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TPS74701
SBVS099G – NOVEMBER 2007 – REVISED OCTOBER 2015
TPS74701 500-mA Low-Dropout Linear Regulator With Programmable Soft-Start
1 Features
3 Description
•
•
•
•
The TPS74701 low-dropout (LDO) linear regulator
provides an easy-to-use, robust power management
solution for a wide variety of applications. Userprogrammable soft-start minimizes stress on the input
power source by reducing capacitive inrush current
on start-up. The soft-start is monotonic and wellsuited for powering many different types of
processors and ASICs. The enable input and power
good output allow easy sequencing with external
regulators. This complete flexibility permits the user to
configure a solution that meets the sequencing
requirements of FPGAs, DSPs, and other
applications with special start-up requirements.
1
•
•
•
•
•
•
VOUT Range: 0.8 V to 3.6 V
Ultralow VIN Range: 0.8 V to 5.5 V
VBIAS Range 2.7 V to 5.5 V
Low Dropout: 50 mV Typically at 500 mA, VBIAS =
5V
Power Good (PG) Output Allows Supply
Monitoring or Provides a Sequencing Signal for
Other Supplies
2% Accuracy Over Line, Load, and Temperature
Programmable Soft-Start Provides Linear Voltage
Start-Up
VBIAS Permits Low VIN Operation With Good
Transient Response
Stable With Any Output Capacitor ≥ 2.2 μF
Available in a Small 3-mm × 3-mm × 1-mm 10-Pin
Package
A precision reference and error amplifier deliver 2%
accuracy over load, line, temperature, and process.
The device is stable with any type of capacitor
greater than or equal to 2.2 μF, and is fully specified
from –40°C to 125°C. The TPS74701 is offered in a
small 3-mm × 3-mm SON-10 package for
compatibility with the TPS74801.
2 Applications
•
•
•
•
•
Device Information(1)
FPGA Applications
DSP Core and I/O Voltages
Post-Regulation Applications
Applications With Special Start-Up Time or
Sequencing Requirements
Hot-Swap and Inrush Controls
PART NUMBER
PACKAGE
TPS74701
VSON (10)
BODY SIZE (NOM)
3.00 mm × 3.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application Circuit (Adjustable)
Turnon Response
CSS = 0nF
CSS = 560pF
VIN
IN
CIN
PG
EN
VBIAS
TPS74701
R1
GND
CSS
VOUT
VOUT
OUT
SS
CBIAS
CSS = 5600pF
0.5V/div
R3
BIAS
COUT
FB
3.8V
R2
1V/div
VEN
1.8V
Time (2ms/div)
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
TPS74701
SBVS099G – NOVEMBER 2007 – REVISED OCTOBER 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
6.1
6.2
6.3
6.4
6.5
6.6
6.7
7
1
1
1
2
3
4
Absolute Maximum Ratings ...................................... 4
ESD Ratings.............................................................. 4
Recommended Operating Conditions....................... 4
Thermal Information .................................................. 5
Electrical Characteristics........................................... 6
Typical Characteristics: VEN = VIN ............................ 7
Typical Characteristics: VEN = VIN = 1.8 V, VOUT =
1.5 V......................................................................... 10
Detailed Description ............................................ 11
7.1
7.2
7.3
7.4
Overview .................................................................
Functional Block Diagram .......................................
Feature Description.................................................
Device Functional Modes........................................
11
11
11
13
8
Application and Implementation ........................ 14
8.1 Application Information............................................ 14
8.2 Typical Application .................................................. 17
9 Power Supply Recommendations...................... 18
10 Layout................................................................... 18
10.1
10.2
10.3
10.4
Layout Guidelines .................................................
Layout Example ....................................................
Power Dissipation .................................................
Estimating Junction Temperature ........................
18
18
18
19
11 Device and Documentation Support ................. 21
11.1
11.2
11.3
11.4
11.5
11.6
Device Support......................................................
Documentation Support ........................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
21
21
21
21
21
22
12 Mechanical, Packaging, and Orderable
Information ........................................................... 22
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision F (November 2010) to Revision G
•
Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation
section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and
Mechanical, Packaging, and Orderable Information section ................................................................................................. 1
Changes from Revision E (August, 2010) to Revision F
•
Page
Page
Corrected equation for Table 3............................................................................................................................................. 14
Changes from Revision D (April, 2009) to Revision E
Page
•
Revised Power Dissipation section ...................................................................................................................................... 18
•
Deleted (previously numbers) Figure 28 through Figure 30................................................................................................. 18
•
Added section ....................................................................................................................................................................... 19
2
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SBVS099G – NOVEMBER 2007 – REVISED OCTOBER 2015
5 Pin Configuration and Functions
DRC Package
10-Pin SON
Top View
IN 1
10 OUT
9 OUT
IN 2
PG 3
BIAS 4
EN 5
Thermal
Pad
8 FB
7 SS
6 GND
Pin Functions
PIN
I/O
DESCRIPTION
NAME
NO.
IN
1, 2
I
Input to the device.
EN
5
I
Enable pin. Driving this pin high enables the regulator. Driving this pin low puts the regulator
into shutdown mode. This pin must not be left unconnected.
SS
7
—
BIAS
4
I
Bias input voltage for error amplifier, reference, and internal control circuits.
Soft-Start pin. A capacitor connected on this pin to ground sets the start-up time. If this pin is
left unconnected, the regulator output soft-start ramp time is typically 200 μs.
PG
3
O
Power Good pin. An open-drain, active-high output that indicates the status of VOUT. When
VOUT exceeds the PG trip threshold, the PG pin goes into a high-impedance state. When
VOUT is below this threshold the pin is driven to a low-impedance state. A pullup resistor from
10 kΩ to 1 MΩ should be connected from this pin to a supply of up to 5.5 V. The supply can
be higher than the input voltage. Alternatively, the PG pin can be left unconnected if output
monitoring is not necessary.
FB
8
I
Feedback pin. The feedback connection to the center tap of an external resistor divider
network that sets the output voltage. This pin must not be left floating.
OUT
9, 10
O
Regulated output voltage. A small capacitor (total typical capacitance ≥ 2.2 μF, ceramic) is
needed from this pin to ground to assure stability.
NC
N/A
I
No connection. This pin can be left floating or connected to GND to allow better thermal
contact to the top-side plane.
GND
6
I
Ground
Thermal Pad
—
I
Should be soldered to the ground plane for increased thermal performance.
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6 Specifications
6.1 Absolute Maximum Ratings
At TJ = –40°C to 125°C, unless otherwise noted. All voltages are with respect to GND. (1)
MIN
MAX
UNIT
VIN, VBIAS
Input voltage
–0.3
6
V
VEN
Enable voltage
–0.3
6
V
VPG
Power good voltage
–0.3
6
V
IPG
PG sink current
0
1.5
mA
VSS
Soft-start voltage
–0.3
6
V
VFB
Feedback voltage
–0.3
6
V
VOUT
Output voltage
–0.3
VIN + 0.3
V
IOUT
Maximum output current
Internally limited
Output short-circuit duration
Indefinite
PDISS
Continuous total power dissipation
TJ
Operating junction temperature
–40
125
°C
Tstg
Storage temperature
–55
150
°C
(1)
See Thermal Information
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
6.2 ESD Ratings
VALUE
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins
V(ESD)
(1)
(2)
Electrostatic discharge
(1)
UNIT
±2000
Charged device model (CDM), per JEDEC specification JESD22-C101, all
pins (2)
±500
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
over operating junction temperature range (unless otherwise noted)
MIN
NOM
MAX
UNIT
VOUT + VDO (VIN)
VOUT + 0.3
5.5
V
0
VIN
5.5
V
VOUT + VDO (VBIAS) (2)
VOUT + 1.4 (2)
5.5
V
VIN
Input supply voltage
VEN
Enable supply voltage
VBIAS (1)
BIAS supply voltage
VOUT
Output voltage
0.8
3.3
V
IOUT
Output current
0
500
mA
COUT
Output capacitor
2.2
µF
CIN
Input capacitor (3)
1
µF
CBIAS
Bias capacitor
0.1
TJ
Operating junction temperature
–40
(1)
(2)
(3)
4
1
µF
125
°C
BIAS supply is required when VIN is below VOUT + 1.62 V.
VBIAS has a minimum voltage of 2.7 V or VOUT + VDO (VBIAS), whichever is higher.
If VIN and VBIAS are connected to the same supply, the recommended minimum capacitor for the supply is 4.7 μF.
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6.4 Thermal Information
TPS74701
THERMAL METRIC (1) (2)
DRC (VSON) (3)
UNIT
10 PINS
RθJA
Junction-to-ambient thermal resistance
41.5
°C/W
RθJC(top)
RθJB
Junction-to-case (top) thermal resistance
78
°C/W
Junction-to-board thermal resistance
N/A
°C/W
ψJT
Junction-to-top characterization parameter
0.7
°C/W
ψJB
Junction-to-board characterization parameter
11.3
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
6.6
°C/W
(1)
(2)
(3)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
For thermal estimates of this device based on PCB copper area, see the TI PCB Thermal Calculator.
Thermal data for the DRC package are derived by thermal simulations based on JEDEC-standard methodology as specified in the
JESD51 series. The following assumptions are used in the simulations:
(a) The exposed pad is connected to the PCB ground layer through a 3×2 thermal via array.
(b) The top and bottom copper layers are assumed to have a 20% thermal conductivity of copper representing a 20% copper coverage.
(c) This data were generated with only a single device at the center of a JEDEC high-K (2s2p) board with 3-inches × 3-inches copper
area. To understand the effects of the copper area on thermal performance, see the Power Dissipation and Estimating Junction
Temperature sections.
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6.5 Electrical Characteristics
At VEN = 1.1 V, VIN = VOUT + 0.3V, CBIAS = 0.1 μF, CIN = COUT = 10 μF, CNR = 1 nF, IOUT = 50 mA, VBIAS = 5 V, and TJ = –40°C
to 125°C, unless otherwise noted. Typical values are at TJ = 25°C.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VIN
Input voltage range
VBIAS
Bias pin voltage range
VREF
Internal reference
(Adjustable)
TJ = 25°C
Output voltage range
VIN = 5 V, IOUT = 500 mA
VREF
Accuracy (1)
2.97 V ≤ VBIAS ≤ 5.5 V,
50 mA ≤ IOUT ≤ 500 mA
–2%
VOUT/VIN
Line regulation
VOUT (NOM) + 0.3 ≤ VIN ≤ 5.5 V
0.03
%/V
VOUT/IOUT
Load regulation
50 mA ≤ IOUT ≤ 500 mA
0.09
%/A
VOUT
VIN dropout voltage
VDO
(2)
ICL
Current limit
VOUT = 80% × VOUT (NOM)
IBIAS
Bias pin current
ISHDN
Shutdown supply current
(IGND)
IFB
Feedback pin current
Power-supply rejection
(VBIAS to VOUT)
V
2.7
5.5
V
0.804
V
3.6
V
IOUT = 500 mA,
VBIAS – VOUT (NOM) ≥ 1.62 V (3)
IOUT = 500 mA, VIN = VBIAS
PSRR
5.5
0.796
VBIAS dropout voltage (2)
Power-supply rejection
(VIN to VOUT)
VOUT + VDO
0.8
±0.5%
50
120
mV
1.31
1.39
V
800
VEN ≤ 0.4 V
–1
2%
1350
mA
1
2
mA
1
50
μA
0.150
1
μA
1 kHz, IOUT = 500 mA,
VIN = 1.8 V, VOUT = 1.5 V
60
300 kHz, IOUT = 500 mA,
VIN = 1.8 V, VOUT = 1.5 V
30
1 kHz, IOUT = 500 mA,
VIN = 1.8 V, VOUT = 1.5 V
50
300 kHz, IOUT = 500 mA,
VIN = 1.8 V, VOUT = 1.5 V
30
dB
dB
Noise
Output noise voltage
100 Hz to 100 kHz,
IOUT = 500 mA, CSS = 0.001 μF
tSTR
Minimum start-up time
RLOAD for IOUT = 1 A, CSS = open
200
μs
ISS
Soft-start charging current
VSS = 0.4 V
440
nA
μVRMS
25 × VOUT
VEN,
HI
Enable input high level
VEN,
LO
Enable input low level
VEN,
HYS
Enable pin hysteresis
50
mV
VEN,
DG
Enable pin deglitch time
20
μs
IEN
Enable pin current
VEN = 5 V
VIT
PG trip threshold
VOUT decreasing
VHYS
PG trip hysteresis
VPG, LO
PG output low voltage
IPG = 1 mA (sinking), VOUT < VIT
IPG, LKG
PG leakage current
VPG = 5.25 V, VOUT > VIT
TJ
Operating junction
temperature
TSD
Thermal shutdown
temperature
(1)
(2)
(3)
6
1.1
5.5
0
0.4
85
V
V
0.1
1
μA
90
94
%VOUT
3
0.1
–40
Shutdown, temperature increasing
165
Reset, temperature decreasing
140
%VOUT
0.3
V
1
μA
125
°C
°C
Adjustable devices tested at 0.8 V; resistor tolerance is not taken into account.
Dropout is defined as the voltage from VIN to VOUT when VOUT is 3% less than nominal.
1.62 V is a test condition of this device and can be adjusted by referring to Figure 6.
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6.6 Typical Characteristics: VEN = VIN
0.20
0.5
0.15
0.4
0.3
0.10
Change in VOUT (%)
Change in VOUT (%)
At TJ = 25°C, VIN = VOUT(TYP) + 0.3 V, VBIAS = 5 V, IOUT = 50 mA, VEN = VIN, CIN = 1 μF, CBIAS = 4.7 μF, and COUT = 10 μF,
unless otherwise noted.
-40°C
0.05
0
+25°C
-0.05
+125°C
-0.01
0.2
-40°C
0.1
0
-0.1
+125°C
-0.2
+25°C
-0.3
-0.15
-0.4
-0.20
-0.5
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0.5
5.0
1.0
1.5
2.0
VIN - VOUT (V)
2.5
3.0
3.5
4.0
VBIAS - VOUT (V)
Figure 1. VIN Line Regulation
Figure 2. VBIAS Line Regulation
1.2
0.5
0.4
0.3
Change in VOUT (%)
Change in VOUT (%)
1.0
0.8
0.6
0.4
0.2
+125°C
0.1
0
-0.1
-40°C
+25°C
-0.2
-0.3
0.2
-0.4
0
-0.5
0
10
20
30
40
0
50
100
500
Figure 4. Load Regulation
200
90
180
80
160
VDO (VIN - VOUT) (mV)
VDO (VIN - VOUT) (mV)
Figure 3. Load Regulation
70
60
50
40
+125°C
+25°C
20
400
IOUT (mA)
100
30
300
200
IOUT (mA)
IOUT = 0.5A
140
120
100
+25°C
80
+125°C
60
40
10
-40°C
20
-40°C
0
0
100
200
300
400
0
500
0
IOUT (mA)
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
VBIAS - VOUT (V)
Figure 5. Dropout Voltage vs IOUT and Temperature (TJ)
Figure 6. Dropout Voltage vs (VBIAS – VOUT) and
Temperature (TJ)
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Typical Characteristics: VEN = VIN (continued)
At TJ = 25°C, VIN = VOUT(TYP) + 0.3 V, VBIAS = 5 V, IOUT = 50 mA, VEN = VIN, CIN = 1 μF, CBIAS = 4.7 μF, and COUT = 10 μF,
unless otherwise noted.
2200
Power-Supply Rejection Ratio (dB)
90
VDO (VBIAS - VOUT) (mV)
2000
1800
1600
1400
+125°C
1200
1000
+25°C
-40°C
800
600
80
IOUT = 0.1A
70
60
50
40
IOUT = 0.5A
30
VIN = 1.8V
VOUT = 1.2V
VBIAS = 5V
CSS = 1nF
20
10
0
0
100
300
200
400
500
10
100
1k
IOUT (mA)
Figure 7. VBIAS Dropout Voltage vs IOUT and Temperature
(TJ)
60
IOUT = 100mA
50
40
30
VIN = 1.8V
VOUT = 1.2V
COUT = 10mF
CSS = 1nF
20
10
100
IOUT = 500mA
Power-Supply Rejection Ratio (dB)
Power-Supply Rejection Ratio (dB)
70
10
10M
80
1kHz
70
60
10kHz
50
40
100kHz
30
500kHz
20
VOUT = 1.2V
IOUT = 500mA
CSS = 1nF
10
0
1k
10k
100k
1M
0
10M
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00 2.25
VIN - VOUT (V)
Frequency (Hz)
Figure 9. VIN PSRR vs Frequency
Figure 10. VIN PSRR vs (VIN – VOUT)
2.0
IOUT = 100mA
VOUT = 1.2V
1.8
+125°C
1.6
1.4
IBIAS (mA)
Output Spectral Noise Density (mV/ÖHz)
1M
90
80
0
CSS = 0nF
0.1
CSS = 10nF
1.2
1.0
0.8
+25°C
0.6
CSS = 1nF
-40°C
0.4
0.2
0
0.01
100
1k
10k
100k
0
100
200
300
400
500
IOUT (mA)
Frequency (Hz)
Figure 11. Noise Spectral Density
8
100k
Figure 8. VBIAS PSRR vs Frequency
90
1
10k
Frequency (Hz)
Figure 12. BIAS Pin Current vs IOUT and Temperature (TJ)
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Typical Characteristics: VEN = VIN (continued)
At TJ = 25°C, VIN = VOUT(TYP) + 0.3 V, VBIAS = 5 V, IOUT = 50 mA, VEN = VIN, CIN = 1 μF, CBIAS = 4.7 μF, and COUT = 10 μF,
unless otherwise noted.
2.0
500
1.8
475
+125°C
1.6
450
1.2
ISS (nA)
IBIAS (mA)
1.4
+25°C
1.0
0.8
425
400
375
0.6
-40°C
0.4
350
325
0.2
300
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
-50
0
-25
VBIAS (V)
Figure 13. BIAS Pin Current vs VBIAS and Temperature (TJ)
50
75
100
125
Figure 14. Soft-Start Charging Current (ISS) vs Temperature
(TJ)
1.0
1.5
0.9
1.4
0.8
1.3
0.7
1.2
Current Limit (A)
VOL Low-Level PG Voltage (V)
25
Junction Temperature (°C)
0.6
0.5
0.4
0.3
+125°C
1.1
1.0
-40°C
0.9
+25°C
0.8
0.2
0.7
0.1
0.6
0
VOUT = 0.8V
0.5
0
2
4
6
8
10
12
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
VBIAS - VOUT (V)
PG Current (mA)
Figure 15. Low-Level PG Voltage vs Current
Figure 16. Current Limit vs (VBIAS – VOUT)
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6.7 Typical Characteristics: VEN = VIN = 1.8 V, VOUT = 1.5 V
At TJ = 25°C, VIN = VOUT(TYP) + 0.3 V, VBIAS = 5 V, IOUT = 50 mA, VEN = VIN = 1.8 V, VOUT = 1.5 V, CIN = 1 μF, CBIAS = 4.7 μF,
and COUT = 10 μF, unless otherwise noted.
CSS = 1nF
COUT = 2.2mF (Ceramic)
COUT = 2.2mF (Ceramic)
50mV/div
50mV/div
CSS = 1nF
3.8V
5.0V
1V/div
1V/div
1V/ms
3.3V
1V/ms
1.8V
Time (50ms/div)
Time (50ms/div)
Figure 17. VBIAS Line Transient
Figure 18. VIN Line Transient
CSS = 0nF
COUT = 470mF (OSCON)
100mV/div
CSS = 560pF
CSS = 1nF
CSS = 5600pF
0.5V/div
VOUT
100mV/div
COUT = 10mF (Ceramic)
100mV/div
3.8V
COUT = 2.2mF (Ceramic)
1V/div
500mA/div
VEN
1.8V
1A/ms
50mA
Time (50ms/div)
Time (2ms/div)
Figure 19. Output Load Transient Response
Figure 20. Turnon Response
1V/div
VIN = VBIAS = VEN
VOUT
VPG
Time (20ms/div)
Figure 21. Power Up and Power Down
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7 Detailed Description
7.1 Overview
The TPS74701 belongs to a family of low-dropout regulators that feature soft-start capability. These regulators
use a low current bias input to power all internal control circuitry, allowing the NMOS pass transistor to regulate
very low input and output voltages.
The use of an NMOS-pass FET offers several critical advantages for many applications. Unlike a PMOS topology
device, the output capacitor has little effect on loop stability. This architecture allows the TPS74701 to be stable
with any capacitor type of value 2.2 μF or greater. Transient response is also superior to PMOS topologies,
particularly for low VIN applications.
The TPS74701 features a programmable voltage-controlled soft-start circuit that provides a smooth, monotonic
start-up and limits start-up inrush currents that may be caused by large capacitive loads. A power good (PG)
output is available to allow supply monitoring and sequencing of other supplies. An enable (EN) pin with
hysteresis and deglitch allows slow-ramping signals to be used for sequencing the device. The low VIN and
VOUT capability allows for inexpensive, easy-to-design, and efficient linear regulation between the multiple
supply voltages often present in processor-intensive systems.
7.2 Functional Block Diagram
IN
Current
Limit
BIAS
UVLO
OUT
Thermal
Limit
0.44mA
VOUT
R1
SS
CSS
Soft-Start
Discharge
0.8V
Reference
FB
PG
EN
Hysteresis
and Deglitch
R2
0.9 ´ VREF
GND
7.3 Feature Description
7.3.1 Programmable Soft-Start
The TPS74701 features a programmable, monotonic, voltage-controlled soft-start that is set with an external
capacitor (CSS). This feature is important for many applications because it eliminates power-up initialization
problems when powering FPGAs, DSPs, or other processors. The controlled voltage ramp of the output also
reduces peak inrush current during start-up, minimizing start-up transient events to the input power bus.
To achieve a linear and monotonic soft-start, the TPS74701 error amplifier tracks the voltage ramp of the
external soft-start capacitor until the voltage exceeds the internal reference. The soft-start ramp time depends on
the soft-start charging current (ISS), soft-start capacitance (CSS), and the internal reference voltage (VREF), and
can be calculated using Equation 1:
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Feature Description (continued)
tSS =
(VREF ´ CSS)
ISS
(1)
If large output capacitors are used, the device current limit (ICL) and the output capacitor may set the start-up
time. In this case, the start-up time is given by Equation 2:
(VOUT(NOM) ´ COUT)
tSSCL =
ICL(MIN)
where
•
•
•
VOUT(NOM) is the nominal output voltage
COUT is the output capacitance
ICL(MIN) is the minimum current limit for the device
(2)
In applications where monotonic start-up is required, the soft-start time given by Equation 1 should be set greater
than Equation 2.
The maximum recommended soft-start capacitor is 0.015 μF. Larger soft-start capacitors can be used, and they
do not damage the device; however, the soft-start capacitor discharge circuit may not be able to fully discharge
the soft-start capacitor when enabled.
Soft-start capacitors larger than 0.015 μF could be a problem in applications where it is necessary to rapidly
pulse the enable pin and still require the device to soft-start from ground. CSS must be low-leakage; X7R, X5R, or
C0G dielectric materials are preferred. See Table 3 for suggested soft-start capacitor values.
7.3.2 Enable and Shutdown
The enable (EN) pin is active high and is compatible with standard digital signaling levels. VEN below 0.4 V turns
the regulator off, while VEN above 1.1 V turns the regulator on. Unlike many regulators, the enable circuitry has
hysteresis and deglitching for use with relatively slowly ramping analog signals. This configuration allows the
TPS74701 to be enabled by connecting the output of another supply to the EN pin. The enable circuitry typically
has 50 mV of hysteresis and a deglitch circuit to help avoid on-off cycling as a result of small glitches in the VEN
signal.
The enable threshold is typically 0.8 V and varies with temperature and process variations. Temperature
variation is approximately –1 mV/°C; process variation accounts for most of the rest of the variation to the 0.4-V
and 1.1-V limits. If precise turnon timing is required, a fast rise-time signal must be used to enable the
TPS74701.
If not used, EN can be connected to either IN or BIAS. If EN is connected to IN, it should be connected as close
as possible to the largest capacitance on the input to prevent voltage droops on that line from triggering the
enable circuit.
7.3.3 Power Good
The power good (PG) pin is an open-drain output and can be connected to any 5.5 V or lower rail through an
external pullup resistor. This pin requires at least 1.1 V on VBIAS to have a valid output. The PG output is highimpedance when VOUT is greater than VIT + VHYS. If VOUT drops below VIT or if VBIAS drops below 1.9 V, the opendrain output turns on and pulls the PG output low. The PG pin also asserts when the device is disabled. The
recommended operating condition of the PG pin sink current is up to 1 mA, so the pullup resistor for PG should
be in the range of 10 kΩ to 1 MΩ. If output voltage monitoring is not needed, the PG pin can be left floating.
7.3.4 Internal Current Limit
The TPS74701 features a factory-trimmed, accurate current limit that is flat over temperature and supply voltage.
The current limit allows the device to supply surges of up to 1 A and maintain regulation. The current limit
responds in about 10 μs to reduce the current during a short-circuit fault.
The internal current limit protection circuitry of the TPS74701 is designed to protect against overload conditions.
It is not intended to allow operation above the rated current of the device. Continuously running the TPS74701
above the rated current degrades device reliability.
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Feature Description (continued)
7.3.5 Thermal Shutdown
Thermal protection disables the output when the junction temperature rises to approximately 160°C, allowing the
device to cool. When the junction temperature cools to approximately 140°C, the output circuitry is enabled.
Depending on power dissipation, thermal resistance, and ambient temperature the thermal protection circuit may
cycle on and off. This cycling limits the dissipation of the regulator, protecting it from damage as a result of
overheating.
Activation of the thermal protection circuit indicates excessive power dissipation or inadequate heatsinking. For
reliable operation, junction temperature should be limited to 125°C maximum. To estimate the margin of safety in
a complete design (including heatsink), increase the ambient temperature until thermal protection is triggered;
use worst-case loads and signal conditions. For good reliability, thermal protection should trigger at least 40°C
above the maximum expected ambient condition of the application. This condition produces a worst-case junction
temperature of 125°C at the highest expected ambient temperature and worst-case load.
The internal protection circuitry of the TPS74701 is designed to protect against overload conditions. It is not
intended to replace proper heatsinking. Continuously running the TPS74701 into thermal shutdown degrades
device reliability.
7.4 Device Functional Modes
7.4.1 Normal Operation
The device regulates to the nominal output voltage under the following conditions:
•
•
•
•
The input voltage and bias voltage are both at least at the respective minimum specifications.
The enable voltage has previously exceeded the enable rising threshold voltage and has not decreased
below the enable falling threshold.
The output current is less than the current limit.
The device junction temperature is less than the maximum specified junction temperature.
7.4.2 Dropout Operation
If the input voltage is lower than the nominal output voltage plus the specified dropout voltage, but all other
conditions are met for normal operation, the device operates in dropout mode. In this condition, the output
voltage is the same as the input voltage minus the dropout voltage. The transient performance of the device is
significantly degraded because the pass device is in a triode state and no longer controls the current through the
LDO. Line or load transients in dropout can result in large output voltage deviations.
7.4.3 Disabled
The device is disabled under the following conditions:
• The input or bias voltages are below the respective minimum specifications.
• The enable voltage is less than the enable falling threshold voltage or has not yet exceeded the enable rising
threshold.
• The device junction temperature is greater than the thermal shutdown temperature.
Table 1 shows the conditions that lead to the different modes of operation.
Table 1. Device Functional Mode Comparison
OPERATING MODE
PARAMETER
VIN
VEN
VBIAS
IOUT
TJ
Normal mode
VIN > VOUT(nom) + VDO (VIN)
VEN > VEN, HI
VBIAS ≥ VOUT + 1.39 V
I OUT < ICL
T J < 125°C
Dropout mode
VIN < VOUT(nom) + VDO (VIN)
VEN > VEN, HI
VBIAS < VOUT + 1.39 V
—
TJ < 125°C
VIN < VIN(min)
VEN < VEN, LO
VBIAS < VBIAS(min)
—
TJ > 165°C
Disabled mode
(any true condition disables
the device)
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8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
R1 and R2 can be calculated for any output voltage using the formula shown in Figure 25. See Table 2 for
sample resistor values of common output voltages. To achieve the maximum accuracy specifications, R2 should
be less than or equal to 4.99 kΩ.
Table 2. Standard 1% Resistor Values for Programming
the Output Voltage (1)
(1)
R1 (kΩ)
R2 (kΩ)
VOUT (V)
Short
Open
0.8
0.619
4.99
0.9
1.13
4.53
1
1.37
4.42
1.05
1.87
4.99
1.1
2.49
4.99
1.2
4.12
4.75
1.5
3.57
2.87
1.8
3.57
1.69
2.5
3.57
1.15
3.3
VOUT = 0.8 × (1 + R1/R2).
Table 3. Standard Capacitor Values for Programming
the Soft-Start Time (1)
tSS(s) =
(1)
CSS
SOFT-START TIME
Open
0.1 ms
270 pF
0.5 ms
560 pF
1 ms
2.7 nF
5 ms
5.6 nF
10 ms
0.01 μF
18 ms
VREF × CSS 0.8V × CSS(F)
=
0.44mA
ISS
where tSS(s) = soft-start
time in seconds.
8.1.1 Input, Output, and Bias Capacitor Requirements
The device is designed to be stable for all available types and values of output capacitors greater than or equal
to 2.2 μF. The device is also stable with multiple capacitors in parallel, which can be of any type or value.
The capacitance required on the IN and BIAS pins strongly depends on the input supply source impedance. To
counteract any inductance in the input, the minimum recommended capacitor for VIN and VBIAS is 1 μF. If VIN and
VBIAS are connected to the same supply, the recommended minimum capacitor for VBIAS is 4.7 μF. Good quality,
low ESR capacitors should be used on the input; ceramic X5R and X7R capacitors are preferred. These
capacitors should be placed as close the pins as possible for optimum performance.
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8.1.2 Transient Response
The TPS74701 was designed to have excellent transient response for most applications with a small amount of
output capacitance. In some cases, the transient response may be limited by the transient response of the input
supply. This limitation is especially true in applications where the difference between the input and output is less
than 300 mV. In this case, adding additional input capacitance improves the transient response much more than
just adding additional output capacitance would do. With a solid input supply, adding additional output
capacitance reduces undershoot and overshoot during a transient event; see Figure 19 in the Typical
Characteristics: VEN = VIN section. Because the TPS74701 is stable with output capacitors as low as 2.2 μF,
many applications may then need very little capacitance at the LDO output. For these applications, local bypass
capacitance for the powered device may be sufficient to meet the transient requirements of the application. This
design reduces the total solution cost by avoiding the need to use expensive, high-value capacitors at the LDO
output.
8.1.3 Dropout Voltage
The TPS74701 offers very low dropout performance, making it well-suited for high-current, low VIN/low VOUT
applications. The low dropout of the TPS74701 allows the device to be used in place of a DC-DC converter and
still achieve good efficiency. This feature provides designers with the power architecture for their applications to
achieve the smallest, simplest, and lowest cost solution.
There are two different specifications for dropout voltage with the TPS74701. The first specification (shown in
Figure 22) is referred to as VIN Dropout and is used when an external bias voltage is applied to achieve low
dropout. This specification assumes that VBIAS is at least 1.39 V (2) above VOUT, which is the case for VBIAS when
powered by a 3.3-V rail with 5% tolerance and with VOUT = 1.5 V. If VBIAS is higher than VOUT +1.39 V(1), VIN
dropout is less than specified.
BIAS
IN
VBIAS = 5V ±5%
VIN = 1.8V
VOUT = 1.5V
IOUT = 500 mA
Efficiency = 83%
OUT
Reference
VOUT
COUT
FB
Simplified Block Diagram
Figure 22. Typical Application of the TPS74701 Using an Auxiliary Bias Rail
VIN
BIAS
IN
VBIAS = 3.3V ±5%
VIN = 3.3V ± 5V
VOUT = 1.5V
Reference
IOUT = 500 mA
Efficiency = 45%
OUT
VOUT
COUT
FB
Simplified Block Diagram
Figure 23. Typical Application of the TPS74701 Without an Auxiliary Bias Rail
(2)
1.62 V is a test condition of this device and can be adjusted by referring to Figure 6.
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The second specification (shown in Figure 23) is referred to as VBIAS Dropout and applies to applications where
IN and BIAS are tied together. This option allows the device to be used in applications where an auxiliary bias
voltage is not available or low dropout is not required. Dropout is limited by BIAS in these applications because
VBIAS provides the gate drive to the pass FET; therefore, VBIAS must be 1.39-V above VOUT. Because of this
usage, IN and BIAS tied together easily consume huge power. Pay attention not to exceed the power rating of
the IC package.
8.1.4 Sequencing Requirements
VIN, VBIAS, and VEN can be sequenced in any order without causing damage to the device. However, for the softstart function to work as intended, certain sequencing rules must be applied. Connecting EN to IN is acceptable
for most applications, as long as VIN is greater than 1.1 V and the ramp rate of VIN and VBIAS is faster than the
set soft-start ramp rate. If the ramp rate of the input sources is slower than the set soft-start time, the output
tracks the slower supply minus the dropout voltage until it reaches the set output voltage. If EN is connected to
BIAS, the device soft-starts as programmed, provided that VIN is present before VBIAS. If VBIAS and VEN are
present before VIN is applied and the set soft-start time has expired, then VOUT tracks VIN. If the soft-start time
has not expired, the output tracks VIN until VOUT reaches the value set by the charging soft-start capacitor.
Figure 24 shows the use of an RC-delay circuit to hold off VEN until VBIAS has ramped. This technique can also
be used to drive EN from VIN. An external control signal can also be used to enable the device after VIN and
VBIAS are present.
NOTE
When VBIAS and VEN are present and VIN is not supplied, this device outputs approximately
50 μA of current from OUT. Although this condition does not cause any damage to the
device, the output current may charge up the OUT node if total resistance between OUT
and GND (including external feedback resistors) is greater than 10 kΩ.
VIN
IN
VOUT
OUT
R1
CIN
BIAS TPS74701
FB
EN
SS
COUT
R2
R
VBIAS
CBIAS
C
GND
CSS
Figure 24. Soft-Start Delay Using an RC Circuit to Enable the Device
8.1.5 Output Noise
The TPS74701 provides low-output noise when a soft-start capacitor is used. When the device reaches the end
of the soft-start cycle, the soft-start capacitor serves as a filter for the internal reference. By using a 0.001-μF
soft-start capacitor, the output noise is reduced by half and is typically 30 μVRMS for a 1.2-V output (10 Hz to 100
kHz). Further increasing CSS has little effect on noise. Because most of the output noise is generated by the
internal reference, the noise is a function of the set output voltage. The RMS noise with a 0.001-μF soft-start
capacitor is given in Equation 3:
(
VN(mVRMS) = 25
mVRMS
V
)x V
OUT(V)
(3)
The low-output noise of the TPS74701 makes it a good choice for powering transceivers, PLLs, or other noisesensitive circuitry.
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8.2 Typical Application
Figure 25 illustrates the typical application circuit for the TPS74701 adjustable output device.
VIN
IN
CIN
1mF
PG
R3
BIAS
EN
VBIAS
TPS74701
R1
SS
CBIAS
1mF
VOUT
OUT
COUT
10mF
FB
GND
CSS
R2
(
VOUT = 0.8 ´ 1 +
R1
R2
)
Figure 25. Typical Application Circuit for the TPS74701 (Adjustable)
8.2.1 Design Requirements
Table 4 shows the design parameters for this application.
Table 4. Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
VIN
1.8 V ± 10%
VBIAS
3.3 V ±10%
VOUT
1.5 V ± 3%
IOUT
500 mA
Start-up time
< 2 ms
8.2.2 Detailed Design Procedure
1. Select R1 and R2 based on the required output voltage. Table 2 gives example calculations for many
common output voltages.
2. Select CSS to be the highest capacitance while still achieving the desired start-up time. Table 3 gives
examples of this calculation.
3. Select a minimum of a 2.2-µF ceramic output capacitor. Increased output capacitance will help the output
load transient response. Figure 27 gives examples of the load transient response with different output
capacitor values and types.
8.2.3 Application Curves
CSS = 0nF
COUT = 470mF (OSCON)
100mV/div
CSS = 560pF
CSS = 1nF
CSS = 5600pF
0.5V/div
VOUT
100mV/div
COUT = 10mF (Ceramic)
100mV/div
3.8V
COUT = 2.2mF (Ceramic)
1V/div
500mA/div
VEN
1.8V
1A/ms
50mA
Time (50ms/div)
Time (2ms/div)
Figure 26. Output Load Transient Response
Figure 27. Turnon Response
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9 Power Supply Recommendations
The TPS74701 is designed to operate from an input voltage up to 5.5 V, provided the bias rail is at least 1.39-V
higher than the input supply and dropout requirements are met. The bias rail and the input supply should both
provide adequate headroom and current for the device to operate normally. Connect a low-output impedance
power supply directly to the IN pin of the TPS74701. This supply must have at least 1 μF of capacitance near the
IN pin for optimal performance. A supply with similar requirements must also be connected directly to the bias rail
with a separate 1-μF or larger capacitor. If the IN pin is tied to the bias pin, a minimum 4.7 μF of capacitance is
needed for performance. To increase the overall PSRR of the solution at higher frequencies, use a pi-filter or
ferrite bead before the input capacitor.
10 Layout
10.1 Layout Guidelines
An optimal layout can greatly improve transient performance, PSRR, and noise. To minimize the voltage droop
on the input of the device during load transients, connect the capacitance on IN, OUT and BIAS as close as
possible to the device. If BIAS is connected to IN, connect BIAS as close to the input supply as possible. This
connection minimizes the voltage droop on BIAS during transient conditions and can improve the turnon
response.
10.2 Layout Example
CIN
Input GND Plane
IN
1
10
OUT
Vin
CBIAS
IN
2
9
OUT
PG
3
8
FB
BIAS
4
7
SS
EN
5
6
GND
Vout
COUT
R1
Css
R2
Output GND Plane
Note: CIN, COUT,and CBIAS are 0603 case size capacitors, while CSS, R1, and R2 are 0402 case size.
Figure 28. TPS547 Layout Recommendation
10.3 Power Dissipation
An optimal layout can greatly improve transient performance, PSRR, and noise. To minimize the voltage drop on
the input of the device during load transients, the capacitance on IN and BIAS should be connected as close as
possible to the device. This capacitance also minimizes the effects of parasitic inductance and resistance of the
input source and can therefore improve stability. To achieve optimal transient performance and accuracy, the top
side of R1 in Figure 25 should be connected as close as possible to the load. If BIAS is connected to IN, TI
recommends connecting BIAS as close to the sense point of the input supply as possible. This connection
minimizes the voltage drop on BIAS during transient conditions and can improve the turnon response.
Knowing the device power dissipation and proper sizing of the thermal plane that is connected to the thermal pad
is critical to avoiding thermal shutdown and ensuring reliable operation. Power dissipation of the device depends
on input voltage and load conditions and can be calculated using Equation 4:
PD = (VIN - VOUT) ´ IOUT
(4)
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Power Dissipation (continued)
Power dissipation can be minimized and greater efficiency can be achieved by using the lowest possible input
voltage necessary to achieve the required output voltage regulation.
On the SON (DRC) package, the primary conduction path for heat is through the exposed pad to the printedcircuit-board (PCB). The pad can be connected to ground or be left floating; however, it should be attached to an
appropriate amount of copper PCB area to ensure the device does not overheat. The maximum junction-toambient thermal resistance depends on the maximum ambient temperature, maximum device junction
temperature, and power dissipation of the device and can be calculated using Equation 5:
(+125°C - TA)
RqJA =
PD
(5)
Knowing the maximum RθJA, the minimum amount of PCB copper area needed for appropriate heatsinking can
be estimated using Figure 29.
140
120
qJA (°C/W)
100
80
60
40
20
0
0
Note:
1
2
4
5
7
3
6
Board Copper Area (in2)
8
9
10
θJA value at board size of 9in2 (that is, 3 inches × 3 inches) is a JEDEC standard.
Figure 29. θJA vs Board Size
Figure 29 shows the variation of θJA as a function of ground plane copper area in the board. It is intended only as
a guideline to demonstrate the effects of heat spreading in the ground plane and should not be used to estimate
actual thermal performance in real application environments.
NOTE
When the device is mounted on an application PCB, TI strongly recommends using ΨJT
and ΨJB, as explained in the section.
10.4 Estimating Junction Temperature
Using the thermal metrics ΨJT and ΨJB, as shown in the Thermal Information table, the junction temperature can
be estimated with corresponding formulas (given in Equation 6). For backwards compatibility, an older θJC,Top
parameter is listed as well.
YJT: TJ = TT + YJT · PD
YJB: TJ = TB + YJB · PD
where
•
•
•
PD is the power dissipation shown by Equation 5.
TT is the temperature at the center-top of the IC package.
TB is the PCB temperature measured 1mm away from the IC package on the PCB surface (as Figure 31
shows).
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Estimating Junction Temperature (continued)
NOTE
Both TT and TB can be measured on actual application boards using a thermo-gun (an
infrared thermometer).
For more information about measuring TT and TB, see the application note SBVA025, Using New Thermal
Metrics, available for download at www.ti.com.
By looking at Figure 30, the new thermal metrics (ΨJT and ΨJB) have very little dependency on board size. That
is, using ΨJT or ΨJB with Equation 6 is a good way to estimate TJ by simply measuring TT or TB, regardless of the
application board size.
12
YJB
YJT and YJB (°C/W)
10
8
6
4
2
YJT
0
0
1
2
3
4
5
6
7
9
8
10
Board Copper Area (in2)
Figure 30. ΨJT and ΨJB vs Board Size
For a more detailed discussion of why TI does not recommend using θJC(top) to determine thermal characteristics,
see application report SBVA025, Using New Thermal Metrics, available for download at www.ti.com. For further
information, see application report SPRA953, Semiconductor and IC Package Thermal Metrics, also available on
the TI website.
TT on top
of IC surface
TB
TB on PCB
TT
1mm
1mm
Figure 31. Measuring Points for TT and TB
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11 Device and Documentation Support
11.1 Device Support
11.1.1 Development Support
11.1.1.1 Evaluation Module
An evaluation module (EVM) is available to assist in the initial circuit performance evaluation using the
TPS74701. The TPS74701EVM-177 evaluation module (and related user guide) can be requested at the Texas
Instruments website through the product folders or purchased directly from the TI eStore.
11.1.1.2 Spice Models
Computer simulation of circuit performance using SPICE is often useful when analyzing the performance of
analog circuits and systems. A SPICE model for TPS74701 is available through the product folders under
Simulation Models.
11.1.2 Device Nomenclature
Table 5. Device Nomenclature (1)
PRODUCT
TPS747xx yyy z
(1)
(2)
(3)
VOUT
(2)
xx is nominal output voltage (for example, 12 = 1.2 V, 15 = 1.5 V, 01 = Adjustable). (3)
YYY is the package designator.
Z is package quantity.
For the most current package and ordering information see the Package Option Addendum at the end of this document, or visit the
device product folder on www.ti.com.
Fixed output voltages from 0.8 V to 3.3 V are available; minimum order quantities may apply. Contact factory for details and availability.
For fixed 0.8-V operation, tie FB to OUT.
11.2 Documentation Support
11.2.1 Related Documentation
For related documentation see the following:
• Using New Thermal Metrics, SBVA025
• Semiconductor and IC Package Thermal Metrics, SPRA953
11.3 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.4 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
11.5 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Submit Documentation Feedback
Copyright © 2007–2015, Texas Instruments Incorporated
Product Folder Links: TPS74701
21
TPS74701
SBVS099G – NOVEMBER 2007 – REVISED OCTOBER 2015
www.ti.com
11.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
22
Submit Documentation Feedback
Copyright © 2007–2015, Texas Instruments Incorporated
Product Folder Links: TPS74701
PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
TPS74701DRCR
ACTIVE
VSON
DRC
10
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
CEG
TPS74701DRCRG4
ACTIVE
VSON
DRC
10
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
CEG
TPS74701DRCT
ACTIVE
VSON
DRC
10
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
CEG
TPS74701DRCTG4
ACTIVE
VSON
DRC
10
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
CEG
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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