LT3512E, LT3512I .............................. –40°C to 125°C
LT3512H ............................................ –40°C to 150°C
LT3512MP.......................................... –55°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
MS PACKAGE
16(12)-LEAD PLASTIC MSOP
θ
JA
= 90°C/W
orDer inForMaTion
LEAD FREE FINISH
LT3512EMS#PBF
LT3512IMS#PBF
LT3512HMS#PBF
LT3512MPMS#PBF
TAPE AND REEL
LT3512EMS#TRPBF
LT3512IMS#TRPBF
LT3512HMS#TRPBF
LT3512MPMS#TRPBF
PART MARKING*
3512
3512
3512
3512
PACKAGE DESCRIPTION
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
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
PARAMETER
Input Voltage Range
Quiescent Current
EN/UVLO Pin Threshold
EN/UVLO Pin Current
Maximum Switching Frequency
Minimum Switching Frequency
Maximum Current Limit
Minimum Current Limit
Switch V
CESAT
R
REF
Voltage
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 24V unless otherwise noted.
CONDITIONS
l
MIN
6
4.5
TYP
MAX
100
15
UNITS
V
V
mA
μA
V
μA
μA
kHz
kHz
V
IN
= BIAS
Not Switching
V
EN/UVLO
= 0.2V
EN/UVLO Pin Voltage Rising
V
EN/UVLO
=1.1V
V
EN/UVLO
=1.4V
l
3.5
0
1.15
2.0
1.21
2.6
0
650
40
420
80
600
120
0.5
l
4.5
1.27
3.3
800
150
1.215
1.23
0.03
400
mA
mA
V
V
V
%/V
nA
V/V
μmhos
3512fb
I
SW
= 200mA
1.18
1.17
1.20
0.01
R
REF
Voltage Line Regulation
R
REF
Pin Bias Current
Error Amplifier Voltage Gain
Error Amplifier Transconductance
6V < V
IN
< 100V
(Note 3)
∆I
= 2µA
l
80
150
140
2
LT3512
elecTrical characTerisTics
PARAMETER
T
C
Current into R
REF
BIAS Pin Voltage
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 24V unless otherwise noted.
CONDITIONS
R
TC
= 53.6k
Internally Regulated
3
MIN
TYP
9.5
3.1
3.2
MAX
UNITS
μA
V
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 LT3512E is guaranteed to meet performance specifications
from 0°C to 125°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
LT3512I is guaranteed to meet performance specifications from –40°C to
125°C operating junction temperature range. The LT3512H is guaranteed
to meet performance specifications from –40°C to 150°C operating
junction temperature range. The LT3511MP is guaranteed over the full
–55°C to 150°C operating junction range. High junction temperatures
degrade operating lifetimes. Operating lifetime is derated at junction
temperatures greater than 125°C.
Note 3:
Current flows out of the R
REF
pin.
Note 4:
The SW pin is rated to 150V for transients. Operating waveforms
of the SW pin should keep the pedestal of the flyback waveform below
100V as shown in Figure 5.
Typical perForMance characTerisTics
Output Voltage
5.25
5.20
5.15
5.10
V
OUT
(V)
5.00
4.95
4.90
4.85
4.80
4.75
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3512 G01
T
A
= 25°C, unless otherwise noted.
BIAS Pin Voltage
4.0
Quiescent Current
8
V
IN
= 48V
6
BIAS VOLTAGE (V)
V
IN
= 24V
V
IN
= 48V
V
IN
= 100V
0
25 50 75 100 125 150
TEMPERATURE (°C)
3512 G02
3.5
I
Q
(mA)
5.05
4
3.0
2
2.5
V
IN
= 24V, 10mA
V
IN
= 24V, NO LOAD
0
25 50 75 100 125 150
TEMPERATURE (°C)
3512 G03
0
–50 –25
2.0
–50 –25
Switch V
CESAT
2000
SWITCH V
CESAT
VOLTAGE (mV)
800
700
1600
CURRENT LIMIT (mA)
600
500
400
300
200
100
0
0
300
100
200
400
SWITCH CURRENT (mA)
500
3512 G04
Switch Current Limit
5
MAXIMUM CURRENT LIMIT
4
Quiescent Current vs V
IN
800
I
Q
(mA)
MINIMUM CURRENT LIMIT
0
25 50 75 100 125 150
TEMPERATURE (°C)
3512 G05
1200
3
2
400
1
0
–50 –25
0
0
20
60
40
VOLTAGE (V)
80
100
3512 G06
3512fb
3
LT3512
Typical perForMance characTerisTics
EN/UVLO Pin (Hysteresis) Current
vs Temperature
5
EN/UVLO = 1.2V
EN/UVLO PIN CURRENT (µA)
30
25
EN/UVLO THRESHOLD (V)
20
15
10
5
0
T
A
= 25°C, unless otherwise noted.
EN/UVLO Threshold
vs Temperature
3.0
2.5
2.0
1.5
1.0
0.5
0
–50 –25
EN/UVLO Pin Current
vs V
EN/UVLO
EN/UVLO PIN CURRENT (µA)
4
3
2
1
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3512 G07
1
20
60
80
V
EN/UVLO
VOLTAGE (V)
40
100
3512 G08
0
25 50 75 100 125 150
TEMPERATURE (°C)
3512 G09
Maximum Frequency
vs Temperature
1000
900
MAXIMUM FREQUENCY (kHz)
MINIMUM FREQUENCY (kHz)
800
700
600
500
400
300
200
100
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3512 G10
Minimum Frequency
vs Temperature
100
90
EN/UVLO THRESHOLD (V)
80
70
60
40
40
30
20
10
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3512 G11
EN/UVLO Shutdown Threshold
vs Temperature
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3512 G14
Boundary Mode Waveform
Light Load Discontinuous
Mode Waveform
20V/DIV
20V/DIV
2µs/DIV
3512 G12
2µs/DIV
3512 G13
3512fb
4
LT3512
pin FuncTions
EN/UVLO (Pin 1):
Enable/Undervoltage Lockout. The EN/
UVLO pin is used to start up the LT3512. Pull the pin to 0V
to shut down the LT3512. This pin has an accurate 1.21V
threshold and can be used to program an undervoltage
lockout (UVLO) threshold using a resistor divider from
supply to ground. A 2.6μA pin current hysteresis allows
the programming of undervoltage lockout (UVLO) hys-
teresis. EN/UVLO can be directly connected to V
IN
. If left
open circuit the part will not power up.
V
IN
(Pin 3):
Input Supply Pin. This pin supplies current to
the internal start-up circuitry, and serves as a reference
voltage for the DCM comparator and feedback circuitry.
Must be locally bypassed with a capacitor.
GND (Pin 5, 8, 9):
Ground Pins. All three pins should be
tied directly to the local ground plane.
BIAS (Pin 6):
Bias Voltage. This pin supplies current to
the switch driver and internal circuitry of the LT3512.
This pin may also be connected to V
IN
if a third winding
is not used and if V
IN
< 20V. The part can operate down
to 4.5V when BIAS and V
IN
are connected together. If a
third winding is used, the BIAS voltage should be lower
than the input voltage and greater than 3.3V for proper
operation. BIAS must be bypassed with a 4.7µF capacitor
placed close to the pin.
VC (Pin 10):
Compensation Pin for Internal Error Amplifier.
Connect a series RC from this pin to ground to compensate
the switching regulator. An additional 100pF capacitor from
this pin to ground helps eliminate noise.
T
C
(Pin 11):
Output Voltage Temperature Compensa-
tion. Connect a resistor to ground to produce a current
proportional to absolute temperature to be sourced into
the R
REF
node.
I
TC
= 0.55V/R
TC
.
R
REF
(Pin 12):
Input Pin for External Ground-Referred
Reference Resistor. The resistor at this pin should be 10k.
For nonisolated applications, a traditional resistor voltage
divider from V
OUT
may be connected to this pin.
R
FB
(Pin 14):
Input Pin for External Feedback Resistor.
This pin is connected to the transformer primary (V
SW
).
The ratio of this resistor to the R
REF
resistor, times the
internal bandgap reference, determines the output volt-
age (plus the effect of any non-unity transformer turns
ratio). For nonisolated applications, this pin should be
connected to V
IN
.
SW (Pin 16):
Switch Pin. Collector of the internal power
switch. Minimize trace area at this pin to minimize EMI
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