LT3012BEDE [Linear]
250mA, 4V to 80V Low Dropout Micropower Linear Regulator; 250毫安， 4V至80V低压差微功耗线性稳压器
| 型号： | LT3012BEDE |
| 厂家： | 
Linear |
| 描述： | 250mA, 4V to 80V Low Dropout Micropower Linear Regulator |
| 文件： | 总16页 (文件大小：207K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT3012B
250mA, 4V to 80V
Low Dropout
Micropower Linear Regulator
U
FEATURES
DESCRIPTIO
The LT®3012B is a high voltage, micropower low dropout
linearregulator.Thedeviceiscapableofsupplying250mA
of output current with a dropout voltage of 400mV. De-
signed for use in battery-powered or high voltage sys-
tems, the low quiescent current (40µA operating) makes
theLT3012Banidealchoice.Quiescentcurrentisalsowell
controlled in dropout.
■
Wide Input Voltage Range: 4V to 80V
■
Low Quiescent Current: 40µA
■
Low Dropout Voltage: 400mV
■
Output Current: 250mA
■
No Protection Diodes Needed
■
Adjustable Output from 1.24V to 60V
■
Stable with 3.3µF Output Capacitor
■
Stable with Aluminum, Tantalum or Ceramic
Other features of the LT3012B include the ability to oper-
ate with very small output capacitors. The regulators are
stable with only 3.3µF on the output while most older
devices require between 10µF and 100µF for stability.
Smallceramiccapacitorscanbeusedwithoutanyneedfor
series resistance (ESR) as is common with other regula-
tors. Internal protection circuitry includes reverse-battery
protection, current limiting, thermal limiting and reverse
current protection.
Capacitors
Reverse-Battery Protection
■
■
No Reverse Current Flow from Output to Input
■
Thermal Limiting
■
Thermally Enhanced 16-Lead TSSOP and 12-Pin
(4mm × 3mm) DFN Packages
U
APPLICATIO S
■
Low Current High Voltage Regulators
The device is available with an adjustable output with a
1.24V reference voltage. The LT3012B regulator is avail-
ableinthe16-leadTSSOPand12pinlowprofile(0.75mm)
(4mm × 3mm) DFN packages with an exposed pad for
enhanced thermal handling capability.
■
Regulator for Battery-Powered Systems
■
Telecom Applications
Automotive Applications
■
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
U
TYPICAL APPLICATIO
Dropout Voltage
400
350
300
250
200
150
100
50
5V Supply
V
OUT
IN
OUT
LT3012B
ADJ
5V
250mA
V
IN
750k
249k
5.4V TO
80V
3.3µF
1µF
GND
3012B TA01
0
50
100
150
250
0
200
OUTPUT CURRENT (mA)
3012B TA02
3012bf
1
LT3012B
W W U W
ABSOLUTE AXI U RATI GS (Note 1)
IN Pin Voltage................................................... ±80V
OUT Pin Voltage ............................................... ±60V
IN to OUT Differential Voltage........................... ±80V
ADJ Pin Voltage .................................................. ±7V
Output Short-Circuit Duration..................... Indefinite
Storage Temperature Range
TSSOP Package ........................... –65°C to 150°C
DFN Package ............................... –65°C to 125°C
Operating Junction Temperature Range
(Notes 3, 9, 10) ........................... –40°C to 125°C
Lead Temperature (Soldering, 10 sec)............ 300°C
U W
U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
TOP VIEW
GND
NC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
GND
NC
IN
NC
OUT
OUT
ADJ
GND
NC
1
2
3
4
5
6
12 NC
11 IN
10 IN
OUT
OUT
ADJ
GND
NC
IN
13
17
9
8
7
NC
NC
NC
NC
NC
NC
GND
GND
DE PACKAGE
12-LEAD (4mm × 3mm) PLASTIC DFN
FE PACKAGE
16-LEAD PLASTIC TSSOP
TJMAX = 125°C, θJA = 40°C/ W, θJC = 16°C/ W
TJMAX = 125°C, θJA = 40°C/ W, θJC = 16°C/ W
EXPOSED PAD (PIN 13) IS GND
MUST BE SOLDERED TO PCB
EXPOSED PAD (PIN 17) IS GND
MUST BE SOLDERED TO PCB
ORDER PART NUMBER
DE PART MARKING
3012B
ORDER PART NUMBER
LT3012BEFE
FE PART MARKING
3012BEFE
LT3012BEDE
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T = 25°C.
J
PARAMETER
CONDITIONS
= 250mA
MIN
TYP
MAX
UNITS
Minimum Input Voltage
ADJ Pin Voltage (Notes 2, 3)
I
●
4
4.5
V
LOAD
V
= 4V, I
= 1mA
1.225
1.2
1.24
1.24
1.255
1.28
V
V
IN
LOAD
4.5V < V < 80V, 1mA < I
< 250mA
●
●
IN
LOAD
Line Regulation
∆V = 4V to 80V, I
IN
= 1mA (Note 2)
0.1
7
5
mV
LOAD
Load Regulation (Note 2)
V
V
= 4.5V, ∆I
= 4.5V, ∆I
= 1mA to 250mA
= 1mA to 250mA
12
25
mV
mV
IN
IN
LOAD
LOAD
●
3012bf
2
LT3012B
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T = 25°C.
J
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Dropout Voltage
I
I
= 10mA
= 10mA
160
230
300
mV
mV
LOAD
LOAD
V
= V
●
●
IN
OUT(NOMINAL)
(Notes 4, 5)
I
I
= 50mA
= 50mA
250
400
340
420
mV
mV
LOAD
LOAD
I
I
= 250mA
= 250mA
490
620
mV
mV
LOAD
LOAD
●
●
GND Pin Current
I
I
I
= 0mA
= 100mA
= 250mA
40
3
10
100
µA
mA
mA
LOAD
LOAD
LOAD
V
= 4.5V
IN
(Notes 4, 6)
●
18
Output Voltage Noise
ADJ Pin Bias Current
Ripple Rejection
Current Limit
C
= 10µF, I
= 250mA, BW = 10Hz to 100kHz
100
30
µV
RMS
OUT
LOAD
(Note 7)
100
25
nA
V
= 7V(Avg), V
= 0.5V , f
= 120Hz, I = 250mA
LOAD
65
75
dB
IN
RIPPLE
P-P RIPPLE
V
V
= 7V, V
= 0V
400
mA
mA
IN
IN
OUT
= 4.5V, ∆V
= –0.1V (Note 2)
●
270
OUT
Reverse Output Current (Note 8)
V
= 1.24V, V < 1.24V (Note 2)
12
µA
OUT
IN
Note 6: GND pin current is tested with V = 4.5V and a current source
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.
IN
load. This means the device is tested while operating close to its dropout
region. This is the worst-case GND pin current. The GND pin current will
decrease slightly at higher input voltages.
Note 7: ADJ pin bias current flows into the ADJ pin.
Note 2: The LT3012B is tested and specified for these conditions with the
ADJ pin connected to the OUT pin.
Note 8: Reverse output current is tested with the IN pin grounded and the
OUT pin forced to the rated output voltage. This current flows into the OUT
pin and out the GND pin.
Note 9: The LT3012BE is guaranteed to meet performance specifications
from 0°C to 125°C operating 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.
Note 3: Operating conditions are limited by maximum junction
temperature. The regulated output voltage specification will not apply for
all possible combinations of input voltage and output current. When
operating at maximum input voltage, the output current range must be
limited. When operating at maximum output current, the input voltage
range must be limited.
Note 4: To satisfy requirements for minimum input voltage, the LT3012B
is tested and specified for these conditions with an external resistor divider
(249k bottom, 549k top) for an output voltage of 4V. The external resistor
divider will add a 5µA DC load on the output.
Note 10: 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 5: Dropout voltage is the minimum input to output voltage differential
needed to maintain regulation at a specified output current. In dropout, the
output voltage will be equal to (V – V
).
IN
DROPOUT
3012bf
3
LT3012B
TYPICAL PERFOR A CE CHARACTERISTICS
U W
Typical Dropout Voltage
Guaranteed Dropout Voltage
Dropout Voltage
600
500
400
300
200
100
0
600
500
600
500
400
300
200
100
0
= TEST POINTS
T
J
≤ 125°C
T
= 125°C
J
I
L
= 250mA
I
= 100mA
400
300
L
T
≤ 25°C
J
T
= 25°C
J
I
= 50mA
L
200
100
0
I
I
= 10mA
= 1mA
L
L
0
50
100
150
200
250
–50
0
25
50
75 100 125
–25
0
50
100
150
200
250
OUTPUT CURRENT (mA)
TEMPERATURE (°C)
OUTPUT CURRENT (mA)
301B2 G02
3012B G03
3012B G01
Quiescent Current
ADJ Pin Voltage
Quiescent Current
1.260
80
70
60
50
40
30
20
10
0
V
= 6V
T
R
V
= 25°C
IN
L
I = 1mA
L
J
L
90
R
I
= ∞
=
∞
1.255
1.250
= 0
= 1.24V
L
OUT
70
60
50
1.245
1.240
1.235
1.230
1.225
30
20
10
0
1.220
–25
0
50
75 100 125
–50
25
–25
0
50
75 100 125
1
2
6
7
9
–50
25
0
3
4
5
8
10
TEMPERATURE (°C)
TEMPERATURE (°C)
INPUT VOLTAGE (V)
3012B G04
3012B G05
3012B G06
GND Pin Current
GND Pin Current vs I
LOAD
GND Pin Current
1.2
1.0
0.8
0.6
0.4
0.2
0
10
9
8
7
6
5
4
3
2
1
0
10
9
8
7
6
5
4
3
2
1
0
T
J
= 25°C, *FOR V
OUT
= 1.24V
R
V
T
= 4.5V
T
= 25°C
IN
J
J
= 25°C
*FOR V
= 1.24V
OUT
V
= 1.24V
OUT
R
I
= 49.6Ω
= 25mA*
= 4.96Ω
L
L
L
I
= 250mA*
L
R
L
= 124Ω
= 10mA*
L
I
R
L
= 12.4Ω
= 100mA*
L
I
R
L
I
L
= 1.24k
= 1mA*
R
= 24.8Ω, I = 50mA*
L
L
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
7
8
9
10
0
50
100
150
200
250
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
LOAD CURRENT (mA)
3012B G07
3012B G08
3012B G09
3012bf
4
LT3012B
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Current Limit
Current Limit
ADJ Pin Bias Current
700
600
500
400
300
200
100
0
50
45
40
35
30
25
20
15
10
5
1000
900
800
700
600
500
400
300
200
100
0
V
= 0V
OUT
T
= 25°C
J
T
= 125°C
J
V
V
= 7V
IN
OUT
= 0V
0
–50
–25
0
25
50
75 100 125
–25
0
50
75 100 125
10 20
60 70
–50
25
0
30 40 50
80
TEMPERATURE (°C)
TEMPERATURE (°C)
INPUT VOLTAGE (V)
3012B G15
3012B G13
3012B G14
Reverse Output Current
Input Ripple Rejection
Reverse Output Current
92
88
84
80
76
72
68
64
60
200
180
160
140
120
100
80
35
30
25
20
15
10
5
T
V
V
= 25°C
V
V
= 0V
= V
J
IN
OUT
= 0V
= 1.24V
ADJ
IN
OUT
= V
ADJ
ADJ
CURRENT FLOWS
INTO OUTPUT PIN
PIN CLAMP
(SEE APPLICATIONS
INFORMATION)
60
40
V
L
V
= 4.5V + 0.5V RIPPLE AT f = 120Hz
IN
P-P
I
= 250mA
20
= 1.24V
OUT
0
0
125
0
1
2
3
4
5
6
7
8
9
10
–50
–25
0
25
50
75 100 125
–50
0
25
50
75
100
–25
TEMPERATURE (°C)
OUTPUT VOLTAGE (V)
TEMPERATURE (°C)
3012B G16
3012B G17
3012B G18
Input Ripple Rejection
Minimum Input Voltage
100
90
4.0
V
= 4.5V + 50mV
= 250mA
RIPPLE
RMS
IN
I
= 250mA
LOAD
I
LOAD
3.5
3.0
80
70
2.5
2.0
1.5
1.0
0.5
60
50
C
= 10µF
OUT
40
30
20
10
0
C
= 3.3µF
OUT
0
10
100
1k
10k
100k
1M
–25
0
50
75 100 125
–50
25
FREQUENCY (Hz)
TEMPERATURE (°C)
3012B G19
3012B G20
3012bf
5
LT3012B
TYPICAL PERFOR A CE CHARACTERISTICS
U W
Output Noise Spectral Density
Load Regulation
10
0
–2
C
I
= 3.3µF
= 250mA
OUT
∆I = 1mA TO 250mA
L
LOAD
–4
–6
1
–8
–10
–12
–14
–16
–18
–20
0.1
0.01
–25
0
50
75 100 125
–50
25
10
100
1k
FREQUENCY (Hz)
10k
100k
TEMPERATURE (°C)
3012B G22
3012B G21
10Hz to 100kHz Output Noise
Transient Response
0.15
0.10
0.05
0
VOUT
100µV/DIV
–0.05
–0.10
–0.15
300
V
V
C
C
= 6V
= 5V
= 3.3µF CERAMIC
IN
OUT
IN
= 3.3µF CERAMIC
LOAD
OUT
∆I
= 100mA TO 200mA
200
C
OUT = 10µF
1ms/DIV
3012B G23
100
IL = 250mA
VOUT = 1.24V
0
0
100
200
300
400
500
TIME (µs)
3012B G24
3012bf
6
LT3012B
U
U
U
PI FU CTIO S
(DFN Package)/(TSSOP Package)
OUT (Pins 2, 3)/(Pins 3, 4): Output. The output supplies
power to the load. A minimum output capacitor of 3.3µF is
required to prevent oscillations. Larger output capacitors
will be required for applications with large transient loads
to limit peak voltage transients. See the Applications
Information section for more information on output ca-
pacitance and reverse output characteristics.
IN (Pins 10, 11)/(Pins 13,14): Input. Power is supplied to
the device through the IN pin. A bypass capacitor is
required on this pin if the device is more than six inches
away from the main input filter capacitor. In general, the
output impedance of a battery rises with frequency, so it
is advisable to include a bypass capacitor in battery-
poweredcircuits. Abypasscapacitorintherangeof1µFto
10µF is sufficient. The LT3012B is designed to withstand
reverse voltages on the IN pin with respect to ground and
the OUT pin. In the case of a reversed input, which can
happen if a battery is plugged in backwards, the LT3012B
will act as if there is a diode in series with its input. There
will be no reverse current flow into the LT3012B and no
reverse voltage will appear at the load. The device will
protect both itself and the load.
ADJ (Pin 4)/(Pin 5): Adjust. This is the input to the error
amplifier. This pin is internally clamped to ±7V. It has a
bias current of 30nA which flows into the pin (see curve of
ADJPinBiasCurrentvsTemperatureintheTypicalPerfor-
mance Characteristics). The ADJ pin voltage is 1.24V
referenced to ground, and the output voltage range is
1.24V to 60V.
GND (Pins 5, 13)/(Pins 1, 6, 8, 9, 16, 17): Ground. The
exposed backside of the package is an electrical connec-
tion for GND. As such, to ensure optimum device opera-
tion and thermal performance, the exposed pad must be
connected directly to pin 5/pin 6 on the PC board.
NC (Pins 1, 6-9, 12)/(Pins 2, 7, 10-12, 15): No Connect.
No Connect pins may be floated, tied to IN or tied to GND.
3012bf
7
LT3012B
W U U
U
APPLICATIO S I FOR ATIO
The LT3012B is a 250mA high voltage low dropout regu-
lator with micropower quiescent current. The device is
capable of supplying 250mA at a dropout voltage of
400mV. Operating quiescent current is only 40µA. In
addition to the low quiescent current, the LT3012B incor-
porates several protection features which make it ideal for
use in battery-powered systems. The device is protected
against both reverse input and reverse output voltages. In
battery backup applications where the output can be held
up by a backup battery when the input is pulled to ground,
theLT3012Bactslikeithasadiodeinserieswithitsoutput
and prevents reverse current flow.
to the ratio of the desired output voltage to 1.24V; (VOUT
/
1.24V). For example, load regulation for an output current
change of 1mA to 250mA is –7mV typical at VOUT = 1.24V.
At VOUT = 12V, load regulation is:
(12V/1.24V) • (–7mV) = –68mV
Output Capacitance and Transient Response
The LT3012B is designed to be stable with a wide range of
output capacitors. The ESR of the output capacitor affects
stability, most notably with small capacitors. A minimum
output capacitor of 3.3µF with an ESR of 3Ω or less is
recommended to prevent oscillations. The LT3012B is a
micropower device and output transient response will be
a function of output capacitance. Larger values of output
capacitance decrease the peak deviations and provide
improved transient response for larger load current
changes. Bypass capacitors, used to decouple individual
components powered by the LT3012B, will increase the
effective output capacitor value.
Adjustable Operation
The LT3012B has an output voltage range of 1.24V to
60V. The output voltage is set by the ratio of two external
resistors as shown in Figure 1. The device servos the
output to maintain the voltage at the adjust pin at 1.24V
referenced to ground. The current in R1 is then equal to
1.24V/R1 and the current in R2 is the current in R1 plus
the ADJ pin bias current. The ADJ pin bias current, 30nA
at 25°C, flows through R2 into the ADJ pin. The output
voltage can be calculated using the formula in Figure 1.
The value of R1 should be less than 250k to minimize
errors in the output voltage caused by the ADJ pin bias
current.
Extra consideration must be given to the use of ceramic
capacitors. Ceramic capacitors are manufactured with a
variety of dielectrics, each with different behavior across
temperature and applied voltage. The most common di-
electrics used are specified with EIA temperature charac-
teristiccodesofZ5U,Y5V,X5RandX7R.TheZ5UandY5V
dielectrics are good for providing high capacitances in a
small package, but they tend to have strong voltage and
temperature coefficients as shown in Figures 2 and 3.
When used with a 5V regulator, a 16V 10µF Y5V capacitor
The adjustable device is tested and specified with the ADJ
pintiedtotheOUTpinanda5µADCload(unlessotherwise
specified) for an output voltage of 1.24V. Specifications
for output voltages greater than 1.24V will be proportional
V
IN
OUT
OUT
+
R2
R1
C1
LT3012B
ADJ
V
IN
GND
3012B F01
R2
R1
V
V
= 1.24V 1 +
+ (I )(R2)
ADJ
OUT
ADJ
(
)
= 1.24V
I
= 30nA AT 25°C
OUTPUT RANGE = 1.24V TO 60V
ADJ
Figure 1. Adjustable Operation
3012bf
8
LT3012B
W U U
APPLICATIO S I FOR ATIO
U
can exhibit an effective value as low as 1µF to 2µF for the
DC bias voltage applied and over the operating tempera-
ture range. The X5R and X7R dielectrics result in more
stable characteristics and are more suitable for use as the
output capacitor. The X7R type has better stability across
temperature, while the X5R is less expensive and is
available in higher values. Care still must be exercised
when using X5R and X7R capacitors; the X5R and X7R
codesonlyspecifyoperatingtemperaturerangeandmaxi-
mum capacitance change over temperature. Capacitance
change due to DC bias with X5R and X7R capacitors is
better than Y5V and Z5U capacitors, but can still be
significant enough to drop capacitor values below appro-
priate levels. Capacitor DC bias characteristics tend to
improve as component case size increases, but expected
capacitance at operating voltage should be verified.
ing region. The protection is designed to provide some
outputcurrentatallvaluesofinputvoltageuptothedevice
breakdown (see curve of Current Limit vs Input Voltage in
the Typical Performance Characteristics).
The LT3012B is limited for operating conditions by maxi-
mum junction temperature. While operating at maximum
input voltage, the output current range must be limited;
when operating at maximum output current, the input
voltage range must be limited. Device specifications will
not apply for all possible combinations of input voltage
and output current. Operating the LT3012B beyond the
maximum junction temperature rating may impair the life
of the device.
Thermal Considerations
The power handling capability of the device will be limited
by the maximum rated junction temperature (125°C). The
power dissipated by the device will be made up of two
components:
Voltage and temperature coefficients are not the only
sources of problems. Some ceramic capacitors have a
piezoelectric response. A piezoelectric device generates
voltage across its terminals due to mechanical stress,
similar to the way a piezoelectric accelerometer or micro-
phone works. For a ceramic capacitor the stress can be
induced by vibrations in the system or thermal transients.
1. Output current multiplied by the input/output voltage
differential: IOUT • (VIN – VOUT) and,
2. GND pin current multiplied by the input voltage:
IGND • VIN.
Current Limit and Safe Operating Area Protection
The GND pin current can be found by examining the GND
Pin Current curves in the Typical Performance Character-
istics.Powerdissipationwillbeequaltothesumofthetwo
components listed above.
Like many IC power regulators, the LT3012B has safe
operating area protection. The safe operating area protec-
tion decreases the current limit as the input voltage
increases and keeps the power transistor in a safe operat-
40
20
20
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
0
X5R
0
–20
X5R
–20
–40
–40
Y5V
–60
–60
Y5V
–80
–80
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
–100
–100
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
0
8
12 14
2
4
6
10
16
DC BIAS VOLTAGE (V)
3012B F03
3012B F02
Figure 2. Ceramic Capacitor DC Bias Characterics
Figure 3. Ceramic Capacitor Temperature Characterics
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9
LT3012B
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APPLICATIO S I FOR ATIO
Continuous operation at large input/output voltage differ-
entials and maximum load current is not practical due to
thermal limitations. Transient operation at high input/
output differentials is possible. The approximate thermal
time constant for a 2500sq mm 3/32" FR-4 board with
maximumtopsideandbacksideareaforoneouncecopper
is 3 seconds. This time constant will increase as more
thermal mass is added (i.e. vias, larger board, and other
components).
The LT3012B has internal thermal limiting designed to
protect the device during overload conditions. For con-
tinuous normal conditions the maximum junction tem-
perature rating of 125°C must not be exceeded. It is
important to give careful consideration to all sources of
thermal resistance from junction to ambient. Additional
heat sources mounted nearby must also be considered.
For surface mount devices, heat sinking is accomplished
by using the heat spreading capabilities of the PC board
and its copper traces. Copper board stiffeners and plated
through-holes can also be used to spread the heat gener-
ated by power devices.
For an application with transient high power peaks, aver-
age power dissipation can be used for junction tempera-
turecalculationsaslongasthepulseperiodissignificantly
less than the thermal time constant of the device and
board.
The following tables list thermal resistance for several
different board sizes and copper areas. All measurements
were taken in still air on 3/32" FR-4 board with one ounce
copper.
Calculating Junction Temperature
Example 1: Given an output voltage of 5V, an input voltage
range of 24V to 30V, an output current range of 0mA to
50mA, and a maximum ambient temperature of 50°C,
what will the maximum junction temperature be?
Table 1. DFN Measured Thermal Resistance
COPPER AREA
THERMAL RESISTANCE
TOPSIDE
2500 sq mm
1000 sq mm
225 sq mm
100 sq mm
BACKSIDE
2500 sq mm
2500 sq mm
2500 sq mm
2500 sq mm
BOARD AREA
2500 sq mm
2500 sq mm
2500 sq mm
2500 sq mm
(JUNCTION-TO-AMBIENT)
40°C/W
The power dissipated by the device will be equal to:
45°C/W
50°C/W
I
OUT(MAX) • (VIN(MAX) – VOUT) + (IGND • VIN(MAX)
where:
IOUT(MAX) = 50mA
)
62°C/W
Table 2. TSSOP Measured Thermal Resistance
COPPER AREA
THERMAL RESISTANCE
VIN(MAX) = 30V
TOPSIDE
2500 sq mm
1000 sq mm
225 sq mm
100 sq mm
BACKSIDE
2500 sq mm
2500 sq mm
2500 sq mm
2500 sq mm
BOARD AREA
2500 sq mm
2500 sq mm
2500 sq mm
2500 sq mm
(JUNCTION-TO-AMBIENT)
IGND at (IOUT = 50mA, VIN = 30V) = 1mA
40°C/W
45°C/W
So:
50°C/W
P = 50mA • (30V – 5V) + (1mA • 30V) = 1.28W
62°C/W
The thermal resistance will be in the range of 40°C/W to
62°C/W depending on the copper area. So the junction
temperature rise above ambient will be approximately
equal to:
The thermal resistance junction-to-case (θJC), measured
at the exposed pad on the back of the die, is 16°C/W.
1.31W • 50°C/W = 65.5°C
3012bf
10
LT3012B
W U U
APPLICATIO S I FOR ATIO
U
The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:
Protection Features
The LT3012B incorporates several protection features
which make it ideal for use in battery-powered circuits. In
addition to the normal protection features associated with
monolithic regulators, such as current limiting and ther-
mal limiting, the device is protected against reverse-input
voltages, and reverse voltages from output to input.
T
JMAX = 50°C + 65.5°C = 115.5°C
Example 2: Given an output voltage of 5V, an input voltage
of 48V that rises to 72V for 5ms(max) out of every 100ms,
and a 5mA load that steps to 50mA for 50ms out of every
250ms, what is the junction temperature rise above ambi-
ent? Using a 500ms period (well under the time constant
of the board), power dissipation is as follows:
Current limit protection and thermal overload protection
areintendedtoprotectthedeviceagainstcurrentoverload
conditions at the output of the device. For normal opera-
tion, the junction temperature should not exceed 125°C.
P1(48V in, 5mA load) = 5mA • (48V – 5V)
+ (200µA • 48V) = 0.23W
The input of the device will withstand reverse voltages of
80V. No negative voltage will appear at the output. The
device will protect both itself and the load. This provides
protection against batteries which can be plugged in
backward.
P2(48V in, 50mA load) = 50mA • (48V – 5V)
+ (1mA • 48V) = 2.20W
P3(72V in, 5mA load) = 5mA • (72V – 5V)
+ (200µA • 72V) = 0.35W
The ADJ pin of the device can be pulled above or below
ground by as much as 7V without damaging the device. If
the input is left open circuit or grounded, the ADJ pin will
act like an open circuit when pulled below ground, and like
alargeresistor(typically100k)inserieswithadiodewhen
pulled above ground. If the input is powered by a voltage
source, pulling the ADJ pin below the reference voltage
will cause the device to current limit. This will cause the
output to go to a unregulated high voltage. Pulling the ADJ
pin above the reference voltage will turn off all output
current.
P4(72V in, 50mA load) = 50mA • (72V – 5V)
+ (1mA • 72V) = 3.42W
Operation at the different power levels is as follows:
76% operation at P1, 19% for P2, 4% for P3, and
1% for P4.
P
EFF = 76%(0.23W) + 19%(2.20W) + 4%(0.35W)
+ 1%(3.42W) = 0.64W
With a thermal resistance in the range of 40°C/W to
62°C/W, this translates to a junction temperature rise
above ambient of 26°C to 38°C.
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11
LT3012B
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APPLICATIO S I FOR ATIO
In situations where the ADJ pin is connected to a resistor
divider that would pull the ADJ pin above its 7V clamp
voltage if the output is pulled high, the ADJ pin input
current must be limited to less than 5mA. For example, a
resistor divider is used to provide a regulated 1.5V output
fromthe1.24Vreferencewhentheoutputisforcedto60V.
The top resistor of the resistor divider must be chosen to
limitthecurrentintotheADJpintolessthan5mAwhenthe
ADJ pin is at 7V. The 53V difference between the OUT and
ADJ pins divided by the 5mA maximum current into the
ADJ pin yields a minimum top resistor value of 10.6k.
ground, pulled to some intermediate voltage, or is left
open circuit. Current flow back into the output will follow
the curve shown in Figure 4. The rise in reverse output
current above 7V occurs from the breakdown of the 7V
clamp on the ADJ pin. With a resistor divider on the
regulator output, this current will be reduced depending
on the size of the resistor divider.
When the IN pin of the LT3012B is forced below the OUT
pin or the OUT pin is pulled above the IN pin, input current
will typically drop to less than 2µA. This can happen if the
input of the LT3012B is connected to a discharged (low
voltage) battery and the output is held up by either a
backup battery or a second regulator circuit.
In circuits where a backup battery is required, several
different input/output conditions can occur. The output
voltage may be held up while the input is either pulled to
200
T
V
V
= 25°C
J
= 0V
180
160
140
120
100
80
IN
OUT
= V
ADJ
ADJ
PIN CLAMP
(SEE ABOVE)
CURRENT FLOWS
INTO OUTPUT PIN
60
40
20
0
0
1
2
3
4
5
6
7
8
9
10
OUTPUT VOLTAGE (V)
3012B F04
Figure 4. Reverse Output Current
3012bf
12
LT3012B
U
TYPICAL APPLICATIO S
LT3012B Automotive Application
IN
OUT
ADJ
NO PROTECTION
DIODE NEEDED!
+
V
IN
LT3012B
GND
750k
249k
3.3µF
12V
1µF
LOAD: CLOCK,
SECURITY SYSTEM
ETC
(LATER 42V)
LT3012B Telecom Application
V
IN
IN
OUT
48V
(72V TRANSIENT)
+
–
LT3012B
750k
249k
BACKUP
BATTERY
NO PROTECTION
DIODE NEEDED!
3.3µF
1µF
LOAD:
SYSTEM MONITOR
ETC
ADJ
GND
3012B TA05
Constant Brightness for Indicator LED over Wide Input Voltage Range
RETURN
IN
LT3012B
ADJ
OUT
1µF
3.3µF
GND
R
SET
–48V
3012B TA06
I
= 1.24V/R
SET
LED
–48V CAN VARY FROM –4V TO –80V
3012bf
13
LT3012B
U
PACKAGE DESCRIPTIO
DE/UE Package
12-Lead Plastic DFN (4mm × 3mm)
(Reference LTC DWG # 05-08-1695 Rev C)
0.70 ±0.05
3.60 ±0.05
2.20 ±0.05 (2 SIDES)
1.70 ±0.05
PACKAGE OUTLINE
0.25 ± 0.05
0.50
BSC
3.30 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.40 ± 0.10
4.00 ±0.10
(2 SIDES)
R = 0.115
TYP
7
12
R = 0.05
TYP
3.00 ±0.10 1.70 ± 0.05
(2 SIDES)
(2 SIDES)
PIN 1
TOP MARK
(NOTE 6)
PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
CHAMFER
(UE12/DE12) DFN 0905 REV C
6
0.25 ± 0.05
1
0.75 ±0.05
0.200 REF
0.50
BSC
3.30 ±0.05
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING PROPOSED TO BE A VARIATION OF VERSION
(WGED) IN JEDEC PACKAGE OUTLINE M0-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
3012bf
14
LT3012B
U
PACKAGE DESCRIPTIO
FE Package
16-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663)
Exposed Pad Variation BB
4.90 – 5.10*
(.193 – .201)
3.58
(.141)
3.58
(.141)
16 1514 13 12 1110
9
6.60 ±0.10
4.50 ±0.10
2.94
(.116)
6.40
(.252)
BSC
SEE NOTE 4
2.94
(.116)
0.45 ±0.05
1.05 ±0.10
0.65 BSC
5
7
8
1
2
3
4
6
RECOMMENDED SOLDER PAD LAYOUT
1.10
(.0433)
MAX
4.30 – 4.50*
(.169 – .177)
0.25
REF
0° – 8°
0.65
(.0256)
BSC
0.09 – 0.20
(.0035 – .0079)
0.50 – 0.75
(.020 – .030)
0.05 – 0.15
(.002 – .006)
0.195 – 0.30
FE16 (BB) TSSOP 0204
(.0077 – .0118)
TYP
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS 4. RECOMMENDED MINIMUM PCB METAL SIZE
FOR EXPOSED PAD ATTACHMENT
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
MILLIMETERS
(INCHES)
2. DIMENSIONS ARE IN
3. DRAWING NOT TO SCALE
3012bf
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
15
LT3012B
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
V : 4.5V to 36V, V
LT1020
125mA, Micropower Regulator and Comparator
= 2.5V, V = 0.4V, I = 40µA, I = 40µA,
OUT(MIN) DO Q SD
IN
Comparator and Reference, Class B Outputs, S16, PDIP14 Packages
LT1120/LT1120A 125mA, Micropower Regulator and Comparator
V : 4.5V to 36V, V = 2.5V, V = 0.4V, I = 40µA, I = 10µA,
Comparator and Reference, Logic Shutdown, Ref Sources and Sinks 2/4mA,
S8, N8 Packages
IN
OUT(MIN)
DO
Q
SD
LT1121/
LT1121HV
150mA, Micropower, LDO
700mA, Micropower, LDO
V : 4.2V to 30/36V, V
Reverse Battery Protection, SOT-223, S8, Z Packages
= 3.75V, V = 0.42V, I = 30µA, I = 16µA,
OUT(MIN) DO Q SD
IN
LT1129
LT1676
LT1761
LT1762
LT1763
V : 4.2V to 30V, V = 3.75V, V = 0.4V, I = 50µA, I = 16µA,
IN
OUT(MIN)
DO
Q
SD
DD, S0T-223, S8,TO220-5, TSSOP20 Packages
60V, 440mA (I ), 100kHz, High Efficiency
V : 7.4V to 60V, V
IN
= 1.24V, I = 3.2mA, I = 2.5µA, S8 Package
Q SD
OUT
OUT(MIN)
Step-Down DC/DC Converter
100mA, Low Noise Micropower, LDO
V : 1.8V to 20V, V
IN
= 1.22V, V = 0.3V, I = 20µA, I = <1µA,
DO Q SD
, Stable with 1µF Ceramic Capacitors, ThinSOT Package
OUT(MIN)
Low Noise < 20µV
RMS
150mA, Low Noise Micropower, LDO
500mA, Low Noise Micropower, LDO
V : 1.8V to 20V, V
= 1.22V, V = 0.3V, I = 25µA, I = <1µA,
OUT(MIN) DO Q SD
IN
Low Noise < 20µV
, MS8 Package
RMS
V : 1.8V to 20V, V
IN
= 1.22V, V = 0.3V, I = 30µA, I = <1µA,
DO Q SD
, S8 Package
OUT(MIN)
Low Noise < 20µV
RMS
LT1764/LT1764A 3A, Low Noise, Fast Transient Response, LDO
V : 2.7V to 20V, V
= 1.21V, V = 0.34V, I = 1mA, I = <1µA,
OUT(MIN) DO Q SD
IN
Low Noise < 40µV
, “A” Version Stable with Ceramic Capacitors,
RMS
DD, TO220-5 Packages
LT1766
LT1776
60V, 1.2A (I ), 200kHz, High Efficiency
Step-Down DC/DC Converter
V : 5.5V to 60V, V
= 1.2V, I = 2.5mA, I = 25µA, TSSOP16/E Package
Q SD
OUT
IN
OUT(MIN)
OUT(MIN)
40V, 550mA (I ), 200kHz, High Efficiency
V : 7.4V to 40V, V
IN
= 1.24V, I = 3.2mA, I = 30µA, N8, S8 Packages
OUT
Q
SD
Step-Down DC/DC Converter
LT1934/
LT1934-1
300mA/60mA, (I ), Constant Off-Time, High
Efficiency Step-Down DC/DC Converter
90% Efficiency, V : 3.2V to 34V, V
ThinSOT Package
= 1.25V, I = 14µA, I = <1µA,
OUT(MIN) Q SD
OUT
IN
LT1956
60V, 1.2A (I ), 500kHz, High Efficiency
Step-Down DC/DC Converter
V : 5.5V to 60V, V
IN
= 1.2V, I = 2.5mA, I = 25µA, TSSOP16/E Package
Q SD
OUT
OUT(MIN)
LT1962
300mA, Low Noise Micropower, LDO
V : 1.8V to 20V, V
= 1.22V, V = 0.27V, I = 30µA, I = <1µA,
DO Q SD
IN
OUT(MIN)
Low Noise < 20µV
, MS8 Package
RMS
LT1963/LT1963A 1.5A, Low Noise, Fast Transient Response, LDO
V : 2.1V to 20V, V
= 1.21V, V = 0.34V, I = 1mA, I = <1µA,
OUT(MIN) DO Q SD
IN
Low Noise < 40µV
, “A” Version Stable with Ceramic Capacitors,
RMS
DD, TO220-5, S0T-223, S8 Packages
LT1964
LT3010
200mA, Low Noise Micropower, Negative LDO
100mA, 3V to 80V, Low Noise Micropower LDO
V : –1.9V to –20V, V = –1.21V, V = 0.34V, I = 30µA, I = 3µA,
IN
OUT(MIN)
DO
Q
SD
Low Noise < 30µV
, Stable with Ceramic Capacitors, ThinSOT Package
RMS
V : 3V to 8V, V
Low Noise < 100µV
= 1.275V, V = 0.3V, I = 30µA, I = 1µA,
IN
OUT(MIN)
DO
Q
SD
, MS8E Package
RMS
3012bf
LT 0206 • PRINTED IN USA
16 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2006
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