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FEATURES DESCRIPTION
APPLICATIONS
SW
C1
10 µF
L1
4.7 µH
VBAT
VOUT
FB
C2
10 µF
EN
GND
TPS61070
VO
3.3 V Up To
100 mA
R1
R2
0.9-V To VO
TPS61070
TPS61071
SLVS510 – JUNE 2004
90% EFFICIENT SYNCHRONOUS BOOST CONVERTER WITH 600-mA SWITCH
•90% Efficient Synchronous Boost Converter
The TPS6107x devices provide a power supplysolution for products powered by either a one-cell,– 75-mA Output Current at 3.3 V From 0.9-V
two-cell, or three-cell alkaline, NiCd or NiMH, orInput
one-cell Li-ion or Li-polymer battery. Output currents– 150-mA Output Current at 3.3 V From 1.8-V
can go as high as 75 mA while using a single-cellInput
alkaline, and discharge it down to 0.9 V. It can also•Device Quiescent Current: 19 µA (Typ)
be used for generating 5 V at 200 mA from a 3.3-Vrail or a Li-ion battery. The boost converter is based•Input Voltage Range: 0.9 V to 5.5 V
on a fixed frequency, pulse-width-modulation (PWM)•Adjustable Output Voltage Up to 5.5 V
controller using a synchronous rectifier to obtain•Power-Save Mode Version Available for
maximum efficiency. At low load currents theImproved Efficiency at Low Output Power
TPS61070 enters the power-save mode to maintain ahigh efficiency over a wide load current range. At the•Load Disconnect During Shutdown
TPS61071 the power-save mode is disabled, forcing•Overtemperature Protection
the converter to operate at a fixed switching fre-•Small 6-Pin Thin SOT23 Package
quency. The maximum peak current in the boostswitch is typically limited to a value of 600 mA.
The TPS6107x output voltage is programmed by an•All One-Cell, Two-Cell, and Three-Cell Alka-
external resistor divider. The converter can be dis-line, NiCd or NiMH or Single-Cell Li
abled to minimize battery drain. During shutdown, theBattery-Powered Products
load is completely disconnected from the battery. The•Portable Audio Players
device is packaged in a 6-pin thin SOT23 package(DDC).•PDAs
•Cellular Phones•Personal Medical Products•White LED Lighting
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of TexasInstruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Copyright © 2004, Texas Instruments IncorporatedProducts conform to specifications per the terms of the TexasInstruments standard warranty. Production processing does notnecessarily include testing of all parameters.
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ABSOLUTE MAXIMUM RATINGS
DISSIPATION RATINGS TABLE
RECOMMENDED OPERATING CONDITIONS
TPS61070
TPS61071
SLVS510 – JUNE 2004
These devices have limited built-in ESD protection. The leads should be shorted together or the deviceplaced in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
AVAILABLE OUTPUT VOLTAGE OPTIONS
OUTPUT VOLTAGE POWER-SAVE PACKAGET
A
PACKAGE PART NUMBER
(1)DC/DC MODE MARKING
Adjustable Enabled AUH TPS61070DDC- 40°C to 85°C 6-Pin TSOT23Adjustable Disabled AUJ TPS61071DDC
(1) The DDC package is available taped and reeled. Add R suffix to device type (e.g., TPS61070DDCR) to order quantities of 3000 devicesper reel.
over operating free-air temperature range (unless otherwise noted)
(1)
TPS6107x
Input voltage range on SW, VOUT, VBAT, EN, FB -0.3 V to 7 VOperating virtual junction temperature range, T
J
-40°C to 150°CStorage temperature range T
stg
-65°C to 150°C
(1) Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratingsonly, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operatingconditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
THERMAL RESISTANCE POWER RATING DERATING FACTOR ABOVEPACKAGE
Θ
JA
T
A
≤25°C T
A
= 25°C
DDC 76 °C/W 1315 mW 13 mW/°C
MIN NOM MAX UNIT
Supply voltage at VBAT, V
I
0.9 5.5 VOperating free air temperature range, T
A
-40 85 °COperating virtual junction temperature range, T
J
-40 125 °C
2
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ELECTRICAL CHARACTERISTICS
TPS61070
TPS61071
SLVS510 – JUNE 2004
over recommended free-air temperature range and over recommended input voltage range (typical at an ambient temperaturerange of 25°C) (unless otherwise noted)
DC/DC STAGE
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
Minimum input voltage range for
R
L
= 270 Ω1.1 1.2start-upV
I
VInput voltage range, after start-up T
A
= 25°C 0.9 5.5V
O
TPS61070 output voltage range 1.8 5.5 VV
(FB)
TPS61070 feedback voltage 495 500 505 mVf Oscillator frequency 960 1200 1440 kHzI
(SW)
Switch current limit VOUT= 3.3 V 500 600 700 mAStart-up current limit 0.5 x I
SW
mASWN switch-on resistance VOUT= 3.3 V 480 mΩSWP switch-on resistance VOUT= 3.3 V 600 mΩTotal accuracy (including line and
3%load regulation)
Line regulation 1%Load regulation 1%VBAT 0.5 1 µAI
O
= 0 mA, V
(EN)
= VBAT = 1.2 V,Quiescent current
VOUT = 3.3 V, T
A
= 25°CVOUT 19 30 µAShutdown current V
(EN)
= 0 V, VBAT = 1.2 V, T
A
= 25°C 0.05 0.5 µA
CONTROL STAGE
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
V
(UVLO)
Undervoltage lockout threshold V
(LBI)
voltage decreasing 0.8 V0.2 ×VV
IL
EN input low voltage
VBAT0.8 ×VV
IH
EN input high voltage
VBATEN input current Clamped on GND or VBAT 0.01 0.1 µAOvertemperature protection 140 °COvertemperature hysteresis 20 °C
3
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PIN ASSIGNMENTS
1
DDC PACKAGE
(TOP VIEW)
SW
EN
VOUT
3
5GND
VBAT
FB
2
6
4
TPS61070
TPS61071
SLVS510 – JUNE 2004
Terminal Functions
TERMINAL
I/O DESCRIPTIONNAME NO.
EN 3 I Enable input (1/VBAT enabled, 0/GND disabled)FB 4 I Voltage feedback for programming the output voltageGND 2 IC ground connection for logic and powerSW 1 I Boost and rectifying switch inputVBAT 6 I Supply voltageVOUT 5 O Boost converter output
4
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Gate
Control
GND
Regulator
Error
Amplifier
Control Logic Oscillator
Temperature
Control
VOUT
FB
SW
VBAT
EN
GND
_
+
Backgate
Control
Vmax
Control
VOUT 5 kΩ
3 pF
_
+
Vref = 0.5 V
GND
5 pF
50 kΩ160 kΩ
PARAMETER MEASUREMENT INFORMATION
SW
C1
Power
Supply
L1
4.7 µH
VBAT
VOUT
FB
C2
EN
GND
TPS6107x
List of Components:
U1 = TPS61070DDC
L1 = Wurth Elektronik 744031004
C1 = 2 x 4.7 F, 0603, X7R/X5R Ceramic
C2 = 4 x 4.7 F, 0603, X7R/X5R Ceramic
VCC
Boost Output
R1
R2
TPS61070
TPS61071
SLVS510 – JUNE 2004
FUNCTIONAL BLOCK DIAGRAM (TPS61070)
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TYPICAL CHARACTERISTICS
Table of Graphs
TPS61070
TPS61071
SLVS510 – JUNE 2004
FIGURE
Maximum output current vs Input voltage 1vs Output current 2vs Output current 3Efficiency vs Output current 4vs Input voltage 5vs Input voltage 6vs Output current 7Output voltage
vs Output current 8No load supply current into VOUT vs Input voltage 9Output voltage in continuous mode (TPS61071) 10Output voltage in continuous mode (TPS61071) 11Output voltage in power-save mode (TPS61070) 12Output voltage in power-save mode (TPS61070) 13Load transient response (TPS61071) 14Load transient response (TPS61071) 15Waveforms
Line transient response (TPS61071) 16Line transient response (TPS61071) 17Start-up after enable (TPS61070) 18Start-up after enable (TPS61070) 19Start-up after enable (TPS61071) 20Start-up after enable (TPS61071) 21
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TYPICAL CHARACTERISTICS
0
10
20
30
40
50
60
70
80
90
100
0.01 0.10 1 10 100 1 k
VBAT = 1.2 V
TPS61070
VO = 1.8 V
TPS61071
VO = 1.8 V
IO − Output Current − mA
Efficiency − %
VBAT = 0.9 V
0
50
100
150
200
250
300
350
400
450
500
550
600
0.9 1.3 1.7 2.1 2.5 2.9 3.3 3.7 4.1 4.5 4.9
VI − Input Voltage − V
Maximum Output Current − mA
VO = 3.3 V
VO = 1.8 V VO = 5 V
0
10
20
30
40
50
60
70
80
90
100
0.01 0.10 1 10 100 1 k
TPS61070
VO = 5 V
TPS61071
VO = 5 V
VBAT = 1.2 V VBAT = 1.8 V
VBAT = 2.4 V
VBAT = 3.6 V
IO − Output Current − mA
Efficiency − %
TPS61070
TPS61071
SLVS510 – JUNE 2004
MAXIMUM OUTPUT CURRENT EFFICIENCYvs vsINPUT VOLTAGE OUTPUT CURRENT
Figure 1. Figure 2.
EFFICIENCY EFFICIENCYvs vsOUTPUT CURRENT OUTPUT CURRENT
Figure 3. Figure 4.
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50
55
60
65
70
75
80
85
90
95
0.9 1.4 1.9 2.4 2.9 3.4 3.9 4.4 4.9
100 TPS61070
VO = 5 V
TPS61071
VO = 5 V
VI − Input Voltage − V
Efficiency − %
IO = 5 mA
IO = 10 mA
IO = 60 mA
IO = 5 mA
50
55
60
65
70
75
80
85
90
95
100
0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3
IO = 5 mA
IO = 50 mA
IO = 100 mA
TPS61070
VO = 3.3 V
TPS61071
VO = 3.3 V
VI − Input Voltage − V
Efficiency − %
3.20
3.25
3.30
3.35
1 10 100 1000
VBAT = 2.4 V TPS61070
VO = 3.3 V
TPS61071
VO = 3.3 V
IO − Output Current − mA
− Output Voltage − V
VO
4.8
4.85
4.9
4.95
5
5.05
5.1
110 100 1000
TPS61070
VO = 5 V
TPS61071
VO = 5 V
VBAT = 3.6 V
IO − Output Current − mA
− Output Voltage − V
VO
TPS61070
TPS61071
SLVS510 – JUNE 2004
TYPICAL CHARACTERISTICS (continued)
EFFICIENCY EFFICIENCYvs vsINPUT VOLTAGE INPUT VOLTAGE
Figure 5. Figure 6.
OUTPUT VOLTAGE OUTPUT VOLTAGEvs vsOUTPUT CURRENT OUTPUT CURRENT
Figure 7. Figure 8.
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Inductor Current
100 mA/div Output Voltage
20 m/div
VI = 1.2 V, RL = 33 , VO = 3.3 V
t − Time − 1 s/div
10
12
14
16
18
22
0.9 1.5 2.5 3.5 4.5 5.5
VI− Input Voltage − V
No Load Supply Current Into VOUT − Aµ
TA = 25C
20 TA = 85C
TA = −40C
VO = 3.3 V
VI = 0.9 V to 5.5 V
Inductor Current
200 mA/div Output Voltage
20 mV/div
VI = 3.6 V, RL = 25 , VO = 5 V
t − Time − 1 s/div
Inductor Current
100 mA/div, DC Output Voltage
20 mV/div, AC
VI = 1.2 V, RL = 330 , VO = 3.3 V
t − Time − 10 s/div
TPS61070
TPS61071
SLVS510 – JUNE 2004
TYPICAL CHARACTERISTICS (continued)
NO LOAD SUPPLY CURRENT INTO VOUTvs TPS61071INPUT VOLTAGE OUTPUT VOLTAGE IN CONTINUOUS MODE
Figure 9. Figure 10.
TPS61071 TPS61070OUTPUT VOLTAGE IN CONTINUOUS MODE OUTPUT VOLTAGE IN POWER-SAVE MODE
Figure 11. Figure 12.
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Output Current
50 mA/div, DC
Output Voltage
50 mV/div, AC
VI = 1.2 V, IL = 20 mA to 80 mA, VO = 3.3 V
t − Time − 2 ms/div
Inductor Current
200 mA/div, DC Output Voltage
100 mV/div, AC
VI = 3.6 V, RL = 250 , VO = 5 V
t − Time − 20 s/div
Output Current
50 mA/div, DC
Output Voltage
50 mV/div, AC
VI = 3.6 V, IL = 20 mA to 80 mA, VO = 5 V
t − Time − 2 ms/div
Output Voltage
20 mV/div, AC Input Voltage
500 mV/div, AC
VI = 1.8 V to 2.4 V, RL = 33 , VO = 3.3 V
t − Time − 2 ms/div
TPS61070
TPS61071
SLVS510 – JUNE 2004
TYPICAL CHARACTERISTICS (continued)
TPS61070 TPS61071OUTPUT VOLTAGE IN POWER-SAVE MODE LOAD TRANSIENT RESPONSE
Figure 13. Figure 14.
TPS61071 TPS61071LOAD TRANSIENT RESPONSE LINE TRANSIENT RESPONSE
Figure 15. Figure 16.
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Output Voltage
50 mV/div, AC Input Voltage
500 mV/div, AC
VI = 3 V to 3.6 V, RL = 25 , VO = 5 V
t − Time − 2 ms/div
Enable
5 V/div, DC
Output Voltage
2 V/div, DC
Inductor Current
200 mA/div, DC
Voltage at SW
2 V/div, DC
VI = 2.4 V,
RL = 33 ,
VO = 3.3 V
t − Time − 200 s/div
Enable
5 V/div, DC
Output Voltage
2 V/div, DC
Inductor Current
200 mA/div, DC
Voltage at SW
2 V/div, DC
VI = 3.6 V,
RL = 50 ,
VO = 5 V
t − Time − 400 s/div
Enable
5 V/div, DC
Output Voltage
1 V/div, DC
Inductor Current
200 mA/div, DC
Voltage at SW
2 V/div, DC
VI = 2.4 V,
RL = 33 ,
VO = 3.3 V
t − Time − 200 s/div
TPS61070
TPS61071
SLVS510 – JUNE 2004
TYPICAL CHARACTERISTICS (continued)
TPS61071 TPS61070LINE TRANSIENT RESPONSE START-UP AFTER ENABLE
Figure 17. Figure 18.
TPS61070 TPS61071START-UP AFTER ENABLE START-UP AFTER ENABLE
Figure 19. Figure 20.
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Enable
5 V/div, DC
Output Voltage
2 V/div, DC
Inductor Current
200 mA/div, DC
Voltage at SW
2 V/div, DC
VI = 3.6 V,
RL = 50 ,
VO = 5 V
t − Time − 200 s/div
TPS61070
TPS61071
SLVS510 – JUNE 2004
TYPICAL CHARACTERISTICS (continued)
TPS61071
START-UP AFTER ENABLE
Figure 21.
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DETAILED DESCRIPTION
CONTROLLER CIRCUIT
Synchronous Rectifier
Device Enable
Undervoltage Lockout
Soft Start
TPS61070
TPS61071
SLVS510 – JUNE 2004
The controller circuit of the device is based on a fixed frequency multiple feedforward controller topology. Inputvoltage, output voltage, and voltage drop on the NMOS switch are monitored and forwarded to the regulator. So,changes in the operating conditions of the converter directly affect the duty cycle and must not take the indirectand slow way through the control loop and the error amplifier. The control loop, determined by the error amplifier,only has to handle small signal errors. The input is the feedback voltage on the FB pin. It is compared with theinternal reference voltage to generate an accurate and stable output voltage.
The peak current of the NMOS switch is also sensed to limit the maximum current flowing through the switch andthe inductor. The typical peak-current limit is set to 600 mA. An internal temperature sensor prevents the devicefrom overheating due to excessive power dissipation.
The device integrates an N-channel and a P-channel MOSFET transistor to realize a synchronous rectifier.Because the commonly used discrete Schottky rectifier is replaced with a low r
DS(on)
PMOS switch, the powerconversion efficiency reaches values above 90%. A special circuit is applied to disconnect the load from the inputduring shutdown of the converter. In conventional synchronous rectifier circuits, the backgate diode of thehigh-side PMOS is forward biased in shutdown and allows current flowing from the battery to the output.However, this device uses a special circuit which takes the cathode of the backgate diode of the high-side PMOSand disconnects it from the source when the regulator is not enabled (EN = low).
The benefit of this feature for the system design engineer is that the battery is not depleted during shutdown ofthe converter. No additional components must be added to the design to make sure that the battery isdisconnected from the output of the converter.
The device is put into operation when EN is set high. It is put into a shutdown mode when EN is set to GND. Inshutdown mode, the regulator stops switching, all internal control circuitry including the low-battery comparator isswitched off, and the load is isolated from the input (as described in the Synchronous Rectifier Section). Thisalso means that the output voltage can drop below the input voltage during shutdown. During start-up of theconverter, the duty cycle and the peak current are limited in order to avoid high-peak currents drawn from thebattery.
An undervoltage lockout function prevents the device from operating if the supply voltage on VBAT is lower thanapproximately 0.8 V. When in operation and the battery is being discharged, the device automatically enters theshutdown mode if the voltage on VBAT drops below approximately 0.8 V. This undervoltage lockout function isimplemented in order to prevent the malfunctioning of the converter.
When the device enables, the internal start-up cycle starts with the first step, the precharge phase. Duringprecharge, the rectifying switch is turned on until the output capacitor is charged to a value close to the inputvoltage. The rectifying switch is current limited during this phase. This also limits the output current undershort-circuit conditions at the output. After charging the output capacitor to the input voltage, the device startsswitching. If the input voltage is below 1.8 V, the device works with a fixed duty cycle of 70% until the outputvoltage reaches 1.8 V. Then the duty cycle is set depending on the input output voltage ratio. Until the outputvoltage reaches its nominal value, the boost switch current limit is set to 50% of its nominal value to avoidhigh-peak currents at the battery during start-up. As soon as the output voltage is reached, the regulator takescontrol, and the switch current limit is set back to 100%.
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Power-Save Mode
TPS61070
TPS61071
SLVS510 – JUNE 2004
DETAILED DESCRIPTION (continued)
The TPS61070 is capable of operating in two different modes. At light loads, when the inductor current becomeszero, it automatically enters the power-save mode to improve efficiency. In the power-save mode, the converteronly operates when the output voltage trips below a set threshold voltage. It ramps up the output voltage withone or several pulses and returns to the power-save mode once the output voltage exceeds the set thresholdvoltage. If output power demand increases and the inductor current no longer goes below zero, the device againenters the fixed PWM mode. In this mode, there is no difference between the PWM only version TPS61071 andthe power-save mode enabled version TPS61070.
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APPLICATION INFORMATION
DESIGN PROCEDURE
Programming the Output Voltage
R1 R2 VO
VFB 1180 kVO
500 mV 1
(1)
CparR1 3 pF 200 k
R2 1
(2)
SW
C1
Power
Supply
L1
VBAT
VOUT
FB
C2
EN
GND
TPS61070
VCC
Boost Output
R1
R2
Inductor Selection
ILIOVOUT
VBAT 0.8
(3)
TPS61070
TPS61071
SLVS510 – JUNE 2004
The TPS6107x dc/dc converters are intended for systems powered by a single-cell, up to triple-cell alkaline,NiCd, NiMH battery with a typical terminal voltage between 0.9 V and 5.5 V. They can also be used in systemspowered by one-cell Li-ion or Li-polymer with a typical voltage between 2.5 V and 4.2 V. Additionally, any othervoltage source with a typical output voltage between 0.9 V and 5.5 V can power systems where the TPS6107x isused. Due to the nature of boost converters, only the output voltage regulation is maintained when the inputvoltage applied is lower than the programmed output voltage.
The output voltage of the TPS61070 dc/dc converter can be adjusted with an external resistor divider. The typicalvalue of the voltage at the FB pin is 500 mV. The maximum recommended value for the output voltage is 5.5 V.The current through the resistive divider should be about 100 times greater than the current into the FB pin. Thetypical current into the FB pin is 0.01 µA, and the voltage across R2 is typically 500 mV. Based on those twovalues, the recommended value for R2 should be lower than 500 kΩ, in order to set the divider current at 1 µA orhigher. Because of internal compensation circuitry, the value for this resistor should be in the range of 200 kΩ.From that, the value of resistor R1, depending on the needed output voltage (V
O
), can be calculated usingEquation 1 :
For example, if an output voltage of 3.3 V is needed, a 1-MΩresistor should be chosen for R1. If for any reasonthe value chosen for R2 is significantly lower than 200 kΩ, additional capacitance in parallel to R1 isrecommended, because the device can show unstable regulation of the output voltage. The required capacitancevalue can be calculated using Equation 2 :
Figure 22. Typical Application Circuit for Adjustable Output Voltage Option
A boost converter normally requires two main passive components for storing energy during the conversion. Aboost inductor and a storage capacitor at the output are required. To select the boost inductor, it isrecommended to keep the possible peak inductor current below the current limit threshold of the power switch inthe chosen configuration. For example, the current limit threshold of the TPS6107x's switch is 600 mA. Thehighest peak current through the inductor and the switch depends on the output load, the input (VBAT), and theoutput voltage (VOUT). Estimation of the maximum average inductor current is done using Equation 3 :
For example, for an output current of 75 mA at 3.3 V, at least 340 mA of average current flows through theinductor at a minimum input voltage of 0.9 V.
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LVBAT (VOUT VBAT)
ILƒVOUT
(4)
Capacitor Selection
Input Capacitor
Output Capacitor
Cmin IOVOUT VBAT
ƒVVOUT
(5)
TPS61070
TPS61071
SLVS510 – JUNE 2004
The second parameter for choosing the inductor is the desired current ripple in the inductor. Normally, it isadvisable to work with a ripple of less than 20% of the average inductor current. A smaller ripple reduces themagnetic hysteresis losses in the inductor, as well as output voltage ripple and EMI. But in the same way,regulation time rises at load changes. In addition, a larger inductor increases the total system costs. With theseparameters, it is possible to calculate the value for the inductor by using Equation 4 :
Parameter fis the switching frequency and ∆I
L
is the ripple current in the inductor, i.e., 40% ×I
L
. In this example,the desired inductor has the value of 4 µH. With this calculated value and the calculated currents, it is possible tochoose a suitable inductor. In typical applications, a 4.7-µH inductance is recommended. The device has beenoptimized to operate with inductance values between 2.2 µH and 10 µH. Nevertheless, operation with higherinductance values may be possible in some applications. Detailed stability analysis is then recommended. Caremust be taken because load transients and losses in the circuit can lead to higher currents as estimated inEquation 4 . Also, the losses in the inductor caused by magnetic hysteresis losses and copper losses are a majorparameter for total circuit efficiency.
The following inductor series from different suppliers have been used with the TPS6107x converters:
Table 1. List of Inductors
VENDOR INDUCTOR SERIES
VLF3010TDK
VLF4012
744031xxxWurth Elektronik
744042xxxEPCOS B82462-G4
SD18Cooper Electronics Technologies
SD20
CB2016B xxxTaiyo Yuden
CB2518B xxx
At least a 10-µF input capacitor is recommended to improve transient behavior of the regulator and EMI behaviorof the total power supply circuit. A ceramic capacitor or a tantalum capacitor with a 100-nF ceramic capacitor inparallel, placed close to the IC, is recommended.
The major parameter necessary to define the output capacitor is the maximum allowed output voltage ripple ofthe converter. This ripple is determined by two parameters of the capacitor, the capacitance and the ESR. It ispossible to calculate the minimum capacitance needed for the defined ripple, supposing that the ESR is zero, byusing Equation 5 :
Parameter fis the switching frequency and ∆V is the maximum allowed ripple.
With a chosen ripple voltage of 10 mV, a minimum capacitance of 4.5 µF is needed. In this value range, ceramiccapacitors are a good choice. The ESR and the additional ripple created are negligible. It is calculated usingEquation 6 :
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VESR IORESR
(6)
Small Signal Stability
A(REG) d
V(FB) 5(R1 R2)
R2 (1 i0.8 s)
(7)
Layout Considerations
APPLICATION EXAMPLES
SW
C1
Power
Supply
L1
4.7 µH
VBAT
VOUT
FB
C2
EN
GND
TPS6107x
List of Components:
U1 = TPS61070DDC
L1 = Wurth Elektronik 744031004
C1 = 2 x 4.7 F, 0603, X7R/X5R Ceramic
C2 = 2 x 4.7 F, 0603, X7R/X5R Ceramic
VCC
Boost Output
R1
R2
TPS61070
TPS61071
SLVS510 – JUNE 2004
The total ripple is the sum of the ripple caused by the capacitance and the ripple caused by the ESR of thecapacitor. Additional ripple is caused by load transients. This means that the output capacitor has to completelysupply the load during the charging phase of the inductor. The value of the output capacitance depends on thespeed of the load transients and the load current during the load change. With the calculated minimum value of4.5 µF and load transient considerations, the recommended output capacitance value is in a 10-µF range.
Care must be taken on capacitance loss caused by derating due to the applied dc voltage and the frequencycharacteristic of the capacitor. For example, larger form factor capacitors (in 1206 size) have their self resonantfrequencies in the same frequency range as the TPS6107x operating frequency. So the effective capacitance ofthe capacitors used is significantly lower. Therefore, the recommendation is to use smaller capacitors in parallelinstead of one larger capacitor.
To analyze small signal stability in more detail, the small signal transfer function of the error amplifier and theregulator, which is given in Equation 7 , can be used:
As for all switching power supplies, the layout is an important step in the design, especially at high-peak currentsand high switching frequencies. If the layout is not carefully done, the regulator could show stability problems aswell as EMI problems. Therefore, use wide and short traces for the main current path and for the power groundtracks. 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 ofground noise. Connect these ground nodes at any place close to the ground pin of the IC.
The feedback divider should be placed as close as possible to the ground pin of the IC. To lay out the controlground, it is recommended to use short traces as well, separated from the power ground traces. This avoidsground shift problems, which can occur due to superimposition of power ground current and control groundcurrent.
Figure 23. Power Supply Solution for Maximum Output Power Operating from a Single orDual Alkaline Cell
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SW
C1
Power
Supply
L1
4.7 µH
VBAT
VOUT
FB
C2
EN
GND
TPS6107x
List of Components:
U1 = TPS61070DDC
L1 = Taiyo Yuden CB2016B4R7M
C1 = 1 x 4.7 F, 0603, X7R/X5R Ceramic
C2 = 2 x 4.7 F, 0603, X7R/X5R Ceramic
VCC
Boost Output
R1
R2
SW
C1
Power
Supply
L1
4.7 µH
VBAT
VOUT
FB
C2
EN
GND
TPS6107x
List of Components:
U1 = TPS61070DDC
L1 = Taiyo Yuden CB2016B4R7M
C1 = 1 x 4.7 F, 0603, X7R/X5R Ceramic
C2 = 2 x 4.7 F, 0603, X7R/X5R Ceramic
LED Current
Up To 30 mA
R1
D1
C5
0.1 µF
DS1
C6
1 µF
VCC2 ~2 x VCC
Unregulated
Auxiliary Output
SW
C1
Power
Supply
L1
4.7 µH
VBAT
VOUT
FB
C2
EN
GND
TPS6107x
List of Components:
U1 = TPS61070DDC
L1 = Wurth Elektronik 744031004
C1 = 2 x 4.7 F, 0603, X7R/X5R Ceramic
C2 = 2 x 4.7 F, 0603, X7R/X5R Ceramic
VCC
Boost Output
R1
R2
TPS61070
TPS61071
SLVS510 – JUNE 2004
Figure 24. Power Supply Solution Having Small Total Solution Size
Figure 25. Power Supply Solution for Powering White LEDs in Lighting Applications
Figure 26. Power Supply Solution With Auxiliary Positive Output Voltage
18
www.ti.com
C5
0.1 µF
DS1 C6
1 µF
VCC2 ~−VCC
Unregulated
Auxiliary Output
SW
C1
Power
Supply
L1
4.7 µH
VBAT
VOUT
FB
C2
EN
GND
TPS6107x
List of Components:
U1 = TPS61070DDC
L1 = Wurth Elektronik 744031004
C1 = 2 x 4.7 F, 0603, X7R/X5R Ceramic
C2 = 2 x 4.7 F, 0603, X7R/X5R Ceramic
VCC
Boost Output
R1
R2
THERMAL INFORMATION
PD(MAX) TJ(MAX) TA
RJA 125°C85°C
76 °CW520 mW
(8)
TPS61070
TPS61071
SLVS510 – JUNE 2004
Figure 27. Power Supply Solution With Auxiliary Negative Output Voltage
Implementation of integrated circuits in low-profile and fine-pitch surface-mount packages typically requiresspecial attention to power dissipation. Many system-dependent issues such as thermal coupling, airflow, addedheat sinks and convection surfaces, and the presence of other heat-generating components affect thepower-dissipation limits of a given component.
Three basic approaches for enhancing thermal performance follow.•Improving the power dissipation capability of the PCB design•Improving the thermal coupling of the component to the PCB•Introducing airflow in the system
The maximum recommended junction temperature (T
J
) of the TPS6107x devices is 125°C. The thermalresistance of the 6-pin thin SOT package (DDC) is R
ΘJA
= 76°C/W. Specified regulator operation is assured to amaximum ambient temperature T
A
of 85°C. Therefore, the maximum power dissipation is about 520 mW. Morepower can be dissipated if the maximum ambient temperature of the application is lower.
19
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