LT1965 Series
1
1965fb
For more information www.linear.com/LT1965
Features
applications
Description
1.1A, Low Noise,
Low Dropout Linear Regulator
The LT
®
1965 series are low noise, low dropout linear regu-
lators. The devices supply 1.1A of output current with a
310mV typical dropout voltage. Operating quiescent current
is 500µA for the adjustable version, reducing to <1µA in
shutdown. Quiescent current is well controlled; it does not
rise in dropout as with many other regulators. The LT1965
regulators have very low output noise which makes them
ideal for sensitive RF and DSP supply applications.
Output voltage ranges from 1.20V to 19.5V. The LT1965
regulators are stable with output capacitors as low as
10µF. Internal protection circuitry includes reverse-battery
protection, current limiting with foldback, thermal limit-
ing and reverse-current protection. The LT1965 series
are available in fixed output voltages of 1.5V, 1.8V, 2.5V,
3.3V, and as an adjustable device with a 1.20V reference
voltage. The package offerings include the 5-lead TO-220,
5-lead DD-Pak as well as the thermally enhanced 8-lead
MSOP and low profile (0.75mm) 8-lead 3mm × 3mm DFN.
3.3V to 2.5V Regulator
n Output Current: 1.1A
n Dropout Voltage: 310mV
n Low Noise: 40µVRMS (10Hz to 100kHz)
n 500µA Quiescent Current (Adjustable Version)
n Wide Input Voltage Range: 1.8V to 20V
n No Protection Diodes Needed
n Controlled Quiescent Current in Dropout
n Adjustable Output from 1.20V to 19.5V
n Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 3.3V
n < 1µA Quiescent Current in Shutdown
n Stable with 10µF Output Capacitor
n Stable with Ceramic or Tantalum Capacitors
n Reverse-Battery Protection
n No Reverse Current
n Current Limit with Foldback Protection
n Thermal Limiting
n 5-Lead TO-220, DD-Pak, Thermally Enhanced 8-Lead
MSOP and 8-Lead 3mm × 3mm DFN Packages
n Logic Power Supplies
n Post Regulator for Switching Supplies
n Low Noise Instrumentation
Dropout Voltage
typical application
OUTPUT CURRENT (A)
0
0
DROPOUT VOLTAGE (mV)
100
200
300
0.2 0.4 0.6 0.8 1
400
50
150
250
350
1.2
1965 TA01b
TJ = 25°C
IN
SHDN
10µF*
*CERAMIC OR TANTALUM
1965 TA01
OUT
VIN > 3V
TO 20V
SENSE
GND
LT1965-2.5
2.5V
1.1A
10µF*
++
L, LT, LT C , LT M, 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.
LT1965 Series
2
1965fb
For more information www.linear.com/LT1965
absolute MaxiMuM ratings
IN Pin Voltage .........................................................±22V
OUT Pin Voltage ......................................................±22V
Input to Output Differential Voltage (Note 2) ......... ±22V
SENSE Pin Voltage ..................................................±22V
ADJ Pin Voltage ........................................................±9V
SHDN Pin Voltage ...................................................±22V
(Note 1)
TOP VIEW
DD PACKAGE
8-LEAD (3mm × 3mm) PLASTIC DFN
5
6
7
8
9
4
3
2
1OUT
OUT
SENSE/ADJ*
GND
IN
IN
SHDN
GND
TJMAX = 150°C, θJA = 65°C/W, θJC = 3°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
*PIN 3 = SENSE FOR LT1965-1.5/LT1965-1.8/LT1965-2.5/LT1965-3.3
*PIN 3 = ADJ FOR LT1965
1
2
3
4
OUT
OUT
SENSE/ADJ*
GND
8
7
6
5
9
IN
IN
SHDN
GND
TOP VIEW
MS8E PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 60°C/W, θJC = 10°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
*PIN 3 = SENSE FOR LT1965-1.5/LT1965-1.8/LT1965-2.5/LT1965-3.3
*PIN 3 = ADJ FOR LT1965
Q PACKAGE
5-LEAD PLASTIC DD-PAK
FRONT VIEW
SENSE/ADJ*
OUT
GND
IN
SHDN
TAB IS
GND
5
4
3
2
1
TJMAX = 150°C, θJA = 30°C/W, θJC = 3°C/W
*PIN 5 = SENSE FOR LT1965-1.5/LT1965-1.8/LT1965-2.5/LT1965-3.3
*PIN 5 = ADJ FOR LT1965
T PACKAGE
5-LEAD PLASTIC TO-220
SENSE/ADJ*
OUT
GND
IN
SHDN
FRONT VIEW
5
4
3
2
1
TAB IS
GND
TJMAX = 150°C, θJA = 50°C/W, θJC = 3°C/W
*PIN 5 = SENSE FOR LT1965-1.5/LT1965-1.8/LT1965-2.5/LT1965-3.3
*PIN 5 = ADJ FOR LT1965
Output Short-Circuit Duration .......................... Indefinite
Operating Junction Temperature Range (Notes 3, 5, 13)
E-, I-Grades .......................................40°C to 125°C
H-Grade ............................................. 40°C to 150°C
Storage Temperature Range ..................65°C to 150°C
Lead Temperature (Soldering, 10 sec)
(Only for MSOP, TO-220, DD-Pak Packages) ....30C
LEAD FREE FINISH TAPE AND REEL PART MARKING*PACKAGE DESCRIPTION TEMPERATURE RANGE
LT1965EDD#PBF LT1965EDD#TRPBF LCXW 8-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
LT1965IDD#PBF LT1965IDD#TRPBF LCXW 8-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
LT1965EDD-1.5#PBF LT1965EDD-1.5#TRPBF LDKW 8-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
LT1965IDD-1.5#PBF LT1965IDD-1.5#TRPBF LDKW 8-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
LT1965EDD-1.8#PBF LT1965EDD-1.8#TRPBF LDKY 8-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
LT1965IDD-1.8#PBF LT1965IDD-1.8#TRPBF LDKY 8-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
LT1965EDD-2.5#PBF LT1965EDD-2.5#TRPBF LDMB 8-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
LT1965IDD-2.5#PBF LT1965IDD-2.5#TRPBF LDMB 8-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
LT1965EDD-3.3#PBF LT1965EDD-3.3#TRPBF LDMD 8-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
pin conFiguration
orDer inForMation
LT1965 Series
3
1965fb
For more information www.linear.com/LT1965
orDer inForMation
LEAD FREE FINISH TAPE AND REEL PART MARKING*PACKAGE DESCRIPTION TEMPERATURE RANGE
LT1965IDD-3.3#PBF LT1965IDD-3.3#TRPBF LDMD 8-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
LT1965EMS8E#PBF LT1965EMS8E#TRPBF LTCXX 8-Lead Plastic MSOP –40°C to 125°C
LT1965IMS8E#PBF LT1965IMS8E#TRPBF LTCXX 8-Lead Plastic MSOP –40°C to 125°C
LT1965EMS8E-1.5#PBF LT1965EMS8E-1.5#TRPBF LTDKX 8-Lead Plastic MSOP –40°C to 125°C
LT1965IMS8E-1.5#PBF LT1965IMS8E-1.5#TRPBF LTDKX 8-Lead Plastic MSOP –40°C to 125°C
LT1965EMS8E-1.8#PBF LT1965EMS8E-1.8#TRPBF LTDKZ 8-Lead Plastic MSOP –40°C to 125°C
LT1965IMS8E-1.8#PBF LT1965IMS8E-1.8#TRPBF LTDKZ 8-Lead Plastic MSOP –40°C to 125°C
LT1965EMS8E-2.5#PBF LT1965EMS8E-2.5#TRPBF LTDMC 8-Lead Plastic MSOP –40°C to 125°C
LT1965IMS8E-2.5#PBF LT1965IMS8E-2.5#TRPBF LTDMC 8-Lead Plastic MSOP –40°C to 125°C
LT1965EMS8E-3.3#PBF LT1965EMS8E-3.3#TRPBF LTDMF 8-Lead Plastic MSOP –40°C to 125°C
LT1965IMS8E-3.3#PBF LT1965IMS8E-3.3#TRPBF LTDMF 8-Lead Plastic MSOP –40°C to 125°C
LT1965EQ#PBF LT1965EQ#TRPBF LT1965Q 5-Lead Plastic DD-Pak –40°C to 125°C
LT1965IQ#PBF LT1965IQ#TRPBF LT1965Q 5-Lead Plastic DD-Pak –40°C to 125°C
LT1965HQ#PBF LT1965HQ#TRPBF LT1965Q 5-Lead Plastic DD-Pak –40°C to 150°C
LT1965EQ-1.5#PBF LT1965EQ-1.5#TRPBF LT1965Q-1.5 5-Lead Plastic DD-Pak –40°C to 125°C
LT1965IQ-1.5#PBF LT1965IQ-1.5#TRPBF LT1965Q-1.5 5-Lead Plastic DD-Pak –40°C to 125°C
LT1965EQ-1.8#PBF LT1965EQ-1.8#TRPBF LT1965Q-1.8 5-Lead Plastic DD-Pak –40°C to 125°C
LT1965IQ-1.8#PBF LT1965IQ-1.8#TRPBF LT1965Q-1.8 5-Lead Plastic DD-Pak –40°C to 125°C
LT1965EQ-2.5#PBF LT1965EQ-2.5#TRPBF LT1965Q-2.5 5-Lead Plastic DD-Pak –40°C to 125°C
LT1965IQ-2.5#PBF LT1965IQ-2.5#TRPBF LT1965Q-2.5 5-Lead Plastic DD-Pak –40°C to 125°C
LT1965EQ-3.3#PBF LT1965EQ-3.3#TRPBF LT1965Q-3.3 5-Lead Plastic DD-Pak –40°C to 125°C
LT1965IQ-3.3#PBF LT1965IQ-3.3#TRPBF LT1965Q-3.3 5-Lead Plastic DD-Pak –40°C to 125°C
LT1965ET#PBF N/A LT1965T 5-Lead Plastic TO-220 –40°C to 125°C
LT1965IT#PBF N/A LT1965T 5-Lead Plastic TO-220 –40°C to 125°C
LT1965HT#PBF N/A LT1965T 5-Lead Plastic TO-220 –40°C to 150°C
LT1965ET-1.5#PBF N/A LT1965T-1.5 5-Lead Plastic TO-220 –40°C to 125°C
LT1965IT-1.5#PBF N/A LT1965T-1.5 5-Lead Plastic TO-220 –40°C to 125°C
LT1965ET-1.8#PBF N/A LT1965T-1.8 5-Lead Plastic TO-220 –40°C to 125°C
LT1965IT-1.8#PBF N/A LT1965T-1.8 5-Lead Plastic TO-220 –40°C to 125°C
LT1965ET-2.5#PBF N/A LT1965T-2.5 5-Lead Plastic TO-220 –40°C to 125°C
LT1965IT-2.5#PBF N/A LT1965T-2.5 5-Lead Plastic TO-220 –40°C to 125°C
LT1965ET-3.3#PBF N/A LT1965T-3.3 5-Lead Plastic TO-220 –40°C to 125°C
LT1965IT-3.3#PBF N/A LT1965T-3.3 5-Lead Plastic TO-220 –40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *Temperature grades are 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/
LT1965 Series
4
1965fb
For more information www.linear.com/LT1965
electrical characteristics
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Input Voltage
(Notes 4, 12)
ILOAD = 0.5A
ILOAD = 1.1A (TJ < 125°C)
ILOAD = 1A (H-Grade, TJ > 125°C)
l
1.65
1.8
2.3
2.3
V
V
V
Regulated Output Voltage
(Note 5)
LT1965-1.5, VIN = 2.1V, ILOAD = 1mA
LT1965-1.5, 2.5 < VIN < 20V, 1mA < ILOAD < 1.1A
l
1.477
1.455
1.5
1.5
1.523
1.545
V
V
LT1965-1.8, VIN = 2.3V, ILOAD = 1mA
LT1965-1.8, 2.8 < VIN < 20V, 1mA < ILOAD < 1.1A
l
1.773
1.746
1.8
1.8
1.827
1.854
V
V
LT1965-2.5, VIN = 3V, ILOAD = 1mA
LT1965-2.5, 3.5 < VIN < 20V, 1mA < ILOAD < 1.1A
l
2.462
2.425
2.5
2.5
2.538
2.575
V
V
LT1965-3.3, VIN = 3.8V, ILOAD = 1mA
LT1965-3.3, 4.3 < VIN < 20V, 1mA < ILOAD < 1.1A
l
3.25
3.201
3.3
3.3
3.35
3.399
V
V
ADJ Pin Voltage (Notes 4, 5) VIN = 2.1V, ILOAD = 1mA
2.3V < VIN < 20V, 1mA < ILOAD < 1.1A (TJ < 125°C)
2.3V < VIN < 20V, 1mA < ILOAD < 1A (H-Grade, TJ > 125°C)
l
1.182
1.164
1.158
1.2
1.2
1.218
1.236
1.236
V
V
V
Line Regulation LT1965-1.5, ∆VIN = 2.1V to 20V, ILOAD = 1mA
LT1965-1.8, ∆VIN = 2.3V to 20V, ILOAD = 1mA
LT1965-2.5, ∆VIN = 3V to 20V, ILOAD = 1mA
LT1965-3.3, ∆VIN = 3.8V to 20V, ILOAD = 1mA
LT1965, ∆VIN = 2.1V to 20V, ILOAD = 1mA (E-, I-Grades) (Note 4)
LT1965, ∆VIN = 2.1V to 20V, ILOAD = 1mA (H-Grade) (Note 4)
l
l
l
l
l
l
3.5
4
4.5
5.5
3
3
9
10
11.5
16
8
12
mV
mV
mV
mV
mV
mV
Load Regulation LT1965-1.5, VIN = 2.5V, ∆ILOAD = 1mA to 1.1A
LT1965-1.5, VIN = 2.5V, ∆ILOAD = 1mA to 1.1A
l
5.25 10
20
mV
mV
LT1965-1.8, VIN = 2.8V, ∆ILOAD = 1mA to 1.1A
LT1965-1.8, VIN = 2.8V, ∆ILOAD = 1mA to 1.1A
l
6.25 12
24
mV
mV
LT1965-2.5, VIN = 3.5V, ∆ILOAD = 1mA to 1.1A
LT1965-2.5, VIN = 3.5V, ∆ILOAD = 1mA to 1.1A
l
8.75 16.5
33
mV
mV
LT1965-3.3, VIN = 4.3V, ∆ILOAD = 1mA to 1.1A
LT1965-3.3, VIN = 4.3V, ∆ILOAD = 1mA to 1.1A
l
11.5 22
44
mV
mV
LT1965, VIN = 2.3V, ∆ILOAD = 1mA to 1.1A (Note 4)
LT1965, VIN = 2.3V, ∆ILOAD = 1mA to 1.1A (TJ < 125°C)
LT1965, VIN = 2.3V, ∆ILOAD = 1mA to 1A (H-Grade, TJ > 125°C)
l
4.25 8
16
22
mV
mV
mV
Dropout Voltage
VIN = VOUT(NOMINAL)
(Notes 6, 7, 12)
ILOAD = 1mA
ILOAD = 1mA
l
0.055 0.08
0.14
V
V
ILOAD = 100mA
ILOAD = 100mA
l
0.12 0.175
0.28
V
V
ILOAD = 500mA
ILOAD = 500mA
l
0.21 0.25
0.36
V
V
ILOAD = 1.1A
ILOAD = 1.1A (TJ < 125°C)
ILOAD = 1A (H-Grade, TJ > 125°C)
l
0.31 0.36
0.49
0.49
V
V
V
GND Pin Current
VIN = VOUT(NOMINAL) + 1V
(Notes 6, 8)
ILOAD = 0mA
ILOAD = 1mA
ILOAD = 100mA
ILOAD = 500mA
ILOAD = 1.1A (TJ < 125°C)
ILOAD = 1A (H-Grade, TJ > 125°C)
l
l
l
l
l
0.5
0.6
2.2
8.2
21
1.1
1.5
5.5
20
40
40
mA
mA
mA
mA
mA
mA
Output Voltage Noise COUT = 10µF, ILOAD = 1.1A, BW = 10Hz to 100kHz 40 µVRMS
ADJ Pin Bias Current
(Notes 4, 9)
1.3 4.5 µA
Shutdown Threshold VOUT = Off to On
VOUT = On to Off
l
l
0.2
0.85
0.45
2 V
V
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 3)
LT1965 Series
5
1965fb
For more information www.linear.com/LT1965
electrical characteristics
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 is not
achievable with all combinations of rated IN pin and OUT pin voltages.
With the IN pin at 22V, the OUT pin may not be pulled below 0V. The total
measured voltage from IN to OUT must not exceed ±22V.
Note 3: The LT1965 regulators are tested and specified under pulse
load conditions such that TJ @ TA. The LT1965E regulators are 100%
tested at TA = 25°C and performance is guaranteed from 0°C to 125°C.
Performance of the LT1965E over the full –40°C to 125°C operating
junction temperature range is assured by design, characterization and
correlation with statistical process controls. The LT1965I regulators are
guaranteed over the full –40°C to 125°C operating junction temperature
range. The LT1965H is tested at 150°C operating junction temperature.
High junction temperatures degrade operating lifetimes. Operating lifetime
is derated at junction temperatures greater than 125°C.
Note 4: The LT1965 adjustable version is tested and specified for these
conditions with the ADJ connected to the OUT pin.
Note 5: Maximum junction temperature limits operating conditions. The
regulated output voltage specification does not apply for all possible
combinations of input voltage and output current. Limit the output current
range if operating at the maximum input voltage. Limit the input-to-output
voltage differential if operating at the maximum output current.
Note 6: To satisfy minimum input voltage requirements, the LT1965
adjustable version is tested and specified for these conditions with an
external resistor divider (bottom 4.02k, top 4.32k) for an output voltage of
2.5V. The external resistor divider adds 300µA of output DC load current.
This external current is not factored into GND pin current.
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 equals: (VIN – VDROPOUT)
Note 8: GND pin current is tested with VIN = VOUT(NOMINAL) + 1V and a
current source load. GND pin current increases slightly in dropout. For
the fixed output versions, an internal resistor divider will typically add
100µA to the GND pin current. See GND pin current curves in the Typical
Performance Characteristics section.
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 of the GND pin.
Note 12: For the LT1965, LT1965-1.5 and LT1965-1.8, the minimum input
voltage specification limits the dropout voltage under some output voltage/
load conditions.
Note 13: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C (LT1965E, LT1965I) or 150°C (LT1965H)
when overtemperature is active. Continuous operation above the specified
maximum operating junction temperature may impair device reliability.
PARAMETER CONDITIONS MIN TYP MAX UNITS
SHDN Pin Current (Note 10) VSHDN = 0V
VSHDN = 20V
0.01
5.5
1
10
µA
µA
Quiescent Current in Shutdown VIN = 6V, VSHDN = 0V 0.01 1 µA
Ripple Rejection VIN – VOUT = 1.5V (AVG), VRIPPLE = 0.5VP-P,
fRIPPLE = 120Hz, ILOAD = 0.75A
57 75 dB
Current Limit VIN = 7V, VOUT = 0
VIN = VOUT(NOMINAL) + 1V, ∆VOUT = 0.1V (TJ < 125°C) (Note 6)
VIN = VOUT(NOMINAL) + 1V, ∆VOUT = 0.1V, (H-Grade, TJ > 125°C) (Note 6)
l
1.2
1.1
2.4 A
A
A
Input Reverse-Leakage Current VIN = –20V, VOUT = 0 1 mA
Reverse-Output Current (Note 11) LT1965-1.5, VOUT = 1.5V, VIN = 0
LT1965-1.8, VOUT = 1.8V, VIN = 0
LT1965-2.5, VOUT = 2.5V, VIN = 0
LT1965-3.3, VOUT = 3.3V, VIN = 0
LT1965 (Note 4), VOUT = 1.2V, VIN = 0
275
275
275
275
175
525
525
525
525
400
µA
µA
µA
µA
µA
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 3)
LT1965 Series
6
1965fb
For more information www.linear.com/LT1965
LT1965-2.5 Output Voltage LT1965-3.3 Output Voltage LT1965 ADJ Pin Voltage
typical perForMance characteristics
Typical Dropout Voltage Guaranteed Dropout Voltage Dropout Voltage
Quiescent Current LT1965-1.5 Output Voltage LT1965-1.8 Output Voltage
OUTPUT CURRENT (A)
0
0
DROPOUT VOLTAGE (mV)
100
200
300
0.2 0.4 0.6 0.8 1
400
500
50
150
250
350
450
1.2
1965 G01
TJ = 125°C
TJ = 25°C
OUTPUT CURRENT (A)
0
0
GUARANTEED DROPOUT VOLTAGE (mV)
100
200
300
0.2 0.4 0.6 0.8 1
400
500
50
150
250
350
450
1.2
1965 G02
= TEST POINTS
TJ = 125°C
TJ = 25°C
–50 –25 0 25 50 75 125100 150
0
DROPOUT VOLTAGE (mV)
100
200
300
400
500
50
150
250
350
450
1965 G03
IL = 1.1A
IL = 500mA
IL = 100mA
IL = 1mA
TEMPERATURE (°C)
IL = 1A
0
QUIESCENT CURRENT (mA)
0.2
0.4
0.6
0.8
1.0
0.1
0.3
0.5
0.7
0.9
1965 G04
TEMPERATURE (°C)
–50 –25 0 25 50 75 125100 150
VIN = 6V
RL = , IL = 0
VSHDN = VIN
LT1965-1.5/-1.8/-2.5/-3.3
LT1965
VSHDN = 0
1.182
ADJ PIN VOLTAGE (V)
1.190
1.198
1.206
1.218
1.186
1.194
1.202
1.210
1.214
1965 G09
TEMPERATURE (°C)
–50 –25 0 25 50 75 125100 150
IL = 1mA
1.477
OUTPUT VOLTAGE (V)
1.487
1.497
1.507
1.522
1.482
1.492
1.502
1.512
1.517
1965 G05
TEMPERATURE (°C)
–50 –25 0 25 50 75 125100 150
IL = 1mA
–50 –25 0 25 50 75 125100 150
1.773
OUTPUT VOLTAGE (V)
1.785
1.797
1.809
1.827
1.779
1.791
1.803
1.815
1.821
1965 G06
TEMPERATURE (°C)
IL = 1mA
2.460
OUTPUT VOLTAGE (V)
2.484
2.500
2.516
2.540
2.476
2.468
2.492
2.508
2.524
2.532
1965 G07
TEMPERATURE (°C)
–50 –25 0 25 50 75 125100 150
IL = 1mA
3.250
OUTPUT VOLTAGE (V)
3.280
3.300
3.320
3.350
3.270
3.260
3.290
3.310
3.330
3.340
1965 G08
TEMPERATURE (°C)
–50 –25 0 25 50 75 125100 150
IL = 1mA
LT1965 Series
7
1965fb
For more information www.linear.com/LT1965
typical perForMance characteristics
LT1965-1.5 Quiescent Current LT1965-1.8 Quiescent Current LT1965-2.5 Quiescent Current
LT1965-3.3 Quiescent Current LT1965 Quiescent Current
LT1965-1.5 GND Pin Current
(Light Load)
LT1965-1.5 GND Pin Current
(Heavy Load)
LT1965-1.8 GND Pin Current
(Light Load)
LT1965-1.8 GND Pin Current
(Heavy Load)
0
QUIESCENT CURRENT (mA)
0.2
0.4
0.6
0.8
1.0
0.1
0.3
0.5
0.7
0.9
1965 G14
INPUT VOLTAGE (V)
0 164 8 12 20142 6 10 18
TJ = 25°C
RL = 4.02k
VSHDN = VIN
VSHDN = 0V
0
QUIESCENT CURRENT (mA)
1
3
5
2
4
1965 G10
INPUT VOLTAGE (V)
012345678910
TJ = 25°C
RL = ∞
VSHDN = VIN
VSHDN = 0V 0
QUIESCENT CURRENT (mA)
1
3
5
2
4
1965 G11
INPUT VOLTAGE (V)
012345678910
TJ = 25°C
RL = ∞
VSHDN = VIN
VSHDN = 0V 0
QUIESCENT CURRENT (mA)
2
6
10
4
8
1965 G12
INPUT VOLTAGE (V)
012345678910
TJ = 25°C
RL = ∞
VSHDN = VIN
VSHDN = 0V
0
QUIESCENT CURRENT (mA)
2
6
10
4
8
1965 G13
INPUT VOLTAGE (V)
012345678910
TJ = 25°C
RL = ∞
VSHDN = VIN
VSHDN = 0V
0
GND PIN CURRENT (mA)
5
15
25
10
20
1965 G16
INPUT VOLTAGE (V)
012345678910
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 1.5V
RL = 3Ω, IL = 500mA*
RL = 15Ω, IL = 100mA*
RL = 1.363Ω, IL = 1.1A*
0
GND PIN CURRENT (mA)
1
3
5
2
4
1965 G15
INPUT VOLTAGE (V)
012345678910
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 1.5V
RL = 30Ω, IL = 50mA*
RL = 150Ω, IL = 10mA*
RL = 1.5k, IL = 1mA*
0
GND PIN CURRENT (mA)
1
3
5
2
4
1965 G17
INPUT VOLTAGE (V)
012345678910
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 1.8V
RL = 36Ω, IL = 50mA*
RL = 180Ω, IL = 10mA*
RL = 1.8k, IL = 1mA*
0
GND PIN CURRENT (mA)
5
15
25
10
20
1965 G18
INPUT VOLTAGE (V)
012345678910
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 1.8V
RL = 3.6Ω, IL = 500mA*
RL = 18Ω, IL = 100mA*
RL = 1.636Ω, IL = 1.1A*
LT1965 Series
8
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For more information www.linear.com/LT1965
typical perForMance characteristics
LT1965-2.5 GND Pin Current
(Light Load)
LT1965-2.5 GND Pin Current
(Heavy Load)
LT1965-3.3 GND Pin Current
(Light Load)
LT1965-3.3 GND Pin Current
(Heavy Load)
LT1965 GND Pin Current
(Light Load)
LT1965 GND Pin Current
(Heavy Load)
GND Pin Current vs ILOAD SHDN Pin Threshold
0
GND PIN CURRENT (mA)
0.4
0.8
1.2
1.6
2.0
0.2
0.6
1.0
1.4
1.8
INPUT VOLTAGE (V)
0 82 4 6 1071 3 5 9
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 1.2V RL = 24Ω, IL = 50mA*
RL = 120Ω, IL = 10mA*
RL = 1.2k, IL = 1mA*
0
GND PIN CURRENT (mA)
5
10
15
20
25
1965 G24
INPUT VOLTAGE (V)
0 82 4 6 1071 3 5 9
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 1.2V
RL = 1.091Ω, IL = 1.1A*
RL = 2.4Ω, IL = 500mA*
RL = 12Ω, IL = 100mA*
LOAD CURRENT (A)
0
0
GND PIN CURRENT (mA)
5.00
10.0
15.0
0.2 0.4 0.6 0.8 1.0
20.0
25.0
2.50
7.50
12.5
17.5
22.5
1.2
1965 G25
VIN = VOUT(NOMINAL) + 1V
0
SHDN PIN THRESHOLD (V)
0.2
0.4
0.6
0.8
1.0
0.1
0.3
0.5
0.7
0.9
1965 G26
TEMPERATURE (°C)
–50 –25 0 25 50 75 125100 150
OFF TO ON
ON TO OFF
0
GND PIN CURRENT (mA)
2
4
8
12
6
10
1965 G19
INPUT VOLTAGE (V)
012345678910
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 2.5V
RL = 250Ω, IL = 10mA*
RL = 50Ω, IL = 50mA*
RL = 2.5k, IL = 1mA*
0
GND PIN CURRENT (mA)
5
15
25
10
20
1965 G20
INPUT VOLTAGE (V)
012345678910
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 2.5V
RL = 5Ω, IL = 500mA*
RL = 25Ω, IL = 100mA*
RL = 2.272Ω, IL = 1.1A*
0
GND PIN CURRENT (mA)
2
4
8
12
6
10
1965 G21
INPUT VOLTAGE (V)
012345678910
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 3.3V
RL = 330Ω, IL = 10mA*
RL = 66Ω, IL = 50mA*
RL = 3.3k, IL = 1mA*
0
GND PIN CURRENT (mA)
5
15
25
10
20
1965 G22
INPUT VOLTAGE (V)
012345678910
TJ = 25°C
VSHDN = VIN
*FOR VOUT = 3.3V
RL = 6.6Ω, IL = 500mA*
RL = 33Ω, IL = 100mA*
RL = 3Ω, IL = 1.1A*
LT1965 Series
9
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typical perForMance characteristics
SHDN Pin Input Current ADJ Pin Bias Current
Current Limit vs VIN – VOUT Current Limit vs Temperature Reverse-Output Current
Reverse-Output Current Ripple Rejection vs Frequency
SHDN Pin Input Current
SHDN PIN VOLTAGE (V)
0
SHDN PIN INPUT CURRENT (µA)
2
4
6
1
3
5
4 8 12 16 20
20 6 10 14 18
1965 G27
5.0
SHDN PIN INPUT CURRENT (µA)
5.2
5.4
5.6
5.8
6.0
5.1
5.3
5.5
5.7
5.9
1965 G28
TEMPERATURE (°C)
–50 –25 0 25 50 75 125100 150
VSHDN = 20V
0
ADJ PIN BIAS CURRENT (µA)
1.0
2.0
3.0
4.0
4.5
0.5
1.5
2.5
3.5
1965 G29
TEMPERATURE (°C)
–50 –25 0 25 50 75 125100 150
0
CURRENT LIMIT (A)
0.5
1.5
2.5
1.0
2.0
1965 G30
INPUT/OUTPUT DIFFERENTIAL (V)
0 2 4 6 8 10 12 14 16 18 20
VOUT = 100mV
TJ = –50°C
TJ = 125°C
TJ = 150°C
TJ = 25°C
0
CURRENT LIMIT (A)
1.0
2.0
3.0
0.5
1.5
2.5
1965 G31
TEMPERATURE (°C)
–50 –25 0 25 50 75 125100 150
VIN = 7V
VOUT = 0V
0
REVERSE OUTPUT CURRENT (mA)
2
4
6
1
3
5
1965 G32
OUTPUT VOLTAGE (V)
0 1 432 5 6 7 8 9
LT1965
LT1965-1.5
LT1965-1.8
LT1965-3.3
TJ = 25°C
VIN = 0V
VOUT = VADJ (LT1965)
VOUT = VSENSE
(LT1965-1.5/-1.8/-2.5/-3.3)
CURRENT FLOWS INTO
OUTPUT PIN
LT1965-2.5
0
REVERSE OUTPUT CURRENT (mA)
0.1
0.5
0.4
0.3
0.2
0.6
1965 G33
TEMPERATURE (°C)
LT1965
VIN = 0V
VOUT = 1.2V (LT1965)
VOUT = 1.5V (LT1965-1.5)
VOUT = 1.8V (LT1965-1.8)
VOUT = 2.5V (LT1965-2.5)
VOUT = 3.3V (LT1965-3.3)
LT1965-1.5/-1.8/-2.5/-3.3
–50 –25 0 25 50 75 125100 150
FREQUENCY (Hz)
20
RIPPLE REJECTION (dB)
30
50
60
80
90
10 1k 10k 1M
10
100 100k
70
40
0
1965 G34
IL = 0.75A
COUT = 10µF CERAMIC
VIN = VOUT(NOMINAL)
+ 1V + 50mVRMS RIPPLE
LT1965 Series
10
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typical perForMance characteristics
Load Regulation
Output Noise Spectral Density
RMS Output Noise vs Load
Current (10Hz to 100kHz)
LT1965-1.8 10Hz to 100kHz
Output Noise
LT1965-3.3 Transient Response
LT1965-2.5 SHDN Transient
Response
Ripple Rejection vs Temperature LT1965 Minimum Input Voltage
RIPPLE REJECTION (dB)
100
1965 G35
TEMPERATURE (°C)
–50 –25 0 25 50 75 125100 150
0
20
40
60
80
10
30
50
70
90
IL = 0.75A
VIN = VOUT(NOMINAL) + 1V + 0.5P-P
RIPPLE AT f = 120Hz
IL = 1.1A
–50 –25 0 25 50 75 125100 150
0
MINIMUM INPUT VOLTAGE (V)
0.5
1.0
1.5
2.0
2.5
1965 G36
TEMPERATURE (°C)
IL = 100mA
IL = 1A
IL = 500mA
LOAD REGULATION (mV)
–30
–25
–20
–15
–50
–45
–40
–35
–10
–5
0
1965 G37
TEMPERATURE (°C)
LT1965
VIN = VOUT(NOMINAL) + 1V
(LT1965-1.5/-1.8/-2.5/-3.3)
VIN = 2.3V (LT1965)
IL = 1mA TO 1.1A
LT1965-3.3
–50 –25 0 25 50 75 125100 150
LT1965-1.5
LT1965-1.8
LT1965-2.5
0.01
0.10
1.00
FREQUENCY (Hz)
10
OUTPUT NOISE SPECTRAL DENSITY (µV Hz)
100 1k 10k 100k
1965 G38
LT1965-3.3
LT1965
LT1965-1.5
LT1965-1.8
LT1965-2.5
COUT = 10µF
IL = 1.1A
LOAD CURRENT (A)
20
OUTPUT NOISE VOLTAGE (µVRMS)
30
50
70
80
0.0001 0.01 0.1 10
10
0.001 1
60
40
0
1965 G39
LT1965-2.5
LT1965-3.3
LT1965-1.8
LT1965
COUT = 10µF
IL = 1.1A
LT1965-1.5 400µs/DIV
VOUT
100µV/DIV
1965 G40
0
0
–100
OUTPUT VOLTAGE
DEVIATION (mV)
LOAD CURRENT (A)
–50
0
50
100
0.5
1.0
1.5
10 20 30 40 50 60 70 80
1965 G41
TIME (µs)
VIN = 4.3V
CIN = 10µF CERAMIC
COUT = 10µF CERAMIC
VOUT = 3.3V
TIME (µs)
0
SHDN AND OUTPUT VOLTAGE (V)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
08020 40 60 1007010 30 50 90
1965 G42
OUTPUT
SHDN
VIN = 3.3V
COUT = 10µF CERAMIC
RL = 2.5k, IL = 1mA FOR VOUT = 2.5V
LT1965 Series
11
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pin Functions
OUT (Pins 1, 2 / 1, 2 / 4 / 4): Output. This pin supplies
power to the load. Use a minimum output capacitor of
10µF to prevent oscillations. Large load transient applica-
tions require larger output capacitors to limit peak voltage
transients. See the Applications Information section for
more information on output capacitance and reverse-output
characteristics.
SENSE (Pin 3 / 3 / 5 / 5): Sense. For fixed voltage versions
of the LT1965 (LT1965-1.5/LT1965-1.8/ LT1965-2.5/
LT1965-3.3), the SENSE pin is the input to the error am-
plifier. Optimum regulation is obtained when the SENSE
pin is connected to the OUT pin of the regulator. In criti-
cal applications, small voltage drops are caused by the
resistance (RP) of PCB traces between the regulator and
the load. These drops 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 PCB traces will add to the dropout
voltage of the regulator. The SENSE pin bias current is
100µA at the nominal rated output voltage.
ADJ (Pin 3 / 3 / 5 / 5): Adjust. This pin is the input to the
error amplifier. It has a typical bias current of 1.3µA that
flows into the pin. The ADJ pin voltage is 1.20V referenced
to ground.
GND (Pins 4, 5 / 4, 5 / 3 / 3): Ground. For the adjustable
LT1965, connect the bottom of the resistor divider, setting
output voltage, directly to GND for optimum regulation.
SHDN (Pin 6 / 6 / 1 / 1): Shutdown. Pulling the SHDN pin
low puts the LT1965 into a low power state and turns the
output off. Drive the SHDN pin with either logic or an open
collector/drain with a pull-up resistor. The resistor sup-
plies the pull-up current to the open collector/drain logic,
normally several microamperes and the SHDN pin current,
typically less than 5.5µA. If unused, connect the SHDN pin
to VIN. The SHDN pin cannot be driven below GND unless
it is tied to the IN pin. If the SHDN pin is driven below
GND while IN is powered, the output will turn on. SHDN
pin logic cannot be referenced to a negative supply rail.
IN (Pins 7, 8 / 7, 8 / 2 / 2): Input. This pin supplies power
to the device. The LT1965 requires a bypass capacitor at
IN if located more than six inches from the main input filter
capacitor. Include a bypass capacitor in battery-powered
circuits as a battery’s output impedance generally rises
with frequency. A bypass capacitor in the range ofF to
10µF suffices. The LT1965’s design withstands reverse
voltages on the IN pin with respect to ground and the
OUT pin. In the case of a reversed input, which occurs if
a battery is plugged in backwards, the LT1965 behaves
as if a diode is in series with its input. No reverse current
flows into the LT1965 and no reverse voltage appears at
the load. The device protects itself and the load.
Exposed Pad (Pin 9 / 9, DFN and MSOP Packages Only):
Ground. Tie this pin directly to Pins 4 and 5 and the PCB
ground. This pin provides enhanced thermal performance
with its connection to the PCB ground. See the Applica-
tions Information section for thermal considerations and
calculating junction temperature.
(DFN/MSOP/DD-Pak/TO-220)
Figure 1. Kelvin Sense Connection
IN
1965 F01
RP
RP
OUT
VIN
SENSESHDN
GND
LT1965
+ + LOAD
LT1965 Series
12
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applications inForMation
The LT1965 series are 1.1A low dropout regulators with
shutdown. The devices are capable of supplying 1.1A at
a typical dropout voltage of 310mV. The low operating
quiescent current (500µA for the adjustable version, 600µA
for the fixed voltage versions) drops to less thanA in
shutdown. In addition to the low quiescent current, the
LT1965 regulators incorporate several protection features
that makes them ideal for use in battery-powered systems.
The devices protect themselves against both reverse-input
and reverse-output voltages. In battery backup applica-
tions, if a backup battery holds up the output when the input
is pulled to ground, the LT1965 performs like it has a diode
in series with its output, preventing reverse-current flow.
Adjustable Operation
The LT1965 adjustable version has an output voltage range
of 1.20V to 19.5V. Figure 2 illustrates that the ratio of
two external resistors sets the output voltage. The device
servos the output to maintain the ADJ pin voltage at 1.20V
referenced to ground. R1’s current equals 1.20V/R1. R2’s
current equals R1’s current plus the ADJ pin bias current.
The ADJ pin bias current, 1.3µA at 25°C, flows through
R2 into the ADJ pin. Use the formula in Figure 2 to calcu-
late output voltage. Linear Technology recommends that
R1’s value be less than 12.1k to minimize output voltage
errors due to the ADJ pin bias current. In shutdown, the
output turns off and the divider current is zero. For curves
depicting ADJ Pin Voltage vs Temperature and ADJ Pin
Bias Current vs Temperature, see the Typical Performance
Characteristics section.
The adjustable device is tested and specified with the ADJ
pin tied to the OUT pin for an output voltage of 1.20V.
Specifications for output voltages greater than 1.20V are
proportional to the ratio of the desired output voltage to
1.20V: VOUT/1.20V. For example, load regulation for an
output current change of 1mA to 1.1A is typically –4.25mV
at VOUT = 1.20V. At VOUT = 5V, load regulation is:
5V
1.20V
4.25mV = 17.71mV
Output Capacitance
The LT1965’s design is stable with a wide range of out-
put capacitors. The ESR of the output capacitor affects
stability, most notably with small capacitors. A minimum
output capacitor of 10µF with an ESR of 0.3W or less is
recommended to prevent oscillations. The LT1965 is a low
quiescent current device and output load transient response
is a function of output capacitance. Larger values of output
capacitance decrease the peak deviations and provide
improved transient response for larger current changes.
Ceramic capacitors require extra consideration. Manufac-
turers make ceramic capacitors with a variety of dielectrics,
each with different behavior across temperature and applied
voltage. The most common dielectrics used are specified
with EIA temperature characteristic codes of Z5U, Y5V,
X5R and X7R. The Z5U and Y5V dielectrics provide high
C-V products in a small package at low cost, but exhibit
strong voltage and temperature coefficients as shown in
Figures 3 and 4. When used with a 5V regulator, a 16V
10µF Y5V capacitor can exhibit an effective value as low
asF toF for the DC bias applied and over the operat-
ing temperature range. The X5R and X7R dielectrics yield
much more stable characteristics and are more suitable
for use as the output capacitor. The X7R type works over
a wider temperature range and has better temperature
stability whereas X5R is less expensive and is available in
higher values. Care still must be exercised when using X5R
and X7R capacitors; the X5R and X7R codes only specify
operating temperature range and maximum capacitance
change over temperature. Capacitance change due to DC
bias with X5R and X7R capacitors is better than Y5V and
Z5U capacitors, but can still be significant enough to drop
capacitor values below appropriate levels. Capacitor DC
bias characteristics tend to improve as component case
size increases, but expected capacitance at operating
voltages should be verified.
Figure 2. Adjustable Operation
IN
1965 F02
R2
OUT
VIN
VOUT
ADJ
GND
LT1965
R1
+
VOUT =1.20V 1+R2
R1
+IADJ R2
VADJ =1.20V
IADJ =1.3µA AT 25ºC
OUTPUT RANGE =1.20V TO19.5V
LT1965 Series
13
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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 micro-
phone 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. A ceramic capacitor produced the trace
in Figure 5 in response to light tapping from a pencil.
Similar vibration induced behavior can masquerade as
increased output voltage noise.
Overload Recovery
Like many IC power regulators, the LT1965 has safe oper-
ating area protection. The safe area protection decreases
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 protective design
provides some output current at all values of input-to-
output voltage up to the device breakdown.
When power is first applied, as input voltage rises, the
output follows the input, allowing the regulator to start up
into very heavy loads. During start-up, as the input voltage
Figure 3. Ceramic Capacitor DC Bias Characteristics Figure 4. Ceramic Capacitor Temperature Characteristics
Figure 5. Noise Resulting from Tapping on a Ceramic Capacitor
DC BIAS VOLTAGE (V)
CHANGE IN VALUE (%)
1965 F03
20
0
–20
–40
–60
–80
–100 04810
2 6 12 14
X5R
Y5V
16
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
TEMPERATURE (°C)
–50
40
20
0
–20
–40
–60
–80
–100 25 75
1965 F04
–25 0 50 100 125
Y5V
CHANGE IN VALUE (%)
X5R
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
1ms/DIV
1mV/DIV
1965 F05
VOUT = 1.3V
COUT = 10µF
ILOAD = 0
LT1965 Series
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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 to
recover. Other regulators, such as the LT1083/LT1084/
LT1085 family, also exhibit this phenomenon, so it is not
unique to the LT1965.
The problem occurs with a heavy output load when the
input voltage is high and the output voltage is low. Com-
mon situations occur immediately after the removal of a
short-circuit or if 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 operat-
ing 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 LT1965 regulators are designed to provide low output
voltage noise over the 10Hz to 100kHz bandwidth while
operating at full load. Output voltage noise is approximately
80nV/√Hz over this frequency bandwidth for the LT1965
adjustable version. For higher output voltages (generated
by using a resistor divider), the output voltage noise gains
up accordingly.
Higher values of output voltage noise may be measured
if care is not exercised with regard to circuit layout and
testing. Crosstalk from nearby traces can induce unwanted
noise onto the LT1965’s output. Power supply ripple rejec-
tion must also be considered; the LT1965 regulators do
not have unlimited power supply rejection and will pass
a small portion of the input noise through to the output.
applications inForMation
Thermal Considerations
The LT1965’s maximum rated junction temperature of
125°C (LT1965E, LT1965I) or 150°C (LT1965H) limits
its power handling capability. Tw o components comprise
the power dissipated by the device:
1. Output current multiplied by the input/output voltage
differential: IOUT • (VIN – VOUT), and
2. GND pin current multiplied by the input voltage:
IGNDVIN
GND pin current is determined using the GND Pin Current
curves in the Typical Performance Characteristics section.
Power dissipation equals the sum of the two components
listed.
The LT1965 regulators have internal thermal limiting that
protect the device during overload conditions. For con-
tinuous normal conditions, do not exceed the maximum
junction temperature rating of 125°C (E-grade, I-grade) or
150°C (H-grade). Carefully consider all sources of thermal
resistance from junction to ambient including other heat
sources mounted in proximity to the LT1965.
The underside of the LT1965 DFN package has exposed
metal (4mm2) from the lead frame to the die attachment.
The underside of the LT1965 MSOP package also has
exposed metal (3.7mm2). Both packages allow heat to
directly transfer from the die junction to the printed circuit
board metal to control maximum operating junction tem-
perature. The dual-in-line pin arrangement allows metal
to extend beyond the ends of the package on the topside
(component side) of a PCB. Connect this metal to GND
on the PCB. The multiple IN and OUT pins of the LT1965
also assist in spreading heat to the PCB.
For surface mount devices, heat sinking is accomplished
by using the heat spreading capabilities of the PC board
and its copper traces. Copper board stiffeners and plated
through-holes can also be used to spread the heat gener-
ated by power devices.
LT1965 Series
15
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For more information www.linear.com/LT1965
applications inForMation
The following tables list thermal resistance for several
different board sizes and copper areas. All measurements
were taken in still air on a 2-layer 1/16" FR-4 board with
one ounce copper.
Table 1. Measured Thermal Resistance for DFN Package
Copper Area Thermal Resistance
Topside* Backside Board Area (Junction-to-Ambient)
2500mm22500mm22500mm260°C/W
1000mm22500mm22500mm262°C/W
225mm22500mm22500mm265°C/W
100mm22500mm22500mm268°C/W
50mm22500mm22500mm270°C/W
*Device is mounted on topside
Table 2. Measured Thermal Resistance for MSOP Package
Copper Area Thermal Resistance
Topside* Backside Board Area (Junction-to-Ambient)
2500mm22500mm22500mm255°C/W
1000mm22500mm22500mm257°C/W
225mm22500mm22500mm260°C/W
100mm22500mm22500mm265°C/W
50mm22500mm22500mm268°C/W
*Device is mounted on topside
Table 3. Measured Thermal Resistance for DD-Pak Package
Copper Area Thermal Resistance
Topside* Backside Board Area (Junction-to-Ambient)
2500mm22500mm22500mm225°C/W
1000mm22500mm22500mm230°C/W
125mm22500mm22500mm235°C/W
*Device is mounted on topside
Measured Thermal Resistance for TO-220 Package
Thermal Resistance (Junction-to-Case) = 3°C/W
Calculating Junction Temperature
Example: Given an output voltage of 2.5V, an input volt-
age range of 3.3V ± 5%, an output current range of 0mA
to 500mA and a maximum ambient temperature of 85°C,
what will the maximum junction temperature be?
The power dissipated by the device equals:
IOUT(MAX) • (VIN(MAX) – VOUT) + IGNDVIN(MAX)
where:
IOUT(MAX) = 500mA
VIN(MAX) = 3.465V
IGND at (IOUT = 500mA, VIN = 3.465V) = 8.2mA
So,
P = 500mA(3.465V – 2.5V) + 8.2mA(3.465V) = 0.511W
Using a DFN package, the thermal resistance will be in
the range of 60°C/W to 70°C/W depending on the cop-
per area. So the junction temperature rise above ambient
approximately equals:
0.511W • 65°C/W = 33.22°C
The maximum junction temperature equals the maximum
ambient temperature plus the maximum junction tempera-
ture rise above ambient or:
TJMAX = 85°C + 33.22°C = 118.22°C
Protection Features
The LT1965 regulators incorporate several protection
features that makes 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 also protect
against reverse-input voltages, reverse-output voltages
and reverse output-to-input voltages.
Current-limit protection and thermal overload protection
protect the device against current overload conditions
at its output. For normal operation, do not exceed the
maximum rated junction temperature of 125°C (LT1965E,
LT1965I) or 150°C (LT1965H).
LT1965 Series
16
1965fb
For more information www.linear.com/LT1965
The input of the device withstands reverse voltages of 22V.
The LT1965 limits current flow to less than 1mA (typically
less than 300µA) and no negative voltage appears at the
output. The device protects both itself and the load against
batteries that are plugged in backwards.
The LT1965 incurs no damage if its output is pulled be-
low ground. If the input is left open-circuit or grounded,
the output can be pulled below ground by 22V. For fixed
voltage versions, the output will act like a large resistor,
typically 5k or higher, limiting current flow to typically
less than 300µA. For the adjustable version, the output
acts like an open circuit and no current flows from the
output. However, current flows out of (but is limited by)
the resistor divider that sets the output voltage. If the input
is powered by a voltage source, the LT1965 protects itself
by shutting off the output.
The LT1965 adjustable version incurs no damage if the
ADJ pin is pulled above or below ground by 9V. If the input
is left open-circuit or grounded, the ADJ pin performs like
a diode in series with typically 1.5k of resistance when
pulled below ground and like a large resistor (typically 5k
up to 3V on the ADJ pin and then 1.5k up to 9V) in series
with a diode when pulled above ground.
In situations where the ADJ pin connects to a resistor
divider that would pull the ADJ pin above its 9V 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 1.20V 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 9V. The 11V difference between the OUT
and ADJ pins divided by the 5mA maximum current into
the ADJ pin yields a minimum top resistor value of 2.2k.
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 follows the
curve shown in Figure 6.
If the LT1965’s IN pin is forced below the OUT pin or the
OUT pin is pulled above the IN pin, input current typically
drops to less thanA. This occurs if the LT1965 input
is connected to a discharged (low voltage) battery and
either a backup battery or a second regulator holds up
the output. The state of the SHDN pin has no effect on
the reverse-output current if the output is pulled above
the input.
Figure 6. Reverse-Output Current
applications inForMation
OUTPUT VOLTAGE (V)
0
0
REVERSE OUTPUT CURRENT (mA)
1
2
3
4
5
6
21 43 65 87 9
1965 F06
LT1965
LT1965-1.5
LT1965-3.3
TJ = 25°C
VIN = 0V
VOUT = VADJ (LT1965)
VOUT = VSENSE
(LT195-1.5/-1.8/-2.5/-3.3)
CURRENT FLOWS INTO
OUTPUT PIN
LT1965-2.5
LT1965-1.8
LT1965 Series
17
1965fb
For more information www.linear.com/LT1965
typical applications
Paralleling of Regulators for Higher Output Current
package Description
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
R1
0.01Ω
R2
0.01Ω
R5
10k
R4
2.2k
R7
4.02k
1%
C2
22µF
1965 TA03
VIN > 3.7V
3.3V
2.2A
8
1
3
2
4
C3
0.01µF
IN OUT
SENSE
GND
LT1965-3.3
SHDN
IN
SHDN
OUT
ADJ
GND
LT1965
SHDN
+
C1
100µF
+
+1/2
LT1366
R6
6.65k
1%
R3
2.2k
3.00 ±0.10
(4 SIDES)
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON TOP AND BOTTOM OF PACKAGE
0.40 ±0.10
BOTTOM VIEW—EXPOSED PAD
1.65 ±0.10
(2 SIDES)
0.75 ±0.05
R = 0.125
TYP
2.38 ±0.10
14
85
PIN 1
TOP MARK
(NOTE 6)
0.200 REF
0.00 – 0.05
(DD8) DFN 0509 REV C
0.25 ±0.05
2.38 ±0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
1.65 ±0.05
(2 SIDES)2.10 ±0.05
0.50
BSC
0.70 ±0.05
3.5 ±0.05
PACKAGE
OUTLINE
0.25 ±0.05
0.50 BSC
DD Package
8-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1698 Rev C)