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TPS61085T
SLVSA41B – NOVEMBER 2009 – REVISED JULY 2016
TPS61085T 650-kHz and 1.2-MHz, 18.5-V Step-Up DC-DC Converter
1 Features
3 Description
•
•
•
The TPS61085 device is a high-frequency highefficiency DC-to-DC boost converter with an
integrated 2-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 regulator for
application conditions. A capacitor connected to the
specific soft-start pin minimizes inrush current at
start-up.
1
•
•
•
•
2.3-V to 6-V Input Voltage Range
18.5-V Boost Converter With 2-A Switch Current
650-kHz or 1.2-MHz Selectable Switching
Frequency
Adjustable Soft Start
Thermal Shutdown
Undervoltage Lockout
8-Pin VSSOP and TSSOP Packages
2 Applications
•
•
•
•
•
•
•
Device Information(1)
Handheld Devices
GPS Receiver
Digital Still Camera
Portable Applications
DSL Modem
PCMCIA Card
TFT LCD Bias Supply
PART NUMBER
TPS61085T
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 data sheet.
Typical Application
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
TPS61085T
CSS
100 nF
CCOMP
1.1 nF
Copyright © 2016, Texas Instruments Incorporated
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.
TPS61085T
SLVSA41B – NOVEMBER 2009 – REVISED JULY 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
6.1
6.2
6.3
6.4
6.5
6.6
3
3
4
4
4
5
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description .............................................. 7
7.1
7.2
7.3
7.4
Overview ...................................................................
Functional Block Diagram .........................................
Feature Description...................................................
Device Functional Modes..........................................
7
7
8
8
8
Application and Implementation .......................... 9
8.1 Application Information.............................................. 9
8.2 Typical Application .................................................... 9
8.3 System Examples ................................................... 14
9 Power Supply Recommendations...................... 18
10 Layout................................................................... 19
10.1 Layout Guidelines ................................................. 19
10.2 Layout Example .................................................... 19
11 Device and Documentation Support ................. 20
11.1
11.2
11.3
11.4
11.5
11.6
Device Support......................................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
20
20
20
20
20
20
12 Mechanical, Packaging, and Orderable
Information ........................................................... 20
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision A (December 2009) 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
•
Removed Ordering Information table, see POA at the end of the data sheet ...................................................................... 1
•
Removed Dissipation Ratings table........................................................................................................................................ 1
•
Added minimum voltage to SW pin in Absolute Maximum Ratings ....................................................................................... 3
•
Changed SW leakage current value from 10 µA to 2 µA..................................................................................................... 4
•
Changed SW leakage current maximum from 10 µA to 2 µA.............................................................................................. 4
•
Changed x-axis of Figure 5 from VCC - Supply Current to VCC - Supply Voltage ................................................................... 6
•
Changed IOUT value from mA to A of Figure 6........................................................................................................................ 6
•
Connected FREQ pin to VIN and removed FREQ pin connection to GND on Figure 18 .................................................... 17
Changes from Original (November 2009) to Revision A
•
2
Page
Added maximum load current graphs..................................................................................................................................... 5
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SLVSA41B – NOVEMBER 2009 – REVISED JULY 2016
5 Pin Configuration and Functions
DGK or PW Package
8-Pin VSSOP or TSSOP
Top View
COMP
1
8
SS
FB
2
7
FREQ
EN
3
6
IN
PGND
4
5
SW
Not to scale
Pin Functions
PIN
TYPE
DESCRIPTION
NO.
NAME
1
COMP
I/O
2
FB
I
Feedback pin
Shutdown control input. Connect this pin to logic high level to enable the device.
Compensation pin
3
EN
I
4
PGND
—
5
SW
I
6
IN
PWR
7
FREQ
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.
8
SS
O
Soft-start control pin. Connect a capacitor to this pin if soft-start required. Open = no soft start
Power ground
Switch pin
Input supply pin
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
MIN
MAX
UNIT
Input voltage, IN (2)
–0.3
7
V
Voltage on pins EN, FB, SS, FREQ, COMP
–0.3
7
V
–0.3
20
V
Voltage on pin SW
Continuous power dissipation
See Thermal Information
Lead temperature (soldering, 10 s)
260
°C
Operating junction temperature
–40
150
°C
Storage temperature, Tstg
–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.
6.2 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 JESD22-C101 (2)
±500
Machine model
±200
UNIT
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.
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6.3 Recommended Operating Conditions
MIN
MAX
2.3
6
VIN + 0.5
18.5
V
Operating free-air temperature
–40
105
°C
Operating junction temperature
–40
125
°C
VIN
Input voltage
VS
Boost output voltage
TA
TJ
UNIT
V
6.4 Thermal Information
TPS61085T
THERMAL METRIC (1)
DGK (VSSOP)
PW (TSSOP)
8 PINS
8 PINS
UNIT
RθJA
Junction-to-ambient thermal resistance
189.3
183.3
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
57.1
66.7
°C/W
RθJB
Junction-to-board thermal resistance
109.9
112.0
°C/W
ψJT
Junction-to-top characterization parameter
3.5
8.3
°C/W
ψJB
Junction-to-board characterization parameter
108.3
110.3
°C/W
(1)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
6.5 Electrical Characteristics
VIN = 3.3 V, EN = IN, VS = 12 V, TA = –40°C to +105°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
70
6
V
100
µA
1
µA
VIN falling
2.2
VIN rising
2.3
Temperature rising, TJ
V
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
VFB
Feedback regulation voltage
gm
Transconductance error amplifier
IFB
Feedback input bias current
RDS(on)
N-channel MOSFET ON-resistance
Ilkg
SW leakage current
ILIM
N-Channel MOSFET current limit
ISS
Soft-start current
fosc
Oscillator frequency
4
VIN + 0.5
1.230
1.238
107
VFB = 1.238 V Ω
µA/V
0.1
µA
VIN = VGS = 5 V, ISW = current limit
0.13
0.2
VIN = VGS = 3.3 V, ISW = current limit
0.15
0.24
2
2.6
3.2
A
7
10
13
µA
EN = GND, VSW = 6 V
VSS = 1.238 V
2
Ω
µA
FREQ = high
0.9
1.2
1.5
MHz
FREQ = low
480
650
820
kHz
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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0.000
2
%/V
0.11
%/A
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SLVSA41B – NOVEMBER 2009 – REVISED JULY 2016
6.6 Typical Characteristics
The typical characteristics are measured with the 3.3-µH inductor for high-frequency (part number-7447789003) or 6.8-µH
inductor for low frequency (part number-B82464G4) and the rectifier diode with part number SL22.
Table 1. Table of Graphs
FIGURE
IOUT(max)
Maximum load current
η
Efficiency
Supply current
Frequency
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
vs Supply voltage
Figure 5
vs Load current
Figure 6
vs Supply voltage
Figure 7
1.6
1.6
fS = 1.2 MHz
fS = 650 kHz
1.4
1.4
VOUT = 9 V
1.2
VOUT = 12 V
1
Output Current (A)
IOUT − Output Current (A)
1.2
VOUT = 9 V
0.8
0.6
0.4
1
VOUT = 12 V
0.8
0.6
0.4
0.2
0.2
VOUT = 15 V
VOUT = 18.5 V
VOUT = 15 V
VOUT = 18.5 V
0
2.5
3.0
3.5
4.0
4.5
5.0
VIN − Input Voltage (V)
5.5
0
2.5
6.0
3.0
3.5
4.0
4.5
Input Voltage (V)
5.0
5.5
G000
Figure 1. Maximum Load Current vs Input Voltage
100
G000
Figure 2. Maximum Load Current vs Input Voltage
100
fS = 650 kHz
L = 6.8 µH
90
80
fS = 650 kHz
L = 6.8 µH
90
80
fS = 1.2 MHz
L = 3.3 µH
fS = 1.2 MHz
L = 3.3 µH
70
Efficiency - %
70
Efficiency - %
6.0
60
50
40
60
50
40
30
30
20
20
VIN = 3.3 V
VS = 12 V
10
0
0
VIN = 3.3 V
VS = 9 V
10
0
0
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
0.10
0.20
0.30
0.40
0.50
0.60
0.70 0.80
IOUT - Load current - A
IOUT - Load current - A
Figure 3. Efficiency vs Load Current, VS = 12 V, VIN = 3.3 V
Figure 4. Efficiency vs Load Current, VS = 9 V, VIN = 3.3 V
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2
1600
1.8
1.2
1
0.8
Switching
fS = 650 kHz
L = 6.8 µH
0.6
FREQ = VIN
L = 3.3 µH
1200
1.4
fS - Frequency - kHz
ICC - Supply Current - mA
1400
Switching
fS = 1.2 MHz
L = 3.3 µH
1.6
1000
800
FREQ = GND
L = 6.8 µH
600
400
0.4
Not Switching
0.2
0
0.0
0
2
2.5
3
VIN = 3.3 V
VS = 12 V
200
3.5
4
4.5
5
VCC - Supply Voltage - V
5.5
6
0.1
0.2
0.3
0.4
0.5
0.6
IOUT - Load current - A
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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SLVSA41B – NOVEMBER 2009 – REVISED JULY 2016
7 Detailed Description
7.1 Overview
The TPS61085T boost converter is designed for output voltages up to 18.5 V with a switch-peak current limit of
2 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 or 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.
The TPS61085T's 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).
Depending on the load current, the converter operates in continuous conduction mode (CCM), discontinuous
conduction mode (DCM), or pulse skip mode to maintain the output voltage.
7.2 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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7.3 Feature Description
7.3.1 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 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 (90% 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 ≈ 800 mV. 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.
7.3.2 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 and smaller inductor
size. Usually, TI recommends using 1.2-MHz switching frequency unless light-load efficiency is a major concern.
7.3.3 Undervoltage Lockout (UVLO)
To avoid misoperation 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.
7.3.4 Thermal Shutdown
A thermal shutdown is implemented to prevent damages due to excessive heat and power dissipation. Typically
the thermal shutdown threshold is at TJ = 150°C. When the thermal shutdown is triggered the device stops
switching until the temperature falls below typically TJ = 136°C. Then the device starts switching again.
7.3.5 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.
7.4 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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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
With the TPS61085T device, a boost regulator with an output voltage of up to 18.5 V can be designed with input
voltage ranging from 2.3 V to 6 V. The TPS61085T device has a peak switch current limit of 2 A minimum. The
device, which operates in a current mode scheme and uses simple external compensation scheme for maximum
flexibility and stability. Selectable switching frequency allows the regulator to be optimized either for smaller size
(1.2 MHz) or for higher system efficiency (650 KHz). A dedicated soft-start (SS) pin allows the designer to control
the inrush current at start-up.
The following section provides a step-by-step design approach for configuring the TPS61085T as a voltage
regulating boost converter.
8.2 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
TPS61085T
CCOMP
1.6 nF
CSS
100 nF
Copyright © 2016, Texas Instruments Incorporated
Figure 8. Typical Application, 3.3 V to 12 V (fsw = 1.2 MHz)
8.2.1 Design Requirements
Table 2 lists the design parameters for this application example.
Table 2. TPS61085T Output Design Requirements
PARAMETER
VALUE
Input voltage
3.3 V ± 20%
Output voltage
12 V
Output current
600 mA
Switching frequency
1.2 MHz
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8.2.2 Detailed 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, for example, 90%.
1. Duty cycle:
D = 1-
VIN ´h
VS
(1)
2. Maximum output current:
DI ö
æ
Iout = ç I swpeak - L ÷ ´ (1 - D )
2 ø
è
(2)
3. Peak switch current:
I swpeak =
I
DI L
+ out
2 1- D
where
DI L =
•
•
•
•
•
•
VIN ´ D
fs ´ L
Iswpeak = converter switch current (minimum switch current limit = 2 A)
fs = Converter switching frequency (typically 1.2 MHz)
L = Selected inductor value
η = Estimated converter efficiency (please use the number from the efficiency plots or 90% as an estimation)
ΔIL = Inductor peak-to-peak ripple current
(3)
The peak switch current is the steady-state peak switch current that the integrated switch, inductor, and external
Schottky diode must be able to handle. The calculation must be done for the minimum input voltage where the
peak switch current is the highest.
8.2.2.1 Inductor Selection
The TPS61085T 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 must be higher than the peak switch current as calculated
in Detailed Design Procedure with additional margin to cover for heavy load transients. An alternative, more
conservative option 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 TPS61085T, 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, TI recommends inductors between 6 µH and 13
µH, typically 6.8 µH. Table 3 shows a few inductors. Customers must verify and validate these components for
suitability with their application before using them.
Typically, TI recommends the inductor current ripple is below 20% of the average inductor current. Calculate the
inductor value using Equation 4.
10
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SLVSA41B – NOVEMBER 2009 – REVISED JULY 2016
2
æ VS-VIN ö æ h ö
æ VIN ö
L= ç
÷ × ç Iout_max×f ÷ × ç 0.35 ÷
S
V
è
ø
ø
è
ø è
where
•
•
•
•
•
•
L is the inductor value
VIN is input voltage
VS is boost output voltage
η is efficiency
Iout_max is the maximum output current
f is frequency
(4)
Table 3. Inductor Selection
L
(µH)
SUPPLIER
COMPONENT
CODE
SIZE
(L×W×H mm)
DCR TYP
(mΩ)
Isat (A)
3.3
Sumida
CDH38D09
4.7
4x4x1
240
1.25
Sumida
CDPH36D13
5 × 5 × 1.5
155
1.36
3.3
Sumida
CDPH4D19F
5.2 x 5.2 x 2
33
1.5
3.3
Sumida
CDRH6D12
6.7 x 6.7 x 1.5
62
2.2
4.7
Würth Elektronik
7447785004
5.9 × 6.2 × 3.3
60
2.5
5
Coilcraft
MSS7341
7.3 × 7.3 × 4.1
24
2.9
6.8
Sumida
CDP14D19
5.2 x 5.2 x 2
50
1
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
1.2 MHz
650 kHz
8.2.2.2 Rectifier Diode Selection
To achieve high efficiency, a Schottky type must be used for the rectifier diode. The reverse voltage rating must
be higher than the maximum output voltage of the converter. The averaged rectified forward current Iavg, the
Schottky diode requirement is rated for, is equal to the output current Iout:
I avg = I out
(5)
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 must be able to dissipate the power. The dissipated power is the average rectified forward current
times the diode forward voltage.
PD = Iavg × Vforward
(6)
Typically the diode must be able to dissipate around 500 mW depending on the load current and forward voltage.
See Table 4 for few diode options. Customers must verify and validate these components for suitability with their
application before using them.
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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
MSS1P2L
µ-SMP
(Low Profile)
1A
20 V
0.44 V / 1 A
Vishay Semiconductor
8.2.2.3 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:
R2 =
Vref
» 18k W
70 m A
æ VS
ö
R1 = R 2 ´ ç
- 1÷
è Vref
ø
(7)
8.2.2.4 Compensation (COMP)
The regulator loop must 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 works for the majority of the applications.
See Table 5 for dedicated compensation networks giving an improved load transient response. Equation 8 can
be used to calculate RCOMP and CCOMP:
SPACE
RCOMP =
110 × VIN × VS × COUT
L × I OUT
CCOMP =
Vs × COUT
7.5 × I OUT × RCOMP
(8)
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
5V
82 kΩ
1.1 nF
3.3 V
75 kΩ
1.6 nF
5V
51 kΩ
1.1 nF
3.3 V
47 kΩ
1.6 nF
5V
30 kΩ
1.1 nF
3.3 V
27 kΩ
1.6 nF
5V
43 kΩ
2.2 nF
3.3 V
39 kΩ
3.3 nF
5V
27 kΩ
2.2 nF
3.3 V
24 kΩ
3.3 nF
5V
15 kΩ
2.2 nF
3.3 V
13 kΩ
3.3 nF
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Table 5 gives conservatives 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 must be performed in
parallel with the load transient response monitoring of TPS61085T.
8.2.2.5 Input Capacitor Selection
For good input voltage filtering, TI recommends low-ESR ceramic capacitors. TPS61085T has an analog input
(IN). Therefore, TI highly recommends placing a 1-uF bypass capacitor as close as possible to the IC from IN to
GND.
One 10-µF ceramic input capacitor is 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.
Customers must verify and validate these components for suitability with their application before using them.
8.2.2.6 Output Capacitor Selection
For best output voltage filtering, TI recommends a low ESR output capacitor like ceramic capacitor. 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.
Pay attention to the derating of capacitor value with the DC voltage.
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
8.2.3 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
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COUT = 20 µF
L = 3.3 µH
RCOMP = 51 kΩ
CCOMP = 1.6 nF
VIN = 3.3 V
VS = 12 V
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
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
8.3 System Examples
Figure 14 to Figure 21 show application circuit examples using the TPS61085T device. These circuits must be
fully validated and tested by customers before using these circuits in their designs. TI does not warrant the
accuracy or completeness of these circuits, nor does TI accept any responsibility for them.
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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
5
D
PMEG2010AEH
VS
12 V/600 mA max
R1
158 kΩ
2
FB
EN
R2
18.2 kΩ
1
7
COUT
2* 10 µF
25 V
COMP
FREQ
4
RCOMP
24 kΩ
8
GND
SS
CSS
TPS61085T
CCOMP
3.3 nF
100 nF
Copyright © 2016, Texas Instruments Incorporated
Figure 14. Typical Application, 3.3 V to 12 V (fsw = 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
5
D
PMEG2010AEH
R1
113 kΩ
2
EN
VS
9 V/800 mA max
FB
R2
18 kΩ
1
7
COUT
2* 10 µF
25 V
COMP
FREQ
4
RCOMP
27 kΩ
8
GND
SS
TPS61085T
CSS
CCOMP
1.6 nF
100 nF
Copyright © 2016, Texas Instruments Incorporated
Figure 15. Typical Application, 3.3 V to 9 V (fsw = 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
VS
9 V/800 mA max
R1
113 kΩ
2
FB
EN
R2
18 kΩ
1
7
COUT
2* 10 µF
25 V
COMP
FREQ
4
RCOMP
13 kΩ
8
GND
SS
CCOMP
3.3 nF
CSS
TPS61085T
100 nF
Copyright © 2016, Texas Instruments Incorporated
Figure 16. Typical Application, 3.3 V to 9 V (fsw = 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
TPS61085T
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
Copyright © 2016, Texas Instruments Incorporated
Figure 17. Typical Application With External Load Disconnect Switch
16
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System Examples (continued)
VGL
-7 V/ 20 mA
T1
BC857B
-VS
C3
100 nF
50 V
C2
R8
7 kΩ 470 nF
25 V
C1
1 µF/
35V
C4
100 nF/
D4
50 V BAT54S
D2
BAT54S
D3
BAT54S
D1
BZX84C7V5
C6
470 nF
50 V
D5
BAT54S
C5
100 nF
50 V
VGH
T2
BC850B
3* VS
R10
13 kΩ
20 V/20 mA
C8
2*Vs
1 µF
35 V
C7
470 nF
50 V
D6
BAT54S
D8
BZX84C 20 V
D7
BAT54S
L
3.3 µH
V IN
3.3 V ± 20%
6
C BY
1 µF
16 V
5
VIN
SW
EN
FB
3
C IN
16 V
7
FREQ
D
PMEG2010AEHG
VS
9V /500 mA
2
R1
113 kΩ
1
R2
18 kΩ
COMP
SS
GND
C SS
TPS61085T
2*10 µF
25 V
R COMP
27 kΩ
8
4
C OUT
C COMP
1.6 nF
100 nF
Copyright © 2016, Texas Instruments Incorporated
Figure 18. Typical Application 3.3 V to 9 V (fsw = 1.2 MHz) for TFT LCD With External Charge Pumps
(VGH, VGL)
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
TPS61085T
RLIMIT
110 Ω
1
RCOMP
24 kΩ
8
CSS
100 nF
RSENSE
15 Ω
CCOMP
3.3 nF
Copyright © 2016, Texas Instruments Incorporated
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
TPS61085T
RSENSE
15 Ω
CCOMP
3.3 nF
CSS
100 nF
Copyright © 2016, Texas Instruments Incorporated
Figure 20. Simple Application (3.3-V 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
TPS61085T
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
Copyright © 2016, Texas Instruments Incorporated
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)
9 Power Supply Recommendations
The TPS61085T is designed to operate from an input voltage supply range from 2.3 V to 6 V. The required
power supply for the TPS61085T must have a current rating according to the output voltage and output current of
the TPS61085T.
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10 Layout
10.1 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.
provides an example of layout design with the TPS61085T device.
• Use wide and short traces for the main current path and for the power ground tracks.
• The input capacitor, output capacitor, and the inductor must 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 must be placed on the same board layer as the IC and as close as possible between the SW pin
and the GND terminal of the IC.
10.2 Layout Example
IN
SW
5
6
7
8
FREQ
VOUT
SS
VIN
PGND
3
EN
4
2
COMP
1
FB
TPS61085T
GND
Figure 22. TPS61085T Layout Example
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11 Device and Documentation Support
11.1 Device Support
11.1.1 Third-Party Products Disclaimer
TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT
CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES
OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER
ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.
11.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
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.
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.
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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)
TPS61085TDGKR
ACTIVE
VSSOP
DGK
8
2000
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 105
PTQI
TPS61085TPWR
ACTIVE
TSSOP
PW
8
2000
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 105
61085T
(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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