LTC3814-5
60V Current Mode
Synchronous Step-Up Controller
FEATURES
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DESCRIPTION
The LTC3814-5 is a synchronous step-up switching regu-
lator controller that can generate output voltages up to
60V. The LTC3814-5 uses a constant off-time peak current
control architecture to deliver very high duty cycles with
accurate cycle-by-cycle current limit without requiring a
sense resistor.
A precise internal reference provides ±0.5% DC accuracy.
A high bandwidth (25MHz) error amplifier provides very
fast line and load transient response. Large 1Ω gate driv-
ers allow the LTC3814-5 to drive large power MOSFETs
for higher current applications. The operating frequency
is selected by an external resistor and is compensated for
variations in V
IN
. A shutdown pin allows the LTC3814-5
to be turned off reducing the supply current to <230μA.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and No R
SENSE
is a trademark of Linear Technology Corporation. All other trademarks are the property of their
respective owners. Protected by U.S. Patents including 5481178, 5847554, 6304066, 6476589,
6580258, 6677210, 6774611.
High Output Voltages: Up to 60V
Large 1Ω Gate Drivers
No Current Sense Resistor Required
Dual N-Channel MOSFET Synchronous Drive
±0.5% 0.8V Voltage Reference
Fast Transient Response
Programmable Soft-Start
Generates 5.5V Driver Supply
Power Good Output Voltage Monitor
Adjustable Off-Time/Frequency: t
OFF(MIN)
< 100ns
Adjustable Cycle-by-Cycle Current Limit
Undervoltage Lockout On Driver Supply
Output Overvoltage Protection
Thermally Enhanced 16-Pin TSSOP Package
APPLICATIONS
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24V Fan Supplies
48V Telecom and Base Station Power Supplies
Networking Equipment, Servers
Automotive and Industrial Control Systems
TYPICAL APPLICATION
High Efficiency High Voltage Step-Up Converter
100
V
OUT
263k
I
OFF
100k
PGOOD
PGOOD
V
RNG
V
OFF
RUN/SS
1000pF
0.01μF
100k
V
FB
100pF
SGND
I
TH
BG
PGND
1μF
1k
BOOST
TG
0.1μF
SW
EXTV
CC
INTV
CC
D1
MBR1100
M2
Si7848DP
29.4k
4.7μH
LTC3814-5
M1
Si7848DP
V
OUT
24V
4A
NDRV
V
IN
4.5V TO 14V
22μF
Efficiency vs Load Current
V
IN
= 12V
95
EFFICIENCY (%)
+
90
V
IN
= 5V
85
+
270μF
×2
80
0
1
2
LOAD (A)
3
38145 TA01b
4
38145 TA01
38145fc
1
LTC3814-5
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW
I
OFF
V
OFF
V
RNG
PGOOD
I
TH
V
FB
RUN/SS
SGND
1
2
3
4
5
6
7
8
17
16 BOOST
15 TG
14 SW
13 PGND
12 BG
11 INTV
CC
10 EXTV
CC
9
NDRV
Supply Voltages
INTV
CC
................................................... –0.3V to 14V
(INTV
CC
– PGND), (BOOST – SW) ......... –0.3V to 14V
BOOST (Continuous) ............................. –0.3V to 85V
BOOST (≤400ms) .................................. –0.3V to 95V
EXTV
CC
.................................................. –0.3V to 15V
(EXTV
CC
– INTV
CC
).................................. –12V to 12V
(NDRV – INTV
CC
) Voltage........................... –0.3V to 10V
SW Voltage (Continuous).............................. –1V to 70V
SW Voltage (400ms) ..................................... –1V to 80V
I
OFF
Voltage (Continuous) .......................... –0.3V to 70V
I
OFF
Voltage (400ms) ................................. –0.3V to 80V
RUN/SS Voltage ........................................... –0.3V to 5V
PGOOD Voltage ............................................ –0.3V to 7V
V
RNG
, V
OFF
Voltages ................................... –0.3V to 14V
FB Voltage ................................................. –0.3V to 2.7V
TG, BG, INTV
CC
, EXTV
CC
RMS Currents .................50mA
Operating Junction Temperature Range
(Notes 2, 3, 7) ....................................... –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
FE PACKAGE
16-LEAD PLASTIC TSSOP
T
JMAX
= 125°C,
θ
JA
= 38°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3814EFE-5#PBF
LTC3814IFE-5#PBF
TAPE AND REEL
LTC3814EFE-5#TRPBF
LTC3814IFE-5#TRPBF
PART MARKING
3814EFE-5
3814IFE-5
PACKAGE DESCRIPTION
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
38145fc
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LTC3814-5
The
l
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C (Note 2), INTV
CC
= V
BOOST
= V
RNG
= V
EXTVCC
= V
NDRV
= V
OFF
= 5V, unless
otherwise specified.
SYMBOL
Main Control Loop
INTV
CC
I
Q
I
BOOST
V
FB
INTV
CC
Supply Voltage
INTV
CC
Supply Current
INTV
CC
Shutdown Current
BOOST Supply Current
Feedback Voltage
RUN/SS > 1.5V (Notes 4, 5)
RUN/SS = 0V
RUN/SS > 1.5V (Note 5)
RUN/SS = 0V
(Note 4)
0°C to 85°C
–40°C to 85°C
–40°C to 125°C
5V < INTV
CC
< 14V (Note 4)
V
RNG
= 2V, V
FB
= 0.76V
V
RNG
= 0V, V
FB
= 0.76V
V
RNG
= INTV
CC
, V
FB
= 0.76V
V
RNG
= 2V, V
FB
= 0.84V
V
RNG
= 0V, V
FB
= 0.84V
V
RNG
= INTV
CC
, V
FB
= 0.84V
V
FB
= 0.8V
65
(Note 6)
0.6
RUN/SS = 0V
INTV
CC
Rising
Hysteresis
I
OFF
= 100μA
I
OFF
= 300μA
I
OFF
= 2000μA
350
V
BG
= 0V
V
TG
– V
SW
= 0V
0.7
0.7
1
1
1
1
V
FB
Rising
V
FB
Falling
V
FB
Returning
I
PGOOD
= 5mA
V
PGOOD
= 5V
7.5
–7.5
10
–10
1.5
0.3
0
1.5
12.5
–12.5
3
0.6
2
1.5
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ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN
4.35
TYP
MAX
14
UNITS
V
mA
μA
μA
μA
V
V
V
V
%/V
mV
mV
mV
mV
mV
mV
3
224
240
0
0.796
0.794
0.792
0.792
256
70
170
0.800
0.800
0.800
0.800
0.002
320
95
215
–300
–85
–200
20
100
25
0.9
1.4
4.2
0.5
1.85
605
6
600
400
5
0.804
0.806
0.806
0.808
0.02
384
120
260
∆V
FB,LINE
V
SENSE(MAX)
Feedback Voltage Line Regulation
Maximum Current Sense Threshold
V
SENSE(MIN)
Minimum Current Sense Threshold
I
VFB
A
VOL
(EA)
f
U
V
RUN/SS
I
RUN/SS
V
VCCUV
Oscillator
t
OFF
t
OFF(MIN)
t
ON(MIN)
Driver
I
BG,PEAK
R
BG,SINK
I
TG,PEAK
R
TG,SINK
PGOOD Output
∆V
FBOV
∆V
FB,HYST
V
PGOOD
I
PGOOD
Feedback Current
Error Amplifier DC Open-Loop Gain
Error Amp Unity Gain Crossover
Frequency
Shutdown Threshold
RUN/SS Source Current
INTV
CC
Undervoltage Lockout
150
nA
dB
MHz
1.2
2.5
4.35
V
μA
V
V
μs
ns
ns
ns
A
Ω
A
Ω
%
%
%
V
μA
0.7
4.05
Off-Time
Minimum Off-Time
Minimum On-Time
BG Driver Peak Source Current
BG Driver Pulldown R
DS(ON)
TG Driver Peak Source Current
TG Driver Pulldown R
DS(ON)
PGOOD Upper Threshold
PGOOD Lower Threshold
PGOOD Hysteresis
PGOOD Low Voltage
PGOOD Leakage Current
1.55
515
2.15
695
100
38145fc
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LTC3814-5
The
l
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C (Note 2), INTV
CC
= V
BOOST
= V
RNG
= V
EXTVCC
= V
NDRV
= V
OFF
= 5V, unless
otherwise specified.
SYMBOL
PG Delay
V
CC
Regulators
V
EXTVCC
EXTV
CC
Switchover Voltage
EXTV
CC
Rising
EXTV
CC
Hysteresis
INTV
CC
Voltage from EXTV
CC
V
EXTVCC
- V
INTVCC
at Dropout
INTV
CC
Load Regulation from EXTV
CC
INTV
CC
Voltage from NDRV Regulator
INTV
CC
Load Regulation from NDRV
Current into NDRV Pin
Maximum Supply Voltage
Maximum Current into NDRV/INTV
CC
6V < V
EXTVCC
< 15V
I
CC
= 20mA, V
EXTVCC
= 5V
I
CC
= 0mA to 20mA, V
EXTVCC
= 10V
Linear Regulator in Operation
I
CC
= 0mA to 20mA, V
EXTVCC
= 0
V
NDRV
– V
INTVCC
= 3V
Trickle Charger Shunt Regulator
Trickle Charger Shunt Regulator,
INTV
CC
≤ 16.7V (Note 8)
10
20
5.2
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ELECTRICAL CHARACTERISTICS
PARAMETER
PGOOD Delay
CONDITIONS
V
FB
Falling
MIN
TYP
125
MAX
UNITS
μs
4.5
0.1
5.2
4.7
0.25
5.5
75
0.01
5.5
0.01
40
15
0.4
5.8
150
5.8
60
V
V
V
mV
%
V
%
μA
V
mA
V
INTVCC,1
∆V
EXTVCC,1
∆V
LOADREG,1
V
INTVCC,2
∆V
LOADREG,2
I
NDRV
V
CCSR
I
CCSR
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 LTC3814-5 is tested under pulsed load conditions such that
T
J
≈
T
A
. The LTC3814E-5 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3814I-5 is guaranteed
to meet performance specifications 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:
LTC3814-5: T
J
= T
A
+ (P
D
• 38°C/W)
Note 4:
The LTC3814-5 is tested in a feedback loop that servos V
FB
to the
reference voltage with the I
TH
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
SW
).
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:
I
CC
is the sum of current into NDRV and INTV
CC
.
TYPICAL PERFORMANCE CHARACTERISTICS
Load Transient Response
V
OUT
200mV/DIV
Start-Up
V
OUT
10V/DIV
Overcurrent Operation
V
OUT
10V/DIV
RUN/SS
4V/DIV
I
OUT
2A/DIV
38145 G01
I
L
5A/DIV
I
L
5A/DIV
100μs/DIV
FRONT PAGE CIRCUIT
V
IN
= 12V
0A TO 4A LOAD STEP
1ms/DIV
FRONT PAGE CIRCUIT
V
IN
= 12V
I
LOAD
= 1A
38145 G02
200μs/DIV
FRONT PAGE CIRCUIT V
RNG
= 1V
R
SHORT
= 1Ω
V
IN
= 12V
38145 G03
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LTC3814-5
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current
100
V
OUT
= 50V
300
V
IN
= 36V
V
IN
= 24V
FREQUENCY (kHz)
V
IN
= 12V
90
280
FREQUENCY (kHz)
I
LOAD
= 0A
260
I
LOAD
= 1A
240
Frequency vs Input Voltage
FRONT PAGE CIRCUIT
300
Frequency vs Load Current
FRONT PAGE CIRCUIT
95
EFFICIENCY (%)
280
V
IN
= 12V
260
240
V
IN
= 5V
220
85
220
80
0
1
2
3
4
5
38145 G04
200
5
7
LOAD (A)
11
9
INPUT VOLTAGE (V)
13
15
38145 G05
200
0
1
3
2
LOAD CURRENT (A)
4
38145 G06
I
TH
Voltage vs Load Current
3
CURRENT SENSE THRESHOLD (mV)
FRONT PAGE CIRCUIT
V
IN
= 12V
V
RNG
= 1V
400
300
200
100
0
–100
–200
–300
–400
Current Sense Threshold
vs I
TH
Voltage
10000
V
RNG
= 2V
1.4V
OFF-TIME (ns)
1V
0.7V
0.5V
1000
Off-Time vs I
OFF
Current
V
OFF
= INTV
CC
I
TH
VOLTAGE (V)
2
1
100
0
0
1
2
3
4
5
38145 G07
10
0
0.5
1
1.5
2
I
TH
VOLTAGE (V)
2.5
3
38145 G08
10
LOAD CURRENT (A)
100
1000
I
OFF
CURRENT (μA)
10000
38145 G09
Off-Time vs Temperature
MAXIMUM CURRENT SENSE THRESHOLD (mV)
680
660
640
620
600
580
560
–50 –25
I
OFF
= 300μA
400
Maximum Current Sense
Threshold vs V
RNG
Voltage
MAXIMUM CURRENT SENSE THRESHOLD (mV)
240
Maximum Current Sense
Threshold vs Temperature
V
RNG
= INTV
CC
230
300
OFF-TIME (ns)
220
200
210
100
200
50
25
75
0
TEMPERATURE (°C)
100
125
38145 G10
0
0.5
1
1.5
2
38145 G11
190
–50
–25
V
RNG
VOLTAGE (V)
50
75
0
25
TEMPERATURE (°C)
100
125
38145 G12
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