FEATURES
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LTC3810
100V Current Mode
Synchronous Switching
Regulator Controller
DESCRIPTION
The LTC3810 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 LTC3810 uses a constant on-time
valley current control architecture to deliver very low 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 drivers
allow the LTC3810 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 LTC3810 to be turned off, reducing the supply
current to 240μA.
Integrated bias control generates gate drive power from the
input supply during start-up and when an output short-
circuit occurs, with the addition of a small external SOT23
MOSFET. When in regulation, power is derived from the
output for higher efficiency.
High Voltage Operation: Up to 100V
Large 1Ω Gate Drivers
No Current Sense Resistor Required
Dual N-Channel MOSFET Synchronous Drive
Extremely Fast Transient Response
±0.5% 0.8V Voltage Reference
Programmable Output Voltage Tracking/Soft-Start
Generates 10V Driver Supply from Input Supply
Synchronizable to External Clock
Selectable Pulse Skip Mode Operation
Power Good Output Voltage Monitor
Adjustable On-Time/Frequency: t
ON(MIN)
< 100ns
Adjustable Cycle-by-Cycle Current Limit
Programmable Undervoltage Lockout
Output Overvoltage Protection
28-Pin SSOP Package
APPLICATIONS
n
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48V Telecom and Base Station Power Supplies
Networking Equipment, Servers
Automotive and Industrial Control Systems
L,
LT, LTC, LTM, Linear Technology, Burst Mode 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.
TYPICAL APPLICATION
High Efficiency High Voltage Step-Down Converter
R
ON
261k
I
ON
PGOOD
V
RNG
C
SS
1000pF
LTC3810
TG
0.1μF
SW
EXTV
CC
DRV
CC
INTV
CC
SENSE
+
BG
SGND
SENSE
–
BGRTN
M2
Si7456DP
R
FB2
1k
D1
MBR1100
R
FB1
14k
M1
Si7456DP
L1
10μH
V
OUT
12V/6A
NDRV
BOOST
100k
M3
ZXMN10A07F
Efficiency vs Load Current
100
V
IN
= 50V
V
IN
= 25V
95
EFFICIENCY (%)
V
IN
= 75V
90
+
V
IN
15V TO 100V
C
IN
22μF
MODE/SYNC
SS/TRACK
SHDN
85
47pF
I
TH
200k
V
FB
+
C
OUT
270μF
80
0
1
2
3
LOAD (A)
4
5
6
3810 TA01b
5pF
1μF
3810 TA01
3810fc
1
LTC3810
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
I
ON
NC
NC
V
ON
V
RNG
PGOOD
MODE/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
ON
Voltage ............................................... –0.3V to 100V
SS/TRACK Voltage ....................................... –0.3V to 5V
PGOOD Voltage ............................................ –0.3V to 7V
V
RNG
, V
ON
, MODE/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 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
PLL/LPF 10
SS/TRACK 11
SGND 12
SHDN
13
UVIN 14
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 80°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC3810EG#PBF
LTC3810IG#PBF
TAPE AND REEL
LTC3810EG#TRPBF
LTC3810IG#TRPBF
PART MARKING
LTC3810EG
LTC3810IG
PACKAGE DESCRIPTION
28-Lead Plastic SSOP
28-Lead Plastic SSOP
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/
The
l
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C (Note 2), INTV
CC
= DRV
CC
= V
BOOST
= V
ON
= V
RNG
=
SHDN
= UV
IN
=
V
EXTVCC
= V
NDRV
= 10V, V
MODE/SYNC
= V
SENSE
+
= V
SENSE
–
= V
BGRTN
= V
SW
=0V, unless otherwise specified.
SYMBOL
Main Control Loop
INTV
CC
I
Q
I
BOOST
V
FB
PARAMETER
INTV
CC
Supply Voltage
INTV
CC
Supply Current
INTV
CC
Shutdown Current
BOOST Supply Current
Feedback Voltage
CONDITIONS
l
ELECTRICAL CHARACTERISTICS
MIN
6.35
TYP
MAX
14
6
600
400
5
0.804
0.806
0.806
0.808
UNITS
V
mA
μA
μA
μA
V
V
V
V
3810fc
SHDN
> 1.5V, I
NTVCC
= 9.5V (Notes 4, 5)
SHDN
= 0V
SHDN
> 1.5V (Note 5)
SHDN
= 0V
(Note 4)
0°C to 85°C
–40°C to 85°C
–40°C to 125°C
l
l
l
0.796
0.794
0.792
0.792
3
240
270
0
0.800
0.800
0.800
0.800
2
LTC3810
ELECTRICAL CHARACTERISTICS
SYMBOL
∆V
FB,LINE
V
SENSE(MAX)
PARAMETER
Feedback Voltage Line Regulation
Maximum Current Sense Threshold
The
l
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C (Note 2), INTV
CC
= DRV
CC
= V
BOOST
= V
ON
= V
RNG
=
SHDN
= UV
IN
=
V
EXTVCC
= V
NDRV
= 10V, V
MODE/SYNC
= V
SENSE
+
= V
SENSE
–
= V
BGRTN
= V
SW
= 0V, unless otherwise specified.
CONDITIONS
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
(Note 6)
V
MODE/SYNC
Rising
MODE/SYNC = 10V
0.75
1.2
V
IN
Rising
V
IN
Falling
Hysteresis
INTV
CC
Rising, I
NDRV
= 100μA
INTV
CC
Rising, NDRV = INTV
CC
= EXTV
CC
INTV
CC
Rising, NDRV = INTV
CC
, EXTV
CC
= 0
INTV
CC
Falling
I
ON
= 100μA
I
ON
= 300μA
I
ON
= 2000μA
l
l
MIN
l
TYP
0.002
320
95
215
–300
–85
–200
20
100
25
0.8
0
1.5
0
0.88
0.80
0.10
6.2
6.2
12
5.7
1.85
605
250
MAX
0.02
384
120
260
UNITS
%/V
mV
mV
mV
mV
mV
mV
nA
dB
MHz
V
μA
V
μA
V
V
V
V
V
V
V
μs
ns
ns
ns
μs
μs
μA
μA
A
256
70
170
V
SENSE(MIN)
Minimum Current Sense Threshold
I
VFB
A
VOL
(EA)
f
U
V
MODE/SYNC
I
MODE/SYNC
V
SHDN
I
SHDN
V
VINUV
Feedback Current
Error Amplifier DC Open Loop Gain
Error Amp Unity-Gain Crossover
Frequency
MODE/SYNC Threshold
MODE/SYNC Current
Shutdown Threshold
SHDN
Pin Input Current
V
IN
Undervoltage Lockout
150
65
0.86
0.78
0.07
6.05
6.05
11.7
0.85
1
2
1
0.92
0.82
0.12
6.35
6.35
12.3
V
VCCUV
INTV
CC
Undervoltage Lockout
Linear Regulator Mode
External Supply Mode
Trickle-Charge Mode
l
l
l
Oscillator and Phase-Locked Loop
On-Time
t
ON
t
ON(MIN)
t
OFF(MIN)
t
ON(PLL)
Minimum On-Time
Minimum Off-Time
t
ON
Modulation Range by PLL
Down Modulation
Up Modulation
Phase Detector Output Current
Sinking Capability
Sourcing Capability
BG Driver Peak Source Current
BG Driver Pull-Down R
DS(ON)
TG Driver Peak Source Current
TG Driver Pull-Down R
DS(ON)
PGOOD Upper Threshold
PGOOD Lower Threshold
PGOOD Hysteresis
PGOOD Low Voltage
PGOOD Leakage Current
PGOOD Delay
1.55
515
2.15
695
100
350
5
1.8
I
ON
= 100μA, V
PLL/LPF
= 0.6V
I
ON
= 100μA, V
PLL/LPF
= 1.8V
f
PLLIN
< f
SW
f
PLLIN
> f
SW
V
BG
= 0V
V
TG
– V
SW
= 0V
2.2
0.6
3.6
1.2
15
–25
I
PLL/LPF
Driver
I
BG,PEAK
R
BG,SINK
I
TG,PEAK
R
TG,SINK
PGOOD Output
∆V
FBOV
∆V
FB,HYST
V
PGOOD
I
PGOOD
PG Delay
1.5
1.5
2
1
2
1
10
–10
1.5
0.3
0
120
1.5
1.5
12.5
–12.5
3
0.6
2
Ω
A
Ω
%
%
%
V
μA
μs
V
FB
Rising
V
FB
Falling
V
FB
Returning
I
PGOOD
= 5mA
V
PGOOD
= 5V
V
FB
Falling
7.5
–7.5
3810fc
3
LTC3810
The
l
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C (Note 2), INTV
CC
= DRV
CC
= V
BOOST
= V
ON
= V
RNG
=
SHDN
= UV
IN
=
V
EXTVCC
= V
NDRV
= 10V, V
MODE/SYNC
= V
SENSE
+
= V
SENSE
–
= V
BGRTN
= V
SW
= 0V, unless otherwise specified.
SYMBOL
Tracking
I
SS/TRACK
V
FB,TRACK
V
CC
Regulators
V
EXTVCC
PARAMETER
SS/TRACK Source Current
Feedback Voltage at Tracking
CONDITIONS
V
SS/TRACK
> 0.5V
V
TRACK
= 0V, I
TH
= 1.2V (Note 4)
V
TRACK
= 0.5V, I
TH
= 1.2V (Note 4)
MIN
0.7
0.48
TYP
1.4
–0.018
0.5
MAX
2.5
0.52
UNITS
μA
V
V
ELECTRICAL CHARACTERISTICS
V
INTVCC,1
∆V
EXTVCC,1
∆V
LOADREG,1
V
INTVCC,2
∆V
LOADREG,2
I
NDRV
I
NDRVTO
V
CCSR
I
CCSR
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
Linear Regulator Timeout Enable
Threshold
Maximum Supply Voltage
Maximum Current into NDRV/INTV
CC
l
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
6.4
0.1
9.4
6.7
0.3
10
170
0.01
10
0.01
40
270
15
0.5
10.6
250
10.6
60
350
V
V
V
mV
%
V
%
μA
μA
V
mA
9.4
20
210
Trickle Charger Shunt Regulator
Trickle Charger Shunt Regulator,
INTV
CC
≤ 16.7V (Note 8)
10
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 LTC3810 is tested under pulsed load conditions such that
T
J
≈
T
A
. The LTC3810E 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 LTC3810I is guaranteed
to meet perfomance 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:
LTC3810: T
J
= T
A
+ (P
D
• 100°C/W)
PARAMETER
Maximum V
IN
MOSFET Gate Drive
INTV
CC
UV
+
INTV
CC
UV
–
LTC3810
100V
6.35V to 14V
6.2V
6V
Note 4:
The LTC3810 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
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:
I
CC
is the sum of current into NDRV and INTV
CC
.
LTC3810-5
60V
4.5V to 14V
4.2V
4V
LTC3812-5
60V
4.5V to 14V
4.2V
4V
3810fc
4
LTC3810
TYPICAL PERFORMANCE CHARACTERISTICS
Load Transient Response
V
OUT
100mV/
DIV
INTV
CC
5V/DIV
V
OUT
5V/DIV
V
IN
50V/DIV
I
L
5A/DIV
50μs/DIV
V
IN
= 48V
0A TO 5A LOAD STEP
FRONT PAGE CIRCUIT
3810 G01
Start-Up
V
OUT
10V/DIV
SS/TRACK
4V/DIV
I
L
5A/DIV
3810 G02
Short-Circuit/
Fault Timeout Operation
INTV
CC
I
OUT
5A/DIV
V
IN
= 48V
500μs/DIV
I
LOAD
= 1A
MODE/SYNC = 0V
FRONT PAGE CIRCUIT
V
IN
= 48V
10ms/DIV
R
SHORT
= 0.1Ω
FRONT PAGE CIRCUIT
3810 G03
Short-Circuit/
Foldback Operation
V
OUT
5V/DIV
V
FB
0.5V/
DIV
V
OUT
5V/DIV
SS/TRACK
0.5V/DIV
V
FB
0.5V/DIV
I
L
5A/DIV
200μs/DIV
V
IN
= 48V
FRONT PAGE CIRCUIT
3810 G04
Tracking
V
OUT
100mV/
DIV
I
TH
0.5V/DIV
I
L
2A/DIV
Pulse Skip Mode Operation
SS/TRACK
V
FB
I
L
5A/DIV
V
IN
= 48V
500μs/DIV
I
LOAD
= 1A
MODE/SYNC = 0V
FRONT PAGE CIRCUIT
3810 G05
V
IN
= 48V
20μs/DIV
I
OUT
= 100mA
MODE/SYNC = INTV
CC
FRONT PAGE CIRCUIT
3810 G06
Efficiency vs Input Voltage
100
I
OUT
= 5A
95
EFFICIENCY (%)
EFFICIENCY (%)
90
I
OUT
= 0.5A
90
85
80
75
70
f = 250kHz
FRONT PAGE CIRCUIT
10
20
50
40
30
60
INPUT VOLTAGE (V)
70
80
70
100
Efficiency vs Load Current
280
V
IN
= 12V
V
IN
= 36V
V
IN
= 60V
FREQUENCY (kHz)
270
Frequency vs Input Voltage
260
I
OUT
= 0A
250
I
OUT
= 5A
80
V
OUT
= 5V
Si7850 MOSFETs
MODE/SYNC = INTV
CC
f = 250kHz
0
1
2
3
4
5
LOAD CURRENT (A)
6
7
3810 G08
240
MODE/SYNC = 0V
FRONT PAGE CIRCUIT
10
20
50
40
30
60
INPUT VOLTAGE (V)
70
80
230
3810 G07
3810 G09
3810fc
5
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