LT1963A Series
1.5A, Low Noise,
Fast Transient Response
LDO Regulators
Features
Description
Optimized for Fast Transient Response
Output Current: 1.5A
n Dropout Voltage: 340mV
n Low Noise: 40µV
RMS (10Hz to 100kHz)
n 1mA Quiescent Current
n No Protection Diodes Needed
n Controlled Quiescent Current in Dropout
n Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 3.3V
n Adjustable Output from 1.21V to 20V
n < 1µA Quiescent Current in Shutdown
n Stable with 10µF Output Capacitor*
n Stable with Ceramic Capacitors*
n Reverse Battery Protection
n No Reverse Current
n Thermal Limiting
n 5-Lead TO-220, DD, 3-Lead SOT-223 and
8-Lead SO Packages
The LT ®1963A series are low dropout regulators optimized
for fast transient response. The devices are capable of
supplying 1.5A of output current with a dropout voltage of
340mV. Operating quiescent current is 1mA, dropping to
< 1µA in shutdown. Quiescent current is well controlled; it
does not rise in dropout as it does with many other regulators. In addition to fast transient response, the LT1963A
regulators have very low output noise which makes them
ideal for sensitive RF supply applications.
Output voltage range is from 1.21V to 20V. The LT1963A
regulators are stable with output capacitors as low as
10µF. Internal protection circuitry includes reverse battery protection, current limiting, thermal limiting and
reverse current protection. The devices are available in
fixed output voltages of 1.5V, 1.8V, 2.5V, 3.3V and as
an adjustable device with a 1.21V reference voltage. The
LT1963A regulators are available in 5-lead TO-220, DD,
3‑lead SOT-223, 8-lead SO and 16-lead TSSOP packages.
n
n
Applications
n
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners. Protected by U.S. Patents including 6118263, 6144250.
n
*See Applications Information Section.
3.3V to 2.5V Logic Power Supplies
Post Regulator for Switching Supplies
Typical Application
Dropout Voltage
400
3.3V to 2.5V Regulator
VIN > 3V
+
IN
10µF*
OUT
LT1963A-2.5
SHDN
+
2.5V
1.5A
10µF*
SENSE
GND
1963A TA01
*TANTALUM,
CERAMIC OR
ALUMINUM ELECTROLYTIC
DROPOUT VOLTAGE (mV)
350
300
250
200
150
100
50
0
0
0.2
0.4 0.6 0.8 1.0 1.2
OUTPUT CURRENT (A)
1.4 1.6
1963A TA02
1963aff
For more information www.linear.com/LT1963A
1
LT1963A Series
Absolute Maximum Ratings
(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
SHDN Pin Voltage .................................................. ±20V
Output Short-Circuit Duration ......................... Indefinite
Operating Junction Temperature Range (Note 3)
LT1963AE............................................– 40°C to 125°C
LT1963AI............................................– 40°C to 125°C
LT1963AMP........................................– 55°C to 125°C
Storage Temperature Range....................– 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
Pin Configuration
TOP VIEW
FRONT VIEW
TAB IS
GND
FRONT VIEW
5
SENSE/ADJ*
5
SENSE/
ADJ*
4
OUT
4
OUT
3
GND
3
GND
2
IN
2
IN
1
SHDN
1
SHDN
TAB IS
GND
Q PACKAGE
5-LEAD PLASTIC DD
1
16 GND
NC
2
15 NC
OUT
3
14 IN
OUT
4
OUT
5
SENSE/ADJ*
6
11 NC
GND
7
10 SHDN
GND
8
9
T PACKAGE
5-LEAD PLASTIC TO-220
GND
TOP VIEW
3
2
1
OUT
GND
IN
ST PACKAGE
3-LEAD PLASTIC SOT-223
TJMAX = 150°C, θJA = 50°C/ W
2
12 IN
*PIN 6 = SENSE FOR LT1963A-1.5/LT1963A-1.8/
LT1963A-2.5/LT1963A-3.3
= ADJ FOR LT1963A
TJMAX = 150°C, θJA = 38°C/ W
FRONT VIEW
TAB IS
GND
13 IN
17
FE PACKAGE
16-LEAD PLASTIC TSSOP
EXPOSED PAD (PIN 17) IS GND. MUST BE
SOLDERED TO THE PCB.
*PIN 5 = SENSE FOR LT1963A-1.5/LT1963A-1.8/
LT1963A-2.5/LT1963A-3.3
= ADJ FOR LT1963A
TJMAX = 150°C, θJA = 50°C/ W
*PIN 5 = SENSE FOR LT1963A-1.5/LT1963A-1.8/
LT1963A-2.5/LT1963A-3.3
= ADJ FOR LT1963A
TJMAX = 150°C, θJA = 30°C/ W
GND
OUT 1
8
IN
SENSE/ADJ* 2
7
GND
GND 3
6
GND
NC 4
5
SHDN
S8 PACKAGE
8-LEAD PLASTIC SO
*PIN 2 = SENSE FOR LT1963A-1.5/LT1963A-1.8/
LT1963A-2.5/LT1963A-3.3
= ADJ FOR LT1963A
TJMAX = 150°C, θJA = 70°C/ W
1963aff
For more information www.linear.com/LT1963A
LT1963A Series
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT1963AEQ#PBF
LT1963AEQ#TRPBF
LT1963AEQ
5-Lead Plastic DD-Pak
–40°C to 125°C
LT1963AIQ#PBF
LT1963AIQ#TRPBF
LT1963AIQ
5-Lead Plastic DD-Pak
–40°C to 125°C
LT1963AMPQ#PBF
LT1963AMPQ#TRPBF
LT1963AMPQ
5-Lead Plastic DD-Pak
–55°C to 125°C
LT1963AEQ-1.5#PBF
LT1963AEQ-1.5#TRPBF
LT1963AEQ-1.5
5-Lead Plastic DD-Pak
–40°C to 125°C
LT1963AEQ-1.8#PBF
LT1963AEQ-1.8#TRPBF
LT1963AEQ-1.8
5-Lead Plastic DD-Pak
–40°C to 125°C
LT1963AEQ-2.5#PBF
LT1963AEQ-2.5#TRPBF
LT1963AEQ-2.5
5-Lead Plastic DD-Pak
–40°C to 125°C
LT1963AEQ-3.3#PBF
LT1963AEQ-3.3#TRPBF
LT1963AEQ-3.3
5-Lead Plastic DD-Pak
–40°C to 125°C
LT1963AET#PBF
LT1963AET#TRPBF
LT1963AET
5-Lead Plastic TO-220
–40°C to 125°C
LT1963AIT#PBF
LT1963AIT#TRPBF
LT1963AIT
5-Lead Plastic TO-220
–40°C to 125°C
LT1963AET-1.5#PBF
LT1963AET-1.5#TRPBF
LT1963AET-1.5
5-Lead Plastic TO-220
–40°C to 125°C
LT1963AET-1.8#PBF
LT1963AET-1.8#TRPBF
LT1963AET-1.8
5-Lead Plastic TO-220
–40°C to 125°C
LT1963AET-2.5#PBF
LT1963AET-2.5#TRPBF
LT1963AET-2.5
5-Lead Plastic TO-220
–40°C to 125°C
LT1963AET-3.3#PBF
LT1963AET-3.3#TRPBF
LT1963AET-3.3
5-Lead Plastic TO-220
–40°C to 125°C
LT1963AEFE#PBF
LT1963AEFE#TRPBF
1963AEFE
16-Lead Plastic TSSOP
–40°C to 125°C
LT1963AIFE#PBF
LT1963AIFE#TRPBF
1963AIFE
16-Lead Plastic TSSOP
–40°C to 125°C
LT1963AEFE-1.5#PBF
LT1963AEFE-1.5#TRPBF
1963AEFE15
16-Lead Plastic TSSOP
–40°C to 125°C
LT1963AEFE-1.8#PBF
LT1963AEFE-1.8#TRPBF
1963AEFE18
16-Lead Plastic TSSOP
–40°C to 125°C
LT1963AEFE-2.5#PBF
LT1963AEFE-2.5#TRPBF
1963AEFE25
16-Lead Plastic TSSOP
–40°C to 125°C
LT1963AEFE-3.3#PBF
LT1963AEFE-3.3#TRPBF
1963AEFE33
16-Lead Plastic TSSOP
–40°C to 125°C
LT1963AEST-1.5#PBF
LT1963AEST-1.5#TRPBF
963A15
3-Lead Plastic SOT-223
–40°C to 125°C
LT1963AEST-1.8#PBF
LT1963AEST-1.8#TRPBF
963A18
3-Lead Plastic SOT-223
–40°C to 125°C
LT1963AEST-2.5#PBF
LT1963AEST-2.5#TRPBF
963A25
3-Lead Plastic SOT-223
–40°C to 125°C
LT1963AEST-3.3#PBF
LT1963AEST-3.3#TRPBF
963A33
3-Lead Plastic SOT-223
–40°C to 125°C
LT1963AES8#PBF
LT1963AES8#TRPBF
1963A
8-Lead Plastic SO
–40°C to 125°C
LT1963AIS8#PBF
LT1963AIS8#TRPBF
1963A
8-Lead Plastic SO
–40°C to 125°C
LT1963AMPS8#PBF
LT1963AMPS8#TRPBF
963AMP
8-Lead Plastic SO
–55°C to 125°C
LT1963AES8-1.5#PBF
LT1963AES8-1.5#TRPBF
963A15
8-Lead Plastic SO
–40°C to 125°C
LT1963AES8-1.8#PBF
LT1963AES8-1.8#TRPBF
963A18
8-Lead Plastic SO
–40°C to 125°C
LT1963AES8-2.5#PBF
LT1963AES8-2.5#TRPBF
963A25
8-Lead Plastic SO
–40°C to 125°C
LT1963AES8-3.3#PBF
LT1963AES8-3.3#TRPBF
963A33
8-Lead Plastic SO
–40°C to 125°C
LEAD BASED FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT1963AEQ
LT1963AEQ#TR
LT1963AEQ
5-Lead Plastic DD-Pak
–40°C to 125°C
LT1963AIQ
LT1963AIQ#TR
LT1963AIQ
5-Lead Plastic DD-Pak
–40°C to 125°C
LT1963AMPQ
LT1963AMPQ#TR
LT1963AMPQ
5-Lead Plastic DD-Pak
–55°C to 125°C
LT1963AEQ-1.5
LT1963AEQ-1.5#TR
LT1963AEQ-1.5
5-Lead Plastic DD-Pak
–40°C to 125°C
LT1963AEQ-1.8
LT1963AEQ-1.8#TR
LT1963AEQ-1.8
5-Lead Plastic DD-Pak
–40°C to 125°C
LT1963AEQ-2.5
LT1963AEQ-2.5#TR
LT1963AEQ-2.5
5-Lead Plastic DD-Pak
–40°C to 125°C
LT1963AEQ-3.3
LT1963AEQ-3.3#TR
LT1963AEQ-3.3
5-Lead Plastic DD-Pak
–40°C to 125°C
LT1963AET
LT1963AET#TR
LT1963AET
5-Lead Plastic TO-220
–40°C to 125°C
LT1963AIT
LT1963AIT#TR
LT1963AIT
5-Lead Plastic TO-220
–40°C to 125°C
1963aff
For more information www.linear.com/LT1963A
3
LT1963A Series
order information
LEAD BASED FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT1963AET-1.5
LT1963AET-1.5#TR
LT1963AET-1.5
5-Lead Plastic TO-220
–40°C to 125°C
LT1963AET-1.8
LT1963AET-1.8#TR
LT1963AET-1.8
5-Lead Plastic TO-220
–40°C to 125°C
LT1963AET-2.5
LT1963AET-2.5#TR
LT1963AET-2.5
5-Lead Plastic TO-220
–40°C to 125°C
LT1963AET-3.3
LT1963AET-3.3#TR
LT1963AET-3.3
5-Lead Plastic TO-220
–40°C to 125°C
LT1963AEFE
LT1963AEFE#TR
1963AEFE
16-Lead Plastic TSSOP
–40°C to 125°C
LT1963AIFE
LT1963AIFE#TR
1963AIFE
16-Lead Plastic TSSOP
–40°C to 125°C
LT1963AEFE-1.5
LT1963AEFE-1.5#TR
1963AEFE15
16-Lead Plastic TSSOP
–40°C to 125°C
LT1963AEFE-1.8
LT1963AEFE-1.8#TR
1963AEFE18
16-Lead Plastic TSSOP
–40°C to 125°C
LT1963AEFE-2.5
LT1963AEFE-2.5#TR
1963AEFE25
16-Lead Plastic TSSOP
–40°C to 125°C
LT1963AEFE-3.3
LT1963AEFE-3.3#TR
1963AEFE33
16-Lead Plastic TSSOP
–40°C to 125°C
LT1963AEST-1.5
LT1963AEST-1.5#TR
963A15
3-Lead Plastic SOT-223
–40°C to 125°C
LT1963AEST-1.8
LT1963AEST-1.8#TR
963A18
3-Lead Plastic SOT-223
–40°C to 125°C
LT1963AEST-2.5
LT1963AEST-2.5#TR
963A25
3-Lead Plastic SOT-223
–40°C to 125°C
LT1963AEST-3.3
LT1963AEST-3.3#TR
963A33
3-Lead Plastic SOT-223
–40°C to 125°C
LT1963AES8
LT1963AES8#TR
1963A
8-Lead Plastic SO
–40°C to 125°C
LT1963AIS8
LT1963AIS8#TR
1963A
8-Lead Plastic SO
–40°C to 125°C
LT1963AMPS8
LT1963AMPS8#TR
963AMP
8-Lead Plastic SO
–55°C to 125°C
LT1963AES8-1.5
LT1963AES8-1.5#TR
963A15
8-Lead Plastic SO
–40°C to 125°C
LT1963AES8-1.8
LT1963AES8-1.8#TR
963A18
8-Lead Plastic SO
–40°C to 125°C
LT1963AES8-2.5
LT1963AES8-2.5#TR
963A25
8-Lead Plastic SO
–40°C to 125°C
LT1963AES8-3.3
LT1963AES8-3.3#TR
963A33
8-Lead Plastic SO
–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.
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/
4
1963aff
For more information www.linear.com/LT1963A
LT1963A Series
Electrical Characteristics
The l denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 3)
PARAMETER
CONDITIONS
TYP
MAX
Minimum Input Voltage (Notes 4,12)
ILOAD = 0.5A
ILOAD = 1.5A
l
1.9
2.1
2.5
V
V
LT1963A-1.5
VIN = 2.21V, ILOAD = 1mA
2.5V < VIN < 20V, 1mA < ILOAD < 1.5A
l
1.477
1.447
1.500
1.500
1.523
1.545
V
V
LT1963A-1.8
VIN = 2.3V, ILOAD = 1mA
2.8V < VIN < 20V, 1mA < ILOAD < 1.5A
l
1.773
1.737
1.800
1.800
1.827
1.854
V
V
LT1963A-2.5
VIN = 3V, ILOAD = 1mA
3.5V < VIN < 20V, 1mA < ILOAD < 1.5A
l
2.462
2.412
2.500
2.500
2.538
2.575
V
V
LT1963A-3.3
VIN = 3.8V, ILOAD = 1mA
4.3V < VIN < 20V, 1mA < ILOAD < 1.5A
l
3.250
3.200
3.300
3.300
3.350
3.400
V
V
LT1963A
VIN = 2.21V, ILOAD = 1mA
2.5V < VIN < 20V, 1mA < ILOAD < 1.5A
l
1.192
1.174
1.210
1.210
1.228
1.246
V
V
Line Regulation
LT1963A-1.5 ∆VIN = 2.21V to 20V, ILOAD = 1mA
LT1963A-1.8 ∆VIN = 2.3V to 20V, ILOAD = 1mA
LT1963A-2.5 ∆VIN = 3V to 20V, ILOAD = 1mA
LT1963A-3.3 ∆VIN = 3.8V to 20V, ILOAD = 1mA
LT1963A (Note 4) ∆VIN = 2.21V to 20V, ILOAD = 1mA
l
l
l
l
l
2.0
2.5
3.0
3.5
1.5
6
7
10
10
5
mV
mV
mV
mV
mV
Load Regulation
LT1963A-1.5
VIN = 2.5V, ∆ILOAD = 1mA to 1.5A
VIN = 2.5V, ∆ILOAD = 1mA to 1.5A
2
●
9
18
mV
mV
LT1963A-1.8
VIN = 2.8V, ∆ILOAD = 1mA to 1.5A
VIN = 2.8V, ∆ILOAD = 1mA to 1.5A
2
●
10
20
mV
mV
LT1963A-2.5
VIN = 3.5V, ∆ILOAD = 1mA to 1.5A
VIN = 3.5V, ∆ILOAD = 1mA to 1.5A
2.5
●
15
30
mV
mV
LT1963A-3.3
VIN = 4.3V, ∆ILOAD = 1mA to 1.5A
VIN = 4.3V, ∆ILOAD = 1mA to 1.5A
3
●
20
35
mV
mV
LT1963A (Note 4)
VIN = 2.5V, ∆ILOAD = 1mA to 1.5A
VIN = 2.5V, ∆ILOAD = 1mA to 1.5A
2
●
8
15
mV
mV
0.02
0.06
0.10
V
V
0.10
0.17
0.22
V
V
0.19
0.27
0.35
V
V
0.34
0.45
0.55
V
V
1.0
1.1
3.8
15
80
1.5
1.6
5.5
25
120
mA
mA
mA
mA
mA
Regulated Output Voltage (Note 5)
ADJ Pin Voltage (Notes 4, 5)
MIN
UNITS
ILOAD = 1mA
ILOAD = 1mA
●
ILOAD = 100mA
ILOAD = 100mA
●
ILOAD = 500mA
ILOAD = 500mA
●
ILOAD = 1.5A
ILOAD = 1.5A
●
GND Pin Current
VIN = VOUT(NOMINAL) + 1V
(Notes 6, 8)
ILOAD = 0mA
ILOAD = 1mA
ILOAD = 100mA
ILOAD = 500mA
ILOAD = 1.5A
●
●
●
●
●
Output Voltage Noise
COUT = 10µF, ILOAD = 1.5A, BW = 10Hz to 100kHz
40
ADJ Pin Bias Current
(Notes 4, 9)
3
10
µA
Shutdown Threshold
VOUT = Off to On
VOUT = On to Off
0.90
0.75
2
V
V
SHDN Pin Current (Note 10)
VSHDN = 0V
VSHDN = 20V
0.01
3
1
30
µA
µA
Quiescent Current in Shutdown
VIN = 6V, VSHDN = 0V
0.01
1
µA
Dropout Voltage
VIN = VOUT(NOMINAL)
(Notes 6, 7, 12)
●
●
0.25
µVRMS
1963aff
For more information www.linear.com/LT1963A
5
LT1963A Series
Electrical Characteristics
The l denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 3)
PARAMETER
CONDITIONS
Ripple Rejection
VIN – VOUT = 1.5V (Avg), VRIPPLE = 0.5VP-P,
fRIPPLE = 120Hz, ILOAD = 0.75A
Current Limit
VIN = 7V, VOUT = 0V
VIN = VOUT(NOMINAL) + 1V, ∆VOUT = – 0.1V
●
Input Reverse Leakage Current (Note 13)
Q, T, S8 Packages VIN = –20V, VOUT = 0
ST Package
VIN = –20V, VOUT = 0
●
●
Reverse Output Current (Note 11)
LT1963A-1.5
LT1963A-1.8
LT1963A-2.5
LT1963A-3.3
LT1963A (Note 4)
VOUT = 1.5V, VIN < 1.5V
VOUT = 1.8V, VIN < 1.8V
VOUT = 2.5V, VIN < 2.5V
VOUT = 3.3V, VIN < 3.3V
VOUT = 1.21V, VIN < 1.21V
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 can not
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 LT1963A regulators are tested and specified under pulse load
conditions such that TJ ≈ TA. The LT1963AE is 100% tested at TA = 25°C.
Performance at –40°C and 125°C is assured by design, characterization and
correlation with statistical process controls. The LT1963AI is guaranteed
over the full –40°C to 125°C operating junction temperature range. The
LT1963AMP is 100% tested and guaranteed over the –55°C to 125°C
operating junction temperature range.
Note 4: The LT1963A (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.
6
MIN
TYP
55
63
dB
2
A
A
1.6
600
600
600
600
300
MAX
UNITS
1
2
mA
mA
1200
1200
1200
1200
600
µA
µA
µA
µA
µA
Note 6: To satisfy requirements for minimum input voltage, the LT1963A
(adjustable version) is tested and specified for these conditions with an
external resistor divider (two 4.12k resistors) for an output voltage of 2.4V.
The external resistor divider will add a 300µA 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) + 1V and a
current source load. The GND pin current will decrease 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.
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 LT1963A, LT1963A-1.5 and LT1963A-1.8 dropout voltage
will be limited by the minimum input voltage specification under some
output voltage/load conditions.
Note 13: For the ST package, the input reverse leakage current increases
due to the additional reverse leakage current for the SHDN pin, which is
tied internally to the IN pin.
1963aff
For more information www.linear.com/LT1963A
LT1963A Series
Typical Performance Characteristics
Typical Dropout Voltage
Guaranteed Dropout Voltage
600
GUARANTEED DROPOUT VOLTAGE (mV)
450
DROPOUT VOLTAGE (mV)
400
350
TJ = 125°C
300
250
TJ = 25°C
200
150
100
50
0
0
0.2
1.4
0.4 0.6 0.8 1.0 1.2
OUTPUT CURRENT (A)
= TEST POINTS
500
450
TJ ≤ 125°C
400
TJ ≤ 25°C
300
200
100
0
1.6
Dropout Voltage
500
350
250
150
0
0.2
1.4
0.4 0.6 0.8 1.0 1.2
OUTPUT CURRENT (A)
0
–50
1.6
1.53
1.83
1.52
1.82
0.2
OUTPUT VOLTAGE (V)
VIN = 6V
RL = ∞, IL = 0
VSHDN = VIN
0
–50 –25
1.84
IL = 1mA
OUTPUT VOLTAGE (V)
LT1963A-1.5/1.8/-2.5/-3.3
0.4
1.51
1.50
1.49
1.48
1.47
50
25
75
0
TEMPERATURE (°C)
100
1.46
–50 –25
125
75
50
25
TEMPERATURE (°C)
0
100
3.36
OUTPUT VOLTAGE (V)
2.54
2.52
2.50
2.48
2.46
2.44
0
25
50
75
1.79
1.78
100
125
TEMPERATURE (°C)
0
25
50
75
125
LT1963A ADJ Pin Voltage
IL = 1mA
1.225
3.34
3.32
3.30
3.28
3.26
3.22
–50
100
1963A G05
1.230
IL = 1mA
1.220
1.215
1.210
1.205
1.200
1.195
–25
0
25
50
75
100
125
1.190
–50
–25
0
25
50
75
100
125
TEMPERATURE (°C)
TEMPERATURE (°C)
1963A G06
–25
TEMPERATURE (°C)
3.24
–25
1.80
1.76
–50
125
ADJ PIN VOLTAGE (V)
IL = 1mA
2.42
–50
1.81
LT1963A-3.3 Output Voltage
3.38
125
100
IL = 1mA
1963A G40
LT1963A-2.5 Output Voltage
2.56
50
25
0
75
TEMPERATURE (°C)
1.77
1963A G04
2.58
–25
LT1963A-1.8 Output Voltage
1.2
0.6
IL = 1mA
1963A G03
LT1963A-1.5 Output Voltage
LT1963A
IL = 100mA
100
1.54
0.8
IL = 0.5A
200
1.4
1.0
IL = 1.5A
300
1963A G02
Quiescent Current
QUIESCENT CURRENT (mA)
400
50
1963A G01
OUTPUT VOLTAGE (V)
DROPOUT VOLTAGE (mV)
500
1963A G07
1963A G08
1963aff
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7
LT1963A Series
TYPICAL PERFORMANCE CHARACTERISTICS
14
TJ = 25°C
R =∞
12 L
VSHDN = VIN
10
8
6
4
2
8
6
4
1
2
3 4 5 6
7
INPUT VOLTAGE (V)
9
8
0
10
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
1.4
8
6
4
2
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1963A G10
LT1963A-1.5 GND Pin Current
1.0
0.8
0.6
0.4
25
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 1.5V
20
15
RL = 150, IL = 10mA*
10
RL = 5, IL = 300mA*
5
RL = 15, IL = 100mA*
0.2
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
0
10
0
2
4
LT1963A-1.8 GND Pin Current
5
RL = 18, IL = 100mA*
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
20
15
RL = 8.33, IL = 300mA*
10
RL = 25, IL = 100mA*
5
8
9 10
1963A G13
3 4 5 6 7
INPUT VOLTAGE (V)
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
10
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 3.3V
20
15
RL = 11, IL = 300mA*
10
RL = 33, IL = 100mA*
5
RL = 250, IL = 10mA*
0
9
8
LT1963A-3.3 GND Pin Current
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 2.5V
RL = 180, IL = 10mA*
0
2
25
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
TJ = 25°C
VSHDN = VIN
20 *FOR VOUT = 1.8V
RL = 6, IL = 300mA*
1
1963A G42
LT1963A-2.5 GND Pin Current
25
15
0
1963A G12
25
10
0
6 8 10 12 14 16 18 20
INPUT VOLTAGE (V)
1963A G11
GND PIN CURRENT (mA)
4
0
10
GND PIN CURRENT (mA)
8
8
9
TJ = 25°C
RL = 4.3k
VSHDN = VIN
1.2
QUIESCENT CURRENT (mA)
QUIESCENT CURRENT (mA)
10
0
6
LT1963A Quiescent Current
TJ = 25°C
RL = ∞
VSHDN = VIN
12
8
1963A G09
LT1963A-3.3 Quiescent Current
14
10
2
2
0
TJ = 25°C
RL = ∞
VSHDN = VIN
12
10
1963A G41
0
14
TJ = 25°C
RL = ∞
VSHDN = VIN
12
QUIESCENT CURRENT (mA)
QUIESCENT CURRENT (mA)
14
0
LT1963A-2.5 Quiescent Current
LT1963A-1.8 Quiescent Current
QUIESCENT CURRENT (mA)
LT1963A-1.5 Quiescent Current
9 10
1963A G14
0
RL = 330, IL = 100mA*
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9 10
1963A G15
1963aff
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LT1963A Series
TYPICAL PERFORMANCE CHARACTERISTICS
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 1.21V
8
RL = 4.33, IL = 300mA*
6
4
RL = 12.1, IL = 100mA*
80
70
60
RL = 1, IL = 1.5A*
50
RL = 1.5, IL = 1A*
40
30
2
RL = 3, IL = 500mA*
20
RL = 121, IL = 10mA*
0
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9 10
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
80
70
0
50
40
RL = 3.3, IL = 1A*
30
RL = 5, IL = 500mA*
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
9
0
10
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
SHDN PIN THRESHOLD (V)
GND PIN CURRENT (mA)
0.9
60
50
40
30
20
9
0
0.2
0.4 0.6 0.8 1.0 1.2
OUTPUT CURRENT (A)
60
1.4
1.6
40
30
1963A G21
RL = 1.21, IL = 1A*
RL = 2.42, IL = 500mA*
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1963A G20
SHDN Pin Threshold (Off-to-On)
1.0
IL = 1mA
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0
–50
10
RL = 0.81, IL = 1.5A*
50
0
10
IL = 1.5A
0.8
0.7
0.6
IL = 1mA
0.5
0.4
0.3
0.2
0.1
0.1
10
0
8
9
70
10
SHDN PIN THRESHOLD (V)
VIN = VOUT (NOMINAL) +1V
70
8
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 1.21V
80
SHDN Pin Threshold (On-to-Off)
1.0
80
3 4 5 6 7
INPUT VOLTAGE (V)
1963A G19
GND Pin Current vs ILOAD
90
2
90
RL = 6.6, IL = 500mA*
1963A G18
100
1
20
10
8
0
100
20
0
RL = 3.6, IL = 500mA*
LT1963A GND Pin Current
RL = 2.2, IL = 1.5A*
60
20
10
RL = 1.8, IL = 1A*
1963A G17
GND PIN CURRENT (mA)
RL = 2.5, IL = 1A*
30
10
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 3.3V
90
50
40
30
LT1963A-3.3 GND Pin Current
RL = 1.67, IL = 1.5A*
60
40
1963A G43
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
70
50
20
9
8
RL = 1.2, IL = 1.5A*
60
0
100
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 2.5V
80
70
0
LT1963A-2.5 GND Pin Current
90
80
10
0
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 1.8V
90
10
1963A G16
100
LT1963A-1.8 GND Pin Current
100
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 1.5V
90
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
LT1963A-1.5 GND Pin Current
100
GND PIN CURRENT (mA)
LT1963A GND Pin Current
10
–25
50
25
0
75
TEMPERATURE (°C)
100
125
1963A G22
0
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
1963A G23
1963aff
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9
LT1963A Series
TYPICAL PERFORMANCE CHARACTERISTICS
SHDN Pin Input Current
SHDN Pin Input Current
7
SHDN PIN INPUT CURRENT (µA)
SHDN PIN INPUT CURRENT (µA)
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0
2
4
VSHDN = 20V
4.5
6
5
4
3
2
1
0
–50 –25
6 8 10 12 14 16 18 20
SHDN PIN VOLTAGE (V)
ADJ Pin Bias Current
5.0
ADJ PIN BIAS CURRENT (µA)
5.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
50
25
75
0
TEMPERATURE (°C)
100
0
–50
125
–25
50
25
0
75
TEMPERATURE (°C)
1963A G25
1963A G24
Current Limit
4.0
3.0
CURRENT LIMIT (A)
TJ = –50°C
TJ = 125°C
1.5
1.0
1963A G26
Current Limit
2.5
2.0
1.5
1.0
0.5
ΔVOUT = 100mV
0
0
2
0
–50
6 8 10 12 14 16 18 20
4
INPUT/OUTPUT DIFFERENTIAL (V)
–25
50
0
75
25
TEMPERATURE (°C)
100
Reverse Output Current
Reverse Output Current
1.0
4.5
LT1963A-1.8
4.0
LT1963A-1.5
3.5
3.0
LT1963A
2.5
2.0
LT1963A-3.3 T = 25°C
J
VIN = 0V
LT1963A-2.5
CURRENT FLOWS INTO
OUTPUT PIN
VOUT = VADJ (LT1963A)
VOUT = VFB (LT1963A-1.5/1.8/-2.5/-3.3)
1.5
1.0
0.5
0
1
2
3 4 5 6 7 8
OUTPUT VOLTAGE (V)
9
REVERSE OUTPUT CURRENT (mA)
5.0
0
125
1963A G28
1963A G27
REVERSE OUTPUT CURRENT (mA)
125
3.0
TJ = 25°C
2.0
0.5
VIN = 0V
0.9 VOUT = 1.21V (LT1963A)
= 1.5V (LT1963A-1.5)
V
0.8 VOUT = 1.8V (LT1963A-1.8)
OUT
0.7 VOUT = 2.5V (LT1963A-2.5)
VOUT = 3.3V (LT1963A-3.3)
0.6
LT1963A-1.8/-2.5/-3.3
0.5
0.4
LT1963A
0.3
0.2
0.1
10
1963A G29
10
100
VIN = 7V
3.5 VOUT = 0V
2.5
CURRENT LIMIT (A)
4.0
0
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
1963A G30
1963aff
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LT1963A Series
TYPICAL PERFORMANCE CHARACTERISTICS
Ripple Rejection
LT1963A Minimum Input Voltage
3.0
70
74
2.5
RIPPLE REJECTION (dB)
60
50
40
COUT = 100µF TANTALUM
+10 × 1µF CERAMIC
30
COUT = 10µF TANTALUM
20
MINIMUM INPUT VOLTAGE (V)
76
72
70
68
66
64 IL = 0.75A
VIN = VOUT(NOMINAL) +1V + 0.5VP-P
RIPPLE AT f = 120Hz
62
50
100
25
75
–50 –25
0
TEMPERATURE (°C)
10 IL = 0.75A
VIN = VOUT(NOMINAL) +1V + 50mVRMS RIPPLE
0
10
1k
10k
1M
100
100k
FREQUENCY (Hz)
1963A G31
125
Load Regulation
0
–15
OUTPUT NOISE SPECTRAL DENSITY (µV/√Hz)
LOAD REGULATION (mV)
LT1963A-1.5
LT1963A
LT1963A-1.8
LT1963A-2.5
LT1963A-3.3
–10
VIN = VOUT(NOMINAL) +1V
(LT1963A-1.8/-2.5/-3.3)
VIN = 2.7V (LT1963A/LT1963A-1.5)
ΔIL = 1mA TO 1.5A
–20
–50 –25
IL = 100mA
1.5
1.0
0.5
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
50
25
75
0
TEMPERATURE (°C)
100
125
125
1.0
COUT = 10µF
IL =1.5A
LT1963A-3.3
0.1
LT1963A-2.5
LT1963A-1.8
LT1963A-1.5
0.01
10
100
LT1963A
1k
10k
FREQUENCY (Hz)
100k
1963A G35
RMS Output Noise vs Load
Current (10Hz to 100kHz)
45
100
1963A G33
1963A G34
50
IL = 500mA
2.0
Output Noise Spectral Density
5
–5
IL = 1.5A
1963A G32
10
OUTPUT NOISE VOLTAGE (µVRMS)
RIPPLE REJECTION (dB)
Ripple Rejection
80
LT1963A-3.3 10Hz to 100kHz Output Noise
COUT = 10µF
40
LT1963A-3.3
35
LT1963A-2.5
30
25
VOUT
100µV/DIV
LT1963A-1.8
20
LT1963A-1.5
15
LT1963A
10
5
0
0.0001
0.001
0.01
0.1
LOAD CURRENT (A)
1
10
COUT = 10µF
ILOAD = 1.5A
1ms/DIV
1963A G37
1963A G36
1963aff
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11
LT1963A Series
TYPICAL PERFORMANCE CHARACTERISTICS
LT1963A-3.3 Transient Response
LT1963A-3.3 Transient Response
150
VIN = 4.3V
150 CIN = 3.3µF TANTALUM
COUT = 10µF TANTALUM
100
OUTPUT VOLTAGE
DEVIATION (mV)
OUTPUT VOLTAGE
DEVIATION (mV)
200
50
0
–50
100
50
0
–50
–100
1.5
LOAD
CURRENT (A)
–150
0.6
LOAD
CURRENT (A)
–100
0.4
0.2
0
0
2
4
6
8
10 12 14 16 18 20
TIME (µs)
VIN = 4.3V
CIN = 33µF TANTALUM
COUT = 100µF TANTALUM
+10 × 1µF CERAMIC
1.0
0.5
0
0
1963A G38
12
50 100 150 200 250 300 350 400 450 500
TIME (µs)
1963A G39
1963aff
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LT1963A Series
Pin Functions
OUT: Output. The output supplies power to the load.
A minimum output capacitor of 10µF 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: Sense. For fixed voltage versions of the LT1963A
(LT1963A-1.5/LT1963A-1.8/LT1963A-2.5/LT1963A-3.3),
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 600µA 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.
ADJ: Adjust. For the adjustable LT1963A, this is the input
to the error amplifier. This pin is internally clamped to ± 7V.
It has a bias current of 3µA which flows into the pin. The
ADJ pin voltage is 1.21V referenced to ground and the
output voltage range is 1.21V to 20V.
SHDN: Shutdown. The SHDN pin is used to put the LT1963A
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 open-collector 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
3µA. If unused, the SHDN pin must be connected to VIN.
The device will be in the low power shutdown state if the
SHDN pin is not connected.
IN: 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 LT1963A
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.
IN
OUT
LT1963A
VIN
+
SHDN
RP
+
SENSE
LOAD
GND
RP
1963A F01
Figure 1. Kelvin Sense Connection
1963aff
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13
LT1963A Series
Applications Information
The LT1963A series are 1.5A low dropout regulators optimized for fast transient response. The devices are capable
of supplying 1.5A at a dropout voltage of 350mV. The low
operating quiescent current (1mA) drops to less than 1µA
in shutdown. In addition to the low quiescent current, the
LT1963A 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 LT1963A‑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 LT1963A has an output
voltage range of 1.21V 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 voltage at
the ADJ pin at 1.21V referenced to ground. The current
in R1 is then equal to 1.21V/R1 and the current in R2 is
the current in R1 plus the ADJ pin bias current. The ADJ
pin bias current, 3µA 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 less than
4.17k 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 1.21V.
Specifications for output voltages greater than 1.21V will
be proportional to the ratio of the desired output voltage
to 1.21V: VOUT/1.21V. For example, load regulation for an
output current change of 1mA to 1.5A is – 3mV typical at
VOUT = 1.21V. At VOUT = 5V, load regulation is:
(5V/1.21V)(–3mV) = –12.4mV
Output Capacitors and Stability
The LT1963A regulator is a feedback circuit. Like any
feedback circuit, frequency compensation is needed to
14
IN
VIN
OUT
LT1963A
R2
+
ADJ
GND
R1
VOUT
R2
VOUT =1.21V 1+ + (IADJ ) (R2)
R1
VADJ =1.21V
IADJ = 3µA AT 25°C
1963A F02
OUTPUT RANGE = 1.21V TO 20V
Figure 2. Adjustable Operation
make it stable. For the LT1963A, the frequency compensation is both internal and external—the output capacitor.
The size of the output capacitor, the type of the output
capacitor, and the ESR of the particular output capacitor
all affect the stability.
In addition to stability, the output capacitor also affects
the high frequency transient response. The regulator
loop has a finite band width. For high frequency transient
loads, recovery from a transient is a combination of the
output capacitor and the bandwidth of the regulator. The
LT1963A was designed to be easy to use and accept a
wide variety of output capacitors. However, the frequency
compensation is affected by the output capacitor and optimum frequency stability may require some ESR, especially
with ceramic capacitors.
For ease of use, low ESR polytantalum capacitors (POSCAP)
are a good choice for both the transient response and
stability of the regulator. These capacitors have intrinsic
ESR that improves the stability. Ceramic capacitors have
extremely low ESR, and while they are a good choice in
many cases, placing a small series resistance element
will sometimes achieve optimum stability and minimize
ringing. In all cases, a minimum of 10µF is required while
the maximum ESR allowable is 3Ω.
The place where ESR is most helpful with ceramics is
low output voltage. At low output voltages, below 2.5V,
some ESR helps the stability when ceramic output capacitors are used. Also, some ESR allows a smaller capacitor value to be used. When small signal ringing occurs
with ceramics due to insufficient ESR, adding ESR or
increasing the capacitor value improves the stability and
reduces the ringing. Table 1 gives some recommended
values of ESR to minimize ringing caused by fast, hard
current transitions.
1963aff
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LT1963A Series
APPLICATIONS INFORMATION
Table 1. Capacitor Minimum ESR
VOUT
10µF
22µF
47µF
100µF
1.2V
20mΩ
15mΩ
10mΩ
5mΩ
1.5V
20mΩ
15mΩ
10mΩ
5mΩ
1.8V
15mΩ
10mΩ
10mΩ
5mΩ
2.5V
5mΩ
5mΩ
5mΩ
5mΩ
3.3V
0mΩ
0mΩ
0mΩ
5mΩ
≥5V
0mΩ
0mΩ
0mΩ
0mΩ
Figures 3 through 8 show the effect of ESR on the transient
response of the regulator. These scope photos show the
transient response for the LT1963A at three different output
voltages with various capacitors and various values of ESR.
The output load conditions are the same for all traces. In
all cases there is a DC load of 500mA. The load steps up
to 1A at the first transition and steps back to 500mA at
the second transition.
At the worst case point of 1.2VOUT with 10µF COUT
(Figure 3), a minimum amount of ESR is required. While
20mΩ is enough to eliminate most of the ringing, a value
closer to 50mΩ provides a more optimum response. At
2.5V output with 10µF COUT (Figure 4) the output rings
at the transitions with 0Ω ESR but still settles to within
10mV in 20µs after the 0.5A load step. Once again a small
value of ESR will provide a more optimum response.
At 5VOUT with 10µF COUT (Figure 5) the response is well
damped with 0Ω ESR.
With a COUT of 100µF at 0Ω ESR and an output of 1.2V
(Figure 6), the output rings although the amplitude is
only 20mVp-p. With COUT of 100µF it takes only 5mΩ to
20mΩ of ESR to provide good damping at 1.2V output.
Performance at 2.5V and 5V output with 100µF COUT shows
similar characteristics to the 10µF case (see Figures 7-8).
At 2.5VOUT 5mΩ to 20mΩ can improve transient response.
At 5VOUT the response is well damped with 0Ω ESR.
Capacitor types with inherently higher ESR can be combined
with 0mΩ ESR ceramic capacitors to achieve both good
high frequency bypassing and fast settling time. Figure
9 illustrates the improvement in transient response that
can be seen when a parallel combination of ceramic and
POSCAP capacitors are used. The output voltage is at the
worst case value of 1.2V. Trace A, is with a 10µF ceramic
output capacitor and shows significant ringing with a peak
amplitude of 25mV. For Trace B, a 22µF/45mΩ POSCAP
is added in parallel with the 10µF ceramic. The output is
well damped and settles to within 10mV in less than 20µs.
For Trace C, a 100µF/35mΩ POSCAP is connected in parallel
with the 10µF ceramic capacitor. In this case the peak output
deviation is less than 20mV and the output settles in about
10µs. For improved transient response the value of the
bulk capacitor (tantalum or aluminum electrolytic) should
be greater than twice the value of the ceramic capacitor.
Tantalum and Polytantalum Capacitors
There is a variety of tantalum capacitor types available,
with a wide range of ESR specifications. Older types have
ESR specifications in the hundreds of mΩ to several Ohms.
Some newer types of polytantalum with multi-electrodes
have maximum ESR specifications as low as 5mΩ. In general the lower the ESR specification, the larger the size and
the higher the price. Polytantalum capacitors have better
surge capability than older types and generally lower ESR.
Some types such as the Sanyo TPE and TPB series have
ESR specifications in the 20mΩ to 50mΩ range, which
provide near optimum transient response.
Aluminum Electrolytic Capacitors
Aluminum electrolytic capacitors can also be used with the
LT1963A. These capacitors can also be used in conjunction
with ceramic capacitors. These tend to be the cheapest
and lowest performance type of capacitors. Care must be
used in selecting these capacitors as some types can have
ESR which can easily exceed the 3Ω maximum value.
Ceramic Capacitors
Extra consideration must be given to the use of ceramic
capacitors. Ceramic capacitors are manufactured with a
variety of dielectrics, each with different behavior over
temperature and applied voltage. The most common
dielectrics used are Z5U, Y5V, X5R and X7R. The Z5U and
1963aff
For more information www.linear.com/LT1963A
15
LT1963A Series
APPLICATIONS INFORMATION
VOUT = 1.2V
IOUT = 500mA WITH
500mA PULSE
COUT = 10µF
RESR (mΩ)
50
5
50mV/DIV
50mV/DIV
20
VOUT = 1.2V
IOUT = 500mA WITH
500mA PULSE
COUT = 100µF
0
RESR (mΩ)
0
10
20
100
20µs/DIV
1963A F03
50µs/DIV
Figure 3
Figure 6
VOUT = 2.5V
IOUT = 500mA WITH
500mA PULSE
COUT = 10µF
RESR (mΩ)
50
VOUT = 2.5V
IOUT = 500mA WITH
500mA PULSE
COUT = 100µF
0
100
5
50mV/DIV
20
50mV/DIV
RESR (mΩ)
0
10
20
20µs/DIV
1963A F04
50µs/DIV
Figure 4
1963A F07
Figure 7
VOUT = 5V
IOUT = 500mA WITH
500mA PULSE
COUT = 10µF
50
5
50mV/DIV
50mV/DIV
20
VOUT = 5V
IOUT = 500mA WITH
500mA PULSE
COUT = 100µF
0
RESR (mΩ)
0
RESR (mΩ)
1963A F06
10
20
100
20µs/DIV
1963A F05
50µs/DIV
1963A F08
Figure 8
Figure 5
50mV/DIV
RESR (mΩ)
A
B
VOUT = 1.2V
IOUT = 500mA WITH 500mA PULSE
COUT =
A = 10µF CERAMIC
B = 10µF CERAMIC II 22µF/45mΩ POLY
C = 10µF CERAMIC II 100µF/35mΩ POLY
C
50µs/DIV
1963A F09
Figure 9
16
1963aff
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LT1963A Series
APPLICATIONS INFORMATION
Y5V dielectrics are good for providing high capacitances in
a small package, but exhibit strong voltage and temperature
coefficients as shown in Figures 10 and 11. 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.
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.
“FREE” Resistance with PC Traces
The resistance values shown in Table 2 can easily be made
using a small section of PC trace in series with the output
capacitor. The wide range of non-critical ESR makes it
easy to use PC trace. The trace width should be sized to
handle the RMS ripple current associated with the load.
The output capacitor only sources or sinks current for a few
microseconds during fast output current transitions. There
is no DC current in the output capacitor. Worst case ripple
current will occur if the output load is a high frequency
(>100kHz) square wave with a high peak value and fast
edges (< 1µs). Measured RMS value for this case is 0.5
times the peak-to-peak current change. Slower edges or
lower frequency will significantly reduce the RMS ripple
current in the capacitor.
Table 2. PC Trace Resistors
20mΩ
30mΩ
0.011" (0.28mm)
0.204" (5.2mm)
0.011" (0.28mm)
0.307" (7.8mm)
0.5oz CU
Width
Length
0.011" (0.28mm)
0.102" (2.6mm)
1.0oz CU
Width
Length
0.006" (0.15mm)
0.110" (2.8mm)
0.006" (0.15mm)
0.220" (5.6mm)
0.006" (0.15mm)
0.330" (8.4mm)
2.0oz CU
Width
Length
0.006" (0.15mm)
0.224" (5.7mm)
0.006" (0.15mm)
0.450" (11.4mm)
0.006" (0.15mm)
0.670" (17mm)
20
40
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
0
20
X5R
CHANGE IN VALUE (%)
CHANGE IN VALUE (%)
10mΩ
–20
–40
–60
Y5V
–80
–100
–20
–40
2
4
8
6
10 12
DC BIAS VOLTAGE (V)
14
16
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
–100
–50 –25
1963A F10
Figure 10. Ceramic Capacitor DC Bias Characteristics
Y5V
–60
–80
0
X5R
0
50
25
75
0
TEMPERATURE (°C)
100
125
1963A F11
Figure 11. Ceramic Capacitor Temperature Characteristics
1963aff
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17
LT1963A Series
APPLICATIONS INFORMATION
This resistor should be made using one of the inner
layers of the PC board which are well defined. The resistivity is determined primarily by the sheet resistance of the
copper laminate with no additional plating steps. Table
2 gives some sizes for 0.75A RMS current for various
copper thicknesses. More detailed information regarding
resistors made from PC traces can be found in Application
Note 69, Appendix A.
Overload Recovery
Like many IC power regulators, the LT1963A-X has safe operating area protection. The safe area protection decreases
the current limit as input-to-output voltage increases and
keeps the power transistor inside a safe operating region
for all values of input-to-output voltage. The protection
is designed to provide some output current at all values
of input-to-output voltage up to the device breakdown.
When power is first turned on, as the input voltage rises,
the output follows the input, allowing the regulator to start
up into very heavy loads. During the start-up, as the input
voltage is rising, the input-to-output voltage differential
is small, allowing the regulator to supply large output
currents. With a high input voltage, a problem can occur
wherein removal of an output short will not allow the
output voltage to recover. Other regulators, such as the
LT1085, also exhibit this phenomenon, so it is not unique
to the LT1963A-X.
The problem occurs with a heavy output load when the
input voltage is high and the output voltage is low. Common
situations are immediately after the removal of a shortcircuit or when the shutdown pin is pulled high after the
input voltage has already been turned on. The load line for
such a load may intersect the output current curve at two
points. If this happens, there are two stable output operating points for the regulator. With this double intersection,
the input power supply may need to be cycled down to
zero and brought up again to make the output recover.
Output Voltage Noise
The LT1963A regulators have been designed to provide
low output voltage noise over the 10Hz to 100kHz bandwidth while operating at full load. Output voltage noise is
18
typically 40nV/√Hz over this frequency bandwidth for
the LT1963A (adjustable version). For higher output
voltages (generated by using a resistor divider), the
output voltage noise will be gained up accordingly. This
results in RMS noise over the 10Hz to 100kHz bandwidth
of 14µVRMS for the LT1963A increasing to 38µVRMS for
the LT1963A-3.3.
Higher values of output voltage noise may be measured
when care is not exercised with regard to circuit layout
and testing. Crosstalk from nearby traces can induce
unwanted noise onto the output of the LT1963A-X.
Power supply ripple rejection must also be considered; the
LT1963A regulators do not have unlimited power supply
rejection and will pass a small portion of the input noise
through to the output.
Thermal Considerations
The power handling capability of the device is limited by the
maximum rated junction temperature (125°C). The power
dissipated by the device is 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 using the GND Pin
Current curves in the Typical Performance Characteristics.
Power dissipation will be equal to the sum of the two
components listed above.
The LT1963A 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.
1963aff
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LT1963A Series
APPLICATIONS INFORMATION
The following tables list 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 3. Q Package, 5-Lead DD
COPPER AREA
TOPSIDE* BACKSIDE
BOARD AREA
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
2500mm2
2500mm2
2500mm2
23°C/W
1000mm2
2500mm2
2500mm2
25°C/W
125mm2
2500mm2
2500mm2
33°C/W
*Device is mounted on topside
Table 4. S0-8 Package, 8-Lead SO
COPPER AREA
TOPSIDE* BACKSIDE
BOARD AREA
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
2500mm2
2500mm2
2500mm2
55°C/W
1000mm2
2500mm2
2500mm2
55°C/W
225mm2
2500mm2
2500mm2
63°C/W
125mm2
2500mm2
2500mm2
69°C/W
IOUT(MAX)(VIN(MAX) – VOUT) + IGND(VIN(MAX))
where,
IOUT(MAX) = 500mA
VIN(MAX) = 6V
IGND at (IOUT = 500mA, VIN = 6V) = 10mA
So,
P = 500mA(6V – 3.3V) + 10mA(6V) = 1.41W
Using a DD package, the thermal resistance will be in the
range of 23°C/W to 33°C/W depending on the copper
area. So the junction temperature rise above ambient will
be approximately equal to:
1.41W(28°C/W) = 39.5°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 + 39.5°C = 89.5°C
*Device is mounted on topside
Protection Features
Table 5. SOT-223 Package, 3-Lead SOT-223
COPPER AREA
TOPSIDE* BACKSIDE
The power dissipated by the device will be equal to:
BOARD AREA
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
2500mm2
2500mm2
2500mm2
42°C/W
1000mm2
2500mm2
2500mm2
42°C/W
225mm2
2500mm2
2500mm2
50°C/W
100mm2
2500mm2
2500mm2
56°C/W
1000mm2
1000mm2
1000mm2
49°C/W
1000mm2
0mm2
1000mm2
52°C/W
*Device is mounted on topside
T Package, 5-Lead TO-220
Thermal Resistance (Junction-to-Case) = 4°C/W
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 500mA and a maximum ambient temperature of 50°C,
what will the maximum junction temperature be?
The LT1963A 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 that can be plugged in backward.
1963aff
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19
LT1963A Series
APPLICATIONS INFORMATION
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 5k) in series with a diode
when pulled above ground.
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 from the
1.21V 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
pins divided by the 5mA maximum current into the ADJ
pin yields a minimum top resistor value of 2.6k.
20
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 12.
When the IN pin of the LT1963A 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.
5.0
REVERSE OUTPUT CURRENT (mA)
The output of the LT1963A 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 5k or higher, limiting current flow
to typically less than 600µA. 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.
LT1963A
VOUT = VADJ
4.5
4.0 LT1963A-1.5
VOUT = VFB
3.5
LT1963A-1.8
3.0
VOUT = VFB
2.5 LT1963A-2.5
VOUT = VFB
2.0
1.5
1.0
0.5
0
0
1
2
LT1963A-3.3
VOUT = VFB
TJ = 25°C
VIN = 0V
CURRENT FLOWS
INTO OUTPUT PIN
3 4 5 6 7 8
OUTPUT VOLTAGE (V)
9
10
1963A F12
Figure 12. Reverse Output Current
1963aff
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LT1963A Series
Typical Applications
SCR Pre-Regulator Provides Efficiency Over Line Variations
L1
500µH
L2
1N4148
10VAC AT
115VIN
90-140
VAC
LT1963A-3.3
IN
OUT
+
SHDN
GND
10000µF
1k
FB
3.3VOUT
1.5A
+
22µF
34k*
10VAC AT
115VIN
1N4002
1N4002
1N4002
TO ALL “+V”
POINTS
+
22µF
12.1k*
+V
“SYNC”
2.4k
+
750Ω
–
C1A
200k
1N4148
1/2
LT1018
0.1µF
+V
C1B
+V
1/2
LT1018
A1
1N4148
+
–
LT1006
10k
–
750Ω
+
0.033µF
10k
10k
+V
1µF
+V
L1 = COILTRONICS CTX500-2-52
L2 = STANCOR P-8559
* = 1% FILM RESISTOR
= NTE5437
LT1004
1.2V
1963A TA03
Paralleling of Regulators for Higher Output Current
R1, 0.01Ω
+
VIN > 3.7V
LT1963A-3.3
IN
OUT
C1
100µF
SHDN
GND
R2
0.01Ω
IN
R3
2.2k
FB
3.3V
3A
C2
22µF
LT1963A
OUT
SHDN
GND
SHDN
+
R4
2.2k
R6
6.65k
FB
R7
4.12k
R5
1k
3
2
+
–
8
1/2
LT1366
1
4
C3
0.01µF
1963A TA05
1963aff
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21
LT1963A Series
PACKAGE DESCRIPTION
Q Package
5-Lead Plastic DD Pak
(Reference LTC DWG # 05-08-1461 Rev F)
.256
(6.502)
.060
(1.524)
TYP
.060
(1.524)
.390 – .415
(9.906 – 10.541)
.165 – .180
(4.191 – 4.572)
.045 – .055
(1.143 – 1.397)
15° TYP
.060
(1.524)
.183
(4.648)
+.008
.004 –.004
+0.203
0.102 –0.102
.059
(1.499)
TYP
.330 – .370
(8.382 – 9.398)
(
)
.095 – .115
(2.413 – 2.921)
.075
(1.905)
DETAIL A
.300
(7.620)
+.012
.143 –.020
+0.305
3.632 –0.508
(
BOTTOM VIEW OF DD PAK
HATCHED AREA IS SOLDER PLATED
COPPER HEAT SINK
.067
(1.702)
.028 – .038 BSC
(0.711 – 0.965)
TYP
)
.013 – .023
(0.330 – 0.584)
.050 ±.012
(1.270 ±0.305)
DETAIL A
0° – 7° TYP
.420
.276
.080
.420
0° – 7° TYP
.325
.350
.205
.585
.585
.320
.090
.090
.067
.042
RECOMMENDED SOLDER PAD LAYOUT
NOTE:
1. DIMENSIONS IN INCH/(MILLIMETER)
2. DRAWING NOT TO SCALE
22
.067
.042
RECOMMENDED SOLDER PAD LAYOUT
FOR THICKER SOLDER PASTE APPLICATIONS
Q(DD5) 0811 REV F
1963aff
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LT1963A Series
PACKAGE DESCRIPTION
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 – .197
(4.801 – 5.004)
NOTE 3
.045 ±.005
.050 BSC
8
.245
MIN
.160 ±.005
.010 – .020
× 45°
(0.254 – 0.508)
2
.053 – .069
(1.346 – 1.752)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
5
.150 – .157
(3.810 – 3.988)
NOTE 3
1
RECOMMENDED SOLDER PAD LAYOUT
.008 – .010
(0.203 – 0.254)
6
.228 – .244
(5.791 – 6.197)
.030 ±.005
TYP
NOTE:
1. DIMENSIONS IN
7
.014 – .019
(0.355 – 0.483)
TYP
INCHES
(MILLIMETERS)
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
3
4
.004 – .010
(0.101 – 0.254)
.050
(1.270)
BSC
SO8 0303
1963aff
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23
LT1963A Series
PACKAGE DESCRIPTION
ST Package
3-Lead Plastic SOT-223
(Reference LTC DWG # 05-08-1630)
.248 – .264
(6.30 – 6.71)
.129 MAX
.114 – .124
(2.90 – 3.15)
.059 MAX
.264 – .287
(6.70 – 7.30)
.248 BSC
.130 – .146
(3.30 – 3.71)
.039 MAX
.059 MAX
.181 MAX
.033 – .041
(0.84 – 1.04)
.0905
(2.30)
BSC
RECOMMENDED SOLDER PAD LAYOUT
10° – 16°
.010 – .014
(0.25 – 0.36)
10°
MAX
.071
(1.80)
MAX
.090
BSC
10° – 16°
.024 – .033
(0.60 – 0.84)
.181
(4.60)
BSC
24
.012
(0.31)
MIN
.0008 – .0040
(0.0203 – 0.1016)
ST3 (SOT-233) 0502
1963aff
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LT1963A Series
PACKAGE DESCRIPTION
T Package
5-Lead Plastic TO-220 (Standard)
(Reference LTC DWG # 05-08-1421)
.390 – .415
(9.906 – 10.541)
.165 – .180
(4.191 – 4.572)
.147 – .155
(3.734 – 3.937)
DIA
.045 – .055
(1.143 – 1.397)
.230 – .270
(5.842 – 6.858)
.460 – .500
(11.684 – 12.700)
.570 – .620
(14.478 – 15.748)
.330 – .370
(8.382 – 9.398)
.700 – .728
(17.78 – 18.491)
.620
(15.75)
TYP
SEATING PLANE
.152 – .202
.260 – .320 (3.861 – 5.131)
(6.60 – 8.13)
BSC
.067
(1.70)
.095 – .115
(2.413 – 2.921)
.155 – .195*
(3.937 – 4.953)
.013 – .023
(0.330 – 0.584)
.028 – .038
(0.711 – 0.965)
.135 – .165
(3.429 – 4.191)
* MEASURED AT THE SEATING PLANE
T5 (TO-220) 0801
1963aff
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25
LT1963A Series
Package Description
FE Package
16-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663 Rev J)
Exposed Pad Variation BB
4.70
(.185)
3.58
(.141)
DETAIL A
4.90 – 5.10*
(.193 – .201)
0.56
(.022)
REF
3.58
(.141)
NOTE 5
16 1514 13 12 1110
9
NOTE 5
6.60 ±0.10
2.94 3.05
(.116) (.120)
4.50 ±0.10
DETAIL A
SEE NOTE 4
2.94 6.40
(.116) (.252)
BSC
0.53
(.021)
REF
DETAIL A IS THE PART OF THE
LEAD FRAM FEATURE FOR
REFERENCE ONLY
NO MEASUREMENT PUROSE
1.05 ±0.10
0.65 BSC
0.45 ±0.05
1 2 3 4 5 6 7 8
RECOMMENDED SOLDER PAD LAYOUT
4.30 – 4.50*
(.169 – .177)
0.09 – 0.20
(.0035 – .0079)
0.25
REF
0.50 – 0.75
(.020 – .030)
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
MILLIMETERS
2. DIMENSIONS ARE IN
(INCHES)
3. DRAWING NOT TO SCALE
4. RECOMMENDED MINIMUM PCB METAL SIZE
FOR EXPOSED PAD ATTACHMENT
26
1.10
(.0433)
MAX
0° – 8°
0.65
(.0256)
BSC
0.195 – 0.30
(.0077 – .0118)
TYP
0.05 – 0.15
(.002 – .006)
FE16 (BB) TSSOP REV J 1012
5. BOTTOM EXPOSED PADDLE MAY HAVE METAL PROTRUSION
IN THIS AREA. THIS REGION MUST BE FREE OF ANY EXPOSED
TRACES OR VIAS ON PBC LAYOUT
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
1963aff
For more information www.linear.com/LT1963A
LT1963A Series
Revision History
(Revision history begins at Rev E)
REV
DATE
DESCRIPTION
PAGE NUMBER
E
02/11
Updated FE and Q package drawings in Package Description section
F
09/13
Replaced graphs with correct versions
22, 26
16
1963aff
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/LT1963A
27
LT1963A Series
Typical Application
Adjustable Current Source
R5
0.01Ω
VIN > 2.7V
+
C1
10µF
R1
1k
LT1004-1.2
R2
80.6k
R3
2k
R4
2.2k
LT1963A-1.8
IN
OUT
R6
2.2k
2
3
C2
3.3µF
NOTE: ADJUST R1 FOR
0A TO 1.5A CONSTANT CURRENT
SHDN
GND
LOAD
FB
R8
100k
C3
1µF
+
–
R7
470Ω
8
1
1/2
LT1366
4
1963A TA04
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
LT1175
500mA, Micropower, Negative LDO
VIN: –20V to –4.3V, VOUT(MIN) = –3.8V, VDO = 0.50V, IQ = 45µA, ISD 10µA,
DD, SOT-223, PDIP8 Packages
LT1185
3A, Negative LDO
VIN: –35V to –4.2V, VOUT(MIN) = –2.40V, VDO = 0.80V, IQ = 2.5mA, ISD
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