fall Times 5V Undervoltage ...

Page 2

LTC3900 absoluTe MaxiMuM raTings (Note 1) Supply Voltage V ........................................................................12V CC Input Voltage – TIMER .............................. – 0. SYNC ...................................................... –12V to 12V Input Current + CS ....................................................................15mA Operating Junction Temperature Range (Note 2) LTC3900E ........................................... ...

Page 3

T SYMBOL PARAMETER t Timer Discharge Time TMRDIS V Timer Pin Clamp Voltage TMRMAX Current Sense + Input Current CS – I – CS Input Current CS + ...

Page 4

LTC3900 Typical perForMance characTerisTics Timeout 5. 25° 51k TMR C = 470pF TMR 5.15 5.10 5.05 5.00 4.95 4.90 4.85 4.80 4. (V) ...

Page 5

Typical perForMance characTerisTics Propagation Delay vs C LOAD 120 T = 25° 110 CC 100 SYNC SYNC ...

Page 6

LTC3900 pin FuncTions + – (Pin 1, 2): Current Sense Differential Input. + Connect CS through a series resistor to the drain of the external catch MOSFET, Q4. Connect CS The LTC3900 monitors the CS inputs 250ns ...

Page 7

Overview 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 ...

Page 8

LTC3900 applicaTions inForMaTion The timer circuit and current sense comparator in LTC3900 are used to prevent reverse current buildup in the output inductor. Timer Figure 3 shows the LTC3900 timer internal and external circuits. The timer operates by using an ...

Page 9

The current sinking capability of the circuit is around 1mA. The timeout function can be disabled by connecting the timer pin to GND. Current Sense The differential input current sense comparator is used for sensing the voltage ...

Page 10

LTC3900 applicaTions inForMaTion The value of the resistors CS1 be calculated using the following formulas to meet both the threshold and clamp voltage requirements • I • R –1 RIPPLE DS(ON {200 ...

Page 11

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 ...

Page 12

LTC3900 applicaTions inForMaTion the driver dissipation, the total gate charge Q This parameter is found on the MOSFET manufacturers data sheet. The power dissipated in each LTC3900 MOSFET driver is • V • f DRIVER G CC ...

Page 13

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 82k 2.2µ LT1952-1 22k 33k 1 COMP S OUT BC857BF ...

Page 14

LTC3900 Typical applicaTions 18V to 40V Input to 14V at 14A Output Converter in 1/4 Brick Footprint V IN 18V TO 40V 6.8µF ×4 LTC4441 1 10 PGND OUT 332k 2 9 220pF BL DRV ...

Page 15

Typical applicaTions 36V to 72V Input to 12V, 14A Output Converter in 1/8th Brick Footprint PZTA42 V IN 36V TO 72V 370k LT1952-1 13.3k 7 SD/V OUT SEC 133k OSC 82k 9 BLANK I SENSE 1µF 5 ...

Page 16

LTC3900 Typical applicaTions 18V to 72V Input to 12V at 13A Active Reset Converter Fits in 1/8th Brick Size V IN 18V TO 72V 2.2µF × BAS516 LTC4440 220pF V FB ...

Page 17

Typical applicaTions PZTA42 V IN 36V TO 72V 82k 2.2µ LT1952-1 22k 33k 1 16 COMP S OUT BC857 1.23V V IN 115k OUT OSC 4 13 SYNC PGND 0.47µF 5 ...

Page 18

LTC3900 package DescripTion .050 BSC .245 MIN .030 ±.005 TYP RECOMMENDED SOLDER PAD LAYOUT NOTE: INCHES 1. DIMENSIONS IN (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL ...

Page 19

Rev B) REV DATE DESCRIPTION B 5/11 Added H- and MP-grade parts. Reflected throughout the data sheet. Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is ...

Page 20

... LTC3726/LTC3725 Synchronous No Opto Forward Converter Controller Chip Set Ideal for Medium Power 24V or 48V Input Isolated Applications LTC3723-1/ Synchronous Push-Pull Controllers LTC3723-2 LTC3721-1/ Nonsynchronous Push-Pull Controllers LTC3721-2 LTC3722/ Synchronous Phase Modulated Full Bridge Controllers LTC3722-2 20 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 ...

Related keywords