1
LT1529
LT1529-3.3/LT1529-5
152935fb
3A Low Dropout Regulators
with Micropower
Quiescent Current
and Shutdown
The LT
®
1529/LT1529-3.3/LT1529-5 are 3A low dropout
regulators with micropower quiescent current and shut-
down. The devices are capable of supplying 3A of output
current with a dropout voltage of 0.6V. Designed for use
in battery-powered systems, the low quiescent current,
50µA operating and 16µA in shutdown, make them an
ideal choice. The quiescent current is well controlled; it
does not rise in dropout as it does with many other low
dropout PNP regulators.
Other features of the LT1529 /LT1529-3.3/LT1529-5 in-
clude the ability to operate with small output capacitors.
They are stable with 22µF on the output while most older
devices require up to 100µF for stability. Small ceramic
capacitors can be used, enhancing manufacturabiltiy.
Also the input may be connected to voltages lower than the
output voltage, including negative voltages, without re-
verse current flow from output to input. This makes the
LT1529/LT1529-3.3/LT1529-5 ideal for backup power
situations where the output is held high and the input is at
ground or reversed. Under these conditions, only 16µA
will flow from the OUTPUT pin to ground. The devices are
available in 5-lead TO-220 and 5-lead DD packages.
■
Dropout Voltage: 0.6V at I
OUT
= 3A
■
Output Current: 3A
■
Quiescent Current: 50µA
■
No Protection Diodes Needed
■
Adjustable Output from 3.8V to 14V
■
3.3V and 5V Fixed Output Voltages
■
Controlled Quiescent Current in Dropout
■
Shutdown I
Q
= 16µA
■
Stable with 22µF Output Capacitor
■
Reverse Battery Protection
■
No Reverse Current
■
Thermal Limiting
OUTPUT CURRENT (A)
0
0
DROPOUT VOLTAGE (V)
0.1
0.2
0.3
0.4
0.6
0.5 1.0 1.5 2.0
LT1529 • TA02
2.5 3.0
0.5
Dropout Voltage
5V Supply with Shutdown
■
High Efficiency Regulator
■
Regulator for Battery-Powered Systems
■
Post Regulator for Switching Supplies
■
5V to 3.3V Logic Regulator
+
V
IN
V
IN
> 5.5V 22µF
5V
3A
1
2
3
LT1529 • TA01
5
4
OUTPUT
SENSE
LT1529-5
SHDN
GND
V
SHDN
(PIN 4)
<0.25
>2.8
NC
OUTPUT
OFF
ON
ON
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
2
LT1529
LT1529-3.3/LT1529-5
152935fb
Output Short-Circuit Duration ......................... Indefinite
Storage Temperature Range ................ – 65°C to 150°C
Operating Junction Temperature Range
Commercial .......................................... 0°C to 125°C
Industrial ......................................... – 45°C to 125°C
Lead Temperature (Soldering, 10 sec).................. 300°C
*For applications requiring input voltage ratings greater than 15V, contact
the factory.
A
U
G
W
A
W
U
W
ARBSOLUTEXI T
IS
Input Voltage ...................................................... ±15V*
OUTPUT Pin Reverse Current .............................. 10mA
SENSE Pin Current .............................................. 10mA
ADJ Pin Current ................................................... 10mA
SHDN Pin Input Voltage (Note 2) .............. 6.5V, – 0.6V
SHDN Pin Input Current (Note 2) .......................... 5mA
WU
U
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
LT1529CQ
LT1529CQ-3.3
LT1529CQ-5
LT1529IQ
LT1529IQ-3.3
LT1529IQ-5
*PIN 2 = SENSE FOR LT1529-3.3/LT1529-5
= ADJ FOR LT1529
ORDER PART
NUMBER
LT1529CT
LT1529CT-3.3
LT1529CT-5
LT1529IT
LT1529IT-3.3
LT1529IT-5
*PIN 2 = SENSE FOR LT1529-3.3/LT1529-5
= ADJ FOR LT1529
T
JMAX
= 125°C, θ
JA
≈ 30°C/W
PARAMETER CONDITIONS MIN TYP MAX UNITS
Regulated Output Voltage LT1529-3.3 V
IN
= 3.8V, I
OUT
= 1mA, T
J
= 25°C 3.250 3.300 3.350 V
(Note 4) 4.3V < V
IN
< 15V, 1mA < I
OUT
< 3A ●3.200 3.300 3.400 V
LT1529-5 V
IN
= 5.5V, I
OUT
= 1mA, T
J
= 25°C 4.925 5.000 5.075 V
6V < V
IN
< 15V, 1mA < I
OUT
< 3A ●4.850 5.000 5.150 V
LT1529 (Note 5) V
IN
= 4.3V, I
OUT
= 1mA, T
J
= 25°C 3.695 3.750 3.805 V
4.8V < V
IN
< 15V, 1mA < I
OUT
< 3A ●3.640 3.750 3.860 V
Line Regulation LT1529-3.3 ∆V
IN
= 3.8V to 15V, I
OUT
= 1mA ●1.5 10 mV
LT1529-5 ∆V
IN
= 5.5V to 15V, I
OUT
= 1mA ●1.5 10 mV
LT1529 (Note 5) ∆V
IN
= 4.3V to 15V, I
OUT
= 1mA ●1.5 10 mV
Load Regulation LT1529-3.3 ∆I
LOAD
= 1mA to 3A, V
IN
= 4.3V, T
J
= 25°C520mV
∆I
LOAD
= 1mA to 3A, V
IN
= 4.3V ●12 30 mV
LT1529-5 ∆I
LOAD
= 1mA to 3A, V
IN
= 6V, T
J
= 25°C520mV
∆I
LOAD
= 1mA to 3A, V
IN
= 6V ●12 30 mV
LT1529 (Note 5) ∆I
LOAD
= 1mA to 3A, V
IN
= 4.8V, T
J
= 25°C520mV
∆I
LOAD
= 1mA to 3A, V
IN
= 4.8V ●12 30 mV
Dropout Voltage I
LOAD
= 10mA, T
J
= 25°C 110 180 mV
(Note 6) I
LOAD
= 10mA ●250 mV
I
LOAD
= 100mA, T
J
= 25°C 200 300 mV
I
LOAD
= 100mA ●400 mV
ELECTRICAL C CHARA TERISTICS
VIN
SHDN
GND
SENSE/ADJ*
OUTPUT
Q PACKAGE
5-LEAD PLASTIC DD PAK
TAB IS
GND
FRONT VIEW
5
4
3
2
1
T PACKAGE
5-LEAD PLASTIC TO-220
FRONT VIEW
TAB IS
GND
5
4
3
2
1
VIN
SHDN
GND
SENSE/ADJ*
OUTPUT
(Note 1)
T
JMAX
= 125°C, θ
JA
≈ 50°C/W
The ● denotes specifications which apply over the operating temperature range, otherwise specificatons are at TA = 25°C. (Note 3)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
3
LT1529
LT1529-3.3/LT1529-5
152935fb
ELECTRICAL C CHARA TERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Dropout Voltage I
LOAD
= 700mA, T
J
= 25°C 320 430 mV
(Note 6) I
LOAD
= 700mA ●550 mV
I
LOAD
= 1.5A, T
J
= 25°C 430 550 mV
I
LOAD
= 1.5A ●700 mV
I
LOAD
= 3A, T
J
= 25°C 600 750 mV
I
LOAD
= 3A ●950 mV
GND Pin Current I
LOAD
= 0mA, T
J
= 25°C 50 100 µA
(Note 7) I
LOAD
= 0mA, T
J
= 125°C (Note 8) 400 µA
I
LOAD
= 100mA, T
J
= 25°C 0.6 1.0 mA
I
LOAD
= 100mA, T
J
= 125°C (Note 8) 1.0 mA
I
LOAD
= 700mA ●5.5 12 mA
I
LOAD
= 1.5A ●20 40 mA
I
LOAD
= 3A ●80 160 mA
ADJ Pin Bias Current (Notes 5, 9) T
J
= 25°C 150 300 nA
Shutdown Threshold V
OUT
= Off to On ●1.20 2.8 V
V
OUT
= On to Off ● 0.25 0.75 V
SHDN Pin Current (Note 10) V
SHDN
= 0V ●4.5 10 µA
Quiescent Current in Shutdown V
IN
= V
OUT
(Nominal) + 1V, V
SHDN
= 0V ●15 30 µA
(Note 11)
Ripple Rejection V
IN
– V
OUT
= 1V (Avg), V
RIPPLE
= 0.5V
P-P
,5062dB
f
RIPPLE
= 120Hz, I
LOAD
= 1.5A
Current Limit V
IN
– V
OUT
= 7V, T
J
= 25°C5A
V
IN
= V
OUT
(Nominal) + 1.5V, ∆V
OUT
= – 0.1V ●3.2 4.7 A
Input Reverse Leakage Current V
IN
= –15V, V
OUT
= 0V ●1.0 mA
Reverse Output Current (Note 12) LT1529-3.3 V
OUT
= 3.3V, V
IN
= 0V 16 µA
LT1529-5 V
OUT
= 5V, V
IN
= 0V 16 µA
LT1529 (Note 6) V
OUT
= 3.8V, V
IN
= 0V 16 µA
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The SHDN pin input voltage rating is required for a low impedance
source. Internal protection devices connected to the SHDN pin will turn on
and clamp the pin to approximately 7V or – 0.6V. This range allows the use
of 5V logic devices to drive the pin directly. For high impedance sources or
logic running on supply voltages greater than 5.5V, the maximum current
driven into the SHDN pin must be limited to less than 5mA.
Note 3: The device is tested under pulse load conditions such that T
J
= T
A
.
Note 4: Operating conditions are limited by maximum junction
temperature. The regulated output voltage specification will not apply for
all possible combinations of input voltage and output current. When
operating at maximum input voltage, the output current range must be
limited. When operating at maximum output current the input voltage
range must be limited.
Note 5: The LT1529 is tested and specified with the ADJ pin connected to
the OUTPUT pin.
Note 6: Dropout voltage is the minimum input/output voltage required to
maintain regulation at the specified output current. In dropout the output
voltage will be equal to (V
IN
– V
DROPOUT
).
Note 7: GND pin current is tested with V
IN
= V
OUT
(nominal) and a current
source load. This means that the device is tested while operating in its
dropout region. This is the worst-case GND pin current. The GND pin
current will decrease slightly at higher input voltages.
Note 8: GND pin current will rise at T
J
> 75°C. This is due to internal
circuitry designed to compensate for leakage currents in the output
transistor at high temperatures. This allows quiescent current to be
minimized at lower temperatures, yet maintain output regulation at high
temperatures with light loads. See quiescent current curve in typical
performance characteristics.
Note 9: ADJ pin bias current flows into the ADJ pin.
Note 10: SHDN pin current at V
SHDN
= 0V flows out of the SHDN pin.
Note 11: Quiescent current in shutdown is equal to the sum total of the
SHDN pin current (5µA) and the GND pin current (10µA).
Note 12: Reverse output current is tested with the V
IN
pin grounded and
the OUTPUT pin forced to the rated output voltage. This current flows into
the OUTPUT pin and out of the GND pin.
The ● denotes specifications which apply over the operating temperature range, otherwise specificatons are at TA = 25°C. (Note 3)
4
LT1529
LT1529-3.3/LT1529-5
152935fb
Quiescent Current
CCHARA TERISTICS
UW
ATYPICALPER
FORCE
TEMPERATURE (°C)
–50
0
QUIESCENT CURRENT (µA)
100
250
050 75
LT1529 • G03
50
200
150
–25 25 100 125
V
IN
= 6V
R
L
=
∞
V
SHDN
= OPEN
V
SHDN
= 0V
Guaranteed Dropout Voltage Dropout Voltage
TEMPERATURE (°C)
–50
DROPOUT VOLTAGE (V)
0.7
A
B
C
D
E
F
25
LT1529 • G02
0.4
0.2
–25 0 50
0.1
0
0.8
0.6
0.5
0.3
75 100 125
A: I
LOAD
= 3A
B: I
LOAD
= 1.5A
C: I
LOAD
= 700mA
D: I
LOAD
= 300mA
E: I
LOAD
= 100mA
F: I
LOAD
= 10mA
LT1529
Quiescent Current
INPUT VOLTAGE (V)
0
QUIESCENT CURRENT (µA)
150
200
250
8
LT1529 • G06
100
50
125
175
225
75
25
0246
19
35710
I
LOAD
= 0
R
L
= ∞
V
OUT
= V
ADJ
V
SHDN
= OPEN (HIGH)
V
SHDN
= 0V
LT1529-3.3
Quiescent Current
INPUT VOLTAGE (V)
0
QUIESCENT CURRENT (µA)
150
200
250
8
LT1529 • G04
100
50
125
175
225
75
25
0246
19
35710
I
LOAD
= 0
R
L
= ∞
V
SHDN
= OPEN (HIGH)
V
SHDN
= 0V
LT1529-5
Quiescent Current
INPUT VOLTAGE (V)
0
QUIESCENT CURRENT (µA)
150
200
250
8
LT1529 • G05
100
50
125
175
225
75
25
0246
19
35710
I
LOAD
= 0
R
L
= ∞
V
SHDN
= OPEN (HIGH)
V
SHDN
= 0V
LT1529-3.3
Output Voltage
TEMPERATURE (°C)
–50
OUTPUT VOLTAGE (V)
3.375
25
LT1529 • G07
3.300
3.250
–25 0 50
3.225
3.200
3.400
3.350
3.325
3.275
75 100 125
I
LOAD
= 1mA
LT1529-5
Output Voltage
TEMPERATURE (°C)
–50
OUTPUT VOLTAGE (V)
5.075
25
LT1529 • G08
5.000
4.950
–25 0 50
4.925
4.900
5.100
5.050
5.025
4.975
75 100 125
I
LOAD
= 1mA
LT1529
ADJ Pin Voltage
TEMPERATURE (°C)
–50
ADJ PIN VOLTAGE (V)
3.825
25
LT1529 • G09
3.750
3.700
–25 0 50
3.675
3.650
3.850
3.800
3.775
3.725
75 100 125
I
LOAD
= 1mA
OUTPUT CURRENT (A)
0
0
DROPOUT VOLTAGE (V)
0.2
0.3
0.4
0.5
0.6
0.7
0.5 1.0 1.5 2.0
LT1529 • G01
2.5
0.8
0.9
1.0
0.1
3.0
= TEST POINT
5
LT1529
LT1529-3.3/LT1529-5
152935fb
CCHARA TERISTICS
UW
ATYPICALPER
FORCE
LT1529-3.3
GND Pin Current
LT1529-5
GND Pin Current
LT1529
GND Pin Current
LT1529-5
GND Pin Current
GND Pin Current
SHDN Pin Threshold
(Off-to-On)
LT1529-3.3
GND Pin Current
LT1529
GND Pin Current
INPUT VOLTAGE (V)
0
GND PIN CURRENT (mA)
60
80
100
8
LT1529 • G15
40
20
50
70
90
30
10
0246
19
35710
T
J
= 25°C
V
OUT
= V
ADJ
*FOR V
OUT
= 3.75V R
LOAD
= 1.25W
I
LOAD
= 3A*
R
LOAD
= 2.5Ω
I
LOAD
= 1.5A*
R
LOAD
= 5.3Ω
I
LOAD
= 700mA*
OUTPUT CURRENT (A)
0
0
GND PIN CURRENT (mA)
20
30
40
50
60
70
0.5 1.0 1.5 2.0
LT1529 • G16
2.5
80
90
100
10
3.0
VIN = 3.75V (LT1529)
VIN = 3.3V (LT1529-3.3)
VIN = 5V (LT1529-5)
DEVICE IS OPERATING
IN DROPOUT
TJ = 125°C
TJ = –50°C
TJ = 25°C
SHDN Pin Threshold
(On-to-Off)
TEMPERATURE (°C)
–50
0
SHDN THRESHOLD (V)
0.2
0.6
0.8
1.0
2.0
1.4
050 75
LT1529 • G17
0.4
1.6
1.8
1.2
–25 25 100 125
ILOAD = 1mA
TEMPERATURE (°C)
–50
0
SHDN THRESHOLD (V)
0.2
0.6
0.8
1.0
2.0
1.4
050 75
LT1529 • G18
0.4
1.6
1.8
1.2
–25 25 100 125
I
LOAD
= 3A
I
LOAD
= 1mA
INPUT VOLTAGE (V)
0
GND PIN CURRENT (mA)
3.0
4.0
5.0
8
LT1529 • G10
2.0
1.0
2.5
3.5
4.5
1.5
0.5
0246
19
35710
T
J
= 25°C
V
OUT
= V
SENSE
*FOR V
OUT
= 3.3V R
LOAD
= 6.6Ω
I
LOAD
= 500mA*
R
LOAD
= 11Ω
I
LOAD
= 300mA*
R
LOAD
= 33Ω
I
LOAD
= 100mA*
R
LOAD
= 330Ω
I
LOAD
= 10mA*
INPUT VOLTAGE (V)
0
GND PIN CURRENT (mA)
60
80
100
8
LT1529 • G13
40
20
50
70
90
30
10
0246
19
35710
T
J
= 25°C
V
OUT
= V
SENSE
R
LOAD
= 1.1Ω
I
LOAD
= 3A*
R
LOAD
= 2.2Ω
I
LOAD
= 1.5A*
R
LOAD
= 4.7Ω
I
LOAD
= 700mA*
*FOR V
OUT
= 3.3V
INPUT VOLTAGE (V)
0
GND PIN CURRENT (mA)
60
80
100
8
LT1529 • G14
40
20
50
70
90
30
10
0246
19
35710
T
J
= 25°C
V
OUT
= V
SENSE
*FOR V
OUT
= 5V R
LOAD
= 1.7Ω
I
LOAD
= 3A*
R
LOAD
= 3.3Ω
I
LOAD
= 1.5A*
R
LOAD
= 7.1Ω
I
LOAD
= 700mA*
INPUT VOLTAGE (V)
0
GND PIN CURRENT (mA)
3.0
4.0
5.0
8
LT1529 • G11
2.0
1.0
2.5
3.5
4.5
1.5
0.5
0246
19
35710
T
J
= 25°C
V
OUT
= V
SENSE
*FOR V
OUT
= 5V R
LOAD
= 10Ω
I
LOAD
= 500mA*
R
LOAD
= 16.6Ω
I
LOAD
= 300mA*
R
LOAD
= 500Ω
I
LOAD
= 10mA*
R
LOAD
= 50Ω
I
LOAD
= 100mA*
INPUT VOLTAGE (V)
0
GND PIN CURRENT (mA)
3.0
4.0
5.0
8
LT1529 • G12
2.0
1.0
2.5
3.5
4.5
1.5
0.5
0246
19
35710
T
J
= 25°C
V
OUT
= V
ADJ
*FOR V
OUT
=
3.75V R
LOAD
= 7.5Ω
I
LOAD
= 500mA*
R
LOAD
= 12.5Ω
I
LOAD
= 300mA*
R
LOAD
= 375Ω
I
LOAD
= 10mA*
R
LOAD
= 38Ω
I
LOAD
= 100mA*
6
LT1529
LT1529-3.3/LT1529-5
152935fb
CCHARA TERISTICS
UW
ATYPICALPER
FORCE
SHDN Pin Current ADJ Pin Bias Current
TEMPERATURE (°C)
–50
0
SHDN PIN CURRENT (µA)
1
3
4
5
10
7
050 75
LT1529 • G19
2
8
9
6
–25 25 100 125
V
SHDN
= 0V
SHDN Pin Input Current
SHDN PIN VOLTAGE (V)
0
0
SHDN PIN INPUT CURRENT (mA)
5
15
20
25
2459
LT1529 • G20
10
13 678
TEMPERATURE (°C)
–50
0
ADJ PIN BIAS CURRENT (nA)
50
150
200
250
500
350
050 75
LT1529 • G21
100
400
450
300
–25 25 100 125
V
ADJ
= V
OUT
= 3.75V
Current LimitCurrent LimitReverse Output Current
TEMPERATURE (°C)
–50
OUTPUT CURRENT (µA)
100
125
150
25 75
LT1529 • G22
75
50
–25 0 50 100 125
25
0
INPUT VOLTAGE (V)
0
SHORT-CIRCUIT CURRENT (A)
4
5
6
35
LT1529 • G23
3
2
12 467
1
0
V
OUT
= 0V
TEMPERATURE (°C)
–50
SHORT-CIRCUIT CURRENT (A)
4
5
6
25 75
LT1529 • G24
3
2
–25 0 50 100 125
1
0
V
IN
= 7V
V
OUT
= 0V
Reverse Output Current
OUTPUT VOLTAGE (V)
0
OUTPUT CURRENT (µA)
60
80
100
8
LT1529 • G25
40
20
50
70
90
30
10
0246
19
35710
LT1529
LT1529-5
LT1529-3.3
T
J
= 25°C, V
IN
= 0V
V
OUT
= V
SENSE
(LT1529-3.3/LT1529-5)
V
OUT
= V
ADJ
(LT1529)
CURRENT FLOWS
INTO DEVICE
Ripple Rejection
TEMPERATURE (°C)
–50
56
58
62
25 75
LT1529 • G26
54
52
–25 0 50 100 125
50
48
60
RIPPLE REJECTION (dB)
(V
IN
– V
OUT
)AVG = 1V
V
RIPPLE
= 0.5V
P-P
I
LOAD
= 1.5A
f = 120Hz
Ripple Rejection
FREQUENCY (Hz)
20
RIPPLE REJECTION (dB)
40
60
50
80
100
10
30
70
90
10 1k 10k 100k
LT1529 • G27
0
100
I
OUT
= 1.5A
V
IN
= V
OUT
(NOMINAL) + 1
+ 50mV
RMS
RIPPLE
C
OUT
= 47µF
C
OUT
= 22µF
7
LT1529
LT1529-3.3/LT1529-5
152935fb
CCHARA TERISTICS
UW
ATYPICALPER
FORCE
PI FU CTIO S
U
UU
OUTPUT (Pin 1): OUTPUT Pin. The OUTPUT pin supplies
power to the load. A minimum output capacitor of 22µF is
required to prevent oscillations. Larger values will be
required to optimize transient response for large load
current deltas. See the Applications Information section
for further information on output capacitance and reverse
output characteristics.
SENSE (Pin 2): SENSE Pin. For fixed voltage versions of
the LT1529 (LT1529-3.3, LT1529-5) the SENSE pin is the
input to the error amplifier. Optimum regulation will be
obtained at the point where the SENSE pin is connected to
the output pin. For most applications the SENSE pin is
connected directly to the OUTPUT pin at the regulator. In
critical applications small voltage drops caused by the
resistance (R
P
) of PC traces between the regulator and the
load, which would normally degrade regulation, may be
eliminated by connecting the SENSE pin to the OUTPUT
pin at the load as shown in Figure 1 (Kelvin Sense Connec-
tion). 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 15µA at the nominal regulated
output voltage. This pin is internally clamped to –0.6V
(one V
BE
).
ADJ (Pin 2): Adjust Pin. For the LT1529 (adjustable
version) the ADJ pin is the input to the error amplifier. This
+
VIN
VIN
1
2
3
LT1529 • F01
5
4
OUTPUT
SENSE
LT1529-5
RP
SHDN
GND
LOAD
+
RP
Figure 1. Kelvin Sense Connection
pin is internally clamped to 6V and –0.6V (one V
BE
). This
pin has a bias current of 150nA which flows into the pin.
See Bias Current curve in the Typical Performance Char-
acteristics. The ADJ pin reference voltage is equal to 3.75V
referenced to ground.
SHDN (Pin 4): Shutdown Pin. This pin is used to put the
device into shutdown. In shutdown the output of the
device is turned off. This pin is active low. The device will
be shut down if the SHDN pin is actively pulled low. The
SHDN pin current with the pin pulled to ground will be 6µA.
The SHDN pin is internally clamped to 7V and –0.6V (one
V
BE
). This allows the SHDN pin to be driven directly by 5V
logic or by open-collector logic with a pull-up resistor. The
pull-up resistor is only required to supply the leakage
current of the open-collector gate, normally several mi-
croamperes. Pull-up current must be limited to a maxi-
mum of 5mA. A curve of SHDN pin input current as a
Load Regulation
TEMPERATURE (°C)
–50
LOAD REGULATION (mV)
–5
0
5
25 75
LT1529 • G28
–10
–15
–25 0 50 100 125
–20
–25
LT1529-5
LT1529-3.3
LT1529
V
IN
= V
OUT
(NOMINAL) + 1V
∆I
LOAD
= 100mA to 3A
V
ADJ
= V
OUT
TIME (µs)
0
OUTPUT VOLTAGE
DEVIATION (V)
LOAD CURRENT (A)
–0.1
0.1
160
LT1529 • G30
2
–0.2
0
0.2
3
1
40 80 120
20 180
60 100 140 200
V
IN
= 6V
C
IN
= 10µF
C
OUT
= 22µF
LT1529-5 Transient Response
TIME (µs)
0
OUTPUT VOLTAGE
DEVIATION (V)
LOAD CURRENT (A)
–0.1
0.1
800
LT1529 • G29
2
–0.2
0
0.2
3
1
200 400 600
100 900
300 500 700 1000
V
IN
= 6V
C
IN
= 3.3µF
C
OUT
= 47µF
LT1529-5 Transient Response
8
LT1529
LT1529-3.3/LT1529-5
152935fb
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function of voltage appears in the Typical Performance
Characteristics. If the SHDN pin is not used it can be left
open circuit. The device will be active, output on, if the
SHDN pin is not connected.
V
IN
(Pin 5): Input Pin. Power is supplied to the device
through the V
IN
pin. The V
IN
pin should be bypassed to
ground if the device is more than six inches away from the
main input filter capacitor. In general, the output imped-
ance of a battery rises with frequency so it is advisable to
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The LT1529 is a 3A low dropout regulator with mi-
cropower quiescent current and shutdown capable of
supplying 3A of output current at a dropout voltage of
0.6V. The device operates with very low quiescent current
(50µA). In shutdown the quiescent current drops to only
16µA. In addition to the low quiescent current the LT1529
incorporates several protection features which make it
ideal for use in battery-powered systems. The device is
protected against reverse input voltages. In battery backup
applications where the output can be held up by a backup
battery when the input is pulled to ground, the LT1529 acts
like it has a diode in series with its output and prevents
reverse current flow.
Adjustable Operation
The adjustable version of the LT1529 has an output
voltage range of 3.75V to 14V. The output voltage is set
by the ratio of two external resistors as shown in Figure 2.
The device servos the output voltage to maintain the
voltage at the ADJ pin at 3.75V. The current in R1 is then
equal to 3.75V/R1. The current in R2 is equal to the sum
of the current in R1 and the ADJ pin bias current. The ADJ
pin bias current, 150nA at 25°C, flows through R2 into the
ADJ pin. The output voltage can be calculated according
to the formula in Figure 2. The value of R1 should be less
than 400k 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.
Curves of ADJ Pin Voltage vs Temperature and ADJ Pin
include a bypass capacitor in battery-powered circuits. A
bypass capacitor in the range of 1µF to 10µF is sufficient.
The LT1529 is designed to withstand reverse voltages on
the V
IN
pin with respect to ground and OUTPUT pin. In the
case of a reversed input, which can happen if a battery is
plugged in backwards, the LT1529 will act as if there is a
diode in series with its input. There will be no reverse
current flow into the LT1529 and no reverse voltage will
appear at the load. The device will protect both itself and
the load.
+
VIN
VOUT = 3.75V + (IADJ × R2)
VIN
VOUT
R2
R1
1
2
3
LT1529 • F02
5
4
OUTPUT
SENSE
LT1529
SHDN
GND
()
1 +
R2
R1
VADJ = 3.75V
IADJ = 150nA AT 25°C
OUTPUT RANGE = 3.3V TO 14V
Figure 2. Adjustable Operation
Bias Current vs Temperature appear in the Typical Perfor-
mance Characteristics. The reference voltage at the ADJ
pin has a positive temperature coefficient of approxi-
mately 15ppm/°C. The ADJ pin bias current has a negative
temperature coefficient. These effects will tend to cancel
each other.
The adjustable device is specified with the ADJ pin tied to
the OUTPUT pin. This sets the output voltage to 3.75V.
Specifications for output voltage greater than 3.75V will be
proportional to the ratio of the desired output voltage to
3.75V (V
OUT
/3.75V). For example: load regulation for an
output current change of 1mA to 3A is –0.5mV typical at
V
OUT
= 3.75V. At V
OUT
= 12V, load regulation would be:
12
375 05 16
V
VmV mV
.–. –.
⎛
⎝
⎜⎞
⎠
⎟
()
=
()
9
LT1529
LT1529-3.3/LT1529-5
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Thermal Considerations
The power handling capability of the device will be limited
by the maximum rated junction temperature (125°C). The
power dissipated by the device will be made up of two
components:
1. Output current multiplied by the input/output voltage
differential: I
OUT
• (V
IN
– V
OUT
), and
2. Ground pin current multiplied by the input voltage:
I
GND
• V
IN
.
The GND pin current can be found by examining the GND
Pin Current curves in the Typical Performance Character-
istics. Power dissipation will be equal to the sum of the two
components listed above.
The LT1529 series regulators have internal thermal limit-
ing designed to protect the device during overload condi-
tions. For continuous normal load conditions the maxi-
mum junction temperature rating of 125°C must not be
exceeded. It is important to give careful consideration to
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. Experiments have shown that the
heat spreading copper layer does not need to be electri-
cally connected to the tab of the device. The PC material
can be very effective at transmitting heat between the pad
area, attached to the tab of the device, and a ground or
power plane layer either inside or on the opposite side of
the board. Although the actual thermal resistance of the PC
material is high, the length/area ratio of the thermal
resistor between layers is small. Copper board stiffeners
and plated through-holes can also be used to spread the
heat generated by power devices.
The following tables list thermal resistances for each
package. For the TO-220 package, thermal resistance is
given for junction-to-case only since this package is
usually mounted to a heat sink. Measured values of
thermal resistance for several different copper areas are
listed for the DD package. All measurements were taken in
still air on 3/32" FR-4 board with 1-oz copper. This data can
be used as a rough guideline in estimating thermal resis-
tance. The thermal resistance for each application will be
affected by thermal interactions with other components as
well as board size and shape. Some experimentation will
be necessary to determine the actual value.
Table 1. Q Package, 5-Lead DD
COPPER AREA
TOPSIDE* BACKSIDE BOARD AREA
2500 sq. mm 2500 sq. mm 2500 sq. mm 23°C/W
1000 sq. mm 2500 sq. mm 2500 sq. mm 25°C/W
125 sq. mm 2500 sq. mm 2500 sq. mm 33°C/W
* Device is mounted on topside.
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
Calculating Junction Temperature
Example: Given an output voltage of 3.3V, an input voltage
range of 4.5V to 5.5V, an output current range of 0mA to
500mA, and a maximum ambient temperature of 50°C,
what will the maximum junction temperature be?
The power dissipated by the device will be equal to:
I
OUT(MAX)
• (V
IN(MAX)
– V
OUT
) + (I
GND
• V
IN(MAX)
)
where, I
OUT(MAX)
= 500mA
V
IN(MAX)
= 5.5V
I
GND
at (I
OUT
= 500mA, V
IN
= 5.5V) = 3.6mA
so, P = 500mA • (5.5V – 3.3V) + (3.6mA • 5.5V)
= 1.12W
If we use a DD package, then the thermal resistance will be
in the range of 23°C/W to 33°C/W depending on copper
area. So the junction temperature rise above ambient will
be approximately equal to:
1.12W • 28°C/W = 31.4°C
The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:
T
JMAX
= 50°C + 31.4°C = 81.4°C
Output Capacitance and Transient Performance
The LT1529 is designed to be stable with a wide range of
output capacitors. The minimum recommended value is
22µF with an ESR of 0.2Ω or less. The LT1529 is a
T Package, 5-Lead TO-220
Thermal Resistance (Junction-to-Case) = 2.5°C/W
10
LT1529
LT1529-3.3/LT1529-5
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micropower device and output transient response will be
a function of output capacitance. See the Transient Re-
sponse curves in the Typical Performance Characteristics.
Larger values of output capacitance will decrease the peak
deviations and provide improved output transient re-
sponse for larger load current deltas. Bypass capacitors,
used to decouple individual components powered by the
LT1529, will increase the effective value of the output
capacitor.
Protection Features
The LT1529 incorporates several protection features which
make it ideal for use in battery-powered circuits. In addi-
tion to the normal protection features associated with
monolithic regulators, such as current limiting and ther-
mal limiting, the device is protected against reverse input
voltages, 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 opera-
tion, the junction temperature should not exceed 125°C.
The input of the device will withstand reverse voltages of
15V. 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 backwards.
For fixed voltage versions of the device, the SENSE pin is
internally clamped to one diode drop below ground. For
the adjustable version of the device, the OUTPUT pin is
internally clamped at one diode drop below ground. If the
OUTPUT pin of an adjustable device, or the SENSE pin of
a fixed voltage device, is pulled below ground, with the
input open or grounded, current must be limited to less
than 5mA.
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 vary
depending on the conditions. Many battery-powered cir-
cuits incorporate some form of power management. The
following information will help optimize battery life. Table
2 summarizes the following information.
The reverse output current will follow the curve in Figure
3 when the input is pulled to ground. This current flows
through the device to ground. The state of the SHDN pin
will have no effect on output current when the V
IN
pin is
pulled to ground.
Table 2. Fault Conditions
V
IN
PIN SHDN PIN OUTPUT/SENSE PINS
<V
OUT
(Nominal) Open (High) Forced to V
OUT
(Nominal) Reverse Output Current ≈ 15µA (See Figure 3), Input Current ≈ 1µA (See Figure 4)
<V
OUT
(Nominal) Grounded Forced to V
OUT
(Nominal) Reverse Output Current ≈ 15µA (See Figure 3), Input Current ≈ 1µA (See Figure 4)
Open Open (High) > 1V Reverse Output Current ≈ 15µA Peak (See Figure 3)
Open Grounded > 1V Reverse Output Current ≈ 15µA (See Figure 3)
≤0.8V Open (High) ≤0V Output Current = 0
≤0.8V Grounded ≤0V Output Current = 0
>1.5V Open (High) ≤0V Output Current = Short-Circuit Current
– 15V < V
IN
< 15V Grounded ≤0V Output Current = 0
OUTPUT VOLTAGE (V)
0
OUTPUT CURRENT (µA)
60
80
100
8
LT1529 • F03
40
20
50
70
90
30
10
0246
19
35710
LT1529
LT1529-5
LT1529-3.3
TJ = 25°C, VIN = 0V
VOUT = VSENSE
(LT1529-3.3/LT1529-5)
VOUT = VADJ (LT1529)
CURRENT FLOWS
INTO DEVICE
Figure 3. Reverse Output Current
11
LT1529
LT1529-3.3/LT1529-5
152935fb
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In some applications it may be necessary to leave the input
to the LT1529 unconnected when the output is held high.
This can happen when the LT1529 is powered from a
rectified AC source. If the AC source is removed, then the
input of the LT1529 is effectively left floating. The reverse
output current also follows the curve in Figure 3 if the V
IN
pin is left open. The state of the SHDN pin will have no
effect on the reverse output current when the V
IN
pin is
floating.
When the input of the LT1529 is forced to a voltage below
its nominal output voltage and its output is held high, the
output current will follow the curve shown in Figure 3 . This
can happen if the input of the LT1529 is connected to a
discharged (low voltage) battery and the output is held up
by either a backup battery or by a second regulator circuit.
When the V
IN
pin is forced below the OUTPUT pin or the
OUTPUT pin is pulled above the V
IN
pin, the input current
will typically drop to less than 2µA (see Figure 4). The state
of the SHDN pin will have no effect on the reverse output
current when the output is pulled above the input.
INPUT VOLTAGE (V)
0
INPUT CURRENT (µA)
3
4
5
4
LT1529 • F04
2
1
01235
LT1529-5LT1529-3.3
V
OUT
= 3.3V (LT1529-3.3)
V
OUT
= 5V (LT1529-5)
Figure 4. Input Current
PACKAGE DESCRIPTIO
U
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of circuits as described herein will not infringe on existing patent rights.
Q Package
5-Lead Plastic DD Pak
(LTC DWG # 05-08-1461)
Q(DD5) 0502
.028 – .038
(0.711 – 0.965)
TYP
.143 +.012
–.020
()
3.632 +0.305
–0.508
.067
(1.702)
BSC
.013 – .023
(0.330 – 0.584)
.095 – .115
(2.413 – 2.921)
.004 +.008
–.004
()
0.102 +0.203
–0.102
.050 ± .012
(1.270 ± 0.305)
.059
(1.499)
TYP
.045 – .055
(1.143 – 1.397)
.165 – .180
(4.191 – 4.572)
.330 – .370
(8.382 – 9.398)
.060
(1.524)
TYP
.390 – .415
(9.906 – 10.541)
15° TYP
.325
.205
.080
.565
.090
RECOMMENDED SOLDER PAD LAYOUT
FOR THICKER SOLDER PASTE APPLICATIONS
.042
.067
.420
.276
.320
.420
.350
.565
.090
.042
.067
RECOMMENDED SOLDER PAD LAYOUT
NOTE:
1. DIMENSIONS IN INCH/(MILLIMETER)
2. DRAWING NOT TO SCALE
.300
(7.620)
.075
(1.905)
.183
(4.648)
.060
(1.524)
.060
(1.524)
.256
(6.502)
BOTTOM VIEW OF DD PAK
HATCHED AREA IS SOLDER PLATED
COPPER HEAT SINK
12
LT1529
LT1529-3.3/LT1529-5
152935fb
© LINEAR TECHNOLOGY CORPORATION 1995
LT/LT 0305 REV B • PRINTED IN USA
PACKAGE DESCRIPTIO
U
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
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Lowest I
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Low Dropout Regulator
T Package
5-Lead Plastic TO-220 (Standard)
(LTC DWG # 05-08-1421)
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
T5 (TO-220) 0801
.028 – .038
(0.711 – 0.965)
.067
(1.70) .135 – .165
(3.429 – 4.191)
.700 – .728
(17.78 – 18.491)
.045 – .055
(1.143 – 1.397)
.095 – .115
(2.413 – 2.921)
.013 – .023
(0.330 – 0.584)
.620
(15.75)
TYP
.155 – .195*
(3.937 – 4.953)
.152 – .202
(3.861 – 5.131)
.260 – .320
(6.60 – 8.13)
.165 – .180
(4.191 – 4.572)
.147 – .155
(3.734 – 3.937)
DIA
.390 – .415
(9.906 – 10.541)
.330 – .370
(8.382 – 9.398)
.460 – .500
(11.684 – 12.700)
.570 – .620
(14.478 – 15.748)
.230 – .270
(5.842 – 6.858)
BSC
SEATING PLANE
* MEASURED AT THE SEATING PLANE
