TI TPS7A45XX

TPS7A45xx
www.ti.com ...................................................................................................................................................................................................... SLVS720 – JUNE 2008
LOW-NOISE, FAST-TRANSIENT-RESPONSE 1.5-A LDO VOLTAGE REGULATORS
FEATURES
1
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Optimized for Fast Transient Response
Output Current: 1.5 A
High Output Voltage Accuracy : 1% at 25°C
Dropout Voltage: 300 mV
Low Noise: 35 µVRMS (10 Hz to 100 kHz)
High Ripple Rejection: 68 dB
1-mA Quiescent Current
No Protection Diodes Needed
Controlled Quiescent Current in Dropout
Fixed Output Voltages: 1.5 V, 1.8 V, 2.5 V, 3.3 V
Adjustable Output from 1.21 V to 20 V
<1-µA Quiescent Current in Shutdown
Stable with 10-µF Output Capacitor
Stable with Ceramic Capacitors
Reverse-Battery Protection
No Reverse Current
Thermal Limiting
APPLICATIONS
•
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3.3-V to 2.5-V Logic Power Supplies
Post Regulator for Switching Supplies
Wireless Infrastructure
Radio-Frequency Systems
DESCRIPTION
The TPS7A45xx devices are low-dropout (LDO)
regulators optimized for fast transient response. The
device can supply 1.5 A of output current with a
dropout voltage of 300 mV. Operating quiescent
current is 1 mA, dropping to less than 1 µA in
shutdown. Quiescent current is well controlled; it does
not rise in dropout, as with many other regulators. In
addition to fast transient response, the TPS7A45xx
regulators have very low output noise, which makes
them ideal for sensitive RF supply applications.
Output voltage range is from 1.21 V to 20 V. The
TPS7A45xx regulators are stable with output
capacitors as low as 10 µF. Small ceramic capacitors
can be used without the necessary addition of ESR,
as is common with other regulators. Internal
protection
circuitry
includes
reverse-battery
protection, current limiting, thermal limiting, and
reverse-current protection. The devices are available
in fixed output voltages of 1.5 V, 1.8 V, 2.5 V, 3.3 V,
and as an adjustable device with a 1.21-V reference
voltage. The TPS7A45xx regulators are available in
the 5-pin TO-263 (KTT) package.
KTT PACKAGE
(TOP VIEW)
5
4
3
2
1
SENSE/ADJ
OUT
GND
IN
SHDN
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PowerPAD, PowerFLEX are trademarks of Texas Instruments.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2008, Texas Instruments Incorporated
TPS7A45xx
SLVS720 – JUNE 2008 ...................................................................................................................................................................................................... www.ti.com
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
ORDERING INFORMATION (1) (2)
PRODUCT
TPS7A45xxyyyz
(1)
(2)
VOUT
xx is nominal output voltage
15 = 1.5 V (PREVIEW), 18 = 1.8 V (PREVIEW), 25 = 2.5 V (PREVIEW),
33 = 3.3 V (ACTIVE), 01 = adjustable (ACTIVE)
yyy is package designator (KTT)
z is package quantity (R = 500)
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
web site at www.ti.com.
Package drawings, thermal data, and symbolization are available at www.ti.com/packaging.
ABSOLUTE MAXIMUM RATINGS (1)
over operating virtual-junction temperature range (unless otherwise noted)
Input voltage range, VIN
IN
–20 V to 20 V
OUT
–20 V to 20 V
Input-to-output differential (2)
–20 V to 20 V
SENSE
–20 V to 20 V
ADJ
–7 V to 7 V
SHDN
–20 V to 20 V
Output short-circuit duration, tshort
Indefinite
Maximum lead temperature (10-s soldering time), Tlead
300°C
Operating virtual junction temperature range, TJ
–40°C to 125°C
Storage temperature range, Tstg
–65°C to 150°C
(1)
(2)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating
Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Absolute maximum input-to-output differential voltage cannot be achieved with all combinations of rated IN pin and OUT pin voltages.
With the IN pin at 20 V, the OUT pin may not be pulled below 0 V. The total measured voltage from IN to OUT can not exceed ±20 V.
PACKAGE THERMAL DATA (1)
(1)
(2)
2
PACKAGE
BOARD
θJA
θJC
θJP (2)
TO-263 (KTT)
High K, JESD 51-5
26.5°C/W
31.8°C/W
0.38°C/W
Maximum power dissipation is a function of TJ(max), θJA, and TA. The maximum allowable power dissipation at any allowable ambient
temperature is PD = (TJ(max) – TA)/θJA. Operating at the absolute maximum TJ of 150°C can affect reliability.
For packages with exposed thermal pads, such as QFN, PowerPAD™, and PowerFLEX™, θJP is defined as the thermal resistance
between the die junction and the bottom of the exposed pad.
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ELECTRICAL CHARACTERISTICS (1)
Over operating temperature range TJ = –40°C to 125°C (unless otherwise noted)
PARAMETER
Minimum input voltage (3) (4)
VIN
TEST CONDITIONS
ILOAD = 1.5 A
Full range
2.1
2.5
VIN = 2.5 V to 20 V,
ILOAD = 1 mA to 1.5 A
VIN = 2.3 V, ILOAD = 1 mA
VIN = 2.8 V to 20 V,
ILOAD = 1 mA to 1.5 A
Regulated output voltage (5)
VIN = 3 V, ILOAD = 1 mA
TPS7A4525
VIN = 3.5 V to 20 V,
ILOAD = 1 mA to 1.5 A
VIN = 3.8 V, ILOAD = 1 mA
TPS7A4533
VIN = 4.3 V to 20 V,
ILOAD = 1 mA to 1.5 A
VIN = 2.21 V, ILOAD = 1 mA
Line regulation
25°C
1.485
1.5
1.515
Full range
1.447
1.5
1.545
25°C
1.782
1.8
1.818
Full range
1.737
1.8
1.854
25°C
2.475
2.5
2.525
Full range
2.412
2.5
2.575
25°C
3.266
3.3
3.333
3.2
3.3
3.4
Full range
25°C
1.197
1.21
1.222
VIN = 2.5 V to 20 V,
ILOAD = 1 mA to 1.5 A
Full range
1.174
1.21
1.246
TPS7A4515
ΔVIN = 2.21 V to 20 V,
ILOAD = 1 mA
Full range
2
6
TPS7A4518
ΔVIN = 2.3 V to 20 V,
ILOAD = 1 mA
Full range
2.5
7
TPS7A4525
ΔVIN = 3 V to 20 V,
ILOAD = 1 mA
Full range
3
10
TPS7A4533
ΔVIN = 3.8 V to 20 V,
ILOAD = 1 mA
Full range
3.5
10
TPS7A4501 (3)
ΔVIN = 2.21 V to 20 V,
ILOAD = 1 mA
Full range
1.5
3
TPS7A4515
VIN = 2.5 V,
ΔILOAD = 1 mA to 1.5 A
TPS7A4518
VIN = 2.8 V,
ΔILOAD = 1 mA to 1.5 A
TPS7A4525
VIN = 3.5 V,
ΔILOAD = 1 mA to 1.5 A
Full range
TPS7A4533
VIN = 4.3 V,
ΔILOAD = 1 mA to 1.5 A
-40°C to
+85°C
30
Full range
70
TPS7A4501
25°C
25°C
25°C
TPS7A4501
(2)
(3)
(4)
(5)
VIN = 2.5 V,
ΔILOAD = 1 mA to 1.5 A
UNIT
V
V
V
mV
9
18
2
Full range
25°C
(3)
2
Full range
25°C
Load regulation
(1)
MAX
1.9
TPS7A4518
ADJ pin voltage (3) (5)
TYP (2)
25°C
VIN = 2.21 V, ILOAD = 1 mA
VADJ
MIN
ILOAD = 0.5 A
TPS7A4515
VOUT
TJ
10
20
2.5
15
30
3
2
20
mV
8
-40°C to
+85°C
8
Full range
18
The TPS7A45xx regulators are tested and specified under pulse load conditions such that TJ ≈ TA. They are fully tested at TA = 25°C.
Performance at –40°C and 125°C is specified by design, characterization, and correlation with statistical process controls.
Typical values represent the likely parametric nominal values determined at the time of characterization. Typical values depend on the
application and configuration and may vary over time. Typical values are not ensured on production material.
The TPS7A4501 is tested and specified for these conditions with the ADJ pin connected to the OUT pin.
For the TPS7A4501, TPS7A4515 and TPS7A4518, dropout voltages are limited by the minimum input voltage specification under some
output voltage/load conditions.
Operating conditions are limited by maximum junction temperature. The regulated output voltage specification does 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.
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ELECTRICAL CHARACTERISTICS (continued)
Over operating temperature range TJ = –40°C to 125°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
VDO
Output voltage noise
IADJ
ADJ pin bias current (3) (9)
Shutdown threshold
ISHDN
0.085
0.10
0.17
0.180
0.13
25°C
Full range
0.300
Full range
0.450
Full range
1
1.5
ILOAD = 1 mA
Full range
1.1
1.6
ILOAD = 100 mA
Full range
3.3
3.5
ILOAD = 500 mA
Full range
15
17
ILOAD = 1.5 A
Full range
80
90
25°C
35
25°C
VOUT = OFF to ON
Full range
VOUT = ON to OFF
Full range
0.25
3
7
0.9
2
0.75
0.01
1
VSHDN = 20 V
25°C
3
20
Quiescent current in
shutdown
VIN = 6 V, VSHDN = 0 V
25°C
0.01
1
Ripple rejection
VIN – VOUT = 1.5 V (avg), VRIPPLE = 0.5 VP-P,
fRIPPLE = 120 Hz, ILOAD = 0.75 A
25°C
68
IIL
Input reverse leakage
current
Reverse output current (10)
VIN = 7 V, VOUT = 0 V
25°C
VIN = VOUT(NOMINAL) + 1
Full range
VIN = –20 V, VOUT = 0 V
Full range
mA
µVRMS
25°C
Current limit
V
0.350
ILOAD = 0 mA
COUT = 10 µF, ILOAD = 1.5 A,
BW = 10 Hz to 100 kHz
UNIT
0.250
25°C
VSHDN = 0 V
SHDN pin current
ILIMIT
IRO
0.05
Full range
ILOAD = 1.5 A
eN
MAX
0.02
0.06
25°C
ILOAD = 100 mA
Dropout voltage
VIN = VOUT(NOMINAL)
GND pin current (7) (8)
VIN = VOUT(NOMINAL) + 1
TYP (2)
Full range
ILOAD = 500 mA
IGND
MIN
25°C
ILOAD = 1 mA
(4) (6) (7)
TJ
µA
V
µA
µA
dB
2
A
1.6
300
TPS7A4515
VOUT = 1.5 V, VIN < 1.5 V
25°C
600
1000
TPS7A4518
VOUT = 1.8 V, VIN < 1.8 V
25°C
600
1000
TPS7A4525
VOUT = 2.5 V, VIN < 2.5 V
25°C
600
1000
TPS7A4533
VOUT = 3.3 V, VIN < 3.3 V
25°C
600
1000
TPS7A4501
VOUT = 1.21 V, VIN < 1.21 V
25°C
300
500
µA
µA
(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 is equal to: VIN – VDROPOUT.
(7) To satisfy requirements for minimum input voltage, the TPS7A4501 is tested and specified for these conditions with an external resistor
divider (two 4.12-kΩ resistors) for an output voltage of 2.4 V. The external resistor divider adds a 300-mA DC load on the output.
(8) GND pin current is tested with VIN = (VOUT(NOMINAL) + 1 V) and a current source load. The GND pin current decreases at higher input
voltages.
(9) ADJ pin bias current flows into the ADJ pin.
(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.
4
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DEVICE INFORMATION
TERMINAL FUNCTIONS
PIN
NO.
1
DESCRIPTION
NAME
SHDN
Shutdown. SHDN is used to put the TPS7A45xx regulators into a low-power shutdown state. The output is
off when SHDN is pulled low. SHDN can be driven either by 5-V logic or open-collector logic with a pullup
resistor. The pullup resistor is required to supply the pullup current of the open-collector gate, normally
several microamperes, and SHDN current, typically 3 mA. If unused, SHDN must be connected to VIN. The
device is in the low-power shutdown state if SHDN is not connected.
Input. Power is supplied to the device through IN. A bypass capacitor is required on this pin if the device is
more than six inches away from the main input filter capacitor. In general, the output impedance of a battery
rises with frequency, so it is advisable to include a bypass capacitor in battery-powered circuits. A bypass
capacitor in the range of 1 µF to 10 µF is sufficient. The TPS7A45xx regulators are designed to withstand
reverse voltages on IN with respect to ground and on OUT. In the case of a reverse input, which can happen
if a battery is plugged in backwards, the device acts as if there is a diode in series with its input. There is no
reverse current flow into the regulator, and no reverse voltage appears at the load. The device protects both
itself and the load.
2
IN
3
GND
Ground
4
OUT
Output. The output supplies power to the load. A minimum output capacitor of 10 µF is required to prevent
oscillations. Larger output capacitors are required for applications with large transient loads to limit peak
voltage transients.
5
ADJ
Adjust. For the adjustable version only (TPS7A4501), this is the input to the error amplifier. ADJ is internally
clamped to ±7 V. It has a bias current of 3 mA that flows into the pin. ADJ voltage is 1.21 V referenced to
ground, and the output voltage range is 1.21 V to 20 V.
SENSE
Sense. For fixed-voltage versions (TPS7A4515, TPS7A4518, TPS7A4525, and TPS7A4533), SENSE is the
input to the error amplifier. Optimum regulation is obtained at the point where SENSE is connected to the
OUT pin of the regulator. In critical applications, small voltage drops are caused by the resistance (RP) of PC
traces between the regulator and the load. These may be eliminated by connecting SENSE to the output at
the load as shown in Figure 32. Note that the voltage drop across the external PC traces adds to the
dropout voltage of the regulator. SENSE bias current is 600 mA at the rated output voltage. SENSE can be
pulled below ground (as in a dual supply system in which the regulator load is returned to a negative supply)
and still allow the device to start and operate.
5
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TYPICAL CHARACTERISTICS
DROPOUT VOLTAGE
vs
OUTPUT CURRENT
DROPOUT VOLTAGE
vs
TEMPERATURE
500
480
450
IOUT = 1.5 A
400
Dropout Voltage – mV
Dropout Voltage – mV
360
350
TA = 125°C
300
250
200
TA = 25°C
150
240
IOUT = 0.5 A
IOUT = 100 mA
120
100
50
IOUT = 1 mA
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0
-50
1.6
25
50
75
Output Current – A
Figure 1.
Figure 2.
QUIESCENT CURRENT
vs
TEMPERATURE
OUTPUT VOLTAGE
vs
TEMPERATURE
100
125
100
125
1.84
VIN = 6 V
1.4
1.3
VOUT Fixed 1.8 V
1.83
IOUT = 0 A
IOUT = 1 mA
VSHDN = VIN
1.82
1.2
1.1
Output Voltage – V
Quiescent Current – mA
0
TA – Free-Air Temperature – °C
1.5
VOUT Fixed 3.3 V
1
0.9
VOUT Adjustable
0.8
1.81
1.8
1.79
1.78
0.7
1.77
0.6
0.5
-50
6
-25
1.76
-25
0
25
50
75
100
125
-50
-25
0
25
50
75
TA – Free-Air Temperature – °C
TA – Free-Air Temperature – °C
Figure 3.
Figure 4.
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TYPICAL CHARACTERISTICS (continued)
OUTPUT VOLTAGE
vs
TEMPERATURE
OUTPUT VOLTAGE
vs
TEMPERATURE
2.58
3.38
VOUT Fixed 2.5 V
2.56
Output Voltage – V
Output Voltage – V
IOUT = 1 mA
3.34
2.54
2.52
2.5
2.48
3.32
3.3
3.28
2.46
3.26
2.44
3.24
2.42
-50
VOUT Fixed 3.3 V
3.36
IOUT = 1 mA
3.22
-25
0
25
50
75
100
-50
125
-25
TA – Free-Air Temperature – °C
Figure 5.
0
OUTPUT VOLTAGE
vs
TEMPERATURE
100
125
TJ = 25°C
VOUT Adjustable
IOUT = 1 mA
ROUT = 4.3 k W
1
VSHDN = VIN
VIN = 6 V
1.215
1.21
1.205
1.2
VOUT Adjustable
0.8
0.6
0.4
0.2
1.195
1.19
-50
75
1.2
Quiescent Current – mA
Output Voltage – V
1.22
50
QUIESCENT CURRENT
vs
INPUT VOLTAGE
1.23
1.225
25
TA – Free-Air Temperature – °C
Figure 6.
0
-25
0
25
50
75
100
125
0
2
TA – Free-Air Temperature – °C
Figure 7.
4
6
8
10
12
14
16
18
20
Input Voltage – V
Figure 8.
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TYPICAL CHARACTERISTICS (continued)
GROUND CURRENT
vs
INPUT VOLTAGE
GROUND CURRENT
vs
INPUT VOLTAGE
100
10
90
TJ = 25°C
VSHDN = VIN
VSHDN = VIN
VOUT Adjustable
80
8
VOUT Adjustable
VOUT = 1.21 V
70
VOUT = 1.21 V
60
Ground Current – mA
Ground Current – mA
TJ = 25°C
IOUT = 1.5 A
50
40
IOUT = 1 A
30
6
IOUT = 300 mA
4
IOUT = 100 mA
20
2
IOUT = 0.5 A
10
IOUT = 10 mA
0
0
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
7
Input Voltage – V
Input Voltage – V
Figure 9.
Figure 10.
GROUND CURRENT
vs
INPUT VOLTAGE
GROUND CURRENT
vs
INPUT VOLTAGE
40
8
9
10
120
TJ = 25°C
TJ = 25°C
VSHDN = VIN
35
VSHDN = VIN
100
VOUT Fixed 3.3 V
VOUT Fixed 3.3 V
Ground Current – mA
Ground Current – mA
30
25
IOUT = 300 mA
20
IOUT = 100 mA
15
IOUT = 10 mA
80
IOUT = 1.5 A
60
40
IOUT = 1 A
10
20
IOUT = 0.5 A
5
0
0
0
8
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
Input Voltage – V
Input Voltage – V
Figure 11.
Figure 12.
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8
9
10
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TYPICAL CHARACTERISTICS (continued)
GROUND CURRENT
vs
OUTPUT CURRENT
SHDN INPUT CURRENT
vs
TEMPERATURE
1
80
VIN = VOUT(nom) + 1
VSHDN = 0 V
70
SHDN Input Current – µA
Ground Current – mA
60
50
40
30
20
0.75
0.5
0.25
10
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0
-50
1.6
-25
0
25
50
75
Output Current – A
TA – Free-Air Temperature – °C
Figure 13.
Figure 14.
SHDN INPUT CURRENT
vs
SHDN INPUT VOLTAGE
SHDN THRESHOLD (OFF TO ON)
vs
TEMPERATURE
2.5
1
2.25
0.9
2
0.8
100
125
100
125
SHDN Input Voltage – V
SHDN Input Current – µA
IOUT = 1 mA
1.75
1.5
1.25
1
0.75
0.7
0.6
0.5
0.4
0.3
0.5
0.2
0.25
0.1
0
0
2
4
6
8
10
12
14
16
18
20
0
-50
-25
0
25
50
75
SHDN Input Voltage – V
TA – Free-Air Temperature – °C
Figure 15.
Figure 16.
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TYPICAL CHARACTERISTICS (continued)
SHDN THRESHOLD (ON TO OFF)
vs
TEMPERATURE
ADJ BIAS CURRENT
vs
TEMPERATURE
5
1
0.9
4.5
0.8
4
0.7
3.5
ADJ Bias Current – µA
SHDN Input Voltage – V
IOUT = 1 mA
0.6
0.5
0.4
0.3
3
2.5
2
1.5
0.2
1
0.1
0.5
0
-50
-25
0
25
50
75
100
0
-50
125
-25
0
25
50
75
TA – Free-Air Temperature – °C
Figure 17.
TA – Free-Air Temperature – °C
CURRENT LIMIT
vs
INPUT/OUTPUT DIFFERENTIAL VOLTAGE
CURRENT LIMIT
vs
TEMPERATURE
100
125
100
125
Figure 18.
3.5
5
D
?VOUT = 100 mV
VIN = 7 V
3
VOUT = 0 V
TA = -40°C
4
TA = 25°C
Current Limit – A
Current Limit – A
2.5
2
TA = 125°C
1.5
3
2
1
1
0.5
0
0
10
2
4
6
8
10
12
14
16
18
20
0
-50
Input/Output Differential Voltage – V
-25
0
25
50
75
TA – Free-Air Temperature – °C
Figure 19.
Figure 20.
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TYPICAL CHARACTERISTICS (continued)
REVERSE OUTPUT CURRENT
vs
OUTPUT VOLTAGE
REVERSE OUTPUT CURRENT
vs
TEMPERATURE
1000
12
TJ = 25°C
VIN = 0 V
VIN = 0 V
Current flows into OUT pin
Reverse Output Current – µA
Reverse Output Current – mA
10
8
VOUT Adjustable
6
VOUT = VADJ
4
2
800
600
VOUT Fixed 3.3V
VOUT = 3.3 V
400
VOUT Adjustable
200
0
VOUT Fixed 3.3 V
VOUT = 1.21 V
VOUT = VFB
-2
0
2
4
6
8
0
-50
10
-25
0
25
50
75
100
125
100
125
TA – Free-Air Temperature – °C
Figure 22.
Output Voltage – V
Figure 21.
RIPPLE REJECTION
vs
FREQUENCY
LOAD REGULATION
vs
TEMPERATURE
80
20
IOUT = 1.5 A
15
70
10
Load Regulation – mV
Ripple Rejection – dB
60
50
40
30
VIN = 2.7 V
CIN = 0
20
COUT = 10 µF
0
-5
-10
-15
VOUT Fixed 1.8 V
VOUT Fixed 2.5 V
-20
-25
IOUT = 750 mA
10
VOUT Adjustable
5
VOUT Fixed 3.3 V
-30
VRipple = 0.05 Vpp
-35
0
10
100
1000
1k
10000
10k
100000
100k
100000
1M
-50
-25
0
25
50
75
TA – Free-Air Temperature – °C
Frequency – Hz
Figure 23.
Figure 24.
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TYPICAL CHARACTERISTICS (continued)
OUTPUT NOISE VOLTAGE
vs
FREQUENCY
LOAD TRANSIENT RESPONSE
1
COUT = 10 µF
Change in
Outupt Voltage
CIN = 10 µF
IOUT = 1.5 A
VOUT Fixed 3.3 V
0.1
Load Current
Output Noise Voltage – µVRMS
VIN = 4.3 V
COUT = 10 µF
VOUT Adjustable
0.01
10
100
1k
Frequency - Hz
20 mV
VOUT
0 mV
-20 mV
500 mA
IOUT
10 mA
500 µs per division
100k
10k
Figure 25.
Figure 26.
LOAD TRANSIENT RESPONSE
VIN = 4.3 V
Change in
Outupt Voltage
CIN = 10 µF
COUT = 10 µF
VOUT
20 mV
0 mV
Load Current
-20 mV
1.5 A
IOUT
10 mA
500 µs per division
Figure 27.
12
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TYPICAL CHARACTERISTICS (continued)
LINE TRANSIENT RESPONSE
IOUT = 1.5 A
CIN = 10 µF
VIN
4.3 V
5 mV
VOUT
-5 mV
Change in
Output Voltage
5.3 V
Input Voltage
COUT = 10 µF
Figure 28.
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APPLICATION INFORMATION
The TPS7A45xx series are 1.5-A low-dropout
regulators optimized for fast transient response. The
devices are capable of supplying 1.5 A at a dropout
voltage of 300 mV. The low operating quiescent
current (1 mA) drops to less than 1 µA in shutdown.
In addition to the low quiescent current, the
TPS7A45xx regulators incorporate several protection
features that make them ideal for use in
battery-powered systems. The devices are protected
against both reverse input and reverse output
voltages. In battery-backup applications where the
output can be held up by a backup battery when the
input is pulled to ground, the TPS7A45xx acts as if it
has a diode in series with its output and prevents
reverse current flow. Additionally, in dual-supply
applications where the regulator load is returned to a
negative supply, the output can be pulled below
ground by as much as 20 V and still allow the device
to start and operate.
Typical Applications
IN
VIN > 3 V
10 µF
(see Note A)
2.5 V at 1.5 A
OUT
10 µF
(see Note A)
TPS7A4525
SHDN
SENSE
GND
Figure 29. 3.3 V to 2.5 V Regulator
R5
0.01k
VIN > 2.7 V
C1
10 µF
TPS7A4518
OUT
IN
R1
1k
+
R2
80.6k
R4
2.2k
R6
2.2k
FB
SHDN
GND
C3
1 µF
R3
2k
+
C2
3.3 µF
LOAD
R8
100k
R7
470k
-
Figure 30. Adjustable Current Source
14
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R1
0.01k
IN
VIN > 3.7 V
3.3 V at 3 A
OUT
TPS7A4533
C1
10 µF
C2
22 µF
FB
SHDN
GND
R2
0.01k
IN
OUT
R6
6.65k
TPS7A4501
SHDN FB
GND
SHDN
R7
4.12k
R3
2.2k
R4
2.2k
R5
1k
+
–
C3
0.01 µF
Figure 31. Paralleling Regulators for Higher Output Current
RP
IN
OUT
TPS7A4501
VIN
SHDN
SENSE
Load
GND
RP
Figure 32. Kelvin Sense Connection
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Adjustable Operation
The adjustable version of the TPS7A45xx has an
output voltage range of 1.21 V to 20 V. The output
voltage is set by the ratio of two external resistors as
shown in Figure 33. The device maintains the voltage
at the ADJ pin at 1.21 V referenced to ground. The
current in R1 is then equal to (1.21 V/R1), and the
current in R2 is the current in R1 plus the ADJ pin
bias current. The ADJ pin bias current, 3 µA at 25°C,
flows through R2 into the ADJ pin. The output voltage
can be calculated using the formula shown in
Figure 33. The value of R1 should be less than
4.17 kΩ 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 is zero.
IN
VOUT
OUT
TPS7A4501
R2
VIN
ADJ
GND
R1
ceramic capacitors. Ceramic capacitors are
manufactured with a variety of dielectrics, each with
different behavior over temperature and applied
voltage. The most common dielectrics used are Z5U,
Y5V, X5R and X7R. The Z5U and Y5V dielectrics are
good for providing high capacitances in a small
package, but exhibit strong voltage and temperature
coefficients. When used with a 5-V regulator, a 10-µF
Y5V capacitor can exhibit an effective value as low as
1 µF to 2 µF over the operating temperature range.
The X5R and X7R dielectrics result in more stable
characteristics and are more suitable for use as the
output capacitor. The X7R type has better stability
across temperature, while the X5R is less expensive
and is available in higher values.
Voltage and temperature coefficients are not the only
sources of problems. Some ceramic capacitors have
a piezoelectric response. A piezoelectric device
generates voltage across its terminals due to
mechanical stress, similar to the way a piezoelectric
accelerometer or microphone works. For a ceramic
capacitor the stress can be induced by vibrations in
the system or thermal transients.
Overload Recovery
R2
+ (I ADJ)(R2)
VOUT = 1.21 V )1 +
R1)
VADJ = 1.21 V
IADJ = 3 µA at 25°C
Output range = 1.21 V to 20 V
Figure 33. Adjustable Operation
The adjustable device is tested and specified with the
ADJ pin tied to the OUT pin for an output voltage of
1.21 V. Specifications for output voltages greater than
1.21 V are proportional to the ratio of the desired
output voltage to 1.21 V: VOUT/1.21 V. For example,
load regulation for an output current change of 1 mA
to 1.5 A is –3 mV (typ) at VOUT = 1.21 V. At VOUT = 5
V, load regulation is:
(5 V/1.21 V)(–3 mV) = –12.4 mV
Output Capacitance and Transient Response
The TPS7A45xx regulators are designed to be stable
with a wide range of output capacitors. The ESR of
the output capacitor affects stability, most notably
with small capacitors. A minimum output capacitor of
10 µF with an ESR of 3 Ω or less is recommended to
prevent oscillations. Larger values of output
capacitance can decrease the peak deviations and
provide improved transient response for larger load
current changes. Bypass capacitors, used to
decouple individual components powered by the
TPS7A45xx, increase the effective output capacitor
value.
Like many IC power regulators, the TPS7A45xx has
safe operating area protection. The safe area
protection
decreases
the
current
limit
as
input-to-output voltage increases and keeps the
power transistor inside a safe operating region for all
values of input-to-output voltage. The protection is
designed to provide some output current at all values
of input-to-output voltage up to the device
breakdown.
When power is first turned on, as the input voltage
rises, the output follows the input, allowing the
regulator to start up into very heavy loads. During
start up, as the input voltage is rising, the
input-to-output voltage differential is small, allowing
the regulator to supply large output currents. With a
high input voltage, a problem can occur wherein
removal of an output short does not allow the output
voltage to recover. Other regulators also exhibit this
phenomenon, so it is not unique to the TPS7A45xx.
The problem occurs with a heavy output load when
the input voltage is high and the output voltage is low.
Common situations occur immediately after the
removal of a short circuit or when the shutdown pin is
pulled high after the input voltage has already been
turned on. The load line for such a load may intersect
the output current curve at two points. If this happens,
there are two stable output operating points for the
regulator. With this double intersection, the input
power supply may need to be cycled down to zero
and brought up again to make the output recover.
Extra consideration must be given to the use of
16
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Output Voltage Noise
The TPS7A45xx regulators have been designed to
provide low output voltage noise over the 10-Hz to
100-kHz bandwidth while operating at full load.
Output voltage noise is typically 35 nV/√Hz over this
frequency bandwidth for the TPS7A4501 (adjustable
version). For higher output voltages (generated by
using a resistor divider), the output voltage noise is
gained up accordingly. This results in RMS noise
over the 10-Hz to 100-kHz bandwidth of 14 µVRMS for
the TPS7A4501, increasing to 38 µVRMS for the
TPS7A4533.
Higher values of output voltage noise may be
measured when care is not exercised with regard to
circuit layout and testing. Crosstalk from nearby
traces can induce unwanted noise onto the output of
the TPS7A45xx. Power-supply ripple rejection must
also be considered; the TPS7A45xx regulators do not
have unlimited power-supply rejection and pass a
small portion of the input noise through to the output.
Thermal Considerations
The power handling capability of the device is limited
by the maximum rated junction temperature (125°C).
The power dissipated by the device is made up of
two components:
1. Output current multiplied by the input/output
voltage differential: IOUT(VIN – VOUT)
2. GND pin current multiplied by the input voltage:
IGNDVIN.
The GND pin current can be found using the GND
Pin Current graphs in Typical Characteristics. Power
dissipation is equal to the sum of the two components
listed above.
The TPS7A45xx series regulators have internal
thermal limiting designed to protect the device during
overload conditions.
For
continuous normal
conditions, the maximum junction temperature rating
of 125°C must not be exceeded. It is important to
give careful consideration to all sources of thermal
resistance from junction to ambient. Additional heat
sources mounted nearby must also be considered.
For surface-mount devices, heat sinking is
accomplished
by
using
the
heat-spreading
capabilities of the PC board and its copper traces.
Copper board stiffeners and plated through-holes can
also be used to spread the heat generated by power
devices.
Table 1 lists thermal resistance for several different
board sizes and copper areas. All measurements
were taken in still air on 1/16" FR-4 board with 1-oz
copper.
Table 1. Thermal Data
COPPER AREA
TOPSIDE (1)
BACKSIDE
BOARD
AREA
THERMAL
RESISTANCE
(JUNCTION TO
AMBIENT)
KTT Package (5-Pin TO-263)
2
2500 mm2
2500 mm2
23°C/W
2
1000 mm
2
2500 mm
2500 mm2
25°C/W
125 mm2
2500 mm2
2500 mm2
33°C/W
2500 mm
(1)
Device is mounted on topside.
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Calculating Junction Temperature
Example: Given an output voltage of 3.3 V, an input
voltage range of 4 V to 6 V, an output current range
of 0 mA to 500 mA, and a maximum ambient
temperature of 50°C, what is the maximum junction
temperature?
The power dissipated by the device is equal to:
IOUT(MAX)(VIN(MAX) – VOUT) + IGND(VIN(MAX))
where,
IOUT(MAX) = 500 mA
VIN(MAX) = 6 V
IGND at (IOUT = 500 mA, VIN = 6 V) = 10 mA
So,
P = 500 mA × (6 V – 3.3 V) + 10 mA × 6 V = 1.41 W
Using a KTT package, the thermal resistance is in the
range of 23°C/W to 33°C/W, depending on the
copper area. So the junction temperature rise above
ambient is approximately equal to:
1.41 W × 28°C/W = 39.5°C
The maximum junction temperature is then be equal
to the maximum junction-temperature rise above
ambient plus the maximum ambient temperature or:
TJMAX = 50°C + 39.5°C = 89.5°C
Protection Features
The TPS7A45xx regulators incorporate several
protection features which make them ideal for use in
battery-powered circuits. In addition to the normal
protection features associated with monolithic
regulators, such as current limiting and thermal
limiting, the devices are protected against reverse
input voltages, reverse output voltages and reverse
voltages from output to input.
Current limit protection and thermal overload
protection are intended to protect the device against
current overload conditions at the output of the
device. For normal operation, the junction
temperature should not exceed 125°C.
The input of the device withstands reverse voltages
of 20 V. Current flow into the device is limited to less
than 1 mA (typically less than 100 µA), and no
negative voltage appears at the output. The device
protects both itself and the load. This provides
protection against batteries that can be plugged in
backward.
18
The output of the TPS7A45xx can be pulled below
ground without damaging the device. If the input is
left open circuit or grounded, the output can be pulled
below ground by 20 V. For fixed voltage versions, the
output acts like a large resistor, typically 5 kΩ or
higher, limiting current flow to typically less than 600
µA. For adjustable versions, the output acts like an
open circuit; no current flows out of the pin. If the
input is powered by a voltage source, the output
sources the short-circuit current of the device and
protects itself by thermal limiting. In this case,
grounding the SHDN pin turns off the device and
stops the output from sourcing the short-circuit
current.
The ADJ pin of the adjustable device can be pulled
above or below ground by as much as 7 V without
damaging the device. If the input is left open circuit or
grounded, the ADJ pin acts like an open circuit when
pulled below ground and like a large resistor (typically
5 kΩ) in series with a diode when pulled above
ground.
In situations where the ADJ pin is connected to a
resistor divider that would pull the ADJ pin above its
7-V clamp voltage if the output is pulled high, the ADJ
pin input current must be limited to less than 5 mA.
For example, a resistor divider is used to provide a
regulated 1.5-V output from the 1.21-V reference
when the output is forced to 20 V. The top resistor of
the resistor divider must be chosen to limit the current
into the ADJ pin to less than 5 mA when the ADJ pin
is at 7 V. The 13-V difference between OUT and ADJ
divided by the 5-mA maximum current into the ADJ
pin yields a minimum top resistor value of 2.6 kΩ.
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.
When the IN pin of the TPS7A45xx is forced below
the OUT pin or the OUT pin is pulled above the IN
pin, input current typically drops to less than 2 µA.
This can happen if the input of the device is
connected to a discharged (low voltage) battery and
the output is held up by either a backup battery or a
second regulator circuit. The state of the SHDN pin
has no effect on the reverse output current when the
output is pulled above the input.
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