LTC3813
100V Current Mode
Synchronous Step-Up Controller
FEATURES
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DESCRIPTION
The LTC3813 is a synchronous step-up switching regulator
controller that can generate output voltages up to 100V.
The LTC3813 uses a constant off-time peak current control
architecture 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 drivers
allow the LTC3813 to drive multiple MOSFETs for higher
current applications. The operating frequency is selected
by an external resistor and is compensated for variations
in V
IN
and can also be synchronized to an external clock
for switching-noise sensitive applications. A shutdown pin
allows the LTC3813 to be turned off, reducing the supply
current to 240μA.
PARAMETER
Maximum V
OUT
MOSFET Gate Drive
INTV
CC
UV
+
INTV
CC
UV
–
LTC3813
100V
6.35V to 14V
6.2V
6V
LTC3814-5
60V
4.5V to 14V
4.2V
4V
High Output Voltages: Up to 100V
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 10V Driver Supply from Input Supply
Synchronizable to External Clock
Power Good Output Voltage Monitor
Adjustable Off-Time/Frequency: t
OFF(MIN)
< 100ns
Adjustable Cycle-by-Cycle Current Limit
Programmable Undervoltage Lockout
Output Overvoltage Protection
28-Pin SSOP Package
APPLICATIONS
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24V Fan Supplies
48V Telecom and Base Station Power Supplies
Networking Equipment, Servers
Automotive and Industrial Control Systems
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 5481178, 5847554, 6304066, 6476589, 6580258, 6677210, 6774611.
TYPICAL APPLICATION
High Efficiency High Voltage Step-Up Converter
50k
V
OUT
500k
I
OFF
PGOOD
V
RNG
1000pF
SYNC
SS
SHDN
0.01μF
I
TH
100k
V
FB
100pF
SGND
LTC3813
NDRV
BOOST
TG
0.1μF
SW
EXTV
CC
DRV
CC
INTV
CC
SENSE
+
BG
SENSE
–
BGRTN
D1
MBR1100
M2
Si7850DP
2x
1μF
499Ω
30.9k
10μH
M1
Si7850DP
V
IN
10V TO 40V
22μF
Efficiency vs Load Current
100
V
IN
= 36V
95
EFFICIENCY (%)
V
IN
= 12V
90
V
IN
= 24V
+
V
OUT
50V/5A
85
+
270μF
2x
80
0
1
2
3
4
5
3813 TA01b
LOAD (A)
3813 TA01
3813fb
1
LTC3813
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
I
OFF
NC
NC
V
OFF
V
RNG
PGOOD
SYNC
I
TH
V
FB
1
2
3
4
5
6
7
8
9
28 BOOST
27 TG
26 SW
25 SENSE
+
24 NC
23 NC
22 NC
21 SENSE
–
20 BGRTN
19 BG
18 DRV
CC
17 INTV
CC
16 EXTV
CC
15 NDRV
Supply Voltages
INTV
CC
, DRV
CC
....................................... –0.3V to 14V
(DRV
CC
- BGRTN), (BOOST - SW).......... –0.3V to 14V
BOOST ................................................. –0.3V to 114V
BGRTN ........................................................ –5V to 0V
EXTV
CC
.................................................. –0.3V to 15V
(NDRV - INTV
CC
) Voltage ........................... –0.3V to 10V
SW, SENSE
+
Voltage ................................... –1V to 100V
I
OFF
Voltage .............................................. –0.3V to 100V
SS Voltage ................................................... –0.3V to 5V
PGOOD Voltage ............................................ –0.3V to 7V
V
RNG
, V
OFF
, SYNC,
SHDN,
UVIN Voltages........................................ –0.3V to 14V
PLL/LPF FB Voltages................................. –0.3V to 2.7V
,
TG, BG, INTV
CC
, EXTV
CC
RMS Currents .................50mA
Operating Temperature Range (Note 2)
LTC3813E............................................. –40°C to 85°C
LTC3813I............................................ –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
PLL/LPF 10
SS 11
SGND 12
SHDN
13
UVIN 14
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 100°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC3813EG#PBF
LTC3813IG#PBF
TAPE AND REEL
LTC3813EG#TRPBF
LTC3813IG#TRPBF
PART MARKING
LTC3813EG
LTC3813IG
PACKAGE DESCRIPTION
28-Lead Plastic SSOP
28-Lead Plastic SSOP
TEMPERATURE RANGE
–40°C to 85°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/
temperature range, otherwise specifications are at T
A
= 25°C, INTV
CC
= DRV
CC
= V
BOOST
= V
OFF
= V
RNG
=
SHDN
= UV
IN
= V
EXTVCC
=
V
NDRV
= 10V, V
SYNC
= V
SENSE
+
= V
SENSE
–
= V
BGRTN
= V
SW
= 0V, unless otherwise specified.
SYMBOL
Main Control Loop
INTV
CC
I
Q
I
BOOST
INTV
CC
Supply Voltage
INTV
CC
Supply Current
INTV
CC
Shutdown Current
BOOST Supply Current
SHDN
> 1.5V, I
NTVCC
= 9.5V (Notes 4, 5)
SHDN
= 0V
SHDN
> 1.5V (Note 5)
SHDN
= 0V
l
ELECTRICAL CHARACTERISTICS
The
l
denotes specifications which apply over the full operating
PARAMETER
CONDITIONS
MIN
6.35
3
240
270
0
TYP
MAX
14
6
600
400
5
UNITS
V
mA
μA
μA
μA
3813fb
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LTC3813
ELECTRICAL CHARACTERISTICS
SYMBOL
V
FB
PARAMETER
Feedback Voltage
The
l
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, INTV
CC
= DRV
CC
= V
BOOST
= V
OFF
= V
RNG
=
SHDN
= UV
IN
= V
EXTVCC
=
V
NDRV
= 10V, V
SYNC
= V
SENSE
+
= V
SENSE
–
= V
BGRTN
= V
SW
= 0V, unless otherwise specified.
CONDITIONS
(Note 4)
0°C to 85°C
–40°C to 85°C
–40°C to 125°C (I-Grade)
7V < 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)
SYNC = 10V
1.2
V
SS
> 0.5V
V
IN
Rising
V
IN
Falling
Hysteresis
INTV
CC
Rising
Hysteresis
I
OFF
= 100μA
I
OFF
= 300μA
I
OFF
= 2000μA
350
I
OFF
= 100μA, V
PLL/LPF
= 0.6V
I
OFF
= 100μA, V
PLL/LPF
= 1.8V
f
PLLIN
< f
SW
f
PLLIN
> f
SW
V
BG
= 0V
V
TG
– V
SW
= 0V
1.5
1.5
2.2
0.6
3.6
1.2
15
–25
2
1
2
1
V
FB
Rising
V
FB
Falling
V
FB
Returning
I
PGOOD
= 5mA
7.5
–7.5
10
–10
1.5
0.3
1.5
12.5
–12.5
3
0.6
1.5
5
1.8
l
l
l
l
l
l
l
MIN
0.796
0.794
0.792
0.792
256
70
170
TYP
0.800
0.800
0.800
0.800
0.002
320
95
215
–300
–85
–200
20
100
25
0
1.5
0
1.4
0.88
0.80
0.10
6.2
0.5
1.85
605
MAX
0.804
0.806
0.806
0.808
0.02
384
120
260
UNITS
V
V
V
V
%/V
mV
mV
mV
mV
mV
mV
ΔV
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
I
SYNC
V
SHDN
I
SHDN
I
SS
V
VINUV
Feedback Current
Error Amplifier DC Open Loop Gain
Error Amp Unity Gain Crossover Frequency
SYNC Current
Shutdown Threshold
SHDN
Pin Input Current
SS Source Current
V
IN
Undervoltage Lockout
150
nA
dB
MHz
1
2
1
2.5
0.92
0.82
0.12
6.35
μA
V
μA
μA
V
V
V
V
V
μs
ns
ns
ns
μs
μs
μA
μA
A
Ω
A
Ω
%
%
%
V
3813fb
0.7
0.86
0.78
0.07
6.05
V
VCCUV
INTV
CC
Undervoltage Lockout
Oscillator and Phase-Locked Loop
t
OFF
t
OFF(MIN)
t
ON(MIN)
t
OFF(PLL)
Off-Time
Minimum Off-Time
Minimum On-Time
t
OFF
Modulation Range by PLL
Down Modulation
Up Modulation
Phase Detector Output Current
Sinking Capability
Sourcing Capability
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
1.55
515
2.15
695
100
I
PLL/LPF
Driver
I
BG,PEAK
R
BG,SINK
I
TG,PEAK
R
TG,SINK
PGOOD Output
ΔV
FBOV
ΔV
FB,HYST
V
PGOOD
3
LTC3813
ELECTRICAL CHARACTERISTICS
SYMBOL
I
PGOOD
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
10.5V < V
EXTVCC
< 15V
I
CC
= 20mA, V
EXTVCC
= 9.1V
I
CC
= 0mA to 20mA, V
EXTVCC
= 12V
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
9.4
l
The
l
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, INTV
CC
= DRV
CC
= V
BOOST
= V
OFF
= V
RNG
=
SHDN
= UV
IN
= V
EXTVCC
=
V
NDRV
= 10V, V
SYNC
= V
SENSE
+
= V
SENSE
–
= V
BGRTN
= V
SW
= 0V, unless otherwise specified.
PARAMETER
PGOOD Leakage Current
PGOOD Delay
CONDITIONS
V
PGOOD
= 5V
V
FB
Falling
MIN
TYP
0
125
MAX
2
UNITS
μA
μs
6.4
0.1
9.4
6.7
0.25
10
170
0.01
10
0.01
40
15
0.5
10.6
250
10.6
60
V
V
V
mV
%
V
%
μA
V
mA
V
INTVCC,1
ΔV
EXTVCC,1
ΔV
LOADREG,1
V
INTVCC,2
ΔV
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 LTC3813E 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 LTC3813I is guaranteed to meet
performance specifications over the full –40°C to 125°C operating
temperature range.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
LTC3813: T
J
= T
A
+ (P
D
• 100°C/W)
Note 4:
The LTC3813 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
.
3813fb
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LTC3813
TYPICAL PERFORMANCE CHARACTERISTICS
Load Transient Response
V
OUT
200mV/
DIV
Start-Up
V
OUT
20V/DIV
Overcurrent Operation
V
OUT
20V/DIV
SS
4V/DIV
I
L
5A/DIV
100μs/DIV
FIGURE 14 CIRCUIT
V
IN
= 12V
0A TO 4A LOAD STEP
3813 G01
I
OUT
2A/DIV
I
L
5A/DIV
1ms/DIV
FRONT PAGE CIRCUIT
V
IN
= 24V
I
LOAD
= 2A
3813 G02
500μs/DIV
FRONT PAGE CIRCUIT
V
IN
= 24V
R
SHORT
= 1Ω
3813 G03
Efficiency vs Load Current
100
V
OUT
= 24V
300
V
IN
= 12V
280
FREQUENCY (kHz)
Frequency vs Input Voltage
FRONT PAGE CIRCUIT
280
270
260
FREQUENCY (kHz)
I
LOAD
= 0A
260
I
LOAD
= 1A
240
250
240
230
220
220
210
Frequency vs Load Current
FRONT PAGE CIRCUIT
95
EFFICIENCY (%)
V
IN
= 24V
90
V
IN
= 5V
85
V
IN
= 12V
80
0
1
2
LOAD (A)
3
3813 G04
4
200
200
10
15
25
30
20
INPUT VOLTAGE (V)
35
40
3813 G05
0
1
3
2
LOAD CURRENT (A)
4
3813 G06
Current Sense Threshold
vs I
TH
Voltage
400
V
RNG
= 2V
CURRENT SENSE THRESHOLD (mV)
300
200
100
0
–100
–200
–300
–400
10
0
0.5
1
1.5
2
I
TH
VOLTAGE (V)
2.5
3
3813 G07
Off-Time vs I
OFF
Current
10000
V
OFF
= INTV
CC
700
600
1.4V
OFF-TIME (ns)
OFF-TIME (ns)
1V
0.7V
0.5V
1000
500
400
300
200
100
0
10
100
1000
I
OFF
CURRENT (μA)
10000
3813 G08
Off-Time vs V
OFF
Voltage
I
OFF
= 300μA
100
0
0.5
2
1.5
1
V
OFF
VOLTAGE (V)
2.5
3
3813 G09
3813fb
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