flyback controller optimized for driving N-channel MOSFETs
in high input voltage applications. The LTC3803-5 operates
from inputs as low as 5V. Constant frequency operation
is maintained down to very light loads, resulting in less
low frequency noise generation over a wide range of load
currents. Slope compensation can be programmed with
an external resistor.
The LTC3803-5 provides ±1.5% output voltage accuracy
and consumes only 240μA of quiescent current. Ground-
referenced current sensing allows LTC3803-5-based con-
verters to accept input supplies beyond the LTC3803-5’s
absolute maximum V
CC
. For simplicity, the LTC3803-5 can
be powered from a high V
IN
through a resistor, due to its
internal shunt regulator. An internal undervoltage lockout
shuts down the IC when the input voltage is too low to
provide sufficient gate drive to the external MOSFET.
The LTC3803-5 is available in a low profile (1mm) 6-lead
SOT-23 (ThinSOT™) package.
V
IN
and V
OUT
Limited Only by External Components
4.8V Undervoltage Lockout Threshold
Operating Junction Temperature from –55°C to
150°C
Adjustable Slope Compensation
Internal Soft-Start
Constant Frequency 200kHz Operation
±1.5% Reference Accuracy
Current Mode Operation for Excellent Line and Load
Transient Response
No Minimum Load Requirement
Low Quiescent Current: 240μA
Low Profile (1mm) SOT-23 Package
APPLICATIONS
n
n
n
n
42V and 12V Automotive Power Supplies
Telecom Power Supplies
Auxiliary/Housekeeping Power Supplies
Power Over Ethernet
L,
LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and ThinSOT and No R
SENSE
are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
TYPICAL APPLICATION
Dual Output Wide Input Range Converter
V
IN
6V TO 50V
PDZ6.8B
22k
VPH5-0155
1μF
100V
×3
MMBTA42
10nF
LTC3803-5
I
TH
/RUN NGATE
GND
8.06k
V
FB
V
CC
SENSE
0.1μF
57.6k
ALL CAPACITORS ARE X7R, TDK
38035 TA01
Efficiency and Power Loss
vs Output Power
13V/0.3A
20mA MIN
LOAD
22μF
10V
90
85 V
IN
= 12V
EFFICIENCY (%)
80
V
IN
= 24V
75
70
V
IN
= 48V
65
60
V
IN
= 12V
0
2
6
8
4
OUTPUT POWER (W)
10
0.5
0
12
1.5
1.0
V
IN
= 8V
3.0
2.5
POWER LOSS (W)
2.0
10MQ100N
7.5k
PHM25NQ10T
1μF
100V
1μF
100V
4.7k
B3100
0.012Ω
6.5V/1.2A
47μF
10V
38035 TA01b
38035fd
1
LTC3803-5
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
I
TH
/RUN 1
GND 2
V
FB
3
6 NGATE
5 V
CC
4 SENSE
V
CC
to GND (Current Fed) ..................... 25mA into V
CC
*
NGATE Voltage .......................................... – 0.3V to V
CC
V
FB
, I
TH
/RUN Voltages............................... –0.3V to 3.5V
SENSE Voltage ............................................ –0.3V to 1V
NGATE Peak Output Current (<10μs) ......................... 1A
Operating Junction Temperature Range (Notes 2, 3)
LTC3803E-5 .......................................– 40°C to 125°C
LTC3803I-5 ........................................– 40°C to 125°C
LTC3803H-5 (Note 3) ......................... –40°C to 150°C
LTC3803MP-5 (Note 3) ...................... –55°C to 150°C
Storage Temperature Range...................– 65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
*LTC3803-5 internal clamp circuit self regulates V
CC
voltage to 8.1V.
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
T
JMAX
= 150°C,
θ
JA
= 192°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC3803ES6-5#PBF
LTC3803IS6-5#PBF
LTC3803HS6-5#PBF
LTC3803MPS6-5#PBF
LEAD BASED FINISH
LTC3803ES6-5
LTC3803IS6-5
LTC3803HS6-5
LTC3803MPS6-5
TAPE AND REEL
LTC3803ES6-5#TRPBF
LTC3803IS6-5#TRPBF
LTC3803HS6-5#TRPBF
LTC3803MPS6-5#TRPBF
TAPE AND REEL
LTC3803ES6-5#TR
LTC3803IS6-5#TR
LTC3803HS6-5#TR
LTC3803MPS6-5#TR
PART MARKING*
LTBPF
LTBMH
LTBMH
LTBMH
PART MARKING*
LTBPF
LTBMH
LTBMH
LTBMH
PACKAGE DESCRIPTION
6-Lead Low Profile (1mm) SOT-23
6-Lead Low Profile (1mm) SOT-23
6-Lead Low Profile (1mm) SOT-23
6-Lead Low Profile (1mm) SOT-23
PACKAGE DESCRIPTION
6-Lead Low Profile (1mm) SOT-23
6-Lead Low Profile (1mm) SOT-23
6-Lead Low Profile (1mm) SOT-23
6-Lead Low Profile (1mm) SOT-23
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°C
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°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/
ELECTRICAL CHARACTERISTICS
SYMBOL
V
TURNON
V
TURNOFF
V
HYST
V
CLAMP1mA
PARAMETER
V
CC
Turn On Voltage
V
CC
Turn Off Voltage
V
CC
Hysteresis
V
CC
Shunt Regulator Voltage at 1mA
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V, unless otherwise noted. (Notes 2, 3)
CONDITIONS
LTC3803E-5
LTC3803I-5, LTC3803H-5, LTC3803MP-5
LTC3803E-5
LTC3803I-5, LTC3803H-5, LTC3803MP-5
V
TURNON
– V
TURNOFF
I
CC
= 1mA, V
ITH/RUN
= 0V
LTC3803E-5
LTC3803I-5, LTC3803H-5
LTC3803MP-5
l
l
l
l
l
l
l
l
MIN
4
3.9
3.3
3.2
0.05
6.2
6.2
5.9
TYP
4.8
4.8
4
4
0.8
8
8
8
MAX
5.7
5.7
4.9
4.9
UNITS
V
V
V
V
V
9.9
10.4
10.4
V
V
V
38035fd
2
LTC3803-5
ELECTRICAL CHARACTERISTICS
SYMBOL
V
CLAMP25mA
PARAMETER
V
CC
Shunt Regulator Voltage at 25mA
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V, unless otherwise noted. (Notes 2, 3)
CONDITIONS
I
CC
= 25mA, V
ITH/RUN
= 0V
LTC3803E-5
LTC3803I-5, LTC3803H-5
LTC3803MP-5
(Note 4)
V
ITH/RUN
= 1.3V
V
CC
= V
TURNON
– 100mV
LTC3803E-5
LTC3803I-5, LTC3803H-5, LTC3803MP-5
V
CC
> V
TURNON
, V
ITH/RUN
Falling
LTC3803E-5
LTC3803I-5, LTC3803H-5
LTC3803MP-5
V
ITH/RUN
= 0V
LTC3803E-5
LTC3803I-5, LTC3803H-5, LTC3803MP-5
(Note 5)
LTC3803E-5:
0°C ≤ T
J
≤ 85°C
–40°C ≤ T
J
≤ 85°C
LTC3803I-5:
0°C ≤ T
J
≤ 85°C
–40°C ≤ T
J
≤ 125°C
LTC3803H-5:
0°C ≤ T
J
≤ 85°C
–40°C ≤ T
J
≤ 150°C
LTC3803MP-5:
0°C ≤ T
J
≤ 85°C
–55°C ≤ T
J
≤ 150°C
I
TH/RUN
Pin Load = ±5μA (Note 5)
(Note 5)
I
TH/RUN
Sinking 5μA (Note 5)
I
TH/RUN
Sourcing 5μA (Note 5)
(Note 5)
V
ITH/RUN
= 1.3V
V
ITH/RUN
= 1.3V, V
FB
= 0.8V
V
ITH/RUN
= 1.3V, V
FB
= 0.8V
C
LOAD
= 3000pF
C
LOAD
= 3000pF (Note 7)
R
SL
= 0 (Note 6)
LTC3803E-5
LTC3803I-5, LTC3803H-5
LTC3803MP-5
(Note 7)
l
l
l
l
l
l
l
l
l
l
l
l
l
MIN
6.3
6.3
6
TYP
8.1
8.1
8.1
240
40
40
MAX
10.3
10.7
10.7
350
90
100
0.45
0.45
0.47
0.8
1
UNITS
V
V
V
μA
μA
μA
V
V
V
μA
μA
I
CC
I
CC,(UV)
Input DC Supply Current in
Normal Operation
Input DC Supply Current in
Undervoltage
Shutdown Threshold (at I
TH
/RUN)
V
ITHSHDN
0.12
0.08
0.08
0.07
0.07
0.28
0.28
0.28
0.34
0.34
I
ITHSTART
Start-Up Current Source
V
FB
Regulated Feedback Voltage
l
l
l
l
0.788
0.780
0.788
0.780
0.788
0.780
0.788
0.780
200
0.800
0.800
0.800
0.800
0.800
0.800
0.800
0.800
333
0.1
3
3
10
0.812
0.816
0.812
0.820
0.812
0.820
0.812
0.820
500
V
V
V
V
V
V
V
V
μA/V
mV/V
mV/μA
mV/μA
g
m
ΔV
O(LINE)
ΔV
O(LOAD)
I
FB
f
OSC
DC
ON(MIN)
DC
ON(MAX)
t
RISE
t
FALL
V
IMAX
Error Amplifier Transconductance
Output Voltage Line Regulation
Output Voltage Load Regulation
V
FB
Input Current
Oscillator Frequency
Minimum Switch On Duty Cycle
Maximum Switch On Duty Cycle
Gate Drive Rise Time
Gate Drive Fall Time
Peak Current Sense Voltage
50
230
8.5
90
nA
kHz
%
%
ns
ns
170
70
200
6.5
80
40
40
90
85
85
100
100
100
5
0.7
115
115
120
mV
mV
mV
μA
ms
I
SLMAX
t
SFST
Peak Slope Compensation Output
Current
Soft-Start Time
38035fd
3
LTC3803-5
ELECTRICAL CHARACTERISTICS
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 LTC3803-5 is tested under pulsed load conditions such
that T
J
≈ T
A
. The LTC3803E-5 is guaranteed to meet specifications
from 0°C to 85°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTC3803I-5 is guaranteed over the –40°C to 125°C operating junction
temperature range, the LTC3803H-5 is guaranteed over the –40°C to
150°C operating junction temperature range and the LTC3803MP-5 is
tested and guaranteed over the full –55°C to 150°C operating junction
temperature range. Note that the maximum ambient temperature
consistent with these specifications is determined by specific operating
conditions in conjunction with board layout, the rated package thermal
impedance and other environmental factors.
Junction temperature (T
J
) is calculated from the ambient temperature T
A
and the power dissipation P
D
in the LTC3803-5 using the formula:
T
J
= T
A
+ (P
D
• 230°C/W)
Note 3:
High junction temperatures degrade operating lifetimes; operating
lifetime is derated for junction temperatures greater than 125°C.
Note 4:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 5:
The LTC3803-5 is tested in a feedback loop that servos V
FB
to the
output of the error amplifier while maintaining I
TH
/RUN at the midpoint of
the current limit range.
Note 6:
Peak current sense voltage is reduced dependent on duty cycle
and an optional external resistor in series with the SENSE pin (R
SL
). For
details, refer to the programmable slope compensation feature in the
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