LTC3901 Datasheet PDF - Linear Technology

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LTC3901
Linear Technology

Part Number LTC3901
Description Secondary Side Synchronous Driver for Push-Pull and Full-Bridge Converters
Page 16 Pages


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LTC3901
Secondary Side
Synchronous Driver for Push-Pull
and Full-Bridge Converters
FEATURES
N-Channel Synchronous MOSFET Driver
Programmable Timeout
Reverse Inductor Current Sense
Gate Drive Transformer Synchronization
Sequence Monitor
Wide VCC Supply Range: 4.5V to 11V
15ns Rise/Fall Times at VCC = 5V, CL = 4700pF
Undervoltage Lockout
Small 16-Lead SSOP Package
U
APPLICATIO S
48V Input Isolated DC/DC Converters
Isolated Telecom Power Supplies
Distributed Power Step-Down Converters
Industrial Control System Power Supplies
Automotive and Heavy Equipment
DESCRIPTIO
The LTC®3901 is a secondary side synchronous rectifier
driver designed to be used in isolated push-pull and full-
bridge converter power supplies. The chip drives two
external N-channel MOSFETs and accepts a transformer-
generated bipolar input to maintain sychronization with
the primary side controller.
The LTC3901 provides a full range of protection features
for the external MOSFETs. A programmable timeout func-
tion is included that disables both drivers when the syn-
chronization signal is missing or incorrect. Additionally,
the chip senses the output inductor current through the
drain-source resistance of the two MOSFETs, turning off
the MOSFETs if the inductor current reverses. The LTC3901
also shuts off the drivers if the supply is low or if the
synchronization sequence is incorrect.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
VIN
36V TO 72V
ISOLATION
BARRIER
T1
MA MB
ME
DRVA
DRVB
LTC3723
PUSH-PULL
CONTROLLER
COMP VFB SDRA SDRB
MF
T2
L1
CSE+
ME
CSE–
VCC
GND
LTC3901
CSF+
PVCC
MF
CSF–
PGND
SYNC TIMER
OUT FB
LT4430 OR LT1431
OPTOCOUPLER
DRIVER
COMP
Figure 1. Simplified Isolated Push-Pull Converter
+
COUT
VOUT
12V
3901 F01
3901f
1



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LTC3901
ABSOLUTE AXI U RATI GS
(Note 1)
Supply Voltage
VCC, PVCC ............................................................................ 12V
Input Voltage
CSE, CSF, TIMER ................. –0.3V to (VCC + 0.3V)
SYNC ...................................................... –12V to 12V
Input Current
CSE+, CSF+ ..................................................................... 15mA
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
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
PVCC 1
ME 2
ME 3
PGND 4
CSE5
CSE+ 6
TIMER 7
GND 8
16 VCC
15 MF
14 MF
13 PGND
12 CSF
11 CSF+
10 GND
9 SYNC
GN PACKAGE
16-LEAD NARROW PLASTIC SSOP
TJMAX = 125°C, θJA = 130°C/W
ORDER PART
NUMBER
LTC3901EGN
GN PART
MARKING
3901
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating
temperature range. VCC = 5V, TA = 25°C unless otherwise specified. (Note 3)
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX
VCC
VUVLO
IVCC
Timer
Supply Voltage Range
4.5 5 11
VCC Undervoltage Lockout Threshold
VCC Undervoltage Lockout Hysteresis
VCC Supply Current
Rising Edge
Rising Edge to Falling Edge
VSYNC = 0V
fSYNC = 100kHz, CME = CMF = 4700pF (Note 4)
4.1 4.5
0.5
0.5 1
7 15
VTMR
Timer Threshold Voltage
ITMR Timer Input Current
tTMRDIS
Timer Discharge Time
VTMRMAX
Timer Pin Clamp Voltage
Current Sense (Note 5)
VTMR = 0V
CTMR = 1000pF, RTMR = 4.7k
CTMR = 1000pF, RTMR = 4.7k
–10%
VCC/5
–6
40
2.5
10%
–10
120
ICS+
ICS
VCSMAX
VCS
CS+ Input Current
CSInput Current
CS+ Pin Clamp Voltage
Current Sense Threshold Voltage
VCS+ = 0V
VCS– = 0V
IIN = 5mA, Driver Off
VCS– = 0V
(Note 6)
7.5
3
±1
±1
11
10.5 13.5
18
SYNC Input
ISYNC
VSYNCP
SYNC Input Current
SYNC Input Positive Threshold
SYNC Positive Input Hysteresis
VSYNC = ±10V
(Note 7)
±1 ±10
1.0 1.4 1.8
0.2
VSYNCN
SYNC Input Negative Threshold
SYNC Negative Input Hysteresis
(Note 7)
–1.8 –1.4 –1.0
0.2
Driver Output
RONH
Driver Pull-Up Resistance
IOUT = –100mA
0.9 1.2
1.6
RONL
Driver Pull-Down Resistance
IOUT = 100mA
0.8 1.2
1.6
IPK
Driver Peak Output Current
(Note 7)
2
UNITS
V
V
V
mA
mA
V
µA
ns
V
µA
µA
V
mV
mV
µA
V
V
V
V
A
3901f
2



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LTC3901
ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating
temperature range. VCC = 5V, TA = 25°C unless otherwise specified. (Note 3)
SYMBOL
PARAMETER
Switching Characteristics (Note 8)
td SYNC Input to Driver Output Delay
tr, tf Driver Rise/Fall Time
CONDITIONS
CME = CMF = 4700pF, VSYNC = ±5V
CME = CMF = 4700pF, VSYNC = ±5V
MIN TYP MAX UNITS
60 120
ns
15 ns
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC3901E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design; characterization and correlation
with statistical process controls.
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.
Note 5: Both CSE+, CSEand CSF+, CSFcurrent sense comparators have
the same performance specifications.
Note 6: The current sense comparator threshold has a 0.33%/°C
temperature coefficient (TC) to match the TC of the external MOSFET
RDSON.
Note 7: Guaranteed by design, not subject to test.
Note 8: 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.
TYPICAL PERFOR A CE CHARACTERISTICS
Timeout vs VCC
5.25
5.20
TA = 25°C
RTMR = 51k
5.15 CTMR = 470pF
5.10
5.05
5.00
4.95
4.90
4.85
4.80
4.75
45 6 78
9 10 11
VCC (V)
3901 G01
Current Sense Threshold vs
Temperature
18
17 VCC = 5V, 11V
16
15
14
13
12
11
10
9
8
7
6
5
4
3
–50 –25 0 25 50 75 100
TEMPERATURE (°C)
125
3901 G04
Timeout vs Temperature
5.25
5.20
VCC = 5V
RTMR = 51k
5.15 CTMR = 470pF
5.10
5.05
5.00
4.95
4.90
4.85
4.80
4.75
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
3901 G02
VCS(MAX) Clamp Voltage vs CS+
Input Current
18
TA = 25°C
17
16
15
14
13
12
11
10
0
5 10 15 20 25
CS+ INPUT CURRENT (mA)
30
3901 G05
Timeout vs RTMR
10
TA = 25°C
9 VCC = 5V
8 CTMR = 470pF
7
6
5
4
3
2
1
0
0 10 20 30 40 50 60 70 80 90 100
RTMR (k)
3901 G03
SYNC Positive Threshold vs
Temperature
1.8
1.7
1.6
1.5
VCC = 11V
1.4
VCC = 5V
1.3
1.2
1.1
1.0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3901 G06
3901f
3



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LTC3901
TYPICAL PERFOR A CE CHARACTERISTICS
SYNC Negative Threshold vs
Temperature
–1.0
VCC = 5V, 11V
–1.1
Propagation Delay vs VCC
120
TA = 25°C
110 CLOAD = 4.7nF
Propagation Delay vs
Temperature
120
VCC = 5V
110 CLOAD = 4.7nF
–1.2 100 100
–1.3 90 90
–1.4 80 80
–1.5
–1.6
–1.7
–1.8
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3901 G07
70
60 SYNC TO ME
50 SYNC TO MF
40
45
6 7 8 9 10 11
VCC (V)
3901 G08
70
60 SYNC TO ME
50
SYNC TO MF
40
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3901 G09
Propagation Delay vs CLOAD
120
TA = 25°C
110 VCC = 5V
100
90
80
70
60 SYNC TO ME
50
SYNC TO MF
40
1 2 3 4 5 6 7 8 9 10
CLOAD (nF)
3901 G10
Rise/Fall Time vs VCC
50
45
TA = 25°C
CLOAD = 4.7nF
40
35
30
25
20
15
10
FALL TIME
5
RISE TIME
0
45
6 7 8 9 10 11
VCC (V)
3901 G11
Rise/Fall Time vs Temperature
50
45
VCC = 5V
CLOAD = 4.7nF
40
35
30
25
20
15 RISE TIME
10
FALL TIME
5
0
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
3901 G12
Rise/Fall Time vs Load
Capacitance
50
45
TA = 25°C
VCC = 5V
40
35
30
25
20
RISE TIME
15
FALL TIME
10
5
0
0 1 2 3 4 5 6 7 8 9 10
CLOAD (nF)
3901 G13
Undervoltage Lockout Threshold
Voltage vs Temperature
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
3.7
3.6
3.5
3.4
3.3
3.2
3.1
3.0
–50
RISING EDGE
FALLING EDGE
–25 0 25 50 75
TEMPERATURE (°C)
100 125
3901 G14
3901f
4



LTC3901 datasheet pdf
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