LT1764A Series
3A, Fast Transient
Response, Low Noise,
LDO Regulators
FEATURES
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DESCRIPTIO
Optimized for Fast Transient Response
Output Current: 3A
Dropout Voltage: 340mV at 3A
Low Noise: 40
µ
V
RMS
(10Hz to 100kHz)
1mA Quiescent Current
Wide Input Voltage Range: 2.7V to 20V
No Protection Diodes Needed
Controlled Quiescent Current in Dropout
Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 3.3V
Adjustable Output from 1.21V to 20V
< 1µA Quiescent Current in Shutdown
Stable with 10µF Output Capacitor*
Stable with Ceramic Capacitors*
Reverse Battery Protection
No Reverse Current
Thermal Limiting
APPLICATIO S
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The LT
®
1764A is a low dropout regulator optimized for
fast transient response. The device is capable of supplying
3A 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 LT1764A has very
low output voltage noise which makes the device ideal for
sensitive RF supply applications.
Output voltage range is from 1.21V to 20V. The LT1764A
regulators are stable with output capacitors as low as 10µF.
Internal protection circuitry includes reverse battery pro-
tection, current limiting, thermal limiting and reverse cur-
rent protection. The device is 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 LT1764A regu-
lators are available in 5-lead TO-220 and DD packages, and
16-lead FE packages.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*See Applications Information Section.
3.3V to 2.5V Logic Power Supply
Post Regulator for Switching Supplies
TYPICAL APPLICATIO
400
3.3V
IN
to 2.5V
OUT
Regulator
DROPOUT VOLTAGE (mV)
2.5V
3A
10µF*
LT1764A-2.5
SHDN SENSE
GND
1764 TA01
350
300
250
200
150
100
50
0
0
0.5
1.0
1.5
2.0
LOAD CURRENT (A)
2.5
3.0
1764 TA02
+
V
IN
> 3V
10µF*
IN
OUT
+
*TANTALUM,
CERAMIC OR
ALUMINUM ELECTROLYTIC
U
Dropout Voltage
1764afb
U
U
1
LT1764A Series
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
IN Pin Voltage ........................................................
±20V
OUT Pin Voltage ....................................................
±20V
Input to Output Differential Voltage (Note 12) .......
±20V
SENSE Pin Voltage ...............................................
±20V
ADJ Pin Voltage ......................................................
±7V
SHDN Pin Voltage .................................................
±20V
Output Short-Circuit Duration ......................... Indefinite
Operating Junction Temperature Range
E Grade ............................................. – 40°C to 125°C
MP Grade ......................................... – 55°C to 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
PACKAGE/ORDER INFORMATION
TOP VIEW
FRONT VIEW
5
4
TAB IS
GND
3
2
1
Q PACKAGE
5-LEAD PLASTIC DD
SENSE/ADJ*
OUT
GND
IN
SHDN
TAB IS
GND
FRONT VIEW
5
4
3
2
1
T PACKAGE
5-LEAD PLASTIC TO-220
*PIN 5 = SENSE FOR LT1764A-1.5/LT1764A-1.8/
LT1764A-2.5/LT1764A-3.3
= ADJ FOR LT1764A
T
JMAX
= 150°C,
θ
JA
= 30°C/ W
*PIN 5 = SENSE FOR LT1764A-1.5/LT1764A-1.8/
LT1764A-2.5/LT1764A-3.3
= ADJ FOR LT1764A
T
JMAX
= 150°C,
θ
JA
= 50°C/ W
ORDER PART NUMBER
LT1764AEQ
LT1764AEQ-1.5
LT1764AEQ-1.8
LT1764AEQ-2.5
LT1764AEQ-3.3
LT1764AMPQ
Order Options
Tape and Reel: Add #TR
ORDER PART NUMBER
LT1764AET
LT1764AET-1.5
LT1764AET-1.8
LT1764AET-2.5
LT1764AET-3.3
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C. (Note 2)
PARAMETER
Minimum Input Voltage
(Notes 3, 11)
CONDITIONS
I
LOAD
= 0.5A
I
LOAD
= 1.5A
E Grade: I
LOAD
= 3A
MP Grade: I
LOAD
= 3A
LT1764A-1.5 V
IN
= 2.21V, I
LOAD
= 1mA
2.7V < V
IN
< 20V, 1mA < I
LOAD
< 3A
LT1764A-1.8 V
IN
= 2.3V, I
LOAD
= 1mA
2.8V < V
IN
< 20V, 1mA < I
LOAD
< 3A
MIN
TYP
1.7
1.9
2.3
2.3
1.477
1.447
1.773
1.737
1.500
1.500
1.800
1.800
MAX
UNITS
V
V
V
V
V
V
V
V
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Regulated Output Voltage
(Note 4)
2
U
U
W
W W
U
W
SENSE/
ADJ*
OUT
GND
IN
SHDN
GND
NC
OUT
OUT
OUT
SENSE/ADJ*
GND
GND
1
2
3
4
5
6
7
8
17
16 GND
15 NC
14 IN
13 IN
12 IN
11 NC
10 SHDN
9
GND
*PIN 6 = SENSE FOR LT1764A-1.5/
LT1764A-1.8/LT1764A-2.5/
LT1764A-3.3
= ADJ FOR LT1764A
FE PACKAGE
16-LEAD PLASTIC TSSOP
PIN 17 IS GND
T
JMAX
= 150°C,
θ
JA
= 38°C/ W
ORDER PART NUMBER
LT1764AEFE
LT1764AEFE-1.5
LT1764AEFE-1.8
LT1764AEFE-2.5
LT1764AEFE-3.3
FE PART MARKING
LT1764AEFE
LT1764AEFE-1.5
LT1764AEFE-1.8
LT1764AEFE-2.5
LT1764AEFE-3.3
●
●
●
●
2.7
2.8
1.523
1.545
1.827
1.854
LT1764A Series
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C. (Note 2)
PARAMETER
CONDITIONS
LT1764A-2.5 V
IN
= 3V, I
LOAD
= 1mA
3.5V < V
IN
< 20V, 1mA < I
LOAD
< 3A
LT1764A-3.3 V
IN
= 3.8V, I
LOAD
= 1mA
4.3V < V
IN
< 20V, 1mA < I
LOAD
< 3A
ADJ Pin Voltage
(Notes 3, 4)
Line Regulation
LT1764A
V
IN
= 2.21V, I
LOAD
= 1mA
E Grade: 2.7V < V
IN
< 20V, 1mA < I
LOAD
< 3A
MP Grade: 2.8V < V
IN
< 20V, 1mA < I
LOAD
< 3A
∆V
IN
= 2.21V to 20V, I
LOAD
= 1mA
∆V
IN
= 2.3V to 20V, I
LOAD
= 1mA
∆V
IN
= 3V to 20V, I
LOAD
= 1mA
∆V
IN
= 3.8V to 20V, I
LOAD
= 1mA
∆V
IN
= 2.21V to 20V, I
LOAD
= 1mA
V
IN
= 2.7V,
∆I
LOAD
= 1mA to 3A
V
IN
= 2.7V,
∆I
LOAD
= 1mA to 3A
V
IN
= 2.8V,
∆I
LOAD
= 1mA to 3A
V
IN
= 2.8V,
∆I
LOAD
= 1mA to 3A
V
IN
= 3.5V,
∆I
LOAD
= 1mA to 3A
V
IN
= 3.5V,
∆I
LOAD
= 1mA to 3A
V
IN
= 4.3V,
∆I
LOAD
= 1mA to 3A
V
IN
= 4.3V,
∆I
LOAD
= 1mA to 3A
●
●
●
●
●
●
●
●
●
●
ELECTRICAL CHARACTERISTICS
MIN
2.462
2.412
3.250
3.183
1.192
1.168
1.168
TYP
2.500
2.500
3.300
3.300
1.210
1.210
1.210
2.5
3
4
4.5
2
3
4
MAX
2.538
2.575
3.350
3.400
1.228
1.246
1.246
10
10
10
10
10
7
23
8
25
10
30
12
40
5
20
20
0.05
0.10
0.13
0.18
0.20
0.27
0.33
0.40
0.45
0.66
1.5
1.6
5
18
75
200
10
2
1
30
1
UNITS
V
V
V
V
V
V
V
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
V
V
V
V
V
V
V
V
V
V
mA
mA
mA
mA
mA
mA
µV
RMS
µA
V
V
µA
µA
µA
dB
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LT1764A-1.5
LT1764A-1.8
LT1764A-2.5
LT1764A-3.3
LT1764A (Note 3)
LT1764A-1.5
LT1764A-1.8
LT1764A-2.5
LT1764A-3.3
Load Regulation
●
4
●
4
●
LT1764A (Note 3) V
IN
= 2.7V,
∆I
LOAD
= 1mA to 3A
E Grade: V
IN
= 2.7V,
∆I
LOAD
= 1mA to 3A
MP Grade: V
IN
= 2.8V,
∆I
LOAD
= 1mA to 3A
Dropout Voltage
V
IN
= V
OUT(NOMINAL)
(Notes 5, 6, 11)
I
LOAD
= 1mA
I
LOAD
= 1mA
I
LOAD
= 100mA
I
LOAD
= 100mA
I
LOAD
= 500mA
I
LOAD
= 500mA
I
LOAD
= 1.5A
I
LOAD
= 1.5A
I
LOAD
= 3A
I
LOAD
= 3A
GND Pin Current
V
IN
= V
OUT(NOMINAL)
+ 1V
(Notes 5, 7)
I
LOAD
= 0mA
I
LOAD
= 1mA
I
LOAD
= 100mA
I
LOAD
= 500mA
I
LOAD
= 1.5A
I
LOAD
= 3A
C
OUT
= 10µF, I
LOAD
= 3A, BW = 10Hz to 100kHz
(Notes 3, 8)
V
OUT
= Off to On
V
OUT
= On to Off
V
SHDN
= 0V
V
SHDN
= 20V
V
IN
= 6V, V
SHDN
= 0V
V
IN
– V
OUT
= 1.5V (Avg), V
RIPPLE
= 0.5V
P-P
,
f
RIPPLE
= 120Hz, I
LOAD
= 1.5A
2
●
●
0.02
●
0.07
●
0.14
●
0.25
●
0.34
●
●
●
●
●
●
●
1
1.1
3.5
11
40
120
40
3
Output Voltage Noise
ADJ Pin Bias Current
Shutdown Threshold
SHDN Pin Current
(Note 9)
Quiescent Current in Shutdown
Ripple Rejection
●
●
0.25
0.9
0.75
0.01
7
0.01
55
63
3
LT1764A Series
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C. (Note 2)
PARAMETER
Current Limit
CONDITIONS
V
IN
= 7V, V
OUT
= 0V
E Grade: LT1764A; LT1764A-1.5;
V
IN
= 2.7V,
∆V
OUT
= – 0.1V
MP Grade: LT1764A
V
IN
= 2.8V,
∆V
OUT
= – 0.1V
Input Reverse Leakage Current
V
IN
= – 20V, V
OUT
= 0V
Reverse Output Current (Note 10) LT1764A-1.5 V
OUT
= 1.5V, V
IN
< 1.5V
LT1764A-1.8 V
OUT
= 1.8V, V
IN
< 1.8V
LT1764A-2.5 V
OUT
= 2.5V, V
IN
< 2.5V
LT1764A-3.3 V
OUT
= 3.3V, V
IN
< 3.3V
LT1764A (Note 3) V
OUT
= 1.21V, V
IN
< 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:
The LT1764A regulators are tested and specified under pulse load
conditions such that T
J
≈
T
A
. The LT1764A (E grade) is 100% tested at
T
A
= 25°C; performance at – 40°C and 125°C is assured by design,
characterization and correlation with statistical process controls. The
LT1764A (MP grade) is 100% tested and guaranteed over the –55°C to
125°C temperature range.
Note 3:
The LT1764A (adjustable version) is tested and specified for these
conditions with the ADJ pin connected to the OUT pin.
Note 4.
Operating conditions are limited by maximum junction temperature.
The regulated output voltage specification will not apply for all possible
combinations of input voltage and output current. When operating at max-
imum input voltage, the output current range must be limited. When operat-
ing at maximum output current, the input voltage range must be limited.
Note 5:
To satisfy requirements for minimum input voltage, the LT1764A
(adjustable version) is tested and specified for these conditions with an
external resistor divider (two 4.12k resistors) for an output voltage of
●
●
●
MIN
3.1
3.1
TYP
4
MAX
UNITS
A
A
A
1
600
600
600
600
300
1200
1200
1200
1200
600
mA
µA
µA
µA
µA
µA
2.42V. The external resistor divider will add a 300µA DC load on the output.
Note 6:
Dropout voltage is the minimum input to output voltage differential
needed to maintain regulation at a specified output current. In dropout, the
output voltage will be equal to: V
IN
– V
DROPOUT
.
Note 7:
GND pin current is tested with V
IN
= V
OUT(NOMINAL)
+ 1V or V
IN
=
2.7V (E grade) or V
IN
= 2.8V (MP grade), whichever is greater, and a current
source load. The GND pin current will decrease at higher input voltages.
Note 8:
ADJ pin bias current flows into the ADJ pin.
Note 9:
SHDN pin current flows into the SHDN pin.
Note 10:
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 11.
For the LT1764A, LT1764A-1.5 and LT1764A-1.8 dropout voltage
will be limited by the minimum input voltage specification under some
output voltage/load conditions.
Note 12.
All combinations of absolute maximum input voltage and
absolute maximum output voltage cannot be achieved. The absolute
maximum differential from input to output is
±20V.
For example, with
V
IN
= 20V, V
OUT
cannot be pulled below ground.
TYPICAL PERFOR A CE CHARACTERISTICS
Typical Dropout Voltage
600
GUARANTEED DROPOUT VOLTAGE (mV)
500
DROPOUT VOLTAGE (mV)
700
600
500
T
J
≤
125°C
400
300
T
J
≤
25°C
200
100
0
DROPOUT VOLTAGE (mV)
400
T
J
= 125°C
300
200
T
J
= 25°C
100
0
0
0.5
1.0
1.5
2.0
OUTPUT CURRENT (A)
4
U W
2.5
Guaranteed Dropout Voltage
= TEST POINTS
600
500
400
Dropout Voltage
I
L
= 3A
300
I
L
= 1.5A
200
I
L
= 0.5A
100
0
–50 –25
I
L
= 100mA
I
L
= 1mA
3.0
1764 G01
0
0.5
2.0
1.5
1.0
OUTPUT CURRENT (A)
2.5
3.0
1764 G02
50
25
75
0
TEMPERATURE (°C)
100
125
1764 G03
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LT1764A Series
TYPICAL PERFOR A CE CHARACTERISTICS
Quiescent Current
1.4
1.2
QUIESCENT CURRENT (mA)
LT1764A-1.5/1.8/2.5/3.3
OUTPUT VOLTAGE (V)
1.0
LT1764A
0.8
0.6
0.4
0.2
1.51
1.50
1.49
1.48
1.47
OUTPUT VOLTAGE (V)
0
–50 –25
V
IN
= 6V
R
L
=
∞
I
L
= 0
V
SHDN
= V
IN
50
25
75
0
TEMPERATURE (°C)
100
125
LT1764A-2.5 Output Voltage
2.58
2.56
I
L
= 1mA
3.38
3.36
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
2.52
2.50
2.48
2.46
2.44
2.42
– 50 – 25
0
75
50
25
TEMPERATURE (°C)
100
125
3.32
3.30
3.28
3.26
3.24
3.22
– 50 – 25
0
75
50
25
TEMPERATURE (°C)
100
125
ADJ PIN VOLTAGE (V)
2.54
LT1764A-1.5 Quiescent Current
40
35
T
J
= 25°C
R
L
=
∞
V
SHDN
= V
IN
40
35
QUIESCENT CURRENT (mA)
30
25
20
15
10
5
0
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
QUIESCENT CURRENT (mA)
QUIESCENT CURRENT (mA)
U W
1764 G04
1756 G06
1764 G41
LT1764A-1.5 Output Voltage
1.54
I
L
= 1mA
1.53
1.52
1.83
1.82
1.81
1.80
1.79
1.78
1.77
0
50
75
25
TEMPERATURE (°C)
100
125
1.84
LT1764A-1.8 Output Voltage
I
L
= 1mA
1.46
– 50 – 25
1.76
– 50 – 25
0
75
50
25
TEMPERATURE (°C)
100
125
1764A G40
1756 G05
LT1764A-3.3 Output Voltage
I
L
= 1mA
1.230
1.225
1.220
1.215
1.210
1.205
1.200
1.195
LT1764A ADJ Pin Voltage
I
L
= 1mA
3.34
1.190
– 50 – 25
0
75
50
25
TEMPERATURE (°C)
100
125
1756 G07
1756 G08
LT1764A-1.8 Quiescent Current
40
T
J
= 25°C
R
L
=
∞
V
SHDN
= V
IN
35
30
25
20
15
10
5
0
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
LT1764A-2.5 Quiescent Current
T
J
= 25°C
R
L
=
∞
V
SHDN
= V
IN
30
25
20
15
10
5
0
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1764 G09
1764 G10
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5
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