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TPS61085
SLVS859B – JUNE 2008 – REVISED DECEMBER 2014
TPS61085 650-kHz,1.2-MHz, 18.5-V Step-Up DC-DC Converter
1 Features
3 Description
•
•
•
•
•
•
•
•
The TPS61085 is a high frequency, high efficiency
DC-DC converter with an integrated 2.0-A, 0.13-Ω
power switch capable of providing an output voltage
up to 18.5 V. The selectable frequency of 650 kHz or
1.2 MHz allows the use of small external inductors
and capacitors and provides fast transient response.
The external compensation allows optimizing the
application for specific conditions. A capacitor
connected to the soft-start pin minimizes inrush
current at startup.
1
2.3 V to 6 V Input Voltage Range
18.5-V Boost Converter With 2.0-A Switch Current
650-kHz/1.2-MHz Selectable Switching Frequency
Adjustable Soft-Start
Thermal Shutdown
Undervoltage Lockout
8-Pin VSSOP Package
8-Pin TSSOP Package
Device Information(1)
2 Applications
•
•
•
•
•
•
•
PART NUMBER
Handheld Devices
GPS Receivers
Digital Still Cameras
Portable Applications
DSL Modems
PCMCIA Cards
TFT LCD Bias Supply
TPS61085
PACKAGE
BODY SIZE (NOM)
VSSOP (8)
3.00 mm × 3.00 mm
TSSOP (8)
3.00 mm × 4.40 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
4 Simplified Schematic
L
3.3 mH
VIN
2.3 V to 6 V
6
CIN
10 µF
16 V
CBY
1 µF
16 V
5
IN
3
D
PMEG2010AEH
VS
12 V/300 mA
SW
EN
2
R1
158 kΩ
1
R2
18.2 kΩ
FB
7
COUT
2* 10 µF
25 V
COMP
FREQ
4
RCOMP
51 kΩ
8
GND
SS
TPS61085
CSS
100 nF
CCOMP
1.1 nF
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.
TPS61085
SLVS859B – JUNE 2008 – REVISED DECEMBER 2014
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
Features ..................................................................
Applications ...........................................................
Description .............................................................
Simplified Schematic.............................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
1
2
3
3
7.1
7.2
7.3
7.4
7.5
7.6
3
3
4
4
4
5
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description .............................................. 7
8.1 Overview ................................................................... 7
8.2 Functional Block Diagram ......................................... 7
8.3 Feature Description................................................... 8
8.4 Device Functional Modes.......................................... 8
9
Application and Implementation .......................... 9
9.1 Application Information.............................................. 9
9.2 Typical Application .................................................... 9
9.3 System Examples ................................................... 15
10 Power Supply Recommendations ..................... 18
11 Layout................................................................... 19
11.1 Layout Guidelines ................................................. 19
11.2 Layout Example .................................................... 19
12 Device and Documentation Support ................. 20
12.1 Trademarks ........................................................... 20
12.2 Electrostatic Discharge Caution ............................ 20
12.3 Glossary ................................................................ 20
13 Mechanical, Packaging, and Orderable
Information ........................................................... 20
5 Revision History
Changes from Revision A (April 2012) to Revision B
•
Page
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 Original (June 2008) to Revision A
Page
•
Changed the circuit illustration value of CCOMP From: 1.6 nF To: 1.1 nF ............................................................................... 1
•
Deleted Lead Temperature from the Abs Max table .............................................................................................................. 3
•
Added a conditions statement and two new graphs (Max Load Current vs Input Voltage) to the Typical
Characteristics graphs ............................................................................................................................................................ 5
•
Added three paragraphs of text to the Detailed Description. ................................................................................................. 7
•
Changed Figure 8 to Figure 17 .............................................................................................................................................. 9
•
Changed the Design Procudures step 3 details following Equation 4 ................................................................................ 10
•
Changed text in the Inductor Selection section "inductor current ripple is below 20%" to " inductor current ripple is
below 35%" .......................................................................................................................................................................... 10
•
Changed Equation 8............................................................................................................................................................. 12
•
Added Used IOUT to Table 5.................................................................................................................................................. 12
•
Added Equation 10 ............................................................................................................................................................... 13
•
Changed the White LED Applications optional Zener connection for Figure 19 to Figure 21.............................................. 17
2
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SLVS859B – JUNE 2008 – REVISED DECEMBER 2014
6 Pin Configuration and Functions
DGK, PW Packages
8 Pins
Top View
COMP
1
8
SS
FB
2
7
FREQ
EN
3
6
IN
PGND
4
5
SW
8-PIN 4.9-mm × 3-mm × 1.1-mm VSSOP (DGK)
8-PIN 6.4-mm × 3-mm × 1.2-mm TSSOP (PW)
Pin Functions
PIN
NAME
NO.
I/O
DESCRIPTION
COMP
1
I/O
EN
3
I
Compensation pin
Shutdown control input. Connect this pin to logic high level to enable the device
FB
2
I
Feedback pin
FREQ
7
I
Frequency select pin. The power switch operates at 650 kHz if FREQ is connected to GND and at 1.2 MHz if
FREQ is connected to IN
IN
6
I
Input supply pin
PGND
4
SS
8
O
Soft-start control pin. Connect a capacitor to this pin if soft-start needed. Open = no soft-start
SW
5
I
Switch pin
Power ground
7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1) (2)
MIN
MAX
UNIT
Input voltage range IN
–0.3
7
V
Voltage range on pins EN, FB, SS, FREQ, COMP
–0.3
7
V
Voltage on pin SW
-0.3
20
V
Continuous power dissipation
See Thermal Information
Operating junction temperature
–40
150
°C
Storage temperature
–65
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
All voltage values are with respect to network ground terminal.
7.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±2000
Charged-device model (CDM), per JEDEC specification JESD22C101 (2)
±500
Machine model (MM)
±200
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. Manufacturing with
less than 500-V HBM is possible with the necessary precautions. Pins listed as ±XXX V may actually have higher performance.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. Manufacturing with
less than 250-V CDM is possible with the necessary precautions. Pins listed as ±YYY V may actually have higher performance.
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7.3 Recommended Operating Conditions
MIN
VIN
Input voltage range
VS
Boost output voltage range
TA
TJ
TYP
MAX
UNIT
2.3
6
VIN + 0.5
18.5
V
V
Operating free-air temperature
–40
85
°C
Operating junction temperature
–40
125
°C
7.4 Thermal Information
TPS61085
THERMAL METRIC (1)
DGK
PW
8 PINS
8 PINS
183.3
RθJA
Junction-to-ambient thermal resistance
189.3
RθJC(top)
Junction-to-case (top) thermal resistance
57.1
66.7
RθJB
Junction-to-board thermal resistance
109.9
112.0
ψJT
Junction-to-top characterization parameter
3.5
8.3
ψJB
Junction-to-board characterization parameter
108.3
110.3
(1)
UNIT
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
7.5 Electrical Characteristics
VIN = 3.3 V, EN = VIN, VS = 12 V, TA = –40°C to 85°C, typical values are at TA = 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
SUPPLY
VIN
Input voltage range
IQ
Operating quiescent current into IN
Device not switching, VFB = 1.3 V
ISDVIN
Shutdown current into IN
EN = GND
UVLO
Undervoltage lockout threshold
TSD
Thermal shutdown
TSD(HYS)
Thermal shutdown hysteresis
2.3
6
V
100
μA
1
μA
VIN falling
2.2
V
VIN rising
2.3
V
70
Temperature rising
150
°C
14
°C
LOGIC SIGNALS EN, FREQ
VIH
High level input voltage
VIN = 2.3 V to 6 V
VIL
Low level input voltage
VIN = 2.3 V to 6 V
2
0.5
V
V
Ilkg
Input leakage current
EN = FREQ = GND
0.1
μA
18.5
V
1.246
V
BOOST CONVERTER
VS
Boost output voltage
VIN +
0.5
VFB
Feedback regulation voltage
1.230
gm
Transconductance error amplifier
IFB
Feedback input bias current
VFB = 1.238 V
rDS(on)
N-channel MOSFET on-resistance
VIN = VGS = 5 V, ISW = current limit
VIN = VGS = 3.3V, ISW = current limit
Ilkg
SW leakage current
ILIM
N-Channel MOSFET current limit
ISS
Soft-start current
VSS = 1.238 V
fS
Oscillator frequency
FREQ = VIN
0.9
FREQ = GND
480
4
1.238
μA/V
107
0.1
μA
0.13
0.20
Ω
0.15
0.24
2.0
2.6
3.2
A
7
10
13
μA
1.2
1.5
MHz
650
820
EN = GND, VSW = 6V TBD
10
Line regulation
VIN = 2.3 V to 6 V, IOUT = 10 mA
Load regulation
VIN = 3.3 V, IOUT = 1 mA to 400 mA
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µA
kHz
0.0002
%/V
0.11
%/A
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7.6 Typical Characteristics
The typical characteristics are measured with the inductors 7447789003 3.3 µH (high frequency) or B82464G4 6.8 µH (low
frequency) from Epcos and the rectifier diode SL22.
Table 1. Table Of Graphs
FIGURE
vs Input voltage at high frequency (1.2 MHz)
Figure 1
vs Input voltage at low frequency (650 kHz)
Figure 2
vs Load current, VS = 12 V, VIN = 3.3 V
Figure 3
vs Load current, VS = 9 V, VIN = 3.3 V
Figure 4
Supply current
vs Supply voltage
Figure 5
Frequency
vs Load current
Figure 6
Frequency
vs Supply voltage
Figure 7
IOUT(max)
Maximum load current
η
Efficiency
1.6
1.6
fS = 1.2 MHz
fS = 1.2 MHz
1.4
1.4
VOUT = 9 V
1
1.2
IOUT − Output Current (A)
IOUT − Output Current (A)
1.2
VOUT = 9 V
VOUT = 12 V
0.8
0.6
0.4
1
VOUT = 12 V
0.8
0.6
0.4
VOUT = 15 V
0.2
0.2
VOUT = 15 V
VOUT = 18.5 V
0
2.5
3.0
3.5
4.0
4.5
5.0
VIN − Input Voltage (V)
VOUT = 18.5 V
5.5
6.0
0
2.5
3.0
3.5
4.0
4.5
5.0
VIN − Input Voltage (V)
5.5
6.0
G000
Figure 1. Maximum Load Current vs Input Voltage
G000
Figure 2. Maximum Load Current vs Input Voltage
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100
100
fS = 650 kHz
L = 6.8 µH
90
80
80
fS = 1.2 MHz
L = 3.3 µH
fS = 1.2 MHz
L = 3.3 µH
70
Efficiency - %
70
Efficiency - %
fS = 650 kHz
L = 6.8 µH
90
60
50
40
60
50
40
30
30
20
20
VIN = 3.3 V
VS = 12 V
10
VIN = 3.3 V
VS = 9 V
10
0
0
0
0
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
0.10
IOUT - Load current - A
0.30
0.40
0.60
0.50
0.70 0.80
IOUT - Load current - A
Figure 3. Efficiency vs Load Current
Figure 4. Efficiency vs Load Current
2
1600
1.8
1400
Switching
fS = 1.2 MHz
L = 3.3 µH
1.6
FREQ = VIN
L = 3.3 µH
1200
1.4
fS - Frequency - kHz
ICC - Supply Current - mA
0.20
1.2
1
0.8
Switching
fS = 650 kHz
L = 6.8 µH
0.6
1000
800
FREQ = GND
L = 6.8 µH
600
400
0.4
200
Not Switching
0.2
0
2
2.5
3
3.5
4
4.5
5
VCC - Supply Current - V
5.5
0
0.0
6
VIN = 3.3 V
VS = 12 V
0.1
0.2
0.3
0.4
0.5
0.6
IOUT - Load current - mA
Figure 5. Supply Current vs Supply Voltage
Figure 6. Frequency vs Load Current
1400
fS - Frequency - kHz
1200
FREQ = VIN
L = 3.3 µH
1000
800
FREQ = GND
L = 6.8 µH
600
400
200
VS = 12 V / 200 mA
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
VCC - Supply Voltage - V
Figure 7. Frequency vs Supply Voltage
6
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8 Detailed Description
8.1 Overview
The boost converter is designed for output voltages up to 18.5 V with a switch peak current limit of 2.0 A
minimum. The device, which operates in a current mode scheme with quasi-constant frequency, is externally
compensated for maximum flexibility and stability. The switching frequency is selectable between 650 kHz and
1.2 MHz and the minimum input voltage is 2.3 V. To control the inrush current at start-up a soft-start pin is
available.
TPS61085 boost converter’s novel topology using adaptive off-time provides superior load and line transient
responses and operates also over a wider range of applications than conventional converters.
The selectable switching frequency offers the possibility to optimize the design either for the use of small sized
components (1.2 MHz) or for higher system efficiency (650 kHz). However, the frequency changes slightly
because the voltage drop across the rDS(on) has some influence on the current and voltage measurement and
thus on the on-time (the off-time remains constant).
The converter operates in continuous conduction mode (CCM) as soon as the input current increases above half
the ripple current in the inductor, for lower load currents it switches into discontinuous conduction mode (DCM). If
the load is further reduced, the part starts to skip pulses to maintain the output voltage.
8.2 Functional Block Diagram
VIN
VS
EN
SS
IN
SW
FREQ
Current limit
and
Soft Start
tOFF Generator
Bias Vref = 1.238V
UVLO
Thermal Shutdown
tON
PWM
Generator
Gate Driver of
Power
Transistor
COMP
GM Amplifier
FB
V ref
PGND
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8.3 Feature Description
8.3.1 Soft-Start
The boost converter has an adjustable soft-start to prevent high inrush current during start-up. To minimize the
inrush current during start-up an external capacitor connected to the soft-start pin SS and charged with a
constant current, is used to slowly ramp up the internal current limit of the boost converter when charged with a
constant current. When the EN pin is pulled high, the soft-start capacitor CSS is immediately charged to 0.3 V.
The capacitor is then charged at a constant current of 10 μA typically until the output of the boost converter VS
has reached its Power Good threshold (roughly 98% of VS nominal value). During this time, the SS voltage
directly controls the peak inductor current, starting with 0 A at VSS = 0.3 V up to the full current limit at VSS =0.8
V. The maximum load current is available after the soft-start is completed. The larger the capacitor the slower the
ramp of the current limit and the longer the soft-start time. A 100 nF capacitor is usually sufficient for most of the
applications. When the EN pin is pulled low, the soft-start capacitor is discharged to ground.
8.3.2 Frequency Select Pin (FREQ)
The frequency select pin FREQ allows to set the switching frequency of the device to 650 kHz (FREQ = low) or
1.2 MHz (FREQ = high). Higher switching frequency improves load transient response but reduces slightly the
efficiency. The other benefits of higher switching frequency are a lower output ripple voltage. The use of the 1.2
MHz switching frequency is recommended unless light load efficiency is a major concern.
8.3.3 Undervoltage Lockout (UVLO)
To avoid mis-operation of the device at low input voltages an undervoltage lockout is included that disables the
device, if the input voltage falls below 2.2 V.
8.3.4 Thermal Shutdown
A thermal shutdown is implemented to prevent damages due to excessive heat and power dissipation. Typically
the thermal shutdown threshold happens at a junction temperature of 150°C. When the thermal shutdown is
triggered the device stops switching until the temperature falls below typically 136°C. Then the device starts
switching again.
8.3.5 Overvoltage Prevention
If overvoltage is detected on the FB pin (typically 3 % above the nominal value of 1.238 V) the part stops
switching immediately until the voltage on this pin drops to its nominal value. This prevents overvoltage on the
output and secures the circuits connected to the output from excessive overvoltage.
8.4 Device Functional Modes
The converter operates in continuous conduction mode (CCM) as soon as the input current increases above half
the ripple current in the inductor, for lower load currents it switches into discontinuous conduction mode (DCM). If
the load is further reduced, the part starts to skip pulses to maintain the output voltage.
8
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9 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.
9.1 Application Information
The TPS61085 is designed for output voltages up to 18.5 V with a switch peak current limit of 2.0 A minimum.
The device, which operates in a current mode scheme with quasi-constant frequency, is externally compensated
for maximum flexibility and stability. The switching frequency is selectable between 650 kHz and 1.2 MHz, and
the input voltage range is 2.3 V to 6.0V. To control the inrush current at start-up a soft-start pin is available. The
following section provides a step-by-step design approach for configuring the TPS61085 as a voltage regulating
boost converter.
9.2 Typical Application
L
3.3 µH
VIN
3.3 V ±20%
6
CIN
10 µF
16 V
CBY
1 µF
16 V
5
IN
3
VS
12 V/600 mA max
SW
R1
158 kΩ
2
EN
FB
R2
18.2 kΩ
1
7
FREQ
4
D
PMEG2010AEH
COUT
2* 10 µF
25 V
COMP
RCOMP
47 kΩ
8
GND
SS
TPS61085
CSS
CCOMP
1.6 nF
100 nF
Figure 8. Typical Application, 3.3 V to 12 V (fS = 1.2 MHz)
9.2.1 Design Requirements
Table 2. TPS61085 12V Output Design Requirements
PARAMETERS
VALUES
Input Voltage
3.3V ± 20%
Output Voltage
12V
Output Current
600mA
Switching Frequency
1.2MHz
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9.2.2 Detailed Design Procedure
9.2.2.1 Design Procedure
The first step in the design procedure is to verify that the maximum possible output current of the boost converter
supports the specific application requirements. A simple approach is to estimate the converter efficiency, by
taking the efficiency numbers from the provided efficiency curves or to use a worst case assumption for the
expected efficiency, e.g. 90%.
1. Duty cycle, D:
D = 1-
VIN ×h
VS
(1)
2. Maximum output current, IOUT(max) :
DI ö
æ
I OUT (max) = ç I LIM (min) - L ÷ × (1 - D )
2 ø
è
(2)
3. Peak switch current in application, ISW(peak) :
I
DI
I SW ( peak ) = L + OUT
2 1- D
(3)
with the inductor peak-to-peak ripple current, ΔIL
DI L =
VIN × D
fS × L
(4)
and
VIN
Minimum input voltage
VS
Output voltage
ILIM(min)
Converter switch current limit (minimum switch current limit = 3.2 A)
fS
Converter switching frequency (typically 1.2 MHz or 650 kHz)
L
Selected inductor value
η
Estimated converter efficiency (please use the number from the efficiency plots or 90% as an estimation)
The peak switch current is the steady state peak switch current that the integrated switch, inductor and external
Schottky diode has to be able to handle. The calculation must be done for the minimum input voltage where the
peak switch current is the highest.
9.2.2.2 Inductor Selection
The TPS61085 is designed to work with a wide range of inductors. The main parameter for the inductor selection
is the saturation current of the inductor which should be higher than the peak switch current as calculated in the
Design Procedure section with additional margin to cover for heavy load transients. An alternative, more
conservative, is to choose an inductor with a saturation current at least as high as the maximum switch current
limit of 3.2 A. The other important parameter is the inductor DC resistance. Usually, the lower the DC resistance
the higher the efficiency. It is important to note that the inductor DC resistance is not the only parameter
determining the efficiency. Especially for a boost converter where the inductor is the energy storage element, the
type and core material of the inductor influences the efficiency as well. At high switching frequencies of 1.2 MHz
inductor core losses, proximity effects and skin effects become more important. Usually, an inductor with a larger
form factor gives higher efficiency. The efficiency difference between different inductors can vary between 2% to
10%. For the TPS61085, inductor values between 3 μH and 6 μH are a good choice with a switching frequency
of 1.2 MHz, typically 3.3 μH. At 650 kHz inductors between 6 μH and 13 μH, typically 6.8 μH are recommended.
Possible inductors are shown in Table 3.
Typically, it is recommended that the inductor current ripple is below 35% of the average inductor current.
Therefore, the following equation can be used to calculate the inductor value, L:
10
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2
æ V ö æ V -V ö æ h ö
L = ç IN ÷ × ç S IN ÷ × ç
÷
è VS ø è I OUT × f S ø è 0.35 ø
(5)
with
VIN
Minimum input voltage
VS
Output voltage
Iout
Maximum output current in the application
fS
Converter switching frequency (typically 1.2 MHz or 650 kHz)
η
Estimated converter efficiency (please use the number from the efficiency plots or 90% as an estimation)
Table 3. Inductor Selection
L
(μH)
SUPPLIER
COMPONENT
CODE
SIZE
(L×W×H mm)
DCR TYP
(mΩ)
Isat (A)
3.3
Sumida
CDH38D09
4x4x1
240
1.25
4.7
Sumida
3.3
Sumida
CDPH36D13
5 × 5 × 1.5
155
1.36
CDPH4D19F
5.2 x 5.2 x 2
33
3.3
Sumida
1.5
CDRH6D12
6.7 x 6.7 x 1.5
62
4.7
2.2
Würth Elektronik
7447785004
5.9 × 6.2 × 3.3
60
2.5
5
Coilcraft
MSS7341
7.3 × 7.3 × 4.1
24
2.9
CDP14D19
5.2 x 5.2 x 2
50
1
1.2 MHz
650 kHz
6.8
Sumida
10
Coilcraft
LPS4414
4.3 × 4.3 × 1.4
380
1.2
6.8
Sumida
CDRH6D12/LD
6.7 x 6.7 x 1.5
95
1.25
10
Sumida
CDR6D23
5 × 5 × 2.4
133
1.75
10
Würth Elektronik
744778910
7.3 × 7.3 × 3.2
51
2.2
6.8
Sumida
CDRH6D26HP
7 x 7 x 2.8
52
2.9
9.2.2.3 Rectifier Diode Selection
To achieve high efficiency, a Schottky type should be used for the rectifier diode. The reverse voltage rating
should be higher than the maximum output voltage of the converter. The averaged rectified forward current Iavg,
the Schottky diode needs to be rated for, is equal to the output current IOUT:
I avg = I OUT
(6)
Usually a Schottky diode with 2 A maximum average rectified forward current rating is sufficient for most
applications. The Schottky rectifier can be selected with lower forward current capability depending on the output
current Iout but has to be able to dissipate the power. The dissipated power, PD , is the average rectified forward
current times the diode forward voltage, Vforward .
PD = I avg × V forward
(7)
Typically the diode should be able to dissipate around 500mW depending on the load current and forward
voltage.
Table 4. Rectifier Diode Selection
CURRENT
RATING Iavg
Vr
Vforward / Iavg
SUPPLIER
COMPONENT
CODE
PACKAGE
TYPE
750 mA
20 V
0.425 V /
750 mA
Fairchild Semiconductor
FYV0704S
SOT 23
1A
20 V
0.39 V / 1 A
NXP
PMEG2010AEH
SOD 123
1A
20 V
0.52 V / 1 A
Vishay Semiconductor
B120
SMA
1A
20 V
0.5 V / 1 A
Vishay Semiconductor
SS12
SMA
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Table 4. Rectifier Diode Selection (continued)
CURRENT
RATING Iavg
Vr
Vforward / Iavg
SUPPLIER
COMPONENT
CODE
PACKAGE
TYPE
1A
20 V
0.44 V / 1 A
Vishay Semiconductor
MSS1P2L
μ-SMP (Low
Profile)
9.2.2.4 Setting the Output Voltage
The output voltage is set by an external resistor divider. Typically, a minimum current of 50 μA flowing through
the feedback divider gives good accuracy and noise covering. A standard low side resistor of 18 kΩ is typically
selected. The resistors are then calculated as:
VS
V
R 2 = FB » 18k W
70 m A
æ V
ö
R1 = R 2 × ç S - 1÷
è VFB
ø
R1
VFB
VFB = 1.238V
R2
(8)
9.2.2.5 Compensation (COMP)
The regulator loop can be compensated by adjusting the external components connected to the COMP pin. The
COMP pin is the output of the internal transconductance error amplifier.
Standard values of RCOMP = 13 kΩ and CCOMP = 3.3 nF will work for the majority of the applications.
See Table 5 for dedicated compensation networks giving an improved load transient response. The following
equations can be used to calculate RCOMP and CCOMP :
Vs × COUT
110 × VIN × VS × COUT
CCOMP =
RCOMP =
7.5 × I OUT × RCOMP
L × I OUT
(9)
with
VIN
Minimum input voltage
VS
Output voltage
Cout
Output capacitance
L
Inductor value, e.g. 3.3 μH or 6.8 μH
IOUT
Maximum output current in the application
Make sure that RCOMP < 120 kΩ and CCOMP> 820 pF, independent of the results of the above formulas.
Table 5. Recommended Compensation Network Values at High/Low Frequency
FREQUENCY
L
VS
15 V
High (1.2 MHz)
3.3 µH
12 V
9V
15 V
Low (650 kHz)
6.8 µH
12 V
9V
12
VIN ± 20%
RCOMP
CCOMP
Used IOUT
5V
82 kΩ
1.1 nF
0.7A
3.3 V
75 kΩ
1.6 nF
0.5A
5V
51 kΩ
1.1 nF
0.9A
3.3 V
47 kΩ
1.6 nF
0.6A
5V
30 kΩ
1.1 nF
1.2A
3.3 V
27 kΩ
1.6 nF
0.8A
5V
43 kΩ
2.2 nF
0.7A
3.3 V
39 kΩ
3.3 nF
0.5A
5V
27 kΩ
2.2 nF
0.9A
3.3 V
24 kΩ
3.3 nF
0.6A
5V
15 kΩ
2.2 nF
1.2A
3.3 V
13 kΩ
3.3 nF
0.8A
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Table 5 gives conservative RCOMP and CCOMP values for certain inductors, input and output voltages providing a
very stable system. For a faster response time, a higher RCOMP value can be used to enlarge the bandwidth, as
well as a slightly lower value of CCOMP to keep enough phase margin. These adjustments should be performed in
parallel with the load transient response monitoring of TPS61087.
9.2.2.6 Input Capacitor Selection
For good input voltage filtering low ESR ceramic capacitors are recommended. TPS61085 has an analog input
IN. Therefore, a 1 μF bypass is highly recommended as close as possible to the IC from IN to GND.
One 10 μF ceramic input capacitors are sufficient for most of the applications. For better input voltage filtering
this value can be increased. Refer to Table 6 and typical applications for input capacitor recommendations.
9.2.2.7 Output Capacitor Selection
For best output voltage filtering a low ESR output capacitor like ceramic capcaitor is recommended. Two 10 μF
ceramic output capacitors (or one 22 μF) work for most of the applications. Higher capacitor values can be used
to improve the load transient response. Refer to Table 6 for the selection of the output capacitor.
Table 6. Rectifier Input and Output Capacitor Selection
CAPACITOR
VOLTAGE RATING
SUPPLIER
COMPONENT CODE
CIN
10 μF/1206
16 V
Taiyo Yuden
EMK212 BJ 106KG
IN bypass
1 μF/0603
16 V
Taiyo Yuden
EMK107 BJ 105KA
COUT
10 μF/1206
25 V
Taiyo Yuden
TMK316 BJ 106KL
To calculate the output voltage ripple, Equation 10 can be used:
V - VIN I OUT
DVC _ ESR = I L ( peak ) × RC _ ESR
DVC = S
×
VS × f S COUT
(10)
with
ΔVC
Output voltage ripple dependent on output capacitance,output current and switching frequency
VS
Output voltage
VIN
Minimum input voltage of boost converter
fS
Converter switching frequency (typically 1.2 MHz or 650 kHz)
Iout
Output capacitance
ΔVC_ESR
Output voltage ripple due to output capacitors ESR (equivalent series resistance)
ISWPEAK
Inductor peak switch current in the application
RC_ESR
Output capacitors equivalent series resistance (ESR)
ΔVC_ESR can be neglected in many cases since ceramic capacitors provide low ESR.
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9.2.3 Application Curves
VSW
5 V/div
VSW
5 V/div
VS_AC
50 mV/div
VS_AC
50 mV/div
VIN = 3.3 V
VS = 12 V/1 mA
fS = 1.2 MHz
IL
1 A/div
VIN = 3.3 V
VS = 12 V/300 mA
fS = 1.2 MHz
IL
200 mA/div
200 ns/div
200 ns/div
Figure 9. PWM Switching Discontinuous Conduction Mode
Figure 10. PWM Switching Continuous Conduction Mode
COUT = 20 µF
L = 3.3 µH
RCOMP = 51 kΩ
CCOMP = 1.6 nF
VIN = 3.3 V
VS = 12 V
VS_AC
200 mV/div
COUT = 20 µF
L = 6.8 µH
RCOMP = 24 kΩ
CCOMP = 3.3 nF
VIN = 3.3 V
VS = 12 V
VS_AC
200 mV/div
IOUT = 50 mA - 200 mA
IOUT = 50 mA - 200 mA
IOUT
100 mA/div
IOUT
100 mA/div
200µs/div
200 µs/div
200 µs/div
Figure 11. Load Transient Response High Frequency (1.2
MHz)
Figure 12. Load Transient Response Low Frequency (650
kHz)
EN
5 V/div
VIN = 3.3 V
VS = 12 V/300 mA
VS
5 V/div
IL
1 A/div
CSS = 100 nF
2 ms/div
Figure 13. Soft-Start
14
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9.3 System Examples
9.3.1 General Boost Application Circuits
L
6.8 µH
VIN
3.3 V ±20%
6
CIN
10 µF
16 V
CBY
1 µF
16 V
SW
IN
3
5
D
PMEG2010AEH
R1
158 kΩ
2
EN
VS
12 V/600 mA max
FB
R2
18.2 kΩ
1
7
FREQ
COUT
2* 10 µF
25 V
COMP
4
RCOMP
24 kΩ
8
GND
SS
CSS
TPS61085
CCOMP
3.3 nF
100 nF
Figure 14. Typical Application, 3.3 V to 12 V (fS = 650 kHz)
L
3.3 µH
VIN
3.3 V ±20%
6
CIN
10 µF
16 V
CBY
1 µF
16 V
SW
IN
3
D
PMEG2010AEH
5
R1
113 kΩ
2
EN
VS
9 V/800 mA max
FB
R2
18 kΩ
1
7
FREQ
COUT
2* 10 µF
25 V
COMP
4
RCOMP
27 kΩ
8
GND
SS
TPS61085
CSS
CCOMP
1.6 nF
100 nF
Figure 15. Typical Application, 3.3 V to 9 V (fS = 1.2 MHz)
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System Examples (continued)
L
6.8 µH
VIN
3.3 V ±20%
6
CIN
10 µF
16 V
CBY
1 µF
16 V
SW
IN
3
D
PMEG2010AEH
5
R1
113 kΩ
2
EN
VS
9 V/800 mA max
FB
R2
18 kΩ
1
7
FREQ
COUT
2* 10 µF
25 V
COMP
4
RCOMP
13 kΩ
8
GND
SS
CCOMP
3.3 nF
CSS
TPS61085
100 nF
Figure 16. Typical Application, 3.3 V to 9 V (fS = 650 kHz)
RISO
10 kΩ
L
6.8 µH
VIN
3.3 V ±20%
CIN
10 µF
16 V
CBY
1 µF/16 V 6
3
7
4
IN
SW
EN
FB
FREQ
COMP
GND
SS
TPS61085
5
D
PMEG2010AEH
CISO
1 µF/ 25 V
2
VS
12 V/300 mA
BC857C
R1
158 kΩ
1
RCOMP
24 kΩ
8
CSS
COUT
2*10 µF
25 V
R2
18.2 kΩ
CCOMP
3.3 nF
100nF
Figure 17. Typical Application With External Load Disconnect Switch
16
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System Examples (continued)
9.3.2 TFT LCD Application Circuit
VGL
-7 V/ 20 mA
T1
BC857B
-VS
C4
100nF/
50V
D2
BAT54S
C3
100 nF
50 V
C2
R8
7 kΩ 470 nF
25 V
C1
1µF/
35V
D3
BAT54S
D1
BZX84C7V5
D4
BAT54S
C6
470 nF
50 V
D5
BAT54S
C5
100 nF
50 V
D6
BAT54S
VGH
20 V/20 mA
T2
BC850B
3* VS
R10
13 kΩ
C8
2*VS
1 µF
35 V
C7
470 nF
50 V
D8
BZX84C 20V
D7
BAT54S
L
3.3µH
VIN
3.3 V± 20%
6
CBY
1 µF
16 V
CIN
10 µF
16 V
5
VIN
SW
EN
FB
3
7
FREQ
2
R1
113 kΩ
1
R2
18 kΩ
COMP
SS
GND
2*10 µF
25 V
CCOMP
1.6 nF
CSS
TPS 61085
COUT
RCOMP
27 kΩ
8
4
VS
9 V/500 mA
D
PMEG2010AEH
100 nF
Figure 18. Typical Application 3.3 V to 9 V (fS = 1.2 MHz) for TFT LCD With External Charge Pumps
(VGH, VGL)
9.3.3 WHITE LED Application Circuits
L
6.8 µH
optional
CBY
1 µF/ 16 V
VIN
5 V ± 20%
5
6
3
DZ
BZX84C 18 V
VS
500 mA
3S3P wLED
LW E67C
SW
IN
CIN
10 µF/
16 V
D
SL22
COUT
2* 10 µF/
25 V
EN
2
FB
7
4
FREQ
COMP
SS
PGND
TPS61085
RLIMIT
110 Ω
1
RCOMP
24 kΩ
8
CSS
100 nF
RSENSE
15 Ω
CCOMP
3.3 nF
Figure 19. Simple Application (3.3 V Input - fsw = 650 kHz) for wLED Supply (3S3P)
(With Optional Clamping Zener Diode)
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System Examples (continued)
L
6.8 µH
optional
CBY
1 µF/ 16 V
VIN
5 V ± 20%
5
6
3
DZ
BZX84C 18 V
COUT
2* 10 µF/
25 V
EN
2
FB
7
PWM
100 Hz to 500 Hz
VS
500 mA
3S3P wLED
LW E67C
SW
IN
CIN
10 µF/
16 V
D
SL22
4
FREQ
COMP
SS
PGND
RLIMIT
110 Ω
1
RCOMP
24 kΩ
8
TPS61085
RSENSE
15 Ω
CCOMP
3.3 nF
CSS
100 nF
Figure 20. Simple Application (3.3V Input - fsw = 650 kHz) for wLED Supply (3S3P) With Adjustable
Brightness Control Using a PWM Signal on the Enable Pin
(With Optional Clamping Zener Diode)
L
6.8 µH
optional
CBY
1 µF/ 16 V
VIN
5 V ± 20%
5
6
3
2
4
VS
500 mA
3S3P wLED
LW E67C
COUT
2* 10 µF/
25 V
EN
FB
7
DZ
BZX84C 18 V
SW
IN
CIN
10 µF/
16 V
D
SL22
COMP
FREQ
PGND
SS
TPS61085
R1
180 kΩ
RLIMIT
110 Ω
1
8
CSS
100 nF
RCOMP
24 kΩ
CCOMP
3.3 nF
R2
127 kΩ
RSENSE
15 Ω
Analog Brightness Control
3.3 V ~ wLED off
0 V ~ lLED = 30 mA (each string)
PWM Signal
Can be used swinging from 0 V to 3.3 V
Figure 21. Simple Application (3.3 V Input - fsw = 650 kHz) for wLED Supply (3S3P) With Adjustable
Brightness Control Using an Analog Signal on the Feedback Pin
(With Optional Clamping Zener Diode)
10 Power Supply Recommendations
The TPS61085 is designed to operate from an input voltage supply range between 2.3 V and 6.0 V. The power
supply to the TPS61085 needs to have a current rating according to the supply voltage, output voltage and
output current of the TPS61085.
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11 Layout
11.1 Layout Guidelines
For all switching power supplies, the layout is an important step in the design, especially at high peak currents
and high switching frequencies. If the layout is not carefully done, the regulator could show stability problems as
well as EMI problems. Therefore, use wide and short traces for the main current path and for the power ground
tracks. The input capacitor, output capacitor, and the inductor should be placed as close as possible to the IC.
Use a common ground node for power ground and a different one for control ground to minimize the effects of
ground noise. Connect these ground nodes at the GND terminal of the IC. The most critical current path for all
boost converters is from the switching FET, through the rectifier diode, then the output capacitors, and back to
ground of the switching FET. Therefore, the output capacitors and their traces should be placed on the same
board layer as the IC and as close as possible between the IC’s SW and GND terminal.
11.2 Layout Example
SW
5
IN
6
7
8
FREQ
VOUT
SS
VIN
3
EN
PGND
4
2
1
COMP
FB
TPS61085
GND
Figure 22. TPS61085 Layout Example
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12 Device and Documentation Support
12.1 Trademarks
All trademarks are the property of their respective owners.
12.2 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.
12.3 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 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.
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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)
TPS61085DGKR
ACTIVE
VSSOP
DGK
8
2500
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
PMKI
TPS61085DGKT
ACTIVE
VSSOP
DGK
8
250
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
PMKI
TPS61085DGKTG4
ACTIVE
VSSOP
DGK
8
250
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
PMKI
TPS61085PW
ACTIVE
TSSOP
PW
8
150
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
61085
TPS61085PWG4
ACTIVE
TSSOP
PW
8
150
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
61085
TPS61085PWR
ACTIVE
TSSOP
PW
8
2000
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
61085
(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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