The LTC3812-5 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
automotive applications. The LTC3812-5 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 driv-
ers allow the LTC3812-5 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 LTC3812-5 to
be turned off reducing the supply current to <230μA.
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.
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.
High Voltage Operation: Up to 60V
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 Soft-Start
Generates 5.5V Driver Supply
Selectable Pulse Skip Mode Operation
Power Good Output Voltage Monitor
Adjustable On-Time/Frequency: t
ON(MIN)
< 100ns
Adjustable Cycle-by-Cycle Current Limit
Undervoltage Lockout On Driver Supply
Output Overvoltage Protection
Thermally Enhanced 16-Pin TSSOP Package
APPLICATIONS
n
n
n
48V Telecom and Base Station Power Supplies
Networking Equipment, Servers
Automotive and Industrial Control Systems
TYPICAL APPLICATION
High Efficiency High Voltage Step-Down Converter
R
ON
110k
I
ON
100k
PGOOD
PGOOD
V
RNG
FCB
RUN/SS
1000pF
47pF
200k
V
FB
5pF
1.89k
SGND
PGND
I
TH
BOOST
TG
SW
EXTV
CC
INTV
CC
BG
1μF
M2
Si7850DP
D1
MBR1100
10k
M1
Si7850DP
L1
4.7μH
LTC3812-5
0.1μF
NDRV
100k
M3
ZXMN-
10A07F
+
V
IN
6V TO 60V
C
IN
22μF
Efficiency vs Load Current
100
V
IN
= 12V
95
EFFICIENCY (%)
V
IN
= 42V
V
IN
= 24V
V
OUT
5V
5A
90
85
+
C
OUT
270μF
80
0
1
2
3
4
LOAD CURRENT (A)
5
6
38125 TA01b
38125 TA01
38125fb
1
LTC3812-5
ABSOLUTE MAXIMUM RATINGS
(Note 1)
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
ON
Voltage (Continuous) ........................... –0.3V to 70V
I
ON
Voltage (400ms) .................................. –0.3V to 80V
RUN/SS Voltage ........................................... –0.3V to 5V
PGOOD Voltage ............................................ –0.3V to 7V
V
RNG
, FCB Voltages .................................... –0.3V to 14V
FB Voltage ................................................. –0.3V to 2.7V
TG, BG, INTV
CC
, EXTV
CC
RMS Currents .................50mA
Operating Temperature Range (Note 2)
LTC3812E-5 ......................................... –40°C to 85°C
LTC3812I-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
PIN CONFIGURATION
TOP VIEW
I
ON
V
RNG
PGOOD
FCB
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
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
LTC3812EFE-5#PBF
LTC3812IFE-5#PBF
LEAD BASED FINISH
LTC3812EFE-5
LTC3812IFE-5
TAPE AND REEL
LTC3812EFE-5#TRPBF
LTC3812IFE-5#TRPBF
TAPE AND REEL
LTC3812EFE-5#TR
LTC3812IFE-5#TR
PART MARKING*
3812EFE-5
3812IFE-5
PART MARKING*
3812EFE-5
3812IFE-5
PACKAGE DESCRIPTION
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
PACKAGE DESCRIPTION
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/
38125fb
2
LTC3812-5
The
l
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, INTV
CC
= V
BOOST
= V
RNG
= V
EXTVCC
= V
NDRV
= 5V, V
FCB
= V
SW
= 0V,
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 (I-grade)
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)
V
FCB
Rising
FCB = 5V
1.2
RUN/SS = 0V
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
= 2500μA
250
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
7.5
–7.5
10
–10
1.5
0.3
1.5
12.5
–12.5
3
0.6
1.5
l
l
l
l
l
l
l
l
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
0.75
0.8
0
1.5
1.4
4.2
4.2
9.0
3.7
1.85
605
0.7
4.05
4.05
8.70
6
600
400
5
0.804
0.806
0.806
0.808
0.02
384
120
260
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
V
FCB
I
FCB
V
RUN/SS
I
RUN/SS
V
VCCUV
Feedback Current
Error Amplifier DC Open-Loop Gain
Error Amp Unity Gain Crossover
Frequency
FCB Threshold
FCB Current
Shutdown Threshold
RUN/SS Source Current
INTV
CC
Undervoltage Lockout
Linear Regulator Mode
External Supply Mode
Trickle-Charge Mode
150
nA
dB
MHz
0.85
1
2
2.5
4.35
4.35
9.30
V
μA
V
μA
V
V
V
V
μs
ns
ns
ns
A
Ω
A
Ω
%
%
%
V
38125fb
Oscillator
t
ON
t
ON(MIN)
t
OFF(MIN)
Driver
I
BG,PEAK
R
BG,SINK
I
TG,PEAK
R
TG,SINK
PGOOD Output
ΔV
FBOV
ΔV
FB,HYST
V
PGOOD
PGOOD Upper Threshold
PGOOD Lower Threshold
PGOOD Hysterisis
PGOOD Low Voltage
BG Driver Peak Source Current
BG Driver Pull-Down R
DS(ON)
TG Driver Peak Source Current
TG Driver Pull-Down R
DS(ON)
On-Time
Minimum On-Time
Minimum Off-Time
1.55
515
2.15
695
100
350
3
LTC3812-5
The
l
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, INTV
CC
= V
BOOST
= V
RNG
= V
EXTVCC
= V
NDRV
= 5V, V
FCB
= V
SW
= 0V,
unless otherwise specified.
SYMBOL
I
PGOOD
PG Delay
V
CC
Regulators
V
EXTVCC
EXTV
CC
Switchover Voltage
EXTV
CC
Rising
EXTV
CC
Hysterisis
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
Trickle Charger Shunt Regulator
Trickle Charger Shunt Regulator,
INTV
CC
≤ 16.7V (Note 8)
10
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
20
210
5.2
l
ELECTRICAL CHARACTERISTICS
PARAMETER
PGOOD Leakage Current
PGOOD Delay
CONDITIONS
V
PGOOD
= 5V
V
FB
Falling
MIN
TYP
0
120
MAX
2
UNITS
μA
μs
4.5
0.1
5.2
4.7
0.25
5.5
75
0.01
5.5
0.01
40
270
15
0.4
5.8
150
5.8
60
350
V
V
V
mV
%
V
%
μA
μA
V
mA
V
INTVCC,1
ΔV
EXTVCC,1
ΔV
LOADREG,1
V
INTVCC,2
ΔV
LOADREG,2
I
NDRV
I
NDRVTO
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 LTC3812E-5 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 LTC3812I-5 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:
LTC3812-5: T
J
= T
A
+ (P
D
• 38°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 LTC3812-5 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
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
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