LT1521IST-5#TR [Linear]
暂无描述;
| 型号： | LT1521IST-5#TR |
| 厂家： | 
Linear |
| 描述： | 暂无描述 稳压器 调节器 光电二极管 输出元件 |
| 文件： | 总16页 (文件大小：298K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1521/LT1521-3
LT1521-3.3/LT1521-5
300mA Low Dropout
Regulators with Micropower
Quiescent Current and Shutdown
U
FEATURES
DESCRIPTION
The LT®1521/LT1521-3/LT1521-3.3/LT1521-5 are low
dropout regulators with micropower quiescent current
and shutdown. These devices are capable of supplying
300mA of output current with a dropout voltage of 0.5V.
Designed for use in battery-powered systems, the low
quiescent current, 12µA operating and 6µA in
shutdown, makes them an ideal choice. The quiescent
current is well controlled; it does not rise in dropout as it
does with many other low dropout PNP regulators.
■
Dropout Voltage: 0.5V
Output Current: 300mA
Quiescent Current: 12µA
■
■
■
■
■
■
■
■
■
■
No Protection Diodes Needed
Adjustable Output from 3.8V to 20V
Fixed Output Voltages: 3V, 3.3V, 5V
Controlled Quiescent Current in Dropout
Shutdown IQ = 6µA
Reverse Battery Protection
No Reverse Current
Other features of the LT1521/LT1521-3/LT1521-3.3/
LT1521-5 include the ability to operate with very small
output capacitors. They are stable with only 1.5µF on the
outputwhilemostolderdevicesrequirebetween10µFand
100µF for stability. Small ceramic capacitors can be used,
enhancing manufacturability. Also, the input may be con-
nectedtovoltageslowerthantheoutputvoltage,including
negative voltages, without reverse current flow from out-
puttoinput.ThismakestheLT1521seriesidealforbackup
power situations where the output is held high and the
input is low or reversed. Under these conditions only 5µA
will flow from the output pin to ground.
Thermal Limiting
U
APPLICATIONS
■
Low Current Regulator
■
Regulator for Battery-Powered Systems
■
Post Regulator for Switching Supplies
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
TYPICAL APPLICATION
Dropout Voltage
5V Battery-Powered Supply with Shutdown
0.6
5V
300mA
8
1
IN
OUT
0.5
+
6V
1µF
1.5µF
LT1521-5
0.4
5
2
SHDN
SENSE
GND
3
0.3
0.2
0.1
V
(PIN 5) OUTPUT
SHDN
<0.25
>2.80
NC
OFF
ON
ON
LT1521 • TA01
0
0
100
150
200
250
300
50
OUTPUT CURRENT (mA)
LT1521 • TA02
1
LT1521/LT1521-3
LT1521-3.3/LT1521-5
W W U W
ABSOLUTE MAXIMUM RATINGS (Note 1)
Input Voltage ...................................................... ± 20V*
Output Pin Reverse Current .................................. 10mA
Adjust Pin Current ................................................ 10mA
Shutdown Pin Input Voltage (Note 1) ..........6.5V, –0.6V
Shutdown Pin Input Current (Note 1) ..................... 5mA
Output Short-Circuit Duration.......................... Indefinite
Storage Temperature Range ................. –65°C to 150°C
Operating Junction Temperature Range (Note 2)
Commercial ........................................... 0°C to 125°C
Industrial ......................................... –40°C to 125°C
Lead Temperature (Soldering, 10 sec).................. 300°C
*For applications requiring input voltage ratings greater than 20V, contact
the factory.
U
W U
PACKAGE/ORDER INFORMATION
TOP VIEW
FRONT VIEW
TOP VIEW
OUT
SENSE/ADJ*
GND
1
2
3
4
8
7
6
5
IN
1
2
3
OUT
GND
IN
OUT
SENSE/ADJ*
NC
1
2
3
4
8 IN
7 NC
6 NC
5 SHDN
GND
GND
SHDN
TAB IS
GND
GND
NC
MS8 PACKAGE
8-LEAD PLASTIC MSOP
S8 PACKAGE
8-LEAD PLASTIC SO
ST PACKAGE
3-LEAD PLASTIC SOT-223
*PIN 2 = SENSE FOR LT1521-3/
LT1521-3.3/LT1521-5
PIN 2 = ADJ FOR LT1521
*PIN 2 = SENSE FOR LT1521-3/LT1521-3.3/LT1521-5
= ADJ FOR LT1521
TJMAX = 125°C, θJA = 70°C/ W
SEE THE APPLICATIONS INFORMATION SECTION
TJMAX = 125°C, θJA = 50°C/ W
SEE THE APPLICATIONS INFORMATION SECTION
TJMAX = 125°C, θJA = 125°C/ W
ORDER PART NUMBER
ORDER PART NUMBER
ORDER PART NUMBER
LT1521CST-3
LT1521CST-3.3
LT1521CST-5
LT1521IST-3
LT1521IST-3.3
LT1521IST-5
LT1521CS8
LT1521CMS8
LT1521CS8-3
LT1521CS8-3.3
LT1521CS8-5
LT1521IS8
LT1521CMS8-3
LT1521CMS8-3.3
LT1521CMS8-5
LT1521IS8-3
LT1521IS8-3.3
LT1521IS8-5
MS8 PART MARKING
ST PART MARKING
S8 PART MARKING
LTEZ
LTFB
LTDU
LTFA
1521
15213
152133
15215
1521I
1521I3
1521I33
1521I5
15213
152133
15215
1521I3
1521I33
1521I5
Consult factory for Military grade parts.
2
LT1521/LT1521-3
LT1521-3.3/LT1521-5
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Regulated Output Voltage
(Note 4)
LT1521-3
V
= 3.5V, I
IN
= 1mA, T = 25°C
2.950
2.900
3.250
3.200
4.925
4.850
3.000
3.000
3.300
3.300
5.000
5.000
3.050
3.100
3.350
3.400
5.075
5.150
V
V
V
V
V
V
IN
OUT
J
4V < V < 20V, 1mA < I
V
4.3V < V < 20V, 1mA < I
V
< 300mA
●
●
●
OUT
LT1521-3.3
LT1521-5
= 3.8V, I
= 1mA, T = 25°C
IN
OUT
J
< 300mA
IN
OUT
= 5.5V, I
= 1mA, T = 25°C
IN
OUT
J
6V < V < 20V, 1mA < I
< 300mA
IN
OUT
LT1521 (Note 5)
V
= 4.3V, I
= 1mA, T = 25°C
3.695
3.640
3.750
3.750
1.5
1.5
1.5
1.5
– 20
– 20
– 25
– 20
– 20
– 20
– 25
– 20
130
3.805
3.860
20
20
20
20
–30
–30
–45
–30
–55
–55
–75
–55
170
250
350
450
420
550
470
600
600
750
20
100
450
1.5
2.5
4.0
12.0
100
2.80
V
V
IN
OUT
J
4.8V < V < 20V, 1mA < I
∆V = 4.5 to 20V, I
∆V = 4.8 to 20V, I
∆V = 5.5 to 20V, I
< 300mA
●
●
●
●
●
IN
OUT
Line Regulation
Load Regulation
LT1521-3
LT1521-3.3
LT1521-5
= 1mA
= 1mA
= 1mA
= 1mA
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
IN
OUT
OUT
OUT
OUT
IN
IN
LT1521 (Note 5) ∆V = 4.3 to 20V, I
IN
LT1521-3
LT1521-3.3
LT1521-5
∆I
∆I
∆I
= 1mA to 300mA, T ≤ 25°C
= 1mA to 300mA, T ≤ 25°C
= 1mA to 300mA, T ≤ 25°C
= 1mA to 300mA, T ≤ 25°C
J
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
J
J
J
LT1521 (Note 5) ∆I
LT1521-3
LT1521-3.3
LT1521-5
∆I
∆I
∆I
= 1mA to 300mA, T >25°C
J
= 1mA to 300mA, T > 25°C
= 1mA to 300mA, T > 25°C
= 1mA to 300mA, T > 25°C
J
J
J
LT1521 (Note 5) ∆I
Dropout Voltage (Note 6)
I
I
= 1mA, T = 25°C
= 1mA
LOAD
LOAD
J
●
●
●
●
I
I
= 50mA, T = 25°C
= 50mA
290
350
400
500
LOAD
LOAD
J
I
I
= 100mA, T = 25°C
= 100mA
LOAD
LOAD
J
I
I
= 150mA, T = 25°C
= 150mA
LOAD
LOAD
J
I
I
= 300mA, T = 25°C
= 300mA
mV
mV
µA
µA
LOAD
LOAD
J
●
●
●
●
●
●
●
●
Ground Pin Current (Note 7)
I
I
I
I
I
I
I
= 0mA
= 1mA
12
65
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
= 10mA
= 50mA
= 100mA
= 150mA
= 300mA
300
0.8
1.4
2.2
6.5
50
µA
mA
mA
mA
mA
nA
Adjust Pin Bias Current (Notes 5, 8)
Shutdown Threshold
T = 25°C
J
V
V
= Off to On
= On to Off
●
●
1.20
0.75
V
V
OUT
OUT
0.25
Shutdown Pin Current (Note 9)
Quiescent Current in Shutdown (Note 10)
Ripple Rejection
V
V
V
= 0V
●
●
2.0
6
58
5.0
12
µA
µA
dB
SHDN
= V
(NOMINAL) + 1V, V
= 0V
IN
OUT
SHDN
– V
= 1V(Avg), V
= 120Hz, I
= 0.5V ,
P–P
50
IN
OUT
RIPPLE
f
= 150mA
RIPPLE
LOAD
Current Limit
V
V
– V
= V
= 7V, T = 25°C
(NOMINAL) + 1.5V, ∆V
400
400
800
mA
mA
IN
IN
OUT
OUT
J
= –0.1V
●
320
OUT
3
LT1521/LT1521-3
LT1521-3.3/LT1521-5
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Reverse Leakage Current
Reverse Output Current (Note 11)
V
= –20V, V
= 0V
OUT
●
1.0
mA
IN
LT1521-3
LT1521-3.3
LT1521-5
V
OUT
V
OUT
V
OUT
V
OUT
= 3V, V < 3V, T = 25°C
5
5
5
5
10
10
10
10
µA
µA
µA
µA
IN
J
= 3.3V, V < 3.3V, T = 25°C
IN
J
= 5V, V < 5V, T = 25°C
IN
J
LT1521 (Note 5)
denotes specifications which apply over the full operating
temperature range.
= 3.8V, V < 3.75V, T = 25°C
IN J
The
●
Note 5: The LT1521 (adjustable version) is tested and specified with the
adjust pin connected to the output pin.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 6: Dropout voltage is the minimum input/output voltage required to
maintain regulation at the specified output current. In dropout the output
voltage will be equal to: (V – V
Note 7: Ground pin current is tested with V = V
current source load. This means the device is tested while operating in its
dropout region. This is the worst-case ground pin current. The ground pin
current will decrease slightly at higher input voltages.
Note 8: Adjust pin bias current flows into the adjust pin.
Note 9: Shutdown pin current at V
pin.
)
IN
DROPOUT
Note 2: The shutdown pin input voltage rating is required for a low
impedance source. Internal protection devices connected to the shutdown
pin will turn on and clamp the pin to approximately 7V or –0.6V. This
range allows the use of 5V logic devices to drive the pin directly. For high
impedance sources or logic running on supply voltages greater than 5.5V,
the maximum current driven into the shutdown pin must be limited to less
than 5mA.
(nominal) and a
OUT
IN
= 0V flows out of the shutdown
SHDN
Note 3: For junction temperatures greater than 110°C, a minimum load of
1mA is recommended. For T > 110°C and I
< 1mA, output voltage
J
OUT
Note 10: Quiescent current in shutdown is equal to the total sum of the
shutdown pin current (2µA) and the ground pin current (4µA).
may increase by 1%.
Note 4: 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 11: Reverse output current is tested with the input pin grounded and
the output pin forced to the rated output voltage. This current flows into
the output pin and out of the ground pin.
W
U
TYPICAL PERFORMANCE CHARACTERISTICS
Guaranteed Dropout Voltage
Dropout Voltage
Quiescent Current
0.8
15.0
12.5
10.0
7.5
5.0
2.5
0
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
= TEST POINTS
0.7
0.6
V
= OPEN
SHDN
I
= 300mA
T
≤ 125°C
LOAD
J
0.5
0.4
0.3
0.2
0.1
I
= 150mA
LOAD
T
≤ 25°C
I
= 100mA
J
LOAD
V
= 0V
SHDN
I
= 50mA
LOAD
I
V
= 6V
IN
L
R
= ∞
= 1mA
LOAD
I
= 0
LOAD
0
–25
0
50
75 100 125
50
100 125
–50
25
–50 –25
0
25
75
50
100
200
0
250
300
150
TEMPERATURE (°C)
TEMPERATURE (°C)
OUTPUT CURRENT (mA)
LT1521 • TPC02
LT1521 • TPC03
LT1521 • TPC01
4
LT1521/LT1521-3
LT1521-3.3/LT1521-5
W
U
TYPICAL PERFORMANCE CHARACTERISTICS
LT1521-3
LT1521-3.3
LT1521-5
Output Voltage
5.08
Output Voltage
Output Voltage
3.08
3.06
3.04
3.02
3.00
2.98
2.96
2.94
2.92
3.38
3.36
3.34
3.32
3.30
3.28
3.26
3.24
3.22
I
= 1mA
OUT
5.06
5.04
5.02
5.00
4.98
4.96
4.94
4.92
–25
0
50
75 100 125
–50 –25
0
25
50
75 100 125
–25
0
50
75 100 125
–50
25
–50
25
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
LT1521 • TPC04
LT1521 • TPC05
LT1521 • TPC06
LT1521-3
Quiescent Current
LT1521
Adjust Pin Voltage
LT1521-3.3
Quiescent Current
3.83
50
45
40
35
30
25
20
15
10
5
50
45
40
35
30
25
20
15
10
5
T
= 25°C
L
J
I
= 1mA
T
= 25°C
L
LOAD
J
R
= ∞
3.81
3.79
R
=
∞
3.77
3.75
3.73
3.71
3.69
V
= OPEN
= 0V
SHDN
V
SHDN
0
3.67
0
–25
0
50
75 100 125
–50
25
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
7
8
9
10
TEMPERATURE (°C)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
LT1521 • TPC08
LT1521 • TPC09
LT1521 • TPC07
LT1521-3
Ground Pin Current
LT1521-5
Quiescent Current
LT1521
Quiescent Current
50
45
40
35
30
25
20
15
10
5
1000
900
800
700
600
500
400
300
200
100
0
50
45
40
35
30
25
20
15
10
5
T
= 25°C
L
T = 25°C
J
T
= 25°C
L
J
J
R
R
=
∞
*FOR V
= 3V
OUT
= ∞
R
= 60Ω
LOAD
LOAD
I
= 50mA*
R
= 120Ω
= 25mA*
LOAD
LOAD
I
R
I
= 300Ω
= 10mA*
LOAD
LOAD
V
= OPEN
V
= OPEN
SHDN
SHDN
R
= 3k
= 1mA*
LOAD
LOAD
V
= 0V
V
= 0V
SHDN
SHDN
I
0
0
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
7
8
9
10
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
LT1521 • TPC11
LT1521 • TPC12
LT1521 • TPC10
5
LT1521/LT1521-3
LT1521-3.3/LT1521-5
W
U
TYPICAL PERFORMANCE CHARACTERISTICS
LT1521-3
Ground Pin Current
LT1521-3.3
Ground Pin Current
LT1521-3.3
Ground Pin Current
8
7
6
5
4
3
2
1
0
8
7
6
5
4
3
2
1
0
1000
900
800
700
600
500
400
300
200
100
0
T
= 25°C
T
= 25°C
T
= 25°C
J
J
J
*FOR V
= 3.3V
*FOR V
= 3V
*FOR V
= 3.3V
OUT
OUT
OUT
R
= 66Ω
LOAD
LOAD
I
= 50mA*
R
= 11Ω
= 300mA*
R
= 10Ω
LOAD
= 300mA*
LOAD
LOAD
I
I
LOAD
R
I
= 132Ω
LOAD
= 25mA*
LOAD
R
I
= 20Ω
LOAD
= 150mA*
R
I
= 22Ω
= 150mA*
LOAD
LOAD
R
I
= 330Ω
LOAD
= 10mA*
LOAD
LOAD
R
I
= 3.3k
= 1mA*
LOAD
LOAD
R
I
= 30Ω
= 100mA*
LOAD
LOAD
R
I
= 33Ω
= 100mA*
LOAD
LOAD
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
7
8
9
10
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
LT1521 • TPC14
LT1521 • TPC13
LT1521 • TPC15
LT1521-5
Ground Pin Current
LT1521-5
Ground Pin Current
LT1521
Ground Pin Current
1000
900
800
700
600
500
400
300
200
100
0
8
7
6
5
4
3
2
1
0
1000
900
800
700
600
500
400
300
200
100
0
T
J
= 25°C
V
OUT
= V
T
= 25°C
OUT
ADJ
J
T
= 25°C
J
R
= 16.7Ω
LOAD
LOAD
*FOR V
= 3.75V
*FOR V
= 5V
OUT
*FOR V
= 5V
R
= 100Ω
OUT
LOAD
LOAD
I
= 300mA*
I
= 50mA*
R
= 75Ω
= 50mA*
LOAD
LOAD
I
R
= 150Ω
= 25mA*
R
I
= 200Ω
= 25mA*
LOAD
LOAD
LOAD
I
LOAD
R
= 500Ω
= 10mA*
LOAD
LOAD
R
= 33.3Ω
= 150mA*
LOAD
LOAD
R
I
= 375Ω
= 10mA*
LOAD
LOAD
I
I
R
I
= 3.8k
= 1mA*
LOAD
LOAD
R
= 5k
= 1mA*
LOAD
LOAD
R
= 50Ω
I
LOAD
LOAD
I
= 100mA*
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
7
8
9
10
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
LT1521 • TPC16
LT1521 • TPC18
LT1521 • TPC17
LT1521
Ground Pin Current
Shutdown Pin Threshold
(On-to-Off)
Ground Pin Current
8
7
6
5
4
3
2
1
0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
10
9
T
= 25°C
J
V
V
V
V
= 3V (LT1521-3)
= 3.3V (LT1521-3.3)
= 5V (LT1521-5)
= 3.75V (LT1521)
IN
IN
IN
IN
I
= 1mA
LOAD
V
= V
OUT
ADJ
*FOR V
= 3.75V
T
T
= 125°C
OUT
J
J
8
7
6
R
I
= 12.5Ω
LOAD
LOAD
=300mA*
DEVICE IS OPERATING
IN DROPOUT
5
4
T
= 25°C
J
= 55°C
R
I
= 25Ω
=150mA*
LOAD
LOAD
3
2
1
0
R
= 37.5Ω
=100mA*
LOAD
LOAD
I
0
1
2
3
4
5
6
7
8
9
10
–50
0
25
50
75 100 125
–25
0
50
150
200
250
300
100
INPUT VOLTAGE (V)
TEMPERATURE (°C)
OUTPUT CURRENT (mA)
LT1521 • TPC19
LT1521 • TPC21
LT1521 • TPC20
6
LT1521/LT1521-3
LT1521-3.3/LT1521-5
W
U
TYPICAL PERFORMANCE CHARACTERISTICS
Shutdown Pin Threshold
(Off-to-On)
Shutdown Pin Input Current
Shutdown Pin Current
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
3.0
2.5
2.0
1.5
1.0
0.5
0
25
V
= 0V
SHDN
I
= 300mA
LOAD
20
15
10
5
I
= 1mA
LOAD
0
50
0
TEMPERATURE (°C)
100 125
25
50
75 100 125
–50 –25
25
75
–50
0
–25
0
1
2
3
4
5
6
7
8
9
TEMPERATURE (°C)
SHUTDOWN PIN VOLTAGE (V)
LT1521 • TPC23
LT1521 • TPC22
LT1521 • TPC24
Adjust Pin Bias Current
Reverse Output Current
Current Limit
200
175
150
125
100
75
50
45
40
35
30
25
20
15
10
5
0.6
0.5
0.4
0.3
0.2
0.1
0
T
= 25°C
IN
LT1521
J
V
V
= 0V
OUT
= 0V
CURRENT FLOWS
INTO OUTPUT PIN
V
(LT1521-3/LT1521-3.3
LT1521-5)
V
= V
OUT
SENSE
= V
(LT1521)
OUT
ADJ
LT1521-3.3
LT1521-3
50
25
LT1521-5
0
0
–25
0
50
75 100 125
–50
25
0
1
2
3
5
6
7
8
9
10
4
6
7
4
0
3
5
1
2
OUTPUT VOLTAGE (V)
TEMPERATURE (°C)
INPUT VOLTAGE (V)
LT1521 • TPC26
LT1521 • TPC25
LT1521 • TPC27
Current Limit
Reverse Output Current
Ripple Rejection
8
7
6
5
4
3
2
1
0
0.6
0.5
0.4
0.3
0.2
0.1
0
66
64
62
60
58
56
54
52
V
= V
(NOMINAL) + 1V + 0.5V
V
V
V
V
V
= 0V
V
V
= 7V
OUT
IN
OUT P-P
IN
IN
RIPPLE AT f = 120Hz
= 150mA
= 3V (LT1521-3)
= 3.3V (LT1521-3.3)
= 5V (LT1521-5)
= 3.75V (LT1521)
= 0V
OUT
OUT
OUT
OUT
I
LOAD
–25
0
50
75 100 125
50
0
TEMPERATURE (°C)
100 125
–50
25
–50 –25
25
75
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
TEMPERATURE (°C)
LT1521 • TPC29
LT1521 • TPC28
LT1521 • TPC30
7
LT1521/LT1521-3
LT1521-3.3/LT1521-5
W
U
TYPICAL PERFORMANCE CHARACTERISTICS
Load Regulation
Ripple Rejection
0
–5
100
I
= 150mA
LOAD
IN
∆I
= 1mA TO 300mA
90
80
70
60
50
40
30
20
10
0
LOAD
V
= 6V + 50mV
RIPPLE
RMS
–10
–15
–20
–25
–30
–35
–40
LT1521-5
LT1521-3
LT1521*
LT1521-3.3
C
= 33µF
OUT
SOLID TANTALUM
C
= 3.3µF
V
= V
ADJ
(NOMINAL + 1V)
OUT
OUT
SOLID TANTALUM
IN
*V
= V
OUT
–25
0
50
75 100 125
–50
25
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
TEMPERATURE (°C)
LT1521 • TPC31
LT1521 • TPC32
LT1521-5
Transient Response
LT1521-5
Transient Response
V
C
C
= 6V
V
C
C
= 6V
IN
IN
IN
IN
0.2
0.1
0.2
0.1
= 0.1µF
= 33µF
= 0.1µF
= 1.5µF
OUT
OUT
0
0
–0.1
–0.2
–0.1
–0.2
150
100
50
300
200
100
0
50 100 150 200 250 300 350 400 450 500
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
TIME (ms)
TIME (µs)
LT1521 • TPC33
LT1521 • TPC34
U
U
U
PIN FUNCTIONS
theoutputpinoftheregulator.Incriticalapplicationssmall
voltage drops caused by the resistance (RP) of PC traces
between the regulator and the load, which would normally
degrade regulation, may be eliminated by connecting the
sense pin to the output at the load as shown in Figure 1
(Kelvin Sense Connection). Note that the voltage drop
across the external PC traces will add to the dropout
voltage of the regulator. The sense pin bias current is 5µA
at the nominal regulated output voltage. This pin is inter-
nally clamped to –0.6V (one VBE).
OUT (Pin 1): The output pin supplies power to the load. A
minimum output capacitor of 1.5µF is required to prevent
oscillations, but larger values of output capacitor will be
necessary to deal with larger load transients. See the
Applications Information section for more on output
capacitance and reverse output characteristics.
SENSE (Pin 2): For fixed voltage versions of the LT1521
(LT1521-3, LT1521-3.3, LT1521-5), the sense pin is the
input to the error amplifier. Optimum regulation will be
obtained at the point where the sense pin is connected to
8
LT1521/LT1521-3
LT1521-3.3/LT1521-5
U
U
U
PIN FUNCTIONS
R
P
5
1
2
VBE). This allows the shutdown pin to be driven directly by
5V logic or by open collector logic with a pull-up resistor.
The pull-up resistor is only required to supply the leakage
current of the open collector gate, normally several micro-
amperes. Pull-upcurrentmustbelimitedtoamaximumof
5mA. A curve of the shutdown pin input current as a
function of voltage appears in the Typical Performance
Characteristics. If the shutdown pin is not used it can be
left open circuit. The device will be active (output on) if the
shutdown pin is not connected.
IN
OUT
LT1521
+
+
4
V
LOAD
IN
SHDN
SENSE
GND
3
R
P
LT1521 • F01
Figure 1. Kelvin Sense Connection
IN (Pin 8): Power is supplied to the device through the
input pin. The input pin should be bypassed to ground if
the device is more than six inches away from the main
input filter capacitor. In general, the output impedance of
battery rises with frequency, so it is advisable to include a
bypass capacitor in battery-powered circuits. A bypass
capacitor in the range of 1µF to 10µF is sufficient. The
LT1521 is designed to withstand reverse voltages on the
input pin with respect to ground and the output pin. In the
case of reversed input, which can happen if a battery is
plugged in backwards, the LT1521 will act as if there is a
diode in series with its input. There will be no reverse
current flow into the LT1521 and no reverse voltage will
appear at the load. The device will protect both itself and
the load.
ADJ (Pin 2): For adjustable LT1521, the adjust pin is the
input to the error amplifier. This pin is internally clamped
to 6V and –0.6V (one VBE). It has a bias current of 50nA
which flows into the pin. See Adjust Pin Bias Current vs
Temperature in the Typical Performance Characteristics
section. The adjust pin reference voltage is 3.75V refer-
enced to ground. The output voltage range that can be
produced by this device is 3.75V to 20V.
SHDN (Pin 5): The shutdown pin is used to put the device
into shutdown. In shutdown the output of the device is
turned off. This pin is active low. The device will be shut
down if the shutdown pin is pulled low. The shutdown pin
current with the pin pulled to ground will be 1.7µA. The
shutdown pin is internally clamped to 7V and –0.6V (one
U
W U U
APPLICATIONS INFORMATION
Adjustable Operation
The LT1521 is a 300mA low dropout regulator with
micropower quiescent current and shutdown. The device
is capable of supplying 300mA at a dropout of 0.5V and
operates with very low quiescent current (12µA). In shut-
down, the quiescent current drops to only 6µA. In addition
to the low quiescent current, the LT1521 incorporates
several protection features which make it ideal for use in
battery-powered systems. The device is protected against
both reverse input voltages 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, the LT1521 acts like it has a diode in series with
its output and prevents reverse current flow.
The adjustable version of the LT1521 has an output
voltage range of 3.75V to 20V. The output voltage is set by
theratiooftwoexternalresistorsasshowninFigure2.The
device servos the output voltage to maintain the voltage at
the adjust pin at 3.75V. The current in R1 is then equal to
3.75V/R1. The current in R2 is equal to the sum of the
currentinR1andtheadjustpinbiascurrent.Theadjustpin
bias current, 50nA at 25°C, flows through R2 into the
adjust pin. The output voltage can be calculated using the
formula in Figure 2. The value of R1 should be less than
400k to minimize errors in the output voltage caused by
the adjust pin bias current. Note that in shutdown the
9
LT1521/LT1521-3
LT1521-3.3/LT1521-5
U
W U U
APPLICATIONS INFORMATION
The ground pin current can be found by examining the
Ground Pin Current curves in the Typical Performance
Characteristics. Powerdissipationwillbeequaltothesum
of the two components listed above.
V
IN
OUT
OUT
+
R2
V
LT1521
GND
IN
SHDN
ADJ
The LT1521 series regulators have internal thermal limit-
ing designed to protect the device during overload condi-
tions. For continuous normal load conditions the maxi-
mum junction temperature rating of 125°C must not be
exceeded. It is important to give careful consideration to
allsourcesofthermalresistancefromjunctiontoambient.
Additional heat sources mounted nearby must also be
considered.
R1
R2
V
V
= 3.75V 1 +
+ (I
ADJ
+ R2)
OUT
ADJ
)
)
R1
= 3.75V
I
= 50nA AT 25°C
ADJ
OUTPUT RANGE = 3.75V TO 20V
LT1521 • F01
Figure 2. Adjustable Operation
output is turned off and the divider current will be zero.
Curves of Adjust Pin Voltage vs Temperature and Adjust
Pin Bias Current vs Temperature appear in the Typical
Performance Characteristics. The reference voltage at the
adjust pin has a positive temperature coefficient of ap-
proximately 15ppm/°C. The adjust pin bias current has a
negativetemperaturecoefficient.Theseeffectswilltendto
cancel each other.
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.
The following tables list thermal resistance for each pack-
age. Measured values of thermal resistance for several
different board sizes and copper areas are listed for each
package. All measurements were taken in still air on
3/32"FR-4boardwithoneouncecopper.AllNCleadswere
connected to the ground plane.
The adjustable device is specified with the adjust pin tied
to the output pin. This sets the output voltage to 3.75V.
Specifications for output voltages greater than 3.75V will
be proportional to the ratio of the desired output voltage
to 3.75V; (VOUT/3.75V). For example: load regulation for
an output current change of 1mA to 300mA is –20mV
typical at VOUT = 3.75V. At VOUT = 12V, load regulation
would be:
Table 1. MS8 Package
COPPER AREA
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
TOPSIDE** BACKSIDE
BOARD AREA
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
1000mm2
225mm2
100mm2
2500mm2
2500mm2
2500mm2
2500mm2
110°C/W
115°C/W
120°C/W
130°C/W
(12V/3.75V)(–20mV) = –64mV
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:
* Pin 4 is ground. ** Device is mounted on topside.
Table 2. S8 Package*
COPPER AREA
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
BOARD AREA
1. Output current multiplied by the input/output voltage
differential: IOUT(VIN – VOUT), and
2. Ground pin current multiplied by the input voltage:
(IGND)(VIN)
TOPSIDE** BACKSIDE
2500mm2
1000mm2
225mm2
100mm2
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
60°C/W
60°C/W
68°C/W
74°C/W
* Pins 3, 6, 7 are ground. ** Device is mounted on topside.
10
LT1521/LT1521-3
LT1521-3.3/LT1521-5
U
W U U
APPLICATIONS INFORMATION
Table 3. SOT-223 Package
is required to prevent oscillations. The LT1521 is a
micropower device and output transient response will be
a function of output capacitance. See the Transient
Response curves in the Typical Performance Characteris-
tics. Larger values of output capacitance will decrease the
peak deviations and provide improved output transient
response for larger load current deltas. Bypass capaci-
tors, used to decouple individual components powered by
the LT1521, will increase the effective value of the output
capacitor.
(Thermal Resistance Junction-to-Tab 20°C/W)
COPPER AREA
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
TOPSIDE*
BACKSIDE
2500mm2
2500mm2
2500mm2
2500mm2
1000mm2
0
BOARD AREA
2500mm2
2500mm2
2500mm2
2500mm2
1000mm2
1000mm2
2500mm2
1000mm2
225mm2
100mm2
1000mm2
1000mm2
50°C/W
50°C/W
58°C/W
64°C/W
57°C/W
60°C/W
* Tab of device attached to topside copper.
Protection Features
Calculating Junction Temperature
TheLT1521incorporatesseveralprotectionfeatureswhich
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, reverse output voltages and reverse voltages
from output to input.
Example: Given an output voltage of 3.3V, an input voltage
range of 4.5V to 7V, an output current range of 0mA to
150mA and a maximum ambient temperature of 50°C,
what will the maximum junction temperature be?
The power dissipated by the device will be equal to:
IOUT(MAX)(VIN(MAX) – VOUT) + IGND(VIN(MAX)
Where,
)
Current limit protection and thermal overload protection
areintendedtoprotectthedeviceagainstcurrentoverload
conditions at the output of the device. For normal opera-
tion, the junction temperatures should not exceed 125°C.
IOUT(MAX) = 150mA
VIN(MAX) = 7V
IGND at (IOUT = 150mA, VIN = 7V) = 2.1mA
The input of the device will withstand reverse voltages of
20V. Current flow into the device will be limited to less
than 1mA (typically less than 100µA) and no negative
voltage will appear at the output. The device will protect
both itself and the load. This provides protection against
batteries that can be plugged in backward.
So,
P = 150mA(7V – 3.3V) + (2.1mA)(7V) = 0.57W
If we use a SOT-223 package, then the thermal resistance
willbein the range of50°C/W to 65°C/W depending onthe
copper area. So the junction temperature rise above
ambient will be approximately equal to:
For fixed voltage versions of the device, the output can be
pulled below ground without damaging the device. If the
input is left open circuit or grounded, the output can be
pulled below ground by 20V. The output will act like an
open circuit, no current will flow out of the pin. If the input
is powered by voltage source, the output will source the
short-circuit current of the device and will protect itself by
thermal limiting. For the adjustable version of the device,
the output pin is internally clamped at one diode drop
below ground. Reverse current for the adjustable device
must be limited to 5mA.
0.57W(60°C/W) = 34.2°C
The maximum junction temperature will then be equal to the
maximum junction temperature rise above ambient plus the
maximum ambient temperature or:
TJMAX = 50°C + 34.2°C = 84.2°C
Output Capacitance and Transient Performance
The LT1521 is designed to be stable with a wide range of
output capacitors. A minimum output capacitor of 1.5µF
11
LT1521/LT1521-3
LT1521-3.3/LT1521-5
U
W U U
APPLICATIONS INFORMATION
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
ground, pulledtosomeintermediatevoltageorisleftopen
circuit. Current flow back into the output will vary depend-
ing on the conditions. Many battery-powered circuits
incorporate some form of power management. The fol-
lowing information will help optimize battery life. Table 4
summarizes the following information.
rectified AC source. If the AC source is removed, then the
input of the LT1521 is effectively left floating. The reverse
outputcurrentalsofollowsthecurveinFigure3iftheinput
pin is left open. The state of the shutdown pin will have no
effect on the reverse output current when the input pin is
floating.
When the input of the LT1521 is forced to a voltage below
its nominal output voltage and its output is held high, the
outputcurrentwillfollowthecurveshowninFigure3. This
can happen if the input of the LT1521 is connected to a
discharged (low voltage) battery and the output is held up
by either a backup battery or by second regulator circuit.
When the input pin is forced below the output pin or the
output pin is pulled above the input pin, the input current
willtypicallydroptolessthan2µA(seeFigure4). Thestate
of the shutdown pin will have no effect on the reverse
output current when the output is pulled above the input.
The reverse output current will follow the curve in Figure
3 when the input is pulled to ground. This current flows
through the output pin to ground. The state of the shut-
down pin will have no effect on output current when the
input pin is pulled to ground.
Insomeapplicationsitmaybenecessarytoleavetheinput
on the LT1521 unconnected when the output is held high.
This can happen when the LT1521 is powered from a
50
5
T
= 25°C
IN
LT1521
J
V
V
OUT
V
OUT
V
OUT
= 3V (LT1521-3)
= 3.3V (LT1521-3.3)
= 5V (LT1521-5)
45
40
35
30
25
20
15
10
5
= 0V
CURRENT FLOWS
INTO OUTPUT PIN
V
(LT1521-3/LT1521-3.3
LT1521-5)
V
4
3
2
1
0
= V
OUT
SENSE
LT1521-3.3
= V
(LT1521)
OUT
ADJ
LT1521-3.3
LT1521-3
LT1521-5
LT1521-3
LT1521-5
0
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
LT1521 • F03
LT1521 • F04
Figure 4. Input Current
Figure 3. Reverse Output Current
12
LT1521/LT1521-3
LT1521-3.3/LT1521-5
U
W U U
APPLICATIONS INFORMATION
Table 4. Fault Conditions
INPUT PIN
SHDN PIN
OUTPUT/SENSE PINS
RESULTING CONDITIONS
< V
< V
(Nominal)
Open (High)
Forced to V
(Nominal)
Reverse Output Current ≈ 5µA (See Figure 3)
Input Current ≈ 1µA (See Figure 4)
OUT
OUT
(Nominal)
Grounded
Forced to V
(Nominal)
Reverse Output Current ≈ 5µA (See Figure 3)
Input Current ≈ 1µA (See Figure 4)
OUT
OUT
Open
Open (High)
Grounded
> 1V
> 1V
≤ 0V
≤ 0V
≤ 0V
≤ 0V
Reverse Output Current ≈ 5µA (See Figure 3)
Reverse Output Current ≈ 5µA (See Figure 3)
Output Current = 0
Open
≤ 0.8V
≤ 0.8V
> 1.5V
Open (High)
Grounded
Output Current = 0
Open (High)
Grounded
Output Current = Short-Circuit Current
Output Current = 0
–20V < V < 20V
IN
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.118 ± 0.004*
(3.00 ± 0.102)
8
7
6
5
0.118 ± 0.004**
(3.00 ± 0.102)
0.192 ± 0.004
(4.88 ± 0.10)
1
2
3
4
0.040 ± 0.006
(1.02 ± 0.15)
0.034 ± 0.004
(0.86 ± 0.102)
0.007
(0.18)
0° – 6° TYP
SEATING
PLANE
0.012
(0.30)
REF
0.021 ± 0.006
(0.53 ± 0.015)
0.006 ± 0.004
(0.15 ± 0.102)
MSOP (MS8) 1197
0.0256
(0.65)
TYP
*
DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
13
LT1521/LT1521-3
LT1521-3.3/LT1521-5
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
7
5
8
6
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.053 – 0.069
3
4
2
0.010 – 0.020
(0.254 – 0.508)
× 45°
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.016 – 0.050
0.406 – 1.270
0.050
(1.270)
TYP
0.014 – 0.019
(0.355 – 0.483)
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
SO8 0996
14
LT1521/LT1521-3
LT1521-3.3/LT1521-5
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
ST Package
3-Lead Plastic SOT-223
(LTC DWG # 05-08-1630)
0.248 – 0.264
(6.30 – 6.71)
0.116 – 0.124
(2.95 – 3.15)
0.264 – 0.287
(6.71 – 7.29)
0.130 – 0.146
(3.30 – 3.71)
0.033 – 0.041
(0.84 – 1.04)
0.090
(2.29)
NOM
10° – 16°
0.010 – 0.014
(0.25 – 0.36)
10°
MAX
0.071
(1.80)
MAX
10° – 16°
0.0008 – 0.0040
(0.0203 – 0.1016)
0.025 – 0.033
(0.64 – 0.84)
0.012
(0.31)
MIN
0.181
(4.60)
NOM
ST3 (SOT-233) 0792
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
LT1521/LT1521-3
LT1521-3.3/LT1521-5
RELATED PARTS
PART NUMBER
LTC®1174
LT1175
DESCRIPTION
COMMENTS
425mA High Efficiency Step-Down Switching Regulator
500mA Micropower Low Dropout Negative Linear Regulator
125mA Micropower Low Dropout Linear Regulator
Micropower Step-Up DC/DC Converter
>90% Efficiency, SO-8 Package
Selectable Current Limit
LT1120A
LT1304
20µA Quiescent Current, Includes Comparator
15µA Quiescent Current, 1.5 Minimum Input
50µA Quiescent Current
LT1529
3A Micropower Low Dropout Regulator
1521335fa LT/TP 0299 REV A 2K • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
16
●
●
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com
LINEAR TECHNOLOGY CORPORATION 1995
相关型号：
LT1521IST-5#TRPBF
LT1521 - 300mA Low Dropout Regulators with Micropower Quiescent Current and Shutdown; Package: SOT; Pins: 3; Temperature Range: -40°C to 85°C
Linear
LT1524J/883
IC 0.1 A SWITCHING CONTROLLER, 300 kHz SWITCHING FREQ-MAX, CDIP16, HERMETIC SEALED, CERDIP-16, Switching Regulator or Controller
Linear
LT1525AJ883C
IC 0.5 A SWITCHING CONTROLLER, 400 kHz SWITCHING FREQ-MAX, CDIP16, HERMETIC SEALED, CERDIP-16, Switching Regulator or Controller
Linear
©2020 ICPDF网 联系我们和版权申明