FEATURES
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LTC3703
100V Synchronous
Switching Regulator
Controller
DESCRIPTION
The LTC
®
3703 is a synchronous step-down switching
regulator controller that can directly step down voltages
from up to 100V, making it ideal for telecom and automo-
tive applications. The LTC3703 drives external N-channel
MOSFETs using a constant frequency (up to 600kHz),
voltage mode architecture.
A precise internal reference provides 1% DC accuracy.
A high bandwidth error amplifier and patented line feed-
forward compensation provide very fast line and load
transient response. Strong 1Ω gate drivers allow the
LTC3703 to drive multiple MOSFETs for higher current ap-
plications. The operating frequency is user programmable
from 100kHz to 600kHz and can also be synchronized to
an external clock for noise-sensitive applications. Cur-
rent limit is programmable with an external resistor and
utilizes the voltage drop across the synchronous MOSFET
to eliminate the need for a current sense resistor. For ap-
plications requiring up to 60V operation with logic-level
MOSFETS, refer to the LTC3703-5 data sheet.
PARAMETER
Maximum V
IN
MOSFET Gate Drive
V
CC
UV
+
V
CC
UV
–
LTC3703-5
60V
4.5V to 15V
3.7V
3.1V
LTC3703
100V
9.3V to 15V
8.7V
6.2V
High Voltage Operation: Up to 100V
Large 1Ω Gate Drivers
No Current Sense Resistor Required
Step-Up or Step-Down DC/DC Converter
Dual N-Channel MOSFET Synchronous Drive
Excellent Line and Load Transient Response
Programmable Constant Frequency: 100kHz to
600kHz
±1% Reference Accuracy
Synchronizable up to 600kHz
Selectable Pulse-Skip Mode Operation
Low Shutdown Current: 50μA Typ
Programmable Current Limit
Undervoltage Lockout
Programmable Soft-Start
16-Pin Narrow SSOP and 28-Pin SSOP Packages
APPLICATIONS
n
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48V Telecom and Base Station Power Supplies
Networking Equipment, Servers
Automotive and Industrial Control
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
5408150, 5055767, 6677210, 5847554, 5481178, 6304066, 6580258.
TYPICAL APPLICATION
V
CC
9.3V TO 15V
+
MODE/SYNC V
IN
30k
f
SET
10k
1000pF 470pF
FB
15k
8.06k
1%
0.1μF
100Ω
2200pF
113k
1%
I
MAX
INV
RUN/SS
GND
VCC
SW
BOOST
LTC3703
TG
COMP
22μF
25V
BAS19
V
IN
15V TO 100V
100
Efficiency vs Load Current
V
IN
= 25V
V
IN
= 50V
V
IN
= 75V
90
+
Si7456DP
0.1μF
8μH
68μF
95
V
OUT
12V
5A
EFFICIENCY (%)
270μF
16V
10Ω
Si7456DP
+
DRV
CC
BG
10μF
BGRTN
1μF
3703 F01
85
MBR1100
80
0
1
3
2
LOAD (A)
4
5
3703 F01b
Figure 1. High Efficiency High Voltage Step-Down Converter
3703fb
1
LTC3703
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltages
V
CC
, DRV
CC
.......................................... –0.3V to 15V
(DRV
CC
– BGRTN), (BOOST – SW) ....... –0.3V to 15V
BOOST ................................................ –0.3V to 115V
BGRTN ....................................................... –5V to 0V
V
IN
Voltage .............................................. –0.3V to 100V
SW Voltage ................................................ –1V to 100V
RUN/SS Voltage .......................................... –0.3V to 5V
MODE/SYNC, INV Voltages ....................... –0.3V to 15V
f
SET
, FB, I
MAX
Voltages ................................ –0.3V to 3V
Peak Output Current <10μs BG,TG..............................5A
Operating Temperature Range (Note 2)
LTC3703E............................................. –40°C to 85°C
LTC3703I............................................ –40°C to 125°C
LTC3703H (Note 9) ............................ –40°C to 150°C
Junction Temperature (Notes 3, 7)
LTC3703E, LTC3703I ......................................... 125°C
LTC3703H (Note 9) ........................................... 150°C
Storage Temperature Range.................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec.) ................. 300°C
PIN CONFIGURATION
TOP VIEW
V
IN
TOP VIEW
MODE/SYNC 1
f
SET
2
COMP 3
FB 4
I
MAX
5
INV 6
RUN/SS 7
GND 8
16 V
IN
15 B00ST
14 TG
13 SW
12 V
CC
11 DRV
CC
10 BG
9
BGRTN
NC
NC
NC
NC
MODE/SYNC
f
SET
COMP
FB
1
2
3
4
5
6
7
8
9
28 BOOST
27 TG
26 SW
25 NC
24 NC
23 NC
22 NC
21 V
CC
20 DRV
CC
19 BG
18 NC
17 NC
16 NC
15 BGRTN
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 100°C/W
I
MAX
10
INV 11
NC 12
RUN/SS 13
GND 14
GN PACKAGE
16-LEAD NARROW PLASTIC SSOP
T
JMAX
= 150°C,
θ
JA
= 110°C/W
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
LTC3703EGN#PBF
LTC3703EGN#TRPBF
3703
LTC3703IGN#PBF
LTC3703IGN#TRPBF
3703I
LTC3703HGN#PBF
LTC3703HGN#TRPBF
3703H
LTC3703EG#PBF
LTC3703EG#TRPBF
LTC3703EG
LEAD BASED FINISH
TAPE AND REEL
PART MARKING
LTC3703EGN
LTC3703EGN#TR
3703
LTC3703IGN
LTC3703IGN#TR
3703I
LTC3703HGN
LTC3703HGN#TR
3703H
LTC3703EG
LTC3703EG#TR
LTC3703EG
Consult LTC Marketing for parts specified with wider operating temperature ranges.
PACKAGE DESCRIPTION
16-Lead Narrow Plastic SSOP
16-Lead Narrow Plastic SSOP
16-Lead Narrow Plastic SSOP
28-Lead Plastic SSOP
PACKAGE DESCRIPTION
16-Lead Narrow Plastic SSOP
16-Lead Narrow Plastic SSOP
16-Lead Narrow Plastic SSOP
28-Lead Plastic SSOP
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
–40°C to 150°C
–40°C to 85°C
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
–40°C to 150°C
–40°C to 85°C
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/
3703fb
2
LTC3703
ELECTRICAL CHARACTERISTICS
SYMBOL
V
CC
, DRV
CC
V
IN
I
CC
I
DRVCC
I
BOOST
PARAMETER
V
CC
, DRV
CC
Supply Voltage
V
IN
Pin Voltage
V
CC
Supply Current
DRV
CC
Supply Current
BOOST Supply Current
V
FB
= 0V
RUN/SS = 0V
(Note 5)
RUN/SS = 0V
(Note 5) T
J
≤ 125°C
T
J
> 125°C
RUN/SS = 0V
(Note 4)
9V < V
CC
< 15V (Note 4)
1V < V
COMP
< 2V (Note 4)
MODE/SYNC Rising
0 ≤ V
MODE/SYNC
≤ 15V
1
0 ≤ V
INV
≤ 15V
V
IN
= 100V
RUN/SS = 0V, V
IN
= 10V
V
IMAX
= 0V
|V
SW
| – V
IMAX
at I
RUN/SS
= 0μA
H Grade
RUN/SS = 0V
|V
SW
| – V
IMAX
≥ 200mV, V
RUN/SS
= 3V
V
CC
Rising
V
CC
Falling
R
SET
= 25k
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= DRV
CC
= V
BOOST
= V
IN
= 10V, V
MODE/SYNC
= V
INV
= V
SW
=
BGRTN = 0V, RUN/SS = I
MAX
= open, R
SET
= 25k, unless otherwise specified.
CONDITIONS
l
l
l
MIN
9.3
TYP
MAX
15
100
UNITS
V
V
mA
μA
μA
μA
μA
μA
μA
V
V
%/V
%
V
mV
μA
V
μA
μA
μA
μA
mV
mV
V
μA
μA
V
V
kHz
kHz
ns
%
A
1.7
50
0
0
360
360
0
0.792
0.788
0.800
0.007
0.01
0.75
0.81
20
0
1.5
0
100
0
10.5
–25
–25
0.7
2.5
9
8.0
5.7
270
100
200
12
10
10
0.9
4
17
8.7
6.2
300
2.5
5
5
500
800
5
0.808
0.812
0.05
0.1
0.87
1
2
1
140
1
13.5
55
65
1.2
5.5
25
9.3
6.8
330
600
Main Control Loop
V
FB
ΔV
FB(LINE)
ΔV
FB(LOAD)
V
MODE/SYNC
ΔV
MODE/SYNC
I
MODE/SYNC
V
INV
I
INV
I
VIN
I
MAX
V
OS(IMAX)
V
RUN/SS
I
RUN/SS
V
UV
Oscillator
f
OSC
f
SYNC
t
ON(MIN)
DC
MAX
Driver
I
BG(PEAK)
R
BG(SINK)
I
TG(PEAK)
R
TG(SINK)
A
VOL
f
U
I
FB
I
COMP
BG Driver Peak Source Current
BG Driver Pull-Down R
DS(ON)
TG Driver Peak Source Current
TG Driver Pull-Down R
DS(ON)
Op Amp DC Open Loop Gain
Op Amp Unity Gain Crossover Frequency
FB Input Current
COMP Sink/Source Current
(Note 8)
(Note 4)
(Note 6)
0 ≤ V
FB
≤ 3V
±5
74
(Note 8)
1.5
1.5
2
1
2
1
85
25
0
±10
1
1.5
1.5
Ω
A
Ω
dB
MHz
μA
mA
3703fb
Feedback Voltage
Feedback Voltage Line Regulation
Feedback Voltage Load Regulation
MODE/SYNC Threshold
MODE/SYNC Hysteresis
MODE/SYNC Current
Invert Threshold
Invert Current
V
IN
Sense Input Current
I
MAX
Source Current
V
IMAX
Offset Voltage
Shutdown Threshold
RUN/SS Source Current
Maximum RUN/SS Sink Current
Undervoltage Lockout
l
l
l
Oscillator Frequency
External Sync Frequency Range
Minimum On-Time
Maximum Duty Cycle
f < 200kHz
89
93
96
Feedback Amplifier
3
LTC3703
ELECTRICAL CHARACTERISTICS
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.
Note 2:
The LTC3703E is guaranteed to meet performance specifications from
0°C to 85°C. Specifications over the –40°C to 85°C operating temperature
range are assured by design, characterization and correlation with statistical
process controls. The LTC3703I is guaranteed over the full –40°C to 125°C
operating junction temperature range. The LTC3703H is guaranteed over the
full –40°C to 150°C operating junction temperature range.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
LTC3703: T
J
= T
A
+ (P
D
• 100 °C/W) G Package
Note 4:
The LTC3703 is tested in a feedback loop that servos V
FB
to the
reference voltage with the COMP pin forced to a voltage between 1V and 2V.
Note 5:
The dynamic input supply current is higher due to the power
MOSFET gate charge being delivered at the switching frequency (Q
G
• f
OSC
).
Note 6:
Guaranteed by design. Not subject to test.
Note 7:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 8:
R
DS(ON)
guaranteed by correlation to wafer level measurement.
Note 9:
High junction temperatures degrade operating lifetimes. Operating
lifetime at junction temperatures greater than 125°C is derated to 1000 hours.
TYPICAL PERFORMANCE CHARACTERISTICS
T
A
= 25°C unless otherwise noted.
Efficiency vs Input Voltage
100
95
EFFICIENCY (%)
90
85
80
75
70
V
OUT
= 12V
f = 300kHz
PULSE SKIP DISABLED
0
10
20
30 40 50 60
INPUT VOLTAGE (V)
70
80
I
OUT
= 0.5A
I
OUT
= 5A
100
95
V
IN
= 15V
EFFICIENCY (%)
90
85
80
75
70
V
OUT
= 5V
f = 250kHz
PULSE SKIP ENABLED
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
LOAD CURRENT (A)
3703 G02
Efficiency vs Load Current
V
OUT
50mV/DIV
V
IN
= 45V
V
IN
= 75V
I
OUT
2A/DIV
Load Transient Response
V
IN
= 50V
50μs/DIV
V
OUT
= 12V
1A TO 5A LOAD STEP
3703 G03
3703 G01
V
CC
Current vs V
CC
Voltage
3.5
3.0
COMP = 1.5V
V
CC
CURRENT (mA)
V
CC
CURRENT (mA)
2.5
2.0
1.5
1.0
0.5
0
6
8
12
V
CC
VOLTAGE (V)
10
14
16
3703 G04
V
CC
Current vs Temperature
4
100
90
3
COMP = 1.5V
V
CC
CURRENT (μA)
80
70
60
50
40
30
20
10
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3703 G05
V
CC
Shutdown Current vs
V
CC
Voltage
V
FB
= 0V
2
V
FB
= 0V
1
0
6
8
12
10
V
CC
VOLTAGE (V)
14
16
3703 G06
3703fb
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LTC3703
TYPICAL PERFORMANCE CHARACTERISTICS
V
CC
Shutdown Current vs
Temperature
70
65
60
V
CC
CURRENT (μA)
55
50
45
40
35
30
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3703 G07
Reference Voltage vs
Temperature
0.803
1.20
1.15
NORMALIZED FREQUENCY
REFERENCE VOLTAGE (V)
0.802
1.10
1.05
1.00
0.95
0.90
0.85
0.798
–50 –25
Normalized Frequency vs
Temperature
0.801
0.800
0.799
0
25 50 75 100 125 150
TEMPERATURE (°C)
3703 G08
0.80
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3703 G09
Driver Peak Source Current vs
Temperature
3.0
2.8
PEAK SOURCE CURRENT (A)
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
–50 –25
0
25
50
75
100 125 150
3703 G10
Driver Pull-Down R
DS(ON)
vs
Temperature
1.6
3.0
V
CC
= 10V
PEAK SOURCE CURRENT (A)
2.5
2.0
1.5
1.0
0.5
0
0
25 50 75 100 125 150
TEMPERATURE (°C)
3703 G11
Driver Peak Source Current vs
Supply Voltage
V
CC
= 10V
1.4
1.2
R
DS(ON)
(Ω)
1.0
0.8
0.6
0.4
0.2
0
–50 –25
5
6
TEMPERATURE (°C)
8 9 10 11 12 13 14 15
7
DRV
CC
/BOOST VOLTAGE (V)
3703 G12
Driver Pull-Down R
DS(ON)
vs
Supply Voltage
1.1
70
60
1.0
RISE/FALL TIME (ns)
50
40
30
20
10
0
6
7
9 10 11 12 13
8
DRV
CC
/BOOST VOLTAGE (V)
14
15
Rise/Fall Time vs Gate
Capacitance
DRV
CC
, BOOST = 10V
RISE
8
7
RUN/SS CURRENT (μA)
10000
3703 G14
RUN/SS Pull-Up Current vs
Temperature
6
5
4
3
2
1
R
DS(ON)
(Ω)
0.9
0.8
FALL
0.7
0.6
0
6000
2000
4000
8000
GATE CAPACITANCE (pF)
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
1573 G15
3703 G13
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