FEATURES
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LT3055 Series
500mA, Linear Regulator
with Precision Current Limit
and Diagnostics
DESCRIPTION
The
LT
®
3055
series are micropower, low noise, low dropout
voltage (LDO) linear regulators. The devices supply 500mA
of output current with a dropout voltage of 350mV. A 10nF
bypass capacitor reduces output noise to 25μV
RMS
in a
10Hz to 100kHz bandwidth and soft starts the reference.
The LT3055’s ±45V input voltage rating combined with its
precision current limit and diagnostic functions make the
IC an ideal choice for robust, high reliability applications.
A single resistor programs the LT3055’s current limit, ac-
curate to ±10% over a wide input voltage and temperature
range. Another resistor programs the LT3055’s minimum
output current monitor, useful for detecting open-circuit
conditions. The current monitor function sources a current
equal to 1/500th of output current. Logic fault pins assert
low if the LT3055 is in current limit (FAULT2), operating
below its minimum output current (FAULT1) or is in thermal
limit (both
FAULT1
and
FAULT2).
PWRGD indicates output
regulation. The TEMP pin indicates average die temperature.
The LT3055 optimizes stability and transient response
with low ESR ceramic capacitors, requiring a minimum of
3.3μF Internal protection circuitry includes current limit-
.
ing, thermal limiting, reverse battery protection, reverse
current protection and reverse output protection.
The LT3055 is available in fixed output voltages of 3.3V
and 5V, and as an adjustable device with an output voltage
range from 0.6V to 40V.
Precision Current Limit, R
IMAX
= 604Ω
550
CURRENT LIMIT FAULT THRESHOLD (mA)
540
530
520
510
500
490
480
470
460
450
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3055 TA01b
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Output Current: 500mA
Dropout Voltage: 350mV
Input Voltage Range: 1.6V to 45V
Programmable Precision Current Limit: ±10%
Output Current Monitor: 1/500th of I
OUT
Programmable Minimum I
OUT
Monitor
Temperature Monitor: 10mV/°C
FAULT Indicator: Current Limit, Thermal Limit or
Minimum I
OUT
Low Noise: 25μV
RMS
(10Hz to 100kHz)
Adjustable Output (V
REF
= V
OUT(MIN)
= 0.6V)
Output Tolerance: ±2% Over Load, Line and Temperature
Stable with Low ESR, Ceramic Output Capacitors
(3.3μF Minimum)
Shutdown Current: <1μA
Reverse Battery and Thermal Limit Protection
16-Lead 4mm
×
3mm DFN and MSOP Packages
APPLICATIONS
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Protected Antenna Supplies
Automotive Telematics
Industrial Applications (Trucks, Forklifts, etc.)
High Reliability Applications
Noise-Sensitive RF or DSP Supplies
All registered trademarks and trademarks are the property of their respective owners.
TYPICAL APPLICATION
5V Supply with 497mA Precision Current Limit, 10mA I
MIN
V
IN
6V
V
OUT(NOMINAL)
= 5V
+
10µF
200k
200k
200k
IN
LT3055-5
OUT
SENSE
ADJ
I
MON
10nF
10µF
5V
SHDN
FAULT1
FAULT2
PWRGD
I
MAX
V
IN
= 7V
V
IN
= 5.6V
22nF
604
(THRESHOLD = 497mA)
1k
(ADC
FULL-SCALE = 1V)
0.1µF
TO
µP
ADC
TO
µP
ADC
0.1µF
120k
(THRESHOLD = 10mA)
TEMP
I
MIN
REF/BYP
GND
10nF
3055 TA01a
Rev. B
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1
LT3055 Series
ABSOLUTE MAXIMUM RATINGS
(Note 1)
IN Pin Voltage .........................................................±50V
OUT Pin Voltage ........................................... +40V, –50V
Input-to-Output Differential Voltage ..............+50V, –40V
ADJ Pin Voltage ......................................................±50V
SENSE Pin Voltage ..................................................±50V
SHDN Pin Voltage ...................................................±50V
FAULT1, FAULT2,
PWRGD Pin Voltage ............–0.3V, 50V
I
MON
Pin Voltage ..............................................–0.3V, 7V
I
MIN
Pin Voltage ...............................................–0.3V, 7V
I
MAX
Pin Voltage ..............................................–0.3V, 7V
TEMP Pin Voltage ............................................–0.3V, 7V
REF/BYP Pin Voltage...................................................1V
Output Short-Circuit Duration .......................... Indefinite
Operating Junction Temperature Range (Notes 2, 3)
E-, I-Grades ....................................... –40°C to 125°C
MP-Grade .......................................... –55°C to 150°C
H-Grade ............................................. –40°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature: (Soldering, 10 sec)
MSOP Package Only ......................................... 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
IN
IN
SHDN
FAULT1
FAULT2
PWRGD
TEMP
I
MON
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
OUT
OUT
ADJ/SENSE**
GND/ADJ*
GND
REF/BYP
I
MAX
I
MIN
IN
IN
SHDN
FAULT1
FAULT2
PWRGD
TEMP
I
MON
1
2
3
4
5
6
7
8
17
GND
16 OUT
15 OUT
14 ADJ/SENSE**
13 GND/ADJ*
12 GND
11 REF/BYP
10 I
MAX
9 I
MIN
17
GND
MSE PACKAGE
16-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 37°C/W,
θ
JC
= 5°C/W TO 10°C/W
T
JMAX
= 150°C FOR H-GRADE
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
*PIN 13 IS GND FOR LT3055; PIN 13 IS ADJ FOR LT3055-3.3 AND LT3055-5.
**PIN 14 IS ADJ FOR LT3055; PIN 14 IS SENSE FOR LT3055-3.3 AND LT3055-5.
DE PACKAGE
16-LEAD (4mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 38°C/W,
θ
JC
= 4.3°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
Rev. B
2
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LT3055 Series
ELECTRICAL CHARACTERISTICS
PARAMETER
FAULT,
PWRGD Pins Logic Low Voltage
FAULT,
PWRGD Pins Leakage Current
I
MIN
Threshold Accuracy (Notes 6, 9)
PWRGD Trip Point
PWRGD Trip Point Hysteresis
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
CONDITIONS
Pull-Up Current = 50μA
V
FAULT1
, V
FAULT2
, V
PWRGD
= 5V
5.6V < V
IN
< 15V, V
OUT
= 5V, R
IMIN
= 1.2M
5.6V < V
IN
< 15V, V
OUT
= 5V, R
IMIN
= 120K
% of Nominal Output Voltage, Output Rising
% of Nominal Output Voltage
l
l
l
l
l
MIN
TYP
0.14
0.01
MAX
0.25
1
1.1
11
94
550
UNITS
V
μA
mA
mA
%
%
mA/mA
V
V
0.9
9
86
450
1
10
90
1
500
0.25
1.25
Current Monitor Ratio (Notes 6,10), Ratio = I
OUT
/I
MON
I
LOAD
= 10mA, 250mA, 500mA
TEMP Voltage (Note 16)
T
J
= 25°C
T
J
= 125°C
TEMP Error (Note 16)
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. Absolute maximum input-to-output differential
voltage is not achievable with all combinations of rated IN pin and OUT pin
voltages. With the IN pin at 50V, the OUT pin may not be pulled below 0V.
The total differential voltage from IN to OUT must not exceed +50V, –40V.
If OUT is pulled above GND and IN, the total differential voltage from OUT
to IN must not exceed 40V.
Note 2:
The LT3055 is tested and specified under pulse load conditions
such that T
J
~ T
A
. The LT3055E is 100% production tested at T
A
= 25°C
and performance is guaranteed from 0°C to 125°C. Performance at –40°C
and 125°C is assured by design, characterization and correlation with
statistical process controls. The LT3055I is guaranteed over the full –40°C
to 125°C operating junction temperature range. The LT3055MP is 100%
tested over the –55°C to 150°C operating junction temperature range. The
LT3055H is 100% tested at 150°C operating junction temperature.
Note 3:
The LT3055 adjustable version is tested and specified for these
conditions with ADJ pin connected to the OUT pin.
Note 4:
Maximum junction temperature limits operating conditions.
Regulated output voltage specifications do not apply for all possible
combinations of input voltage and output current. If operating at the
maximum input voltage, limit the output current range. If operating at
the maximum output current, limit the input voltage range. Current limit
foldback limits the maximum output current as a function of input-to-
output voltage. See Current Limit vs V
IN
-V
OUT
in the Typical Performance
Characteristics section.
Note 5:
Dropout voltage is the minimum differential IN-to-OUT voltage
needed to maintain regulation at a specified output current. In dropout,
the output voltage equals (V
IN
– V
DROPOUT
). For some output voltages,
minimum input voltage requirements limit dropout voltage.
Note 6:
To satisfy minimum input voltage requirements, the LT3055
adjustable version is tested and specified for these conditions with an
external resistor divider (60k bottom, 440k top) which sets V
OUT
to 5V. The
external resistor divider adds 10μA of DC load on the output. This external
current is not factored into GND pin current.
Note 7:
GND pin current is tested with V
IN
= V
OUT(NOMINAL)
+ 0.6V and a
current source load. GND pin current increases in dropout. For the fixed
output voltage versions, an internal resistor divider adds about 10µA to
GND pin current. See GND pin current curves in the Typical Performance
Characteristics section.
l
–0.08
0.08
V
Note 8:
Current limit varies inversely with the external resistor value tied
from the I
MAX
pin to GND. For detailed information on how to set the I
MAX
pin resistor value, please see the Operation section. If a programmed
current limit is not needed, tie the I
MAX
pin to GND and internal protection
circuitry implements short-circuit protection as specified.
Note 9:
The I
MIN
fault condition asserts if the output current falls below the
I
MIN
threshold defined by an external resistor from the I
MIN
pin to GND.
For detailed information on how to set the I
MIN
pin resistor value, please
see the Operation section. If the I
MIN
fault condition is not needed, the I
MIN
pin must be left floating (unconnected).
Note 10:
Current monitor ratio is tested with the I
MON
pin fixed at
V
OUT
– 0.5V and with the input range limited to V
OUT
+ 0.6V < V
IN
< V
OUT
+ 10V for I
OUT
= 10mA; V
OUT
+ 0.6V < V
IN
< V
OUT
+ 4V for I
OUT
= 250mA,
and V
OUT
+ 0.6V < V
IN
< V
OUT
+ 2V for I
OUT
= 500mA. Input voltage range
conditions are set to limit power dissipation in the IC to 1W maximum for
test purposes. The current monitor ratio varies slightly when in current
limit or when the I
MON
voltage exceeds V
OUT
– 0.5V. Please see the
Operation section for more information. If the current monitor function is
not needed, tie the IMON pin to GND.
Note 11:
To satisfy requirements for minimum input voltage, current limit
is tested at V
IN
= V
OUT(NOMINAL)
+ 1V or V
IN
= 2.2V, whichever is greater.
Note 12:
ADJ pin bias current flows out of the ADJ pin.
Note 13:
SHDN
pin current flows into the
SHDN
pin.
Note 14:
Reverse output current is tested with the IN pin grounded and the
OUT pin forced to the specified voltage. This current flows into the OUT
pin and out of the GND pin.
Note 15:
500mA of output current does not apply to the full range of input
voltage due to the internal current limit foldback.
Note 16:
The TEMP output voltage represents the average temperature of
the die while dissipating quiescent power. Due to the pass device power
dissipation and temperature gradients across the die, the TEMP output
voltage measurement does not guarantee that absolute maximum junction
temperature is not exceeded.
Note 17:
Minimum Input Voltage is the input voltage at which the output
voltage is decreased 1% from nominal. At elevated temperatures, an input
voltage greater than this is necessary for correct operation of the TEMP
pin. See Temp Pin Minimum Input Voltage in the Typical Performance
Characteristics section.
Rev. B
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