LINER LT1529CQ 3a low dropout regulators with micropower quiescent current and shutdown Datasheet

LT1529
LT1529-3.3/LT1529-5
3A Low Dropout Regulators
with Micropower
Quiescent Current
and Shutdown
DESCRIPTIO
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FEATURES
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Dropout Voltage: 0.6V at IOUT = 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 IQ = 16µA
Stable with 3.3µF Output Capacitor
Reverse Battery Protection
No Reverse Current
Thermal Limiting
The LT ®1529/LT1529-3.3/LT1529-5 are 3A low dropout
regulators with micropower quiescent current and shutdown. 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 include the ability to operate with small output capacitors.
They are stable with only 3.3µF on the output while most
older devices require between 10µF and 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 reverse 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.
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APPLICATIO S
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High Efficiency Regulator
Regulator for Battery-Powered Systems
Post Regulator for Switching Supplies
5V to 3.3V Logic Regulator
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
Dropout Voltage
0.6
5V Supply with Shutdown
VIN > 5.5V
VIN
OUTPUT
1
+
LT1529-5
4
SHDN SENSE
2
3.3µF
SOLID
TANT
GND
3
5V
3A
DROPOUT VOLTAGE (V)
5
0.5
0.4
0.3
0.2
0.1
VSHDN (PIN 4)
< 0.25
> 2.8
NC
OUTPUT
OFF
ON
ON
0
LT1529 • TA01
0
0.5
1.0
1.5
2.0
OUTPUT CURRENT (A)
2.5
3.0
LT1529 • TA02
1
LT1529
LT1529-3.3/LT1529-5
W W
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AXI U
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ABSOLUTE
RATI GS
(Note 1)
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
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.
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PACKAGE/ORDER I FOR ATIO
FRONT VIEW
5
4
3
2
1
TAB IS
GND
VIN
SHDN
GND
SENSE/ADJ*
OUTPUT
Q PACKAGE
5-LEAD PLASTIC DD PAK
*PIN 2 = SENSE FOR LT1529-3.3/LT1529-5
= ADJ FOR LT1529
ORDER PART
NUMBER
LT1529CQ
LT1529CQ-3.3
LT1529CQ-5
LT1529IQ
LT1529IQ-3.3
LT1529IQ-5
TJMAX = 125°C, θJA ≈ 30°C/ W
FRONT VIEW
5
4
3
2
1
TAB IS
GND
VIN
SHDN
GND
SENSE/ADJ*
OUTPUT
T PACKAGE
5-LEAD PLASTIC TO-220
*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
TJMAX = 125°C, θJA ≈ 50°C/ W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the operating temperature range, otherwise specificatons are at TA = 25°C. (Note 3)
PARAMETER
CONDITIONS
Regulated Output Voltage
(Note 4)
LT1529-3.3
MIN
TYP
MAX
UNITS
●
3.250
3.200
3.300
3.300
3.350
3.400
V
V
VIN = 5.5V, IOUT = 1mA, TJ = 25°C
6V < VIN < 15V, 1mA < IOUT < 3A
●
4.925
4.850
5.000
5.000
5.075
5.150
V
V
VIN = 4.3V, IOUT = 1mA, TJ = 25°C
4.8V < VIN < 15V, 1mA < IOUT < 3A
●
3.695
3.640
3.750
3.750
3.805
3.860
V
V
LT1529-3.3
∆VIN = 3.8V to 15V, IOUT = 1mA
●
1.5
10
mV
LT1529-5
∆VIN = 5.5V to 15V, IOUT = 1mA
∆VIN = 4.3V to 15V, IOUT = 1mA
●
1.5
10
mV
LT1529-5
LT1529 (Note 5)
Line Regulation
LT1529 (Note 5)
Load Regulation
LT1529-3.3
LT1529-5
LT1529 (Note 5)
Dropout Voltage
(Note 6)
2
VIN = 3.8V, IOUT = 1mA, TJ = 25°C
4.3V < VIN < 15V, 1mA < IOUT < 3A
●
1.5
10
mV
∆ILOAD = 1mA to 3A, VIN = 4.3V, TJ = 25°C
∆ILOAD = 1mA to 3A, VIN = 4.3V
●
5
12
20
30
mV
mV
∆ILOAD = 1mA to 3A, VIN = 6V, TJ = 25°C
∆ILOAD = 1mA to 3A, VIN = 6V
●
5
12
20
30
mV
mV
∆ILOAD = 1mA to 3A, VIN = 4.8V, TJ = 25°C
∆ILOAD = 1mA to 3A, VIN = 4.8V
●
5
12
20
30
mV
mV
110
180
250
mV
mV
200
300
400
mV
mV
ILOAD = 10mA, TJ = 25°C
ILOAD = 10mA
●
ILOAD = 100mA, TJ = 25°C
ILOAD = 100mA
●
LT1529
LT1529-3.3/LT1529-5
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the operating temperature range, otherwise specificatons are at TA = 25°C. (Note 3)
PARAMETER
Dropout Voltage
(Note 6)
GND Pin Current
(Note 7)
ADJ Pin Bias Current (Notes 5, 9)
Shutdown Threshold
SHDN Pin Current (Note 10)
Quiescent Current in Shutdown
(Note 11)
Ripple Rejection
Current Limit
Input Reverse Leakage Current
Reverse Output Current (Note 12)
CONDITIONS
ILOAD = 700mA, TJ = 25°C
ILOAD = 700mA
ILOAD = 1.5A, TJ = 25°C
ILOAD = 1.5A
ILOAD = 3A, TJ = 25°C
ILOAD = 3A
ILOAD = 0mA, TJ = 25°C
ILOAD = 0mA, TJ = 125°C (Note 8)
ILOAD = 100mA, TJ = 25°C
ILOAD = 100mA, TJ = 125°C (Note 8)
ILOAD = 700mA
ILOAD = 1.5A
ILOAD = 3A
TJ = 25°C
VOUT = Off to On
VOUT = On to Off
VSHDN = 0V
VIN = VOUT (Nominal) + 1V, VSHDN = 0V
VIN – VOUT = 1V (Avg), VRIPPLE = 0.5VP-P,
fRIPPLE = 120Hz, ILOAD = 1.5A
VIN – VOUT = 7V, TJ = 25°C
VIN = VOUT (Nominal) + 1.5V, ∆VOUT = – 0.1V
VIN = – 15V, VOUT = 0V
LT1529-3.3
VOUT = 3.3V, VIN = 0V
LT1529-5
VOUT = 5V, VIN = 0V
LT1529 (Note 6)
VOUT = 3.8V, VIN = 0V
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 TJ = TA.
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 (VIN – VDROPOUT).
MIN
TYP
320
●
430
●
600
●
●
●
●
●
●
0.25
●
●
●
50
400
0.6
1.0
5.5
20
80
150
1.20
0.75
4.5
15
MAX
430
550
550
700
750
950
100
1.0
12
40
160
300
2.8
10
30
UNITS
mV
mV
mV
mV
mV
mV
µA
µA
mA
mA
mA
mA
mA
nA
V
V
µA
µA
50
62
dB
3.2
5
4.7
A
A
mA
µA
µA
µA
1.0
●
16
16
16
Note 7: GND pin current is tested with VIN = VOUT (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 TJ > 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 VSHDN = 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 VIN 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.
3
LT1529
LT1529-3.3/LT1529-5
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Dropout Voltage
0.8
0.9
0.7
DROPOUT VOLTAGE (V)
0.7
0.6
0.5
0.4
0.3
A: ILOAD = 3A
E: ILOAD = 100mA
B: ILOAD = 1.5A
F: ILOAD = 10mA
C: ILOAD = 700mA
D: ILOAD = 300mA
A
0.6
VIN = 6V
RL = ∞
0.5
B
0.4
C
0.3
D
0.2
E
0.2
0
0.5
2.5
1.5
2.0
1.0
OUTPUT CURRENT (A)
0
– 50 – 25
3.0
0
50
75
25
TEMPERATURE (°C)
100
LT1529-3.3
Quiescent Current
QUIESCENT CURRENT (µA)
175
150
VSHDN = OPEN (HIGH)
125
100
75
50
VSHDN = 0V
25
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
9
150
VSHDN = OPEN (HIGH)
125
100
75
50
VSHDN = 0V
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
LT1529 • G04
200
175
150
100
75
50
8
9
0
10
5.050
3.800
ADJ PIN VOLTAGE (V)
3.350
OUTPUT VOLTAGE (V)
3.825
5.025
5.000
4.975
4.950
4.925
75
50
25
TEMPERATURE (°C)
100
125
LT1529 • G07
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
ILOAD = 1mA
5.075
0
2
3.850
3.375
3.200
– 50 – 25
1
LT1529
ADJ Pin Voltage
ILOAD = 1mA
3.225
0
LT1529 • G06
5.100
3.250
VSHDN = 0V
25
LT1529 • G05
ILOAD = 1mA
3.275
VSHDN = OPEN (HIGH)
125
LT1529-5
Output Voltage
3.300
ILOAD = 0
RL = ∞
VOUT = VADJ
225
175
LT1529-3.3
Output Voltage
125
LT1529
Quiescent Current
200
0
10
3.325
100
250
25
8
50
25
0
75
TEMPERATURE (°C)
LT1529 • G03
ILOAD = 0
RL = ∞
225
200
4
VSHDN = 0V
0
– 50 – 25
125
250
ILOAD = 0
RL = ∞
225
QUIESCENT CURRENT (µA)
VSHDN = OPEN
50
LT1529-5
Quiescent Current
250
OUTPUT VOLTAGE (V)
100
LT1529 • G02
LT1529 • G01
3.400
150
F
= TEST POINT
0
0
200
0.1
0.1
QUIESCENT CURRENT (µA)
DROPOUT VOLTAGE (V)
0.8
Quiescent Current
250
QUIESCENT CURRENT (µA)
Guaranteed Dropout Voltage
1.0
4.900
–50 –25
3.775
3.750
3.725
3.700
3.675
75
50
25
TEMPERATURE (˚C)
0
100
125
LT1529 • G08
3.650
– 50 – 25
75
50
25
TEMPERATURE (°C)
0
100
125
LT1529 • G09
LT1529
LT1529-3.3/LT1529-5
U W
TYPICAL PERFOR A CE CHARACTERISTICS
LT1529-5
GND Pin Current
LT1529-3.3
GND Pin Current
RLOAD = 6.6Ω
ILOAD = 500mA*
3.5
3.0
RLOAD = 330Ω
ILOAD = 10mA*
2.5
2.0
RLOAD = 11Ω
ILOAD = 300mA*
1.5
RLOAD = 33Ω
ILOAD = 100mA*
1.0
3.5
2.5
1.5
RLOAD = 50Ω
ILOAD = 100mA*
1.0
0.5
0
2
RLOAD = 16.6Ω
ILOAD = 300mA*
2.0
0
1
RLOAD = 500Ω
ILOAD = 10mA*
3.0
0.5
0
3 4 5 6 7
INPUT VOLTAGE (V)
9
8
10
RLOAD = 10Ω
ILOAD = 500mA*
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
100
80
60
50
RLOAD = 4.7Ω
ILOAD = 700mA*
40
30
RLOAD = 2.2Ω
ILOAD = 1.5A*
20
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
9
8
50
30
0
RLOAD = 3.3Ω
ILOAD = 1.5A*
TJ = 125°C
40
TJ = – 50°C
30
30
0
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
LT1529 • G16
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
SHDN Pin Threshold
(Off-to-On)
2.0
ILOAD = 1mA
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0
– 50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
LT1529 • G17
ILOAD = 3A
1.4
1.2
1.0
ILOAD = 1mA
0.8
0.6
0.2
3.0
RLOAD = 2.5Ω
ILOAD = 1.5A*
LT1529 • G15
0.4
2.5
RLOAD = 5.3Ω
ILOAD = 700mA*
40
0.2
1.5
2.0
1.0
OUTPUT CURRENT (A)
RLOAD = 1.25Ω
ILOAD = 3A*
50
0.4
0.5
10
60
10
0
9
70
20
0
8
10
1.6
50
3 4 5 6 7
INPUT VOLTAGE (V)
LT1529 • G14
1.8
TJ = 25°C
60
2
20
SHDN THRESHOLD (V)
70
1
TJ = 25°C
90 VOUT = VADJ
*FOR VOUT = 3.75V
80
RLOAD = 1.7Ω
ILOAD = 3A*
2.0
80
0
LT1529 • G12
SHDN Pin Threshold
(On-to-Off)
VIN = 3.75V (LT1529)
VIN = 3.3V (LT1529-3.3)
VIN = 5V (LT1529-5)
DEVICE IS OPERATING
IN DROPOUT
RLOAD = 38Ω
ILOAD = 100mA*
100
40
10
SHDN THRESHOLD (V)
GND PIN CURRENT (mA)
10
RLOAD = 7.1Ω
ILOAD = 700mA*
60
GND Pin Current
90
1.5
LT1529
GND Pin Current
LT1529 • G13
100
RLOAD = 12.5Ω
ILOAD = 300mA*
2.0
0.5
10
0
2.5
1.0
70
20
10
0
TJ = 25°C
VOUT = VSENSE
*FOR VOUT = 5V
90
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
70
RLOAD = 375Ω
ILOAD = 10mA*
3.0
LT1529-5
GND Pin Current
TJ = 25°C
*FOR VOUT = 3.3V
VOUT = VSENSE
RLOAD = 1.1Ω
ILOAD = 3A*
80
9
RLOAD = 7.5Ω
ILOAD = 500mA*
LT1529 • G11
LT1529-3.3
GND Pin Current
90
TJ = 25°C
4.5 VOUT = VADJ
*FOR VOUT =
4.0
3.75V
3.5
0
0
LT1529 • G10
100
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
4.0
TJ = 25°C
4.5 VOUT = VSENSE
*FOR VOUT = 5V
4.0
GND PIN CURRENT (mA)
4.5
5.0
5.0
TJ = 25°C
VOUT = VSENSE
*FOR VOUT = 3.3V
GND PIN CURRENT (mA)
5.0
LT1529
GND Pin Current
0
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
LT1529 • G18
5
LT1529
LT1529-3.3/LT1529-5
U W
TYPICAL PERFOR A CE CHARACTERISTICS
SHDN Pin Input Current
SHDN Pin Current
10
VSHDN = 0V
VADJ = VOUT = 3.75V
450
8
7
6
5
4
3
2
20
ADJ PIN BIAS CURRENT (nA)
SHDN PIN INPUT CURRENT (mA)
SHDN PIN CURRENT (µA)
9
ADJ Pin Bias Current
500
25
15
10
5
400
350
300
250
200
150
100
50
1
0
– 50 –25
50
25
0
75
TEMPERATURE (°C)
100
0
–50 –25
0
125
0
1
2
7
3
5
6
4
SHDN PIN VOLTAGE (V)
LT1529 • G19
8
9
Reverse Output Current
Current Limit
6
VIN = 7V
VOUT = 0V
VOUT = 0V
50
25
5
SHORT-CIRCUIT CURRENT (A)
SHORT-CIRCUIT CURRENT (A)
4
3
2
1
0
0
– 50 – 25
50
25
75
0
TEMPERATURE (°C)
100
125
0
1
4
3
5
2
INPUT VOLTAGE (V)
Reverse Output Current
TJ = 25°C, VIN = 0V
VOUT = VSENSE
(LT1529-3.3/LT1529-5)
VOUT = VADJ (LT1529)
CURRENT FLOWS
INTO DEVICE
60
60
RIPPLE REJECTION (dB)
OUTPUT CURRENT (µA)
70
LT1529
50
40
30
LT1529-3.3
20
0
1
2
1
50
25
75
0
TEMPERATURE (°C)
100
125
LT1529 • G24
Ripple Rejection
(VIN – VOUT)AVG = 1V
VRIPPLE = 0.5VP-P
ILOAD = 1.5A
f = 120Hz
58
56
54
52
IOUT = 1.5A
VIN = VOUT (NOMINAL) + 1
+ 50mVRMS RIPPLE
90
80
70
COUT = 47µF
SOLID TANT
60
50
40
COUT = 3.3µF
SOLID TANT
30
20
3 4 5 6 7 8
OUTPUT VOLTAGE (V)
9
10
LT1529 • G25
6
2
100
50
LT1529-5
10
3
0
– 50 – 25
7
62
80
4
Ripple Rejection
100
90
5
LT1529 • G23
LT1529 • G22
0
6
RIPPLE REJECTION (dB)
OUTPUT CURRENT (µA)
75
125
Current Limit
6
100
100
LT1529 • G21
LT1529 • G20
150
125
50
25
0
75
TEMPERATURE (°C)
48
– 50 – 25
10
0
50
25
75
0
TEMPERATURE (°C)
100
125
LT1529 • G26
10
100
1k
10k
FREQUENCY (Hz)
100k
LT1529 • G27
LT1529
LT1529-3.3/LT1529-5
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Load Regulation
LT1529-5 Transient Response
LT1529-5 Transient Response
5
–10
–15
–20
VIN = VOUT (NOMINAL) + 1V
∆ILOAD = 100mA to 3A
VADJ = VOUT
–25
– 50 – 25
50
25
75
0
TEMPERATURE (°C)
100
125
0.1
VIN = 6V
CIN = 3.3µF TANT
COUT = 47µF TANT
OUTPUT VOLTAGE
DEVIATION (V)
LT1529-3.3
LT1529
–5
LOAD CURRENT (A)
LOAD REGULATION (mV)
0
0.2
0
– 0.1
– 0.2
3
2
1
0.1
0
– 0.1
– 0.2
3
2
1
0 100 200 300 400 500 600 700 800 900 1000
TIME (µs)
LT1529 • G28
VIN = 6V
CIN = 10µF TANT
COUT = 4.7µF TANT
0.2
LOAD CURRENT (A)
OUTPUT VOLTAGE
DEVIATION (V)
LT1529-5
0
20 40 60 80 100 120 140 160 180 200
TIME (µs)
LT1529 • G29
LT1529 • G30
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OUTPUT (Pin 1): OUTPUT Pin. The OUTPUT pin supplies
power to the load. A minimum output capacitor of 3.3µF 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 (RP) 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 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 15µA at the nominal regulated
output voltage. This pin is internally clamped to – 0.6V
(one VBE).
ADJ (Pin 2): Adjust Pin. For the LT1529 (adjustable
version) the ADJ pin is the input to the error amplifier. This
5
VIN
OUTPUT
1
RP
LT1529-5
+
VIN
4
SHDN SENSE
2
+
LOAD
GND
3
RP
LT1529 • F01
Figure 1. Kelvin Sense Connection
pin is internally clamped to 6V and – 0.6V (one VBE). This
pin has a bias current of 150nA which flows into the pin.
See Bias Current curve in the Typical Performance Characteristics. 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
VBE). 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 microamperes. Pull-up current must be limited to a maximum of 5mA. A curve of SHDN pin input current as a
7
LT1529
LT1529-3.3/LT1529-5
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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.
VIN (Pin 5): Input Pin. Power is supplied to the device
through the VIN pin. The VIN 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 impedance of a battery rises with frequency so it is advisable to
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The LT1529 is a 3A low dropout regulator with micropower 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
8
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 VIN 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.
5
VIN
VIN
OUTPUT
1
LT1529
4
SHDN SENSE
GND
R2
+
VOUT
2
R1
3
( )
LT1529 • F02
VOUT = 3.75V 1 + R2 + (IADJ × 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 Performance Characteristics. The reference voltage at the ADJ
pin has a positive temperature coefficient of approximately 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 (VOUT/3.75V). For example: load regulation for an
output current change of 1mA to 3A is – 0.5mV typical at
VOUT = 3.75V. At VOUT = 12V, load regulation would be:
 12V 

 ( – 0.5 mV) = ( –1.6mV )
 3.75V 
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: IOUT • (VIN – VOUT), and
2. Ground pin current multiplied by the input voltage:
IGND • VIN .
The GND pin current can be found by examining the GND
Pin Current curves in the Typical Performance Characteristics. Power dissipation will be equal to the sum of the two
components listed above.
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
THERMAL RESISTANCE
BOARD AREA (JUNCTION-TO-AMBIENT)
2500 sq. mm 2500 sq. mm
2500 sq. mm
1000 sq. mm 2500 sq. mm
2500 sq. mm
25°C/W
125 sq. mm
2500 sq. mm
33°C/W
2500 sq. mm
23°C/W
* Device is mounted on topside.
T Package, 5-Lead TO-220
Thermal Resistance (Junction-to-Case) = 2.5°C/W
The LT1529 series regulators have internal thermal limiting designed to protect the device during overload conditions. For continuous normal load 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.
Calculating Junction Temperature
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 electrically 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.
where, IOUT(MAX) = 500mA
VIN(MAX) = 5.5V
IGND at (IOUT = 500mA, VIN = 5.5V) = 3.6mA
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-
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:
IOUT(MAX) • (VIN(MAX) – VOUT) + (IGND • VIN(MAX))
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:
TJMAX = 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
3.3µF with an ESR of 2Ω or less. The LT1529 is a
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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 Response curves in the Typical Performance Characteristics.
Larger values of output capacitance will decrease the peak
deviations and provide improved output transient response for larter 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 addition to the normal protection features associated with
monolithic regulators, such as current limiting and thermal 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 operation, the junction temperature should not exceed 125°C.
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 circuits 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 VIN pin is
pulled to ground.
100
TJ = 25°C, VIN = 0V
VOUT = VSENSE
(LT1529-3.3/LT1529-5)
VOUT = VADJ (LT1529)
CURRENT FLOWS
INTO DEVICE
90
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 CURRENT (µA)
80
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.
70
60
LT1529
50
40
30
LT1529-3.3
20
LT1529-5
10
0
0
1
2
3 4 5 6 7 8
OUTPUT VOLTAGE (V)
9
10
LT1529 • F03
Figure 3. Reverse Output Current
Table 2. Fault Conditions
VIN PIN
SHDN PIN
< VOUT (Nominal)
Open (High)
Forced to VOUT (Nominal)
Reverse Output Current ≈ 15µA (See Figure 3), Input Current ≈ 1µA (See Figure 4)
< VOUT (Nominal)
Grounded
Forced to VOUT (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 < VIN < 15V
Grounded
≤0V
Output Current = 0
10
OUTPUT/SENSE PINS
LT1529
LT1529-3.3/LT1529-5
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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 VIN
pin is left open. The state of the SHDN pin will have no
effect on the reverse output current when the VIN pin is
floating.
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.
5
VOUT = 3.3V (LT1529-3.3)
VOUT = 5V (LT1529-5)
4
INPUT CURRENT (µA)
APPLICATI
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 VIN pin is forced below the OUTPUT pin or the
OUTPUT pin is pulled above the VIN pin, the input current
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PACKAGE DESCRIPTIO
LT1529-3.3
LT1529-5
3
2
1
0
0
1
3
2
INPUT VOLTAGE (V)
4
5
LT1529 • F04
Figure 4. Input Current
Dimensions in inches (millimeters) unless otherwise noted.
Q Package
5-Lead Plastic DD Pak
(LTC DWG # 05-08-1461)
0.256
(6.502)
0.060
(1.524)
TYP
0.060
(1.524)
0.390 – 0.415
(9.906 – 10.541)
0.165 – 0.180
(4.191 – 4.572)
15° TYP
0.060
(1.524)
0.183
(4.648)
0.059
(1.499)
TYP
0.330 – 0.370
(8.382 – 9.398)
BOTTOM VIEW OF DD PAK
HATCHED AREA IS SOLDER PLATED
COPPER HEAT SINK
(
+0.008
0.004 –0.004
+0.203
0.102 –0.102
)
0.095 – 0.115
(2.413 – 2.921)
0.075
(1.905)
0.300
(7.620)
0.045 – 0.055
(1.143 – 1.397)
(
+0.012
0.143 –0.020
+0.305
3.632 –0.508
)
0.057 – 0.077
(1.447 – 1.955)
0.028 – 0.038
(0.711 – 0.965)
0.013 – 0.023
(0.330 – 0.584)
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 circuits as described herein will not infringe on existing patent rights.
0.050 ± 0.012
(1.270 ± 0.305)
Q(DD5) 0396
11
LT1529
LT1529-3.3/LT1529-5
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PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
T Package
5-Lead Plastic TO-220 (Standard)
(LTC DWG # 05-08-1421)
0.390 – 0.415
(9.906 – 10.541)
0.165 – 0.180
(4.191 – 4.572)
0.147 – 0.155
(3.734 – 3.937)
DIA
0.045 – 0.055
(1.143 – 1.397)
0.230 – 0.270
(5.842 – 6.858)
0.460 – 0.500
(11.684 – 12.700)
0.570 – 0.620
(14.478 – 15.748)
0.330 – 0.370
(8.382 – 9.398)
0.620
(15.75)
TYP
0.700 – 0.728
(17.78 – 18.491)
0.095 – 0.115
(2.413 – 2.921)
0.152 – 0.202
0.260 – 0.320 (3.861 – 5.131)
(6.60 – 8.13)
0.013 – 0.023
(0.330 – 0.584)
0.057 – 0.077
(1.448 – 1.956)
0.028 – 0.038
(0.711 – 0.965)
0.135 – 0.165
(3.429 – 4.191)
0.155 – 0.195
(3.937 – 4.953)
T5 (TO-220) 0398
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DESCRIPTION
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12
Linear Technology Corporation
152935fa LT/TP 0499 2K REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 1995
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