LT1962 Series
300mA, Low Noise,
Micropower
LDO Regulators
Features
Description
Low Noise: 20µVRMS (10Hz to 100kHz)
nn Output Current: 300mA
nn Low Quiescent Current: 30µA
nn Wide Input Voltage Range: 1.8V to 20V
nn Low Dropout Voltage: 270mV
nn Very Low Shutdown Current: < 1µA
nn No Protection Diodes Needed
nn Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 3V, 3.3V, 5V
nn Adjustable Output from 1.22V to 20V
nn Stable with 3.3µF Output Capacitor
nn Stable with Aluminum, Tantalum or
Ceramic Capacitors
nn Reverse Battery Protection
nn No Reverse Current
nn Overcurrent and Overtemperature Protected
nn 8-Lead MSOP Package
The LT®1962 series are micropower, low noise, low dropout
regulators. The devices are capable of supplying 300mA
of output current with a dropout voltage of 270mV. Designed for use in battery-powered systems, the low 30µA
quiescent current makes them an ideal choice. Quiescent
current is well controlled; it does not rise in dropout as it
does with many other regulators.
nn
Applications
Cellular Phones
Battery-Powered Systems
nn Noise-Sensitive Instrumentation Systems
nn
nn
A key feature of the LT1962 regulators is low output noise.
With the addition of an external 0.01µF bypass capacitor,
output noise drops to 20µVRMS over a 10Hz to 100kHz
bandwidth. The LT1962 regulators are stable with output
capacitors as low as 3.3µF. Small ceramic capacitors can
be used without the series resistance required by other
regulators.
Internal protection circuitry includes reverse battery protection, current limiting, thermal limiting and reverse current
protection. The parts come in fixed output voltages of 1.5V,
1.8V, 2.5V, 3V, 3.3V and 5V, and as an adjustable device
with a 1.22V reference voltage. The LT1962 regulators are
available in the 8-lead MSOP package.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
Typical Application
Dropout Voltage
400
3.3V Low Noise Regulator
IN
OUT
1µF
+
SENSE
10µF
LT1962-3.3
SHDN
GND
0.01µF
BYP
1962 TA01
DROPOUT VOLTAGE (mV)
VIN
3.7V TO
20V
350
3.3V AT 300mA
20µVRMS NOISE
300
250
200
150
100
50
0
0
50
100
150
200
LOAD CURRENT (mA)
250
300
1962 TA02
1962fb
1962fa
For more information www.linear.com/LT1962
1
LT1962 Series
Absolute Maximum Ratings
Pin Configuration
(Note 1)
IN Pin Voltage..........................................................±20V
OUT Pin Voltage.......................................................±20V
Input to Output Differential Voltage (Note 2)............±20V
SENSE Pin Voltage...................................................±20V
ADJ Pin Voltage.........................................................±7V
BYP Pin Voltage......................................................±0.6V
SHDN Pin Voltage....................................................±20V
Output Short-Circuit Duration........................... Indefinite
Operating Junction Temperature Range
(Note 3).............................................. –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................... 300°C
TOP VIEW
OUT
SENSE/ADJ*
BYP
GND
8
7
6
5
1
2
3
4
IN
NC
NC
SHDN
MS8 PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 150°C, θJA = 125°C/W
*PIN 2: SENSE FOR LT1962-1.5/LT1962-1.8/
LT1962-2.5/LT1962-3/LT1962-3.3/
LT1962-5. ADJ FOR LT1962
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT1962EMS8#PBF
LT1962IMS8#PBF
LT1962EMS8-1.5#PBF
LT1962EMS8-1.8#PBF
LT1962EMS8-2.5#PBF
LT1962EMS8-3#PBF
LT1962EMS8-3.3#PBF
LT1962EMS8-5#PBF
LT1962EMS8#TRPBF
LT1962IMS8#TRPBF
LT1962EMS8-1.5#TRPBF
LT1962EMS8-1.8#TRPBF
LT1962EMS8-2.5#TRPBF
LT1962EMS8-3#TRPBF
LT1962EMS8-3.3#TRPBF
LT1962EMS8-5#TRPBF
LTML
LTML
LTSZ
LTTA
LTPT
LTPQ
LTPS
LTPR
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on nonstandard lead based finish parts.
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
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 3)
PARAMETER
CONDITIONS
Minimum Operating Voltage
LT1962
Regulated Output Voltage
(Notes 4, 5)
VIN = 2V, ILOAD = 1mA
LT1962-1.5
2.5V < VIN < 20V, 1mA < ILOAD < 300mA
2
MIN
TYP
1.8
2.3
V
l
1.485
1.462
1.500
1.500
1.515
1.538
V
V
LT1962-1.8
VIN = 2.3V, ILOAD = 1mA
2.8V < VIN < 20V, 1mA < ILOAD < 300mA
l
1.782
1.755
1.800
1.800
1.818
1.845
V
V
LT1962-2.5
VIN = 3V, ILOAD = 1mA
3.5V < VIN < 20V, 1mA < ILOAD < 300mA
l
2.475
2.435
2.500
2.500
2.525
2.565
V
V
LT1962-3
VIN = 3.5V, ILOAD = 1mA
4V < VIN < 20V, 1mA < ILOAD < 300mA
l
2.970
2.925
3.000
3.000
3.030
3.075
V
V
LT1962-3.3
VIN = 3.8V, ILOAD = 1mA
4.3V < VIN < 20V, 1mA < ILOAD < 300mA
l
3.267
3.220
3.300
3.300
3.333
3.380
V
V
LT1962-5
VIN = 5.5V, ILOAD = 1mA
6V < VIN < 20V, 1mA < ILOAD < 300mA
l
4.950
4.875
5.000
5.000
5.050
5.125
V
V
ILOAD = 300mA (Notes 4, 12)
l
MAX
UNITS
1962fb
1962fa
For more information www.linear.com/LT1962
LT1962 Series
Electrical
Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 3)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
ADJ Pin Voltage
(Notes 4, 5)
VIN = 2V, ILOAD = 1mA
LT1962
2.3V < VIN < 20V, 1mA < ILOAD < 300mA
l
1.208
1.190
1.220
1.220
1.232
1.250
V
V
Line Regulation
LT1962-1.5 ∆VIN = 2V to 20V, ILOAD = 1mA
LT1962-1.8 ∆VIN = 2.3V to 20V, ILOAD = 1mA
LT1962-2.5 ∆VIN = 3V to 20V, ILOAD = 1mA
LT1962-3 ∆VIN = 3.5V to 20V, ILOAD = 1mA
LT1962-3.3 ∆VIN = 3.8V to 20V, ILOAD = 1mA
LT1962-5 ∆VIN = 5.5V to 20V, ILOAD = 1mA
LT1962 (Note 4) ∆VIN = 2V to 20V, ILOAD = 1mA
l
l
l
l
l
l
l
1
1
1
1
1
1
1
5
5
5
5
5
5
5
mV
mV
mV
mV
mV
mV
mV
Load Regulation
LT1962-1.5
VIN = 2.5V, ∆ILOAD = 1mA to 300mA
VIN = 2.5V, ∆ILOAD = 1mA to 300mA
3
l
8
15
mV
mV
LT1962-1.8
VIN = 2.8V, ∆ILOAD = 1mA to 300mA
VIN = 2.8V, ∆ILOAD = 1mA to 300mA
4
l
9
18
mV
mV
LT1962-2.5
VIN = 3.5V, ∆ILOAD = 1mA to 300mA
VIN = 3.5V, ∆ILOAD = 1mA to 300mA
5
l
12
25
mV
mV
LT1962-3
VIN = 4V, ∆ILOAD = 1mA to 300mA
VIN = 4V, ∆ILOAD = 1mA to 300mA
7
l
15
30
mV
mV
LT1962-3.3
VIN = 4.3V, ∆ILOAD = 1mA to 300mA
VIN = 4.3V, ∆ILOAD = 1mA to 300mA
7
l
17
33
mV
mV
LT1962-5
VIN = 6V, ∆ILOAD = 1mA to 300mA
VIN = 6V, ∆ILOAD = 1mA to 300mA
12
l
25
50
mV
mV
2
6
12
mV
mV
0.10
0.15
0.21
V
V
0.15
0.20
0.28
V
V
0.18
0.24
0.33
V
V
0.27
0.33
0.43
V
V
30
65
1.1
2
8
75
120
1.6
3
12
µA
µA
mA
mA
mA
LT1962 (Note 4) VIN = 2.3V, ∆ILOAD = 1mA to 300mA
VIN = 2.3V, ∆ILOAD = 1mA to 300mA
l
ILOAD = 10mA
ILOAD = 10mA
l
ILOAD = 50mA
ILOAD = 50mA
l
ILOAD = 100mA
ILOAD = 100mA
l
ILOAD = 300mA
ILOAD = 300mA
l
GND Pin Current
VIN = VOUT(NOMINAL)
(Notes 6, 8)
ILOAD = 0mA
ILOAD = 1mA
ILOAD = 50mA
ILOAD = 100mA
ILOAD = 300mA
l
l
l
l
l
Output Voltage Noise
COUT = 10µF, CBYP = 0.01µF, ILOAD = 300mA, BW = 10Hz to 100kHz
Dropout Voltage
VIN = VOUT(NOMINAL)
(Notes 6, 7, 12)
ADJ Pin Bias Current
(Notes 4, 9)
Shutdown Threshold
VOUT = Off to On
VOUT = On to Off
SHDN Pin Current
(Note 10)
20
µVRMS
30
100
nA
0.8
0.65
2
V
V
VSHDN = 0V
VSHDN = 20V
0.01
1
0.5
5
µA
µA
Quiescent Current in Shutdown
VIN = 6V, VSHDN = 0V
0.1
1
µA
Ripple Rejection
VIN – VOUT = 1.5V (Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz,
ILOAD = 300mA
Current Limit
VIN = 7V, VOUT = 0V
VIN = VOUT(NOMINAL) + 1V, ∆VOUT = –0.1V
l
VIN = –20V, VOUT = 0V
l
Input Reverse Leakage Current
l
l
0.25
55
320
65
dB
700
mA
mA
1
mA
1962fb
1962fa
For more information www.linear.com/LT1962
3
LT1962 Series
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 3)
PARAMETER
CONDITIONS
Reverse Output Current
(Note 11)
LT1962-1.5
LT1962-1.8
LT1962-2.5
LT1962-3
LT1962-3.3
LT1962-5
LT1962 (Note 4)
MIN
VOUT = 1.5V, VIN < 1.5V
VOUT = 1.8V, VIN < 1.8V
VOUT = 2.5V, VIN < 2.5V
VOUT = 3V, VIN < 3V
VOUT = 3.3V, VIN < 3.3V
VOUT = 5V, VIN < 5V
VOUT = 1.22V, VIN < 1.22V
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: Absolute maximum input to output differential voltage cannot
be achieved with all combinations of rated IN pin and OUT pin voltages.
With the IN pin at 20V, the OUT pin may not be pulled below 0V. The total
measured voltage from in to out can not exceed ±20V.
Note 3: The LT1962 is tested and specified under pulse load conditions
such that TJ ≈ TA. The LT1962E is tested at TA = 25°C and performance
is guaranteed from 0°C to 125°C. Performance of the LT1962E over the
full –40°C to 125°C operating temperature range is assured by design,
characterization, and correlation with statistical process controls. The
LT1962I is guaranteed over the full –40°C to 125°C operating junction
temperature range.
Note 4: The LT1962 (adjustable version) is tested and specified for these
conditions with the ADJ pin connected to the OUT pin.
Note 5: 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.
TYP
MAX
10
10
10
10
10
10
5
20
20
20
20
20
20
10
UNITS
µA
µA
µA
µA
µA
µA
µA
Note 6: To satisfy requirements for minimum input voltage, the LT1962
(adjustable version) is tested and specified for these conditions with an
external resistor divider (two 250k resistors) for an output voltage of
2.44V. The external resistor divider will add a 5µA DC load on the output.
Note 7: 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: VIN – VDROPOUT.
Note 8: GND pin current is tested with VIN = VOUT(NOMINAL) or VIN = 2.3V
(whichever is greater) and a current source load. This means the device is
tested while operating in its dropout region. This is the worst-case GND
pin current. The GND pin current will decrease slightly at higher input
voltages.
Note 9: ADJ pin bias current flows into the ADJ pin.
Note 10: SHDN pin current flows into the SHDN pin. This current is
included in the specification for GND pin current.
Note 11: 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 12: For the LT1962, LT1962-1.5 and LT1962-1.8 dropout voltage
will be limited by the minimum input voltage specification under some
output voltage/load conditions. See the curve of Minimum Input Voltage
in the Typical Performance Characteristics section. For other fixed voltage
versions of the LT1962, the minimum input voltage is limited by the
dropout voltage.
Typical Performance Characteristics
Guaranteed Dropout Voltage
350
450
TJ = 125°C
300
250
200
TJ = 25°C
150
100
50
0
4
0
50
100
200
250
150
OUTPUT CURRENT (mA)
300
1962 G01
Dropout Voltage
400
= TEST POINTS
350
TJ ≤ 125°C
400
350
DROPOUT VOTLAGE (mV)
500
GUARANTEED DROPOUT VOLTAGE (mV)
DROPOUT VOLTAGE (mV)
Typical Dropout Voltage
400
TJ ≤ 25°C
300
250
200
150
100
250
IL = 100mA
200
IL = 50mA
150
IL = 10mA
100
50
50
0
IL = 300mA
300
0
50
150
200
250
100
OUTPUT CURRENT (mA)
300
1962 G02
0
–50 –25
IL = 1mA
0
50
75
25
TEMPERATURE (°C)
100
125
1962 G03
1962fb
1962fa
For more information www.linear.com/LT1962
LT1962 Series
Typical Performance Characteristics
Quiescent Current
LT1962-1.5 Output Voltage
1.532
40
OUTPUT VOLTAGE (V)
QUIESCENT CURRENT (µA)
45
35
30
25
20
15
10
5
VIN = 6V
VSHDN = VIN
RL = ∞, IL = 0 (LT1962-1.5/-1.8
/2.5/-3/-3.3/-5)
RL = 250k, IL = 5µA (LT1962)
0
–50
–25
50
25
0
75
TEMPERATURE (°C)
IL = 1mA
1.524
1.827
1.516
1.818
1.508
1.500
1.492
1.484
1.476
100
1.468
–50
125
LT1962-2.5 Output Voltage
IL = 1mA
1.791
1.782
–25
50
75
0
25
TEMPERATURE (°C)
1.764
–50
125
100
IL = 1mA
3.030
3.330
2.49
2.48
3.015
3.000
2.985
2.970
2.955
–25
0
50
75
25
TEMPERATURE (°C)
100
IL = 1mA
5.050
1.230
ADJ PIN VOLTAGE (V)
1.235
5.025
5.000
4.975
4.950
4.925
0
50
75
25
TEMPERATURE (°C)
100
125
0
50
75
25
TEMPERATURE (°C)
3.285
3.270
3.240
–50
100
125
1962 G10
0
50
75
25
TEMPERATURE (°C)
1.225
1.220
1.215
1.210
50
75
25
TEMPERATURE (°C)
1962 G09
600
500
400
300
200
VSHDN = 0V
100
0
125
TJ = 25°C
RL = ∞
700
–25
100
LT1962-1.5 Quiescent Current
800
IL = 1mA
1.200
–50
–25
1962 G08
1.205
–25
3.300
LT1962 ADJ Pin Voltage
1.240
5.075
4.900
–50
–25
1962 G07
LT1962-5 Output Voltage
IL = 1mA
3.255
2.940
–50
125
1962 G06
3.315
QUIESCENT CURRENT (µA)
2.46
–50
5.100
OUTPUT VOLTAGE (V)
2.52
2.50
125
100
LT1962-3.3 Output Voltage
3.360
3.345
2.51
50
75
0
25
TEMPERATURE (°C)
–25
1962 G05
3.045
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
1.800
2.53
2.47
OUTPUT VOLTAGE (V)
1.809
LT1962-3 Output Voltage
3.060
IL = 1mA
1.773
1962 G04
2.54
LT1962-1.8 Output Voltage
1.836
OUTPUT VOLTAGE (V)
50
100
125
1962 G11
0
VSHDN = VIN
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1962 G12
1962fb
1962fa
For more information www.linear.com/LT1962
5
LT1962 Series
Typical Performance Characteristics
TJ = 25°C
RL = ∞
600
500
400
300
VSHDN = 0V
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
400
300
9
0
10
QUIESCENT CURRENT (µA)
QUIESCENT CURRENT (µA)
400
300
0
VSHDN = 0V
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
250
0
0
1
2
RL = 1.5k
IL = 1mA*
3 4 5 6 7
INPUT VOLTAGE (V)
2
8
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
1250
RL = 180Ω
IL = 10mA*
9
10
0
0
1
2
RL = 1.8k
IL = 1mA*
3 4 5 6 7
INPUT VOLTAGE (V)
8
8
9
10
1962 G15
25
20
15
10
VSHDN = 0V
0
2
4
6 8 10 12 14 16 18 20
INPUT VOLTAGE (V)
1962 G18
LT1962-2.5 GND Pin Current
750
500
3 4 5 6 7
INPUT VOLTAGE (V)
VSHDN = VIN
1962 G17
RL = 36Ω
IL = 50mA*
1000
2
30
0
10
1500
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 1.8V
250
1962 G19
6
1
1
5
VSHDN = VIN
1500
GND PIN CURRENT (µA)
GND PIN CURRENT (µA)
RL = 150Ω
IL = 10mA*
VSHDN = 0V
0
0
TJ = 25°C
35 RL = 250k
300
200
VSHDN = 0V
VSHDN = VIN
LT1962 Quiescent Current
LT1962-1.8 GND Pin Current
750
500
200
40
400
1962 G16
RL = 30Ω
IL = 50mA*
1000
300
1962 G14
500
0
10
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 1.5V
1250
400
0
10
600
LT1962-1.5 GND Pin Current
1500
9
TJ = 25°C
RL = ∞
100
VSHDN = VIN
0
8
3 4 5 6 7
INPUT VOLTAGE (V)
700
500
100
2
500
LT1962-5 Quiescent Current
600
200
1
800
TJ = 25°C
RL = ∞
700
0
600
100
VSHDN = VIN
1962 G13
LT1962-3.3 Quiescent Current
800
VSHDN = 0V
100
VSHDN = VIN
0
500
QUIESCENT CURRENT (µA)
100
600
200
TJ = 25°C
RL = ∞
700
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 2.5V
1250
GND PIN CURRENT (µA)
200
LT1962-3 Quiescent Current
800
TJ = 25°C
RL = ∞
700
QUIESCENT CURRENT (µA)
700
QUIESCENT CURRENT (µA)
LT1962-2.5 Quiescent Current
800
QUIESCENT CURRENT (µA)
LT1962-1.8 Quiescent Current
800
RL = 50Ω
IL = 50mA*
1000
750
RL = 250Ω
IL = 10mA*
500
250
9
10
1962 G20
0
0
1
2
RL = 2.5k
IL = 1mA*
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1962 G21
1962fb
1962fa
For more information www.linear.com/LT1962
LT1962 Series
Typical Performance Characteristics
RL = 60Ω
IL = 50mA*
750
RL = 300Ω
IL = 10mA*
500
RL = 3k
IL = 1mA*
250
0
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
RL = 66Ω
IL = 50mA*
1000
750
RL = 330Ω
IL = 10mA*
500
RL = 3.3k
IL = 1mA*
250
9
8
0
10
0
1
3 4 5 6 7
INPUT VOLTAGE (V)
2
8
1962 G22
750
500
250
6
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
9
8
5
3
5
0
1
2
3
RL = 25Ω
IL = 100mA*
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
1
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
5
9
10
1962 G28
10
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 1.8V
3
RL = 18Ω
IL = 100mA*
2
5
RL = 15Ω
IL = 200mA*
4
3
RL = 30Ω
IL = 100mA*
2
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1962 G27
LT1962-3.3 GND Pin Current
RL = 10Ω
IL = 300mA*
6
0
9
8
RL = 9Ω
IL = 200mA*
4
1962 G26
1
0
RL = 6Ω
IL = 300mA*
6
0
10
8
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 3V
7
RL = 12.5Ω
IL = 200mA*
4
3 4 5 6 7
INPUT VOLTAGE (V)
7
LT1962-3 GND Pin Current
RL = 8.33Ω
IL = 300mA*
2
1
8
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
6
1
LT1962-1.8 GND Pin Current
RL = 15Ω
IL = 100mA*
2
0
10
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 2.5V
7
0
8
RL = 7.5Ω
IL = 200mA*
4
LT1962-2.5 GND Pin Current
8
RL = 5k
IL = 1mA*
1962 G24
1
0
500
0
10
RL = 5Ω
IL = 300mA*
1962 G25
0
9
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 3.3V
7
GND PIN CURRENT (mA)
0
RL = 1.22k
IL = 1mA*
RL = 122Ω
IL = 10mA*
RL = 500Ω
IL = 10mA*
250
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 1.5V
7
GND PIN CURRENT (mA)
GND PIN CURRENT (µA)
RL = 24.4Ω
IL = 50mA*
1000
750
LT1962-1.5 GND Pin Current
8
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 1.22V
1250
RL = 100Ω
IL = 50mA*
1000
1962 G23
LT1962 GND Pin Current
1500
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 5V
1250
GND PIN CURRENT (mA)
1000
LT1962-5 GND Pin Current
1500
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 3.3V
1250
GND PIN CURRENT (µA)
1250
GND PIN CURRENT (µA)
LT1962-3.3 GND Pin Current
1500
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 3V
GND PIN CURRENT (µA)
LT1962-3 GND Pin Current
1500
6
RL = 11Ω
IL = 300mA*
5
RL = 16.5Ω
IL = 200mA*
4
3
RL = 33Ω
IL = 100mA*
2
1
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1962 G29
0
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1962 G30
1962fb
1962fa
For more information www.linear.com/LT1962
7
LT1962 Series
Typical Performance Characteristics
LT1962 GND Pin Current
8
6
RL = 16.7Ω
IL = 300mA*
5
RL = 25Ω
IL = 200mA*
4
3
RL = 50Ω
IL = 100mA*
2
1
6
5
4
2
RL = 12.2Ω
IL = 100mA*
1
1
0
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
0
10
0
1
2
1962 G31
3 4 5 6 7
INPUT VOLTAGE (V)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
100
0.7
0.6
IL = 1mA
0.5
0.4
0.3
0.2
–25
50
25
0
75
TEMPERATURE (°C)
100
0.4
0.8
0.6
0.4
0.2
75
50
25
TEMPERATURE (°C)
100
125
1962 G37
0
1
2
3
7 8
4 5 6
SHDN PIN VOLTAGE (V)
9
VOUT = 0V
0.9
0.8
25
20
15
10
0
–50 –25
10
Current Limit
0.7
0.6
0.5
0.4
0.3
0.2
5
0.2
0
1.0
1.0
CURRENT LIMIT (A)
0.6
1962 G33
1962 G36
35
ADJ PIN BIAS CURRENT (nA)
0.8
300
1.2
0
125
30
1.0
100
200
250
150
OUTPUT CURRENT (mA)
SHDN Pin Input Current
ADJ Pin Bias Current
1.2
50
0
1962 G35
VSHDN = 20V
–25
2
1962 G32
IL = 300mA
0
–50
125
1.4
0
–50
3
0
10
0.8
SHDN Pin Input Current
1.6
SHDN PIN INPUT CURRENT (µA)
9
0.1
50
25
0
75
TEMPERATURE (°C)
4
1.4
1962 G34
8
8
0.9
0.8
–25
5
SHDN Pin Threshold (Off-to-On)
IL = 1mA
0
–50
6
1
1.0
SHDN PIN THRESHOLD (V)
SHDN PIN THRESHOLD (V)
0.9
RL = 6.1Ω
IL = 200mA*
3
SHDN Pin Threshold (On-to-Off)
1.0
RL = 4.07Ω
IL = 300mA*
VIN = VOUT(NOMINAL) + 1V
7
SHDN PIN INPUT CURRENT (µA)
0
TJ = 25°C
VIN = VSHDN
*FOR VOUT = 1.22V
7
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
TJ = 25°C
7 VIN = VSHDN
*FOR VOUT = 5V
GND Pin Current vs ILOAD
8
GND PIN CURRENT (mA)
LT1962-5 GND Pin Current
8
0.1
50
25
75
0
TEMPERATURE (°C)
100
125
1962 G38
0
0
1
4
3
2
5
INPUT VOLTAGE (V)
6
7
1962 G39
1962fb
1962fa
For more information www.linear.com/LT1962
LT1962 Series
Typical Performance Characteristics
Current Limit
0.8
0.6
0.4
0.2
TJ = 25°C
90 VIN = 0V
CURRENT FLOWS
80 INTO OUTPUT PIN
70 VOUT = VADJ (LT1962)
50
25
75
0
TEMPERATURE (°C)
50
40
100
COUT = 10µF
40
30
COUT = 3.3µF
20
10
1k
10k
FREQUENCY (Hz)
100
70
100k
1M
1962 G43
50
40
LOAD REGULATION (mV)
IL = 1mA
1.00
0.75
0.50
–25
9
10
1962 G41
CBYP = 100pF
50
25
0
75
TEMPERATURE (°C)
100
125
1962 G46
LT1962-1.8
LT1962-3.3
LT1962-3
LT1962-2.5
–15
100k
1962 G42
62
60
58
56
LT1962-5
100
125
1962 G47
100
TEMPERATURE (°C)
1962 G44
LT1962-1.5
50
25
75
0
TEMPERATURE (°C)
64
IL = 300mA
54 VIN = VOUT(NOMINAL) + 1V
+ 0.5VP-P RIPPLE AT f = 120Hz
52
75
0
50
25
–50 –25
1M
VIN = VOUT(NOMINAL) + 1V
∆IL = 1mA TO 300mA
–25
–50 –25
125
66
CBYP = 1000pF
–5
–10
100
Ripple Rejection
CBYP = 0.01µF
LT1962
50
25
75
0
TEMPERATURE (°C)
68
20 IL = 300mA
VIN = VOUT(NOMINAL) + 1V
10 + 50mVRMS RIPPLE
COUT = 10µF
0
10
1k
10k
100
FREQUENCY (Hz)
–20
0.25
0
–50
3 4 5 6 7 8
OUTPUT VOLTAGE (V)
30
0
1.25
2
Load Regulation
IL = 300mA
1.50
1
LT1962
5
VOUT = 1.22V
1.75
0
60
LT1962 Minimum Input Voltage
2.00
5
0
–50 –25
RIPPLE REJECTION (dB)
50
10
Input Ripple Rejection
80
RIPPLE REJECTION (dB)
RIPPLE REJECTION (dB)
60
VIN = 0V
VOUT = 1.22V (LT1962)
25 VOUT = 1.5V (LT1962-1.5)
VOUT = 1.8V (LT1962-1.8)
VOUT = 2.5V (LT1962-2.5)
20 V
OUT = 3V (LT1962-3)
VOUT = 3.3V (LT1962-3.3)
= 5V (LT1962-5)
V
15 OUT
LT1962-1.5/-1.8/-2.5/-3/-3.3/-5
LT1962-5
1962 G40
10
MINIMUM INPUT VOLTAGE (V)
LT1962-3.3
20
0
125
IL = 300mA
VIN = VOUT(NOMINAL) + 1V
+ 50mVRMS RIPPLE
CBYP = 0
70
2.25
LT1962-3
30
Input Ripple Rejection
80
2.50
LT1962-1.5
LT1962-1.8
LT1962-2.5
60
10
0
–50 –25
0
LT1962
REVERSE OUTPUT CURRENT (µA)
VIN = 7V
VOUT = 0V
Reverse Output Current
30
OUTPUT NOISE SPECTRIAL DENSITY (µV/√Hz)
CURRENT LIMIT (A)
1.0
Reverse Output Current
100
REVERSE OUTPUT CURRENT (µA)
1.2
10
125
1962 G45
Output Noise Spectral Density
IL = 300mA
COUT = 10µF
CBYP = 0
LT1962-5
LT1962-3.3
LT1962-3
1
LT1962
0.1
0.01
10
LT1962-2.5
LT1962-1.8
LT1962-1.5
100
1k
10k
FREQUENCY (Hz)
100k
1962 G48
1962fb
1962fa
For more information www.linear.com/LT1962
9
LT1962 Series
Typical Performance Characteristics
RMS Output Noise
vs Bypass Capacitor
160
IL = 300mA
COUT = 10µF
CBYP = 1000pF
1
CBYP = 100pF
LT1962
CBYP = 0.01µF
0.1
160
IL = 300mA
COUT = 10µF
f = 10Hz to 100kHz
140
LT1962-5
RMS Output Noise
vs Load Current (10Hz to 100kHz)
120
LT1962-5
100
80
LT1962-3
LT1962-3.3
LT1962-2.5
LT1962-1.8
LT1962-1.5
60
40
LT1962
20
10
100
1k
10k
FREQUENCY (Hz)
0
100k
100
10
1k
CBYP (pF)
1962 G49
VOUT
100µV/DIV
1962 G52
1ms/DIV
1962 G53
–0.2
–0.4
300
200
100
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
TIME (ms)
1962 G56
10
LT1962
0.1
1
10
100
LOAD CURRENT (mA)
1000
1962 G51
COUT = 10µF
IL = 300mA
1962 G54
1ms/DIV
LT1962-5 Transient Response
VIN = 6V
0.4 CIN = 10µF
COUT = 10µF
0.2 C
BYP = 0
0
0
LT1962-5
LT1962-5 10Hz to 100kHz
Output Noise (CBYP = 1000pF)
OUTPUT VOLTAGE
DEVIATION (mV)
OUTPUT VOLTAGE
DEVIATION (V)
1962 G55
LOAD CURRENT (mA)
1ms/DIV
40
LT1962-5 Transient Response
VOUT
100µV/DIV
LT1962
VOUT
100µV/DIV
COUT = 10µF
IL = 300mA
LT1962-5 10Hz to 100kHz
Output Noise (CBYP = 0.01µF)
COUT = 10µF
IL = 300mA
60
1962 G50
VOUT
100µV/DIV
1ms/DIV
80
0
0.01
10k
LT1962-5
100
LT1962-5 10Hz to 100kHz
Output Noise (CBYP = 100pF)
LT1962-5 10Hz to 100kHz
Output Noise (CBYP = 0)
COUT = 10µF
IL = 300mA
120
20
LOAD CURRENT (mA)
0.01
COUT = 10µF
CBYP = 0µF
CBYP = 0.01µF
140
OUTPUT NOISE (µVRMS)
10
OUTPUT NOISE (µVRMS)
OUTPUT NOISE SPECTRAL DENSITY (µV/√Hz)
Output Noise Spectral Density
VIN = 6V
CIN = 10µF
COUT = 10µF
CBYP = 0.01µF
0.10
0.05
0
–0.05
–0.10
300
200
100
0
0
50 100 150 200 250 300 350 400 450 500
TIME (µs)
1962 G57
1962fb
1962fa
For more information www.linear.com/LT1962
LT1962 Series
Pin Functions
OUT (Pin 1): 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 capacitance and
reverse output characteristics.
SENSE (Pin 2): Sense. For fixed voltage versions of the
LT1962 (LT1962-1.5/LT1962-1.8/LT1962-2.5/LT1962-3/
LT1962-3.3/LT1962-5), 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 the OUT pin of
the regulator. In critical applications, small voltage drops
are caused by the resistance (RP) of PC traces between
the regulator and the load. These 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 10µA at the nominal rated output voltage. The
SENSE pin can be pulled below ground (as in a dual supply
system where the regulator load is returned to a negative
supply) and still allow the device to start and operate.
8
IN
OUT
1
RP
LT1962
VIN
+
5
SHDN
SENSE
+
2
LOAD
GND
4
RP
1962 F01
Figure 1. Kelvin Sense Connection
ADJ (Pin 2): Adjust. For the adjustable LT1962, 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. The ADJ pin voltage is 1.22V referenced to ground
and the output voltage range is 1.22V to 20V.
BYP (Pin 3): Bypass. The BYP pin is used to bypass the
reference of the LT1962 to achieve low noise performance
from the regulator. The BYP pin is clamped internally to
±0.6V (one VBE). A small capacitor from the output to
this pin will bypass the reference to lower the output voltage noise. A maximum value of 0.01µF can be used for
reducing output voltage noise to a typical 20µVRMS over
a 10Hz to 100kHz bandwidth. If not used, this pin must
be left unconnected.
GND (Pin 4): Ground.
SHDN (Pin 5): Shutdown. The SHDN pin is used to put
the LT1962 regulators into a low power shutdown state.
The output will be off when the SHDN pin is pulled low.
The SHDN pin can be driven either by 5V logic or opencollector logic with a pull-up resistor. The pull-up resistor is
required to supply the pull-up current of the open-collector
gate, normally several microamperes, and the SHDN pin
current, typically 1µA. If unused, the SHDN pin must be
connected to VIN. The device will not function if the SHDN
pin is not connected.
NC (Pins 6, 7): No Connect. These pins are not internally
connected. For improved power handling capabilities,
these pins can be connected to the PC board.
IN (Pin 8): 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-powered circuits. A
bypass capacitor in the range of 1µF to 10µF is sufficient.
The LT1962 regulators are designed to withstand reverse
voltages on the IN pin with respect to ground and the OUT
pin. In the case of a reverse input, which can happen if
a battery is plugged in backwards, the device will act as
if there is a diode in series with its input. There will be
no reverse current flow into the regulator and no reverse
voltage will appear at the load. The device will protect both
itself and the load.
1962fb
1962fa
For more information www.linear.com/LT1962
11
LT1962 Series
Applications Information
The LT1962 series are 300mA low dropout regulators with
micropower quiescent current and shutdown. The devices
are capable of supplying 300mA at a dropout voltage of
300mV. Output voltage noise can be lowered to 20µVRMS
over a 10Hz to 100kHz bandwidth with the addition of a
0.01µF reference bypass capacitor. Additionally, the reference bypass capacitor will improve transient response of
the regulator, lowering the settling time for transient load
conditions. The low operating quiescent current (30µA)
drops to less than 1µA in shutdown. In addition to the
low quiescent current, the LT1962 regulators incorporate
several protection features which make them ideal for use
in battery-powered systems. The devices are 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, the LT1962-X acts like it has a diode in series with
its output and prevents reverse current flow. Additionally,
in dual supply applications where the regulator load is
returned to a negative supply, the output can be pulled
below ground by as much as 20V and still allow the device
to start and operate.
Adjustable Operation
The adjustable version of the LT1962 has an output voltage
range of 1.22V to 20V. The output voltage is set by the
ratio of two external resistors as shown in Figure 2. The
device servos the output to maintain the ADJ pin voltage
at 1.22V referenced to ground. The current in R1 is then
equal to 1.22V/R1 and the current in R2 is the current in
IN
VIN
OUT
LT1962
R2
VOUT
+
ADJ
GND
R1
1962 F02
⎛ R2 ⎞
VOUT = 1.22V ⎜1+ ⎟ + (IADJ) (R2)
⎝ R1⎠
VADJ = 1.22V
IADJ = 30nA at 25°C
OUTPUT RANGE = 1.22V to 20V
Figure 2. Adjustable Operation
12
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 2. The value of R1 should be no greater than 250k
to minimize errors in the output voltage caused by the
ADJ pin bias current. Note that in shutdown the output is
turned off and the divider current will be zero.
The adjustable device is tested and specified with the ADJ
pin tied to the OUT pin for an output voltage of 1.22V.
Specifications for output voltages greater than 1.22V will
be proportional to the ratio of the desired output voltage
to 1.22V: VOUT/1.22V. For example, load regulation for an
output current change of 1mA to 300mA is –2mV typical
at VOUT = 1.22V. At VOUT = 12V, load regulation is:
(12V/1.22V)(–2mV) = –19.7mV
Bypass Capacitance and Low Noise Performance
The LT1962 regulators may be used with the addition
of a bypass capacitor from VOUT to the BYP pin to lower
output voltage noise. A good quality low leakage capacitor
is recommended. This capacitor will bypass the reference
of the regulator, providing a low frequency noise pole. The
noise pole provided by this bypass capacitor will lower the
output voltage noise to as low as 20µVRMS with the addition
of a 0.01µF bypass capacitor. Using a bypass capacitor has
the added benefit of improving transient response. With no
bypass capacitor and a 10µF output capacitor, a 10mA to
300mA load step will settle to within 1% of its final value
in less than 100µs. With the addition of a 0.01µF bypass
capacitor, the output will settle to within 1% for a 10mA
to 300mA load step in less than 10µs, with total output
voltage deviation of less than 2% (see LT1962-5 Transient
Response in the Typical Performance Characteristics section). However, regulator start-up time is proportional to
the size of the bypass capacitor, slowing to 15ms with a
0.01µF bypass capacitor and 10µF output capacitor.
Output Capacitance and Transient Response
The LT1962 regulators are 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.
1962fb
1962fa
For more information www.linear.com/LT1962
LT1962 Series
Applications Information
The LT1962-X 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 LT1962,
will increase the effective output capacitor value. With
larger capacitors used to bypass the reference (for low
noise operation), larger values of output capacitance are
needed. For 100pF of bypass capacitance, 4.7µF of output
capacitor is recommended. With a 1000pF bypass capacitor or larger, a 6.8µF output capacitor is recommended.
The shaded region of Figure 3 defines the range over
which the LT1962 regulators are stable. The minimum ESR
needed is defined by the amount of bypass capacitance
used, while the maximum ESR is 3Ω.
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
dielectrics used are Z5U, Y5V, X5R and X7R. The Z5U and
Y5V dielectrics are good for providing high capacitance
in a small package, but exhibit strong voltage and temperature coefficients as shown in Figures 4 and 5. When
used with a 5V regulator, a 10µF Y5V capacitor can exhibit
an effective value as low as 1µF to 2µF over the operating
temperature 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.
4.0
20
3.5
STABLE REGION
2.5
ESR (Ω)
CHANGE IN VALUE (%)
0
3.0
2.0
CBYP = 0
CBYP = 100pF
1.5
1.0
0.5
0
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
CBYP = 330pF
CBYP ≥ 1000pF
–40
–60
Y5V
–80
3
2
4 5 6 7 8 9 10
OUTPUT CAPACITANCE (µF)
1
X5R
–20
–100
0
1962 F03
2
4
8
6
10 12
DC BIAS VOLTAGE (V)
14
16
1962 F04
Figure 3. Stability
Figure 4. Ceramic Capacitor DC Bias Characteristics
40
CHANGE IN VALUE (%)
20
LT1962-5
COUT = 10µF
CBYP = 0.01µF
ILOAD = 100mA
X5R
0
–20
–40
VOUT
500µV/DIV
Y5V
–60
–80
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
–100
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
100ms/DIV
1962 F06
1962 F05
Figure 5. Ceramic Capacitor Temperature Characteristics
Figure 6. Noise Resulting from Tapping on a Ceramic Capacitor
1962fb
1962fa
For more information www.linear.com/LT1962
13
LT1962 Series
Applications Information
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
microphone works. For a ceramic capacitor the stress can
be induced by vibrations in the system or thermal transients.
The resulting voltages produced can cause appreciable
amounts of noise, especially when a ceramic capacitor is
used for noise bypassing. A ceramic capacitor produced
Figure 6’s trace in response to light tapping from a pencil.
Similar vibration induced behavior can masquerade as
increased output voltage noise.
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:
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).
The GND pin current can be found by examining the GND
Pin Current curves in the Typical Performance Characteristics section. Power dissipation will be equal to the sum
of the two components listed above.
The LT1962 series regulators have internal thermal
limiting designed to protect the device during overload
conditions. For continuous normal conditions, the maximum junction temperature 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 generated by power devices.
14
The following table lists thermal resistance for several
different board sizes and copper areas. All measurements
were taken in still air on 1/16" FR-4 board with one ounce
copper.
Table 1. Measured Thermal Resistance
COPPER AREA
TOPSIDE*
BACKSIDE
BOARD AREA
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
2500mm2
2500mm2
2500mm2
110°C/W
1000mm2
2500mm2
2500mm2
115°C/W
225mm2
2500mm2
2500mm2
120°C/W
100mm2
2500mm2
2500mm2
130°C/W
50mm2
2500mm2
2500mm2
140°C/W
*Device is mounted on topside.
Calculating Junction Temperature
Example: Given an output voltage of 3.3V, an input voltage range of 4V to 6V, an output current range of 0mA
to 100mA 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,
IOUT(MAX) = 100mA
VIN(MAX) = 6V
IGND at (IOUT = 100mA, VIN = 6V) = 2mA
So,
P = 100mA(6V – 3.3V) + 2mA(6V) = 0.28W
The thermal resistance will be in the range of 110°C/W to
140°C/W depending on the copper area. So the junction
temperature rise above ambient will be approximately
equal to:
0.28W(125°C/W) = 35.3°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 + 35.3°C = 85.3°C
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For more information www.linear.com/LT1962
LT1962 Series
Applications Information
The LT1962 regulators incorporate several protection
features which make them ideal for use in battery-powered
circuits. In addition to the normal protection features
associated with monolithic regulators, such as current
limiting and thermal limiting, the devices are protected
against reverse input voltages, reverse output voltages
and reverse voltages from output to input.
Current limit protection and thermal overload protection
are intended to protect the device against current overload
conditions at the output of the device. For normal operation, the junction temperature should not exceed 125°C.
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 which can be plugged in backward.
The output of the LT1962 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. For fixed voltage versions, the output will act like
a large resistor, typically 500k or higher, limiting current
flow to less than 40µA. For adjustable versions, the output
will act like an open circuit; no current will flow out of the
pin. If the input is powered by a voltage source, the output
will source the short-circuit current of the device and will
protect itself by thermal limiting. In this case, grounding
the SHDN pin will turn off the device and stop the output
from sourcing the short-circuit current.
The ADJ pin of the adjustable 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 a large resistor (typically 100k) in series
with a diode when pulled above ground.
divider is used to provide a regulated 1.5V output from the
1.22V reference when the output is forced to 20V. The top
resistor of the resistor divider must be chosen to limit the
current into the ADJ pin to less than 5mA when the ADJ
pin is at 7V. The 13V difference between OUT and ADJ pin
divided by the 5mA maximum current into the ADJ pin
yields a minimum top resistor value of 2.6k.
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, pulled to some intermediate voltage or is left
open circuit. Current flow back into the output will follow
the curve shown in Figure 7.
When the IN pin of the LT1962 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 device is connected to a discharged
(low voltage) battery and the output is held up by either
a backup battery or a second regulator circuit. The state
of the SHDN pin will have no effect on the reverse output
current when the output is pulled above the input.
100
REVERSE OUTPUT CURRENT (µA)
Protection Features
TJ = 25°C
90 VIN = 0V
CURRENT FLOWS
80 INTO OUTPUT PIN
70 VOUT = VADJ (LT1962)
LT1962-1.5
60
LT1962-1.8
50
LT1962-2.5
40
LT1962-3
30
LT1962
LT1962-3.3
20
10
0
LT1962-5
0
1
2
3 4 5 6 7 8
OUTPUT VOLTAGE (V)
9
10
1962 F07
Figure 7. Reverse Output Current
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
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For more information www.linear.com/LT1962
15
LT1962 Series
Package Description
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
MS8 Package
8-Lead
Plastic MSOP
MS8 Package
(LTC
DWGPlastic
# 05-08-1660
8-Lead
MSOPRev G)
(Reference LTC DWG # 05-08-1660 Rev G)
0.889 ±0.127
(.035 ±.005)
5.10
(.201)
MIN
3.20 – 3.45
(.126 – .136)
3.00 ±0.102
(.118 ±.004)
(NOTE 3)
0.65
(.0256)
BSC
0.42 ± 0.038
(.0165 ±.0015)
TYP
8
7 6 5
0.52
(.0205)
REF
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
4.90 ±0.152
(.193 ±.006)
DETAIL “A”
0° – 6° TYP
GAUGE PLANE
0.53 ±0.152
(.021 ±.006)
DETAIL “A”
1
2 3
4
1.10
(.043)
MAX
0.86
(.034)
REF
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
0.65
(.0256)
BSC
0.1016 ±0.0508
(.004 ±.002)
MSOP (MS8) 0213 REV G
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
16
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For more information www.linear.com/LT1962
LT1962 Series
Revision History
(Revision history begins at Rev B)
REV
DATE
DESCRIPTION
B
5/15
Clarified the Order Information table.
PAGE NUMBER
Added I-grade option.
2
2, 4
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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 representation that the interconnection
of its circuits
as described
herein will not infringe on existing patent rights.
For more
information
www.linear.com/LT1962
17
LT1962 Series
Typical Application
Adjustable Current Source
R1
0.1Ω
R5
0.1Ω
+
VIN
>2.7V
C1
10µF
Paralleling of Regulators for Higher Output Current
IN
R1*
1k
OUT
SHDN
LT1004-1.2
R2
40.2k
R3
2k
LOAD
LT1962-2.5
R6
2.2k
VIN > 3.7V
+
IN
C1
10µF
IN
+
C5
0.01µF
LT1962
BYP
1962 TA04
C2
10µF
OUT
C3
0.33µF
1/2 LT1490
3.3V
300mA
SHDN
BYP
GND
R2
0.1Ω
*ADJUST R1 FOR 0mA TO 300mA
CONSTANT CURRENT
C4
0.01µF
LT1962-3.3
R7
100k
R4
2.2k
–
+
FB
FB
GND
OUT
SHDN
SHDN
ADJ
GND
C2
1µF
R3
2.2k
R4
2.2k
3
2
R7
1.21k
8
+
1
1/2 LT1490
–
R6
2k
R5
10k
4
1962 TA03
C3
0.01µF
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COMMENTS
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100mA, Low Noise, Low Dropout Micropower Regulator in SOT-23
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LT1762
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LT1763
500mA, Low Noise, LDO Micropower Regulator
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3A, Fast Transient Response Low Dropout Regulator
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Constant Frequency Current Mode Step-Down DC/DC Controller
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1.5A, Fast Transient Response Low Dropout Regulator
SO-8, SOT-223 Packages
18 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LT1962
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LT1962
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LT 0515 REV B • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 2000
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