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LTC3703-5
1
37035f
APPLICATIO S
U
DESCRIPTIO
U
FEATURES
TYPICAL APPLICATIO
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
s
High Voltage Operation: Up to 60V
s
Large 1
Gate Drivers (with 5V Supply)
s
No Current Sense Resistor Required
s
Step-Up or Step-Down DC/DC Converter
s
Dual N-Channel MOSFET Synchronous Drive
s
Excellent Transient Response and DC Line Regulation
s
Programmable Constant Frequency: 100kHz to
600kHz
s
1% Reference Accuracy
s
Synchronizable up to 600kHz
s
Selectable Pulse Skip Mode Operation
s
Low Shutdown Current: 25
A Typ
s
Programmable Current Limit
s
Undervoltage Lockout
s
Programmable Soft-Start
s
16-Pin Narrow SSOP and 28-Pin SSOP Packages
The LTC
3703-5 is a synchronous step-down switching
regulator controller that can directly step-down voltages
from up to 60V, making it ideal for telecom and automotive
applications. The LTC3703-5 drives external logic level
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 1
gate drivers allow the
LTC3703-5 to drive multiple MOSFETs for higher current
applications. The operating frequency is user program-
mable from 100kHz to 600kHz and can also be synchro-
nized to an external clock for noise-sensitive applications.
Current 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 applications requiring up to 100V operation, refer to
the LTC3703 data sheet.
60V Synchronous
Switching Regulator Controller
Efficiency vs Load Current
High Efficiency High Voltage Step-Down Converter
LTC3703-5
MODE/SYNC
FSET
COMP
FB
I
MAX
INV
RUN/SS
GND
V
IN
BOOST
TG
SW
VCC
DRV
CC
BG
BGRTN
22
F
2
1000pF
2200pF
10k
100
113k
1%
21.5k
1%
10
12k
30k
0.1
F
V
IN
6V TO 60V
8
H
D1
MBR1100
V
OUT
5V
5A
270
F
16V
MMDL770T1
V
CC
5V
0.1
F
37035 TA04
10
F
1
F
+
+
+
Si7850DP
Si7850DP
22
F
470pF
LOAD CURRENT (A)
0
EFFICIENCY (
%
)
100
95
90
85
80
4
37053 TA04b
1
2
3
5
V
IN
= 12V
V
IN
= 42V
V
IN
= 24V
s
48V Telecom and Base Station Power Supplies
s
Networking Equipment, Servers
s
Automotive and Industrial Control
PARAMETER
LTC3703-5
LTC3703
Maximum V
IN
60V
100V
MOSFET Gate Drive
4.5V to 15V
9.3V to 15V
V
CC
UV
+
3.7V
8.7V
V
CC
UV
3.1V
6.2V
*U.S. Patent Numbers: 5408150, 5055767, 6677210, 5847554, 5481178, 6304066, 6580258;
Others Pending.
LTC3703-5
2
37035f
Supply Voltages
V
CC
, DRV
CC
.......................................... 0.3V to 15V
(DRV
CC
BGRTN), (BOOST SW) ...... 0.3V to 15V
BOOST (Continuous) ............................ 0.3V to 85V
BOOST (400ms) ................................... 0.3V to 95V
BGRTN ...................................................... 5V to 0V
V
IN
Voltage (Continuous) .......................... 0.3V to 70V
V
IN
Voltage (400ms) ................................. 0.3V to 80V
SW Voltage (Continuous) ............................ 1V to 70V
SW Voltage (400ms) ................................... 1V to 80V
Run/SS Voltage .......................................... 0.3V to 5V
ABSOLUTE AXI U
RATI GS
W
W
W
U
(Note 1)
ELECTRICAL CHARACTERISTICS
The
q
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
= 5V, V
MODE/SYNC
= V
INV
= V
SW
=
BGRTN = 0V, RUN/SS = I
MAX
= open, R
SET
= 25k, unless otherwise specified.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
, DRV
CC
V
CC
, DRV
CC
Supply Voltage
q
4.1
15
V
V
IN
V
IN
Pin Voltage
q
60
V
I
CC
V
CC
Supply Current
V
FB
= 0V
q
1.7
2.5
mA
RUN/SS = 0V
25
40
A
I
DRVCC
DRV
CC
Supply Current
(Note 5)
0
5
A
RUN/SS = 0V
0
5
A
I
BOOST
BOOST Supply Current
(Note 5)
q
360
500
A
RUN/SS = 0V
0
5
A
MODE/SYNC, INV Voltages ....................... 0.3V to 15V
f
SET
, FB, I
MAX
, COMP Voltages ................... 0.3V to 3V
Driver Outputs
TG ................................ SW 0.3V to BOOST + 0.3V
BG ........................... BGRTN 0.3V to DRV
CC
+ 0.3V
Peak Output Current <10
s BG,TG ............................ 5A
Operating Temperature Range (Note 2) .. 40
C to 85
C
Junction Temperature (Notes 3, 7) ....................... 125
C
Storage Temperature Range ................. 65
C to 150
C
Lead Temperature (Soldering, 10 sec.)................. 300
C
ORDER PART
NUMBER
GN PART
MARKING
T
JMAX
= 125
C,
JA
= 110
C/W
37035
LTC3703EGN-5
PACKAGE/ORDER I FOR ATIO
U
U
W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ORDER PART
NUMBER
LTC3703EG-5
1
2
3
4
5
6
7
8
9
10
11
12
13
14
TOP VIEW
G PACKAGE
28-LEAD PLASTIC SSOP
28
27
26
25
24
23
22
21
20
19
18
17
16
15
BOOST
TG
SW
NC
NC
NC
NC
V
CC
DRV
CC
BG
NC
NC
NC
BGRTN
V
IN
NC
NC
NC
NC
MODE/SYNC
f
SET
COMP
FB
I
MAX
INV
NC
RUN/SS
GND
TOP VIEW
GN PACKAGE
16-LEAD NARROW PLASTIC SSOP
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
MODE/SYNC
f
SET
COMP
FB
I
MAX
INV
RUN/SS
GND
V
IN
B00ST
TG
SW
V
CC
DRV
CC
BG
BGRTN
T
JMAX
= 125
C,
JA
= 100
C/W
LTC3703-5
3
37035f
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC3703-5 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: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
LTC3703-5: T
J
= T
A
+ (P
D
100
C/W) G Package
Note 4: The LTC3703-5 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.
ELECTRICAL CHARACTERISTICS
The
q
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
= 5V, V
MODE/SYNC
= V
INV
= V
SW
=
BGRTN = 0V, RUN/SS = I
MAX
= open, R
SET
= 25k, unless otherwise specified.
Note 5: The dynamic input supply current is higher due to the power
MOSFET gate charging 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.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Main Control Loop
V
FB
Feedback Voltage
(Note 4)
0.792
0.800
0.808
V
q
0.788
0.812
V
V
FB, LINE
Feedback Voltage Line Regulation
5V < V
CC
< 15V (Note 4)
q
0.007
0.05
%/V
V
FB, LOAD
Feedback Voltage Load Regulation
1V < V
COMP
< 2V (Note 4)
q
0.01
0.1
%
V
MODE/SYNC
MODE/SYNC Threshold
MODE/SYNC Rising
0.75
0.8
0.87
V
V
MODE/SYNC
MODE/SYNC Hysteresis
20
mV
I
MODE/SYNC
MODE/SYNC Current
0
V
MODE/SYNC
15V
0
1
A
V
INV
Invert Threshold
1
1.5
2
V
I
INV
Invert Current
0
V
INV
15V
0
1
A
I
VIN
V
IN
Sense Input Current
V
IN
= 60V
80
130
A
RUN/SS = 0V, V
IN
= 10V
0
1
A
I
MAX
I
MAX
Source Current
V
IMAX
= 0V
10.5
12
13.5
A
V
OS,
IMAX
V
IMAX
Offset Voltage
|V
SW
| V
IMAX
at I
RUN/SS
= 0
A
25
10
55
mV
V
RUN/SS
Shutdown Threshold
0.7
0.9
1.2
V
I
RUN/SS
RUN/SS Source Current
RUN/SS = 0V
2.3
3.8
5.3
A
Maximum RUN/SS Sink Current
|V
SW
| V
IMAX
> 100mV
9
17
25
A
V
UV
Undervoltage Lockout
V
CC
Rising
q
3.4
3.7
4.1
V
V
CC
Falling
q
2.8
3.1
3.4
V
Hysteresis
q
0.45
0.65
0.85
V
Oscillator
f
OSC
Oscillator Frequency
R
SET
= 25k
270
300
330
kHz
f
SYNC
External Sync Frequency Range
100
600
kHz
t
ON, MIN
Minimum On-Time
200
ns
DC
MAX
Maximum Duty Cycle
f < 200kHz
89
93
96
%
Driver
I
BG, PEAK
BG Driver Peak Source Current
0.75
1
A
R
BG, SINK
BG Driver Pull-Down R
DS, ON
(Note 8)
1.2
1.8
I
TG, PEAK
TG Driver Peak Source Current
0.75
1
A
R
TG, SINK
TG Driver Pull-Down R
DS, ON
(Note 8)
1.2
1.8
Feedback Amplifier
A
VOL
Op Amp DC Open Loop Gain
(Note 4)
74
85
dB
f
U
Op Amp Unity Gain Crossover Frequency (Note 6)
25
MHz
I
FB
FB Input Current
0
V
FB
3V
0
1
A
I
COMP
COMP Sink/Source Current
5
10
mA
LTC3703-5
4
37035f
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Efficiency vs Input Voltage
Efficiency vs Load Current
Load Transient Response
V
CC
Current vs V
CC
Voltage
V
CC
Current vs Temperature
V
CC
Shutdown Current vs V
CC
Voltage
V
CC
Shutdown Current
vs Temperature
Reference Voltage
vs Temperature
Normalized Frequency
vs Temperature
TEMPERATURE (
C)
60 40 20
0
60
100
20
40
80
TEMPERATURE (
C)
60 40 20
0
60
100
20
40
80
60 40 20
0
20
40
60
80
100
TEMPERATURE (
C)
NORMALIZED FREQUENCY
37035 G09
1.20
1.15
1.10
1.05
1.00
0.95
0.90
0.85
0.80
LOAD CURRENT (A)
0
EFFICIENCY (%)
100
95
90
85
80
1
2
3
4
37035 G02
5
V
CC
VOLTAGE (V)
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
7.5
37035 G04
2.5
5
10
12.5
15
V
CC
CURRENT (mA)
TEMPERATURE (
C)
60 40 20
0
V
CC
CURRENT (mA)
60
100
37035 G05
20
40
80
4
3
2
1
0
37035 G03
V
CC
CURRENT (
A)
37035 G07
35
30
25
20
15
10
5
0
REFERENCE VOLTAGE (V)
0.803
0.802
0.801
0.800
0.799
0.798
37035 G08
V
OUT
= 12V
f = 250kHz
PULSE SKIP ENABLED
V
IN
= 42V
V
IN
= 24V
V
OUT
50mV/DIV
I
OUT
2A/DIV
V
IN
= 50V
V
OUT
= 12V
1A TO 5A LOAD STEP
50
s/DIV
V
FB
= 0V
V
CC
RISING
V
CC
= 5V
COMP = 1.5V
V
FB
= 0V
COMP = 1.5V
INPUT VOLTAGE (V)
0
80
EFFICIENCY (%)
85
90
95
100
10
20
30
40
37035 G01
50
60
I
OUT
= 1A
V
OUT
= 5V
f = 250kHz
FORCED CONTINUOUS
I
OUT
= 5A
V
CC
VOLTAGE (V)
0
0
V
CC
CURRENT (
A)
20
40
60
80
4
8
12
16
37035 G06
100
120
2
6
10
14
T
A
= 25
C (unless otherwise noted).
LTC3703-5
5
37035f
PEAK SOURCE CURRENT (A)
1.2
1.1
1.0
0.9
0.8
37035 G10
TEMPERATURE (
C)
R
DS(ON)
(
)
37035 G11
DRV
CC
/BOOST VOLTAGE (V)
0
2.5
7.5
10
12.5
PEAK SOURCE CURRENT (A)
3.0
2.5
2.0
1.5
1.0
0.5
0
5
37035 G12
15
60 40 20
0
20
40
60
80
100
60 40 20
0
20
40
60
80
100
TEMPERATURE (
C)
V
CC
= 5V
V
CC
= 5V
V
CC
= 5V
|SW| VOLTAGE (V)
0
25
20
15
10
5
0
5
10
0.3
0.5
37035 G17
0.1
0.2
0.4
0.6
0.7
RUN/SS SINK CURRENT (
A)
RUN VOLTAGE (V)
0.5
MAX DUTY CYCLE (%)
100
90
80
70
60
50
40
30
20
10
0
10
2.5
37035 G18
1.0
1.5
2.0
3.0
I
MAX
= 0.3V
TEMPERATURE (
C)
RUN/SS CURRENT (
A)
15735 G15
5
4
3
2
1
0
60
20
20
40
40
0
60
80
100
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
DRV
CC
/BOOST VOLTAGE (V)
2.5
1.1
1.2
1.3
12.5
37035 G13
1.0
0.9
5
7.5
10
15
0.8
0.7
0.6
R
DS(ON)
(
)
GATE CAPACITANCE (nF)
0
RISE/FALL TIME (ns)
100
150
20
37035 G14
50
0
5
10
15
200
RISE TIME
FALL TIME
V
CC
= 5V
V
CC
VOLTAGE (V)
0
0
RUN/SS PULL-UP CURRENT (
A)
1
2
3
4
5
2.5
5
7.5
10
37035 G16
12.5
15
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Driver Peak Source Current
vs Temperature
Driver Pull-Down R
DS(ON)
vs Temperature
Driver Peak Source Current
vs Supply Voltage
Rise/Fall Time
vs Gate Capacitance
RUN/SS Pull-Up Current
vs Temperature
RUN/SS Pull-Up Current
vs V
CC
Voltage
RUN/SS Sink Current
vs SW
Voltage
Max % DC vs RUN/SS Voltage
Driver Pull-Down R
DS(ON)
vs Supply Voltage
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