LTC3703-5
60V Synchronous
Switching Regulator Controller
FEATURES
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DESCRIPTIO
High Voltage Operation: Up to 60V
Large 1
Ω
Gate Drivers (with 5V Supply)
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: 25µA Typ
Programmable Current Limit
Undervoltage Lockout
Programmable Soft-Start
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 input, making it ideal for telecom and au-
tomotive 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 1Ω 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.
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
APPLICATIO S
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48V Telecom and Base Station Power Supplies
Networking Equipment, Servers
Automotive and Industrial Control
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*U.S. Patent Numbers: 5408150, 5055767, 6677210, 5847554, 5481178, 6304066, 6580258;
Others Pending.
TYPICAL APPLICATIO
High Efficiency High Voltage Step-Down Converter
V
CC
5V
+
22µF
MODE/SYNC V
IN
30k
FSET
10k
1000pF
21.5k
1%
470pF
12k
I
MAX
INV
0.1µF
100Ω
2200pF
113k
1%
RUN/SS
GND
VCC
DRV
CC
10Ω
COMP
TG
LTC3703-5
FB
SW
0.1µF
BOOST
MMDL770T1
V
IN
6V TO 60V
+
Si7850DP
22µF
×2
EFFICIENCY (%)
8µH
270µF
16V
Si7850DP
+
V
OUT
5V
5A
BG
10µF
BGRTN
1µF
D1
MBR1100
37035 TA04
U
Efficiency vs Load Current
100
V
IN
= 12V
95
V
IN
= 42V
90
V
IN
= 24V
85
80
0
1
3
2
LOAD CURRENT (A)
4
5
37053 TA04b
U
U
37035fa
1
LTC3703-5
ABSOLUTE
AXI U RATI GS
(Note 1)
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 <10µs BG,TG ............................ 5A
Operating Temperature Range (Note 2)
LTC3703E-5 ........................................ –40°C to 85°C
LTC3703I-5 ....................................... –40°C to 125°C
Junction Temperature (Notes 3, 7) ....................... 125°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec.)................. 300°C
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
PACKAGE/ORDER I FOR ATIO
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
ORDER PART
NUMBER
LTC3703EGN-5
LTC3703IGN-5
GN PART
MARKING
37035
3703I5
GN PACKAGE
16-LEAD NARROW PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 110°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
●
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
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
CONDITIONS
●
●
ELECTRICAL CHARACTERISTICS
V
FB
= 0V
RUN/SS = 0V
(Note 5)
RUN/SS = 0V
(Note 5)
RUN/SS = 0V
2
U
U
W
W W
U
W
TOP VIEW
V
IN
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
ORDER PART
NUMBER
LTC3703EG-5
LTC3703IG-5
I
MAX
10
INV 11
NC 12
RUN/SS 13
GND 14
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 100°C/W
MIN
4.1
TYP
●
●
1.7
25
0
0
360
0
MAX
15
60
2.5
40
5
5
500
5
UNITS
V
V
mA
µA
µA
µA
µA
µA
37035fa
LTC3703-5
The
●
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
Main Control Loop
V
FB
Feedback Voltage
∆V
FB, LINE
∆V
FB, LOAD
V
MODE/SYNC
∆V
MODE/SYNC
I
MODE/SYNC
V
INV
I
INV
I
VIN
I
MAX
V
OS, IMAX
V
RUN/SS
I
RUN/SS
V
UV
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
CONDITIONS
(Note 4)
●
ELECTRICAL CHARACTERISTICS
MIN
0.792
0.788
TYP
0.800
0.007
0.01
0.8
20
0
1.5
0
80
0
12
10
0.9
3.8
17
3.7
3.1
0.65
300
200
93
1
1.2
1
1.2
85
25
0
±10
MAX
0.808
0.812
0.05
0.1
0.87
1
2
1
130
1
13.5
55
1.2
5.3
25
4.1
3.4
0.85
330
600
96
UNITS
V
V
%/V
%
V
mV
µA
V
µA
µA
µA
µA
mV
V
µA
µA
V
V
V
kHz
kHz
ns
%
A
Ω
A
Ω
dB
MHz
µA
mA
5V < V
CC
< 15V (Note 4)
1V < V
COMP
< 2V (Note 4)
MODE/SYNC Rising
0
≤
V
MODE/SYNC
≤
15V
●
●
0.75
1
0
≤
V
INV
≤
15V
V
IN
= 60V
RUN/SS = 0V, V
IN
= 10V
V
IMAX
= 0V
|V
SW
| – V
IMAX
at I
RUN/SS
= 0µA
RUN/SS = 0V
|V
SW
| – V
IMAX
> 100mV
V
CC
Rising
V
CC
Falling
Hysteresis
R
SET
= 25kΩ
●
●
●
10.5
– 25
0.7
2.3
9
3.4
2.8
0.45
270
100
89
0.75
Oscillator
f
OSC
f
SYNC
t
ON, MIN
DC
MAX
Driver
I
BG, PEAK
R
BG, SINK
I
TG, PEAK
R
TG, SINK
Feedback Amplifier
A
VOL
f
U
I
FB
I
COMP
Oscillator Frequency
External Sync Frequency Range
Minimum On-Time
Maximum Duty Cycle
BG Driver Peak Source Current
BG Driver Pull-Down R
DS, ON
TG Driver Peak Source Current
TG Driver Pull-Down R
DS, ON
f < 200kHz
(Note 8)
0.75
(Note 8)
74
1.8
1.8
Op Amp DC Open Loop Gain
(Note 4)
Op Amp Unity Gain Crossover Frequency (Note 6)
FB Input Current
0
≤
V
FB
≤
3V
COMP Sink/Source Current
1
±5
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. The LTC3703I-5 is guaranteed over the full
–40°C to 125°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:
LTC3703-5: 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.
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.
37035fa
3
LTC3703-5
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Input Voltage
100
100
V
IN
= 24V
95
95
V
IN
= 42V
V
OUT
50mV/DIV
AC COUPLED
EFFICIENCY (%)
I
OUT
= 5A
90
EFFICIENCY (%)
I
OUT
= 1A
85
V
OUT
= 5V
f = 250kHz
FORCED CONTINUOUS
0
10
20
30
40
INPUT VOLTAGE (V)
50
60
37035 G01
80
V
CC
Current vs V
CC
Voltage
3.5
3.0
V
CC
RISING
COMP = 1.5V
3
4
V
CC
CURRENT (mA)
V
CC
CURRENT (mA)
V
CC
CURRENT (µA)
2.5
2.0
1.5
1.0
0.5
0
0
2.5
10
7.5
V
CC
VOLTAGE (V)
5
12.5
15
V
FB
= 0V
V
CC
Shutdown Current
vs Temperature
35
30
V
CC
= 5V
0.803
NORMALIZED FREQUENCY
REFERENCE VOLTAGE (V)
V
CC
CURRENT (µA)
25
20
15
10
5
0
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
37035 G07
4
U W
37035 G04
T
A
= 25°C (unless otherwise noted).
Load Transient Response
Efficiency vs Load Current
90
I
OUT
2A/DIV
85
V
OUT
= 12V
f = 250kHz
PULSE SKIP ENABLED
0
1
2
3
LOAD CURRENT (A)
4
5
37035 G02
80
50µs/DIV
V
IN
= 50V
V
OUT
= 12V
1A TO 5A LOAD STEP
37035 G03
V
CC
Current vs Temperature
120
100
COMP = 1.5V
80
60
40
20
0
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
37035 G05
V
CC
Shutdown Current vs V
CC
Voltage
2
V
FB
= 0V
1
0
0
2
4
10 12
6
8
V
CC
VOLTAGE (V)
14
16
37035 G06
Reference Voltage
vs Temperature
1.20
1.15
0.802
1.10
1.05
1.00
0.95
0.90
0.85
0.798
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
37035 G08
Normalized Frequency
vs Temperature
0.801
0.800
0.799
0.80
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
37035 G09
37035fa
LTC3703-5
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Peak Source Current
vs Temperature
1.2
V
CC
= 5V
2
V
CC
= 5V
1.8
1.6
PEAK SOURCE CURRENT (A)
1.1
PEAK SOURCE CURRENT (A)
R
DS(ON)
(Ω)
1.0
0.9
0.8
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
37035 G10
Driver Pull-Down R
DS(ON)
vs Supply Voltage
1.3
1.2
200
RISE/FALL TIME (ns)
1.1
RUN/SS CURRENT (µA)
R
DS(ON)
(Ω)
1.0
0.9
0.8
0.7
0.6
2.5
5
12.5
DRV
CC
/BOOST VOLTAGE (V)
7.5
10
RUN/SS Pull-Up Current
vs V
CC
Voltage
5
25
RUN/SS PULL-UP CURRENT (µA)
4
RUN/SS SINK CURRENT (µA)
15
10
5
0
–5
–10
MAX DUTY CYCLE (%)
3
2
1
0
0
2.5
5
7.5
10
V
CC
VOLTAGE (V)
U W
37035 G13
Driver Pull-Down R
DS(ON)
vs Temperature
3.0
2.5
2.0
1.5
1.0
0.5
0
Driver Peak Source Current
vs Supply Voltage
1.4
1.2
1
0.8
0.6
0.4
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
37035 G11
0
2.5
7.5
10
12.5
5
DRV
CC
/BOOST VOLTAGE (V)
15
37035 G12
Rise/Fall Time
vs Gate Capacitance
V
CC
= 5V
6
5
150
RISE TIME
100
4
3
2
1
RUN/SS Pull-Up Current
vs Temperature
V
CC
= 5V
50
FALL TIME
15
0
0
10
15
5
GATE CAPACITANCE (nF)
20
37035 G14
0
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
15735 G15
RUN/SS Sink Current
vs SW Voltage
100
I
MAX
= 0.3V
20
90
80
70
60
50
40
30
20
10
0
12.5
15
0
0.1
0.5
0.2 0.3 0.4
|SW| VOLTAGE (V)
0.6
0.7
Max % DC vs RUN/SS Voltage
–10
0.5
1.0
2.0
1.5
RUN VOLTAGE (V)
2.5
3.0
37035 G18
37035 G16
37035 G17
37035fa
5
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