User’ s Gu ide
September 2004 PMP EVMs
SLVU068A
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Copyright 2004, Texas Instruments Incorporated
EVM IMPORTANT NOTICE
Texas Instruments (TI) provides the enclosed product(s) under the following conditions:
This evaluation kit being sold by TI is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION
PURPOSES ONLY and is not considered by TI to be fit for commercial use. As such, the goods being provided
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As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic
compatibility and therefore may not meet the technical requirements of the directive.
Should this evaluation kit not meet the specifications indicated in the EVM User’s Guide, the kit may be returned
within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE
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The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user
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TI assumes no liability for applications assistance, customer product design, software performance, or
infringement of patents or services described herein.
Please read the EVM User’s Guide and, specifically, the EVM Warnings and Restrictions notice in the EVM
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Copyright 2004, Texas Instruments Incorporated
EVM WARNINGS AND RESTRICTIONS
It is important to operate this EVM within the specified input and output ranges described in
the EVM User’s Guide. This EVM is designed to operate over an input range of 1.8 V to 6 V
and over a load range of 0.1 mA to 20 mA.
Exceeding the specified input range may cause unexpected operation and/or irreversible
damage to the EVM. If there are questions concerning the input range, please contact a TI
field representative prior to connecting the input power.
Applying loads outside of the specified output range may result in unintended operation and/or
possible permanent damage to the EVM. Please consult the EVM User’s Guide prior to
connecting any load to the EVM output. If there is uncertainty as to the load specification,
please contact a TI field representative.
During normal operation, some circuit components may have case temperatures greater than
60°C. The EVM is designed to operate properly with certain components above 60°C as long
as the input and output ranges are maintained. These components include but are not limited
to linear regulators, switching transistors, pass transistors, and current sense resistors. These
types of devices can be identified using the EVM schematic located in the EVM User’s Guide.
When placing measurement probes near these devices during operation, please be aware
that these devices may be very warm to the touch.
Mailing Address:
Texas Instruments
Post Office Box 655303
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Copyright 2004, Texas Instruments Incorporated
About This Manual
Related Documentation From Texas Instruments
Preface
This user’s guide describes the characteristics, operation, and use of the
TPS61040EVM−002 white light LED bias supply evaluation module (EVM).
This EVM is a Texas Instruments high-efficiency boost converter configured
to supply 20 mA of bias current to four white light LEDs, from a single-cell Li-ion
battery. The user’s guide includes a schematic diagram, bill of materials
(BOM), and test data.
How to Use This Manual
This document contains the following chapters:
- Chapter 1 – Introduction
- Chapter 2 – Setup and Test Results
- Chapter 3 – Board Layout
- Chapter 4 – Schematic and Bill of Materials
Related Documentation From Texas Instruments
TPS61040/41 data sheet (literature number SLVS413)
FCC Warning
This equipment is intended for use in a laboratory test environment only. It generates, uses, and can radiate radio frequency energy and has not been tested
for compliance with the limits of computing devices pursuant to subpart J of
part 15 of FCC rules, which are designed to provide reasonable protection
against radio frequency interference. Operation of this equipment in other environments may cause interference with radio communications, in which case
the user at his own expense will be required to take whatever measures may
be required to correct this interference.
v
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vi
Contents
1 Introduction 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1 Background 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Performance Specification Summary 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Setup and Test Results 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1 Input/Output Connections 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 EVM Operation 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.1 Analog Dimming With Analog Voltage 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.2 Analog Dimming With PWM Voltage 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.3 PWM Dimming Using Enable 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.4 PWM Dimming Using Injected Voltage on FB 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Setup 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4 Start-up 2-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5 LED Ripple Current 2-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6 Switching Waveforms 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.7 Efficiency 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.8 Analog Dimming With Analog Voltage Data 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.9 Analog Dimming With PWM Voltage Data 2-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.10 PWM Dimming Using Enable Data 2-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.11 PWM Dimming Using Injected Voltage on FB Data 2-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 Board Layout 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1 Board Layout 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 Schematic and Bill of Materials 4-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.1 Schematic 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Bill of Materials 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
vii
Contents
2−1 Start-up Waveforms 2-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−2 Output Ripple Current 2-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−3 SW Waveform 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−4 Typical Efficienty 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−5 Output Current vs Control Voltage 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−6 PWM Control Converted to Analog Control Voltage 2-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−7 Input Current and Output Current With PWM Dimming Using Enable 2-10. . . . . . . . . . . . . . .
2−8. Output Current vs Duty Cycle for PWM Dimming Using Enable 2-11. . . . . . . . . . . . . . . . . . . . .
2−9 Control Voltage and Output Current 2-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−10 Output Current vs Duty Cycle 2-13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3−1 Assembly Layer 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3−2 Top Layer Routing 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3−3 Bottom Layer Routing 3-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1−1 Performance Specification Summary 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−1 Input/Output Connections 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
viii
Chapter 1
This chapter contains background information for the TPS61040 and support
documentation for the TPS61040EVM-002 evaluation module.
Topic Page
1.1 Background 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Performance Specification Summary 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction
1-1
Background
1.1 Background
The TPS61040EVM uses the TPS61040 boost converter to provide 20 mA of
bias current to a four-element white LED from a single-cell Li-ion battery (3 V
to 4.2 V). The EVM operates over an input voltage range of 1.8 V to 6.0 V , but
has been optimized over a 3-V to 4.2-V input range. Operation with an input
voltage down to 1.8 V is possible, depending on the number of LEDs and the
desired bias current. The EVM can also be configured for higher or lower
output currents. For lower currents, the pin-for-pin compatible TPS61041 may
replace the TPS61040. The EVM includes two adjust pins that allow the user
to dim the LEDs using either an analog or a PWM dimming scheme. A third
dimming method available to the user is to apply a PWM signal to the enable
pin of the device. More information about output voltage and current ratings
of TPS61040/41 devices can be found in the data sheet, literature number
SLVS413.
1.2 Performance Specification Summary
Table 1−1 provides a summary of the TPS61040EVM−002 performance
specifications. All specifications are given for an ambient temperature of 25°C.
Although the EVM is designed for four LEDs, it may be modified to provide
power for fewer or greater than four LEDs. See the TPS61040 data sheet for
detailed specifications. The EVM may also be modified to operate at voltages
down to 1.8 V and up to 6.0 V to match the TPS61040 data sheet
specifications.
Table 1−1.Performance Specification Summary
Specification Test Conditions Min Typ Max Units
Input voltage range Iout = 20 mA 3.0 4.2 V
Load Iout = 20 mA Four white light LEDs
Output current 0.1 20 mA
Efficiency Vin = 4.2 V 86.5 %
1-2
Chapter 2
This chapter describes how to properly connect, set up, and use the
TPS61040EVM−002. It also presents the test results for the EVM. All test
results are measured with the EVM driving four white light LEDs.
Topic Page
2.1 Input/Output Connections 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 EVM Operation 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Setup 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4 Start-up 2-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5 LED Ripple Current 2-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6 Switching Waveforms 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.7 Efficiency 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.8 Analog Dimming With Analog Voltage Data 2-8. . . . . . . . . . . . . . . . . . . . .
2.9 Analog Dimming With PWM Voltage Data 2-9. . . . . . . . . . . . . . . . . . . . . . .
2.10 PWM Dimming Using Enable Data 2-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.11 PWM Dimming Using Injected Voltage on FB Data 2-12. . . . . . . . . . . . . .
Setup and Test Results
2-1
Input/Output Connections
2.1 Input/Output Connections
The TPS61040EVM−002 PWB has several connections, which are described
in Table 2−1.
Table 2−1.Input/Output Connections
Reference
Designator
J1 Vin This is the positive connection to the input power supply. Input supply leads (Vin
J2 GND This is the return connection for the input power supply.
J3 DIM1 Input for dimming adjust of LED current
J3 DIM2 Input for dimming adjust of LED current
J3 GND Ground connection for the dimming adjust signal
J4 LED Anode Output to anode of LED
J5 LED
J6 GND Ground connection
JP1 Enable Use this connector to enable and disable the power supply. Connect a jumper
Name Description
and GND) should be a twisted pair and kept as short as possible.
Output to cathode of LED
Cathode
between the ON pin and the center pin to enable the supply. Connect a jumper
between the OFF pin and the center pin to disable the supply. If this pin is left open,
the EVM does not operate correctly. This pin is also used for PWM dimming control
of the LED current.
2.2 EVM Operation
The EVM is configured as a constant current supply. Current regulation is
accomplished by regulating the voltage across a current sense resistor. The
EVM does not operate correctly unless a load is placed between J4 (LED
Anode) and J5 (LED Cathode). With no load, the output voltage increases until
clamped by the 27−V zener diode shown in the schematic.
The EVM provides the user with a place to add up to four LEDs (D2 through
D6). More or fewer than four LEDs may be used, but the connections to the
board must be made such that the load current flows from the LED anode
connection to the LED cathode connection. If a resistive load is being
substituted for LEDs, the load resistance must be small enough so that the
resistance times the programmed load current is less than 27 V.
This EVM is designed to accommodate several LED-dimming techniques.
Because of this flexibility, circuitry may be present on the EVM that is not
needed for the particular dimming method you choose. Depending on the
PWM dimming technique used, component values may need to be changed
to provide the desired LED current level. Before using the EVM, determine the
method of dimming. Descriptions of several dimming techniques follow.
2.2.1 Analog Dimming With Analog Voltage
One method for dimming the LEDs is to inject a voltage through a resistor into
the FB pin of the TPS61040. The injected voltage artificially raises the voltage
2-2
EVM Operation
seen at the FB pin, which lowers the LED current. If the resistor values are
chosen correctly , the analog control voltage varies the output current between
0 mA and maximum programmed current. This dimming method is the default
configuration of the EVM, and is accomplished by injecting an analog voltage
into the DIM 1 p i n o n J3. When using this method, R1 and C2 do not af fect the
operation of the EVM. The EVM is designed so that an analog voltage of 0 V
to 3.3 V varies the LED current from 20 mA to 0 mA. Use the following
equations to calculate the required resistor values.
Where:
- V
- V
- V
- I
- I
- R2 is a dimming resistor.
- Ref Des corresponds to the EVM schematic shown in Chapter 4.
is the TPS61040 reference voltage = 1.233 V.
REF
adj_min
adj_max
out_min
out_max
is the minimum adjust voltage.
is the maximum adjust voltage.
is the minimum output current.
is the maximum output current.
ǒ
I
R2 ) V
R3 + V
R4 +
REF
ǒ
VFB I
R2 ) VFB R3–V
V
FB
R2–VFB) V
I
o_min
For the EVM, V
I
out_max
= 20 mA, and R2 = 249 kΩ. Using these values, R3 is calculated to be
o_min
o_max
REF
* V
adj_max
= 1.233 V , V
148.3 kΩ, and R4 is calculated to be 98.4 Ω.
2.2.2 Analog Dimming With PWM Voltage
The second method for dimming the LEDs is to inject a pulse width modulated
(PWM) voltage for analog dimming. With this method, an RC filter is used to
convert the PWM control voltage into an analog voltage. The component
values of the RC filter depend on the frequency of the PWM voltage and the
amount of allowable ripple on the converted analog signal. The converted
analog voltage is then injected into the FB pin of the TPS61040 as in the
Analog Dimming With Analog Voltage method. The output current decreases
as the duty cycle increases. Inject the PWM control voltage into the DIM2 pin
on J3. Assuming that the PWM control voltage amplitude varies between 0 V
and 3.3 V, the resistor values calculated in the Analog Dimming with Analog
Voltage method may still be used. The PWM control voltage is converted to
its equivalent analog control voltage using the following equation.
adj_max
adj_max
adj_max
I
o_max
R3
adj_min
* I
* VFB I
= 0 V , V
o_max
adj_max
R2* V
) V
o_min
= 3.3 V , I
adj_min
adj_min
out_min
Ǔ
I
= 0 A,
o_min
Ǔ
Vanalog = Vpwm_pk × D + Vmin
Where:
- Vpwm_pk is the peak-to-peak voltage of the injected PWM signal.
- D is the duty cycle of the injected PWM signal.
- Vmin is the minimum voltage of the injected PWM signal.
Setup and Test Results
2-3
Setup
2.2.3 PWM Dimming Using Enable
The third method for dimming the LEDs is to inject a PWM voltage into the EN
pin of the TPS61040. When the EN pin is high, the supply turns on and the
output current is at the programmed maximum current. When the EN pin is low ,
the supply turns off and the output current goes to 0 mA. If the frequency of
the PWM voltage is greater than 100 Hz, the human eye can not detect the on
and off state of the LED current. The human eye averages the on and off state
of the LED and sees a dimmed diode rather than a pulsed brightness. This
dimming method provides a controlled inrush current at turnon, but limits the
maximum PWM frequency to about 200 Hz, due to the fact that the IC enters
soft start during the first 1.5 ms of each pulse. A PWM duty cycle of 0%
produces 0 mA o f output current; a duty cycle of 100% produces the maximum
programmed output current. For this dimming method, remove R2 and C2,
short R3, and inject the PWM signal into the center pin of JP1. R4 is calculated
by the following equation where Vref is the reference voltage of the TPS61040
(1.233 V) and Imax is the maximum desired output current. The reference
designators correspond to the EVM schematic shown in Chapter 4.
V
R4 +
REF
I
max
For an output current of 20 mA, R4 = 61.6 Ω.
2.2.4 PWM Dimming Using Injected Voltage on FB
The fourth method for dimming the LEDs is to inject a PWM control voltage into
the FB pin of the TPS61040. When the control voltage is low, the output current
is at its maximum programmed value. When the control voltage is high, the
output current is 0 mA. As with the PWM dimming using the enable pin, the
PWM frequency should be at least 100 Hz. Because the device does not enter
soft start during each pulse cycle, the maximum PWM frequency can be
increased to over 20 kHz. The equations for determining the resistor values
are the same as for the Analog Dimming With Analog Voltage method. For this
dimming method, remove R1 and C2, and inject the PWM signal into the DIM1
pin on J3.
2.3 Setup
After the EVM has been modified for the appropriate dimming method,
connect an input supply between J1 and J2. Connect the LEDs between the
LED anode and LED cathode connection points. The EVM operates between
1.8 V and 6.0 V. Ensure that the input voltage never exceeds the TPS61040
absolute maximum input voltage rating of 7.0 V. Move the adjust jumper from
the Off position to the On position to enable the supply.
2-4
2.4 Start-up
When enabled, the EVM goes through its programmed three-stage soft-start
sequence to reduce inrush current at turnon. Figure 2−1 shows the startup
sequence of the EVM when powered from a 4.0-V Li-ion battery. The top
oscilloscope trace is the input current and the bottom trace is the output
current.
Figure 2−1.Start-up Waveforms
3
0.5 ms
100 mA
4
0.5 ms
10 mA
Start-up
1
2
3
4
0.5 ms
5 mV
0.2 V
0.1 V
10 mV
BWL
AC
x10
DC x10
DC
DC
3 DC 60 mA
500 kS/s
STOPPED
Setup and Test Results
2-5
LED Ripple Current
2.5 LED Ripple Current
Figure 2−2 shows the output ripple current with Iout = 20 mA. The top
oscilloscope trace shows the ripple with 3.6-V input, and the bottom trace
shows the ripple with a 4.2-V input. The difference in switching frequency
between the two traces is expected and is explained in the data sheet.
Figure 2−2.Output Ripple Current
:M1
A
2 µs
2 mA/div
1
2 µs
2 mA/div
1
2
3
4
2 µs
12.4 mV
0.2 V
0.1 V
10 mV
BWL
DC x10
DC x10
DC
DC
1 DC 45 mV
200 MS/s
STOPPED
2-6
2.6 Switching Waveforms
Figure 2−3 shows the switching waveform at the SW pin of the TPS61040.
When the internal FET turns on, the voltage at the SW pin is pulled to ground
until the inductor current reaches 400 mA. When the inductor current reaches
400 mA, the FET turns off and the voltage at the SW pin rises to the output
voltage plus the forward voltage drop of the diode. During this time, the
inductor transfers its stored energy to the load and the output capacitor . When
the inductor current decays to zero, the SW node rings at a frequency
determined by the output inductor and the drain capacitance of the internal
FET. This ringing indicates a discontinuous boost power supply topology, and
confirms that the inductor current has gone discontinuous.
Figure 2−3.SW Waveform
1
1 µs
5 V
Switching Waveforms
1
2
3
4
1 µs
0.5 V
0.2 V
0.1 V
10 mV
RIS BWL
DC x10
DC x10
DC
DC
1 DC 11.3 V
400 MS/s
AUTO
Setup and Test Results
2-7
Efficiency
2.7 Efficiency
Figure 2−4 shows the measured efficiency of the TPS61040.
Figure 2−4.Typical Efficiency
90
89
88
87
86
85
84
Efficiency %
83
82
81
80
2.5 5 7.5 10 12.5 15 17.5 20
IO − Output Current − mA
VI = 6 V
2.8 Analog Dimming With Analog Voltage Data
The EVM was modified to generate a 0 mA to 20 mA output when the control
voltage is varied from 3.3 V to 0 V. The appropriate component values may be
calculated using the equations provided in the Analog Dimming with Analog
Voltage section. Using the closest standard values available, R2 = 249 kΩ,
R3 = 147 kΩ, and R4 = 100 Ω. Figure 2−5 shows the linear relationship
between the output current and the control voltage injected into DIM1.
VI = 4.2 V
VI = 3.6 V
VI = 2.5 V
Figure 2−5.Output Current vs Control Voltage
20
15
10
Diode Current − mA
5
0
01 2 3
Control Voltage − V
2-8
Analog Dimming With PWM Voltage Data
2.9 Analog Dimming With PWM Voltage Data
For the Analog Dimming With PWM Voltage method, the EVM is configured
identically with the Analog Dimming With Analog Voltage method with the
exception that the control voltage is injected into the DIM2 pin on J3. R1 and
C2 are chosen to be 10 kΩ and 1 µF to adequately filter a 1-kHz control
voltage. Figure 2−6 shows how the PWM control voltage at the DIM2 pin on
J3 is converted into an equivalent analog voltage on the DIM1 pin on J3. The
graph of the output current versus the control voltage is identical to Figure 2−5
after the PWM control voltage is converted into its average dc equivalent.
Figure 2−6.PWM Control Converted to Analog Control Voltage
1
0.5 ms
0.5 V
2
0.5 ms
0.5 V
1
2
3
4
0.5 ms
50 mV
50 mV
10 mV
0.2 V
BWL
DC x10
DC x10
DC
DC
x10
2 DC 0.24 V
100 kS/s
AUTO
Setup and Test Results
2-9
PWM Dimming Using Enable Data
2.10 PWM Dimming Using Enable Data
For the PWM Dimming Using Enable method, the EVM is configured with
R2= open and R3 = short. Setting R4 = 61.9 Ω programs the maximum output
current to 20 mA. Figure 2−7 shows input current and output current with the
PWM frequency set to 100 Hz and 50% duty cycle. The top oscilloscope trace
is the output current and the bottom trace is the control voltage seen on the
EN pin. Note the three-stage soft start during the first 1.5 ms of each cycle.
Figure 2−8 shows the output current versus the duty cycle of the control
voltage.
Figure 2−7.Input Current and Output Current With PWM Dimming Using Enable
1
2 ms
10 mA/div
2
2 ms
2 V
1
2
3
4
2 ms
62 mV
0.2 V
0.1 V
50 mV
BWL
DC x10
DC x10
DC
DC
2 DC 1.64 V
1 MS/s
AUTO
2-10
PWM Dimming Using Enable Data
Figure 2−8.Output Current vs Duty Cycle for PWM Dimming Using Enable
25
20
15
Current − mA
10
5
0
0 20 40 60 80 100
Duty Cycle − %
Setup and Test Results
2-11
PWM Dimming Using Injected Voltage on FB Data
2.11 PWM Dimming Using Injected Voltage on FB Data
For the PWM Dimming Using Injected Voltage on FB method, a 0-V to 3.3-V
control voltage is used to program a maximum LED current of 20 mA. Use the
equations found in the Analog Dimming Using Analog Voltage section to
calculate the resistor values. The following component values are used:
R2 = 249 kΩ, R3 = 147 kΩ, R4 = 100 Ω. R2 and C2 are unpopulated (left open)
for this configuration. The control voltage is injected into DIM1 on J3.
Figure 2−9 shows the control voltage and the output current for a 5-kHz, 50%
duty cycle control voltage waveform. The top oscilloscope trace is the output
current and the bottom trace is the control voltage. Figure 2−10 shows the
output current versus duty cycle for dif ferent PWM frequencies. The increased
current at higher frequencies results from the fact that the discharge time of
the output capacitor takes a larger percentage of the overall off time.
Figure 2−9.Control Voltage and Output Current
1
50 µs
0.5 V
2
50 µs
2 V
2-12
1
2
3
4
50 µs
12.4 mV
0.2 V
0.1 V
50 mV
BWL
DC x10
DC x10
DC
DC
2 DC 1.64 V
10 MS/s
AUTO
Figure 2−10. Output Current vs Duty Cycle
20
18
16
14
PWM Dimming Using Injected Voltage on FB Data
20 kHz
10 kHz
12
10
8
Current − mA
6
4
2
0
0 20 40 60 80 100
100 Hz
Duty Cycle − %
5 kHz
1 kHz
Setup and Test Results
2-13
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2-14
Chapter 3
This chapter provides the TPS61040EVM-002 board layout and illustrations.
Topic Page
3.1 Board Layout 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Board Layout
3-1
Board Layout
3.1 Board Layout
Board layout is critical for all switch mode power supplies. Figures 3−1, 3−2,
and 3−3 show the board layout for the TPS61040EVM−002 PWB. The nodes
with a high switching frequency are short and are isolated from the
noise-sensitive feedback circuitry. Careful attention is given to the routing of
high-frequency current loops. See the data sheet for specific layout guidelines.
Figure 3−1.Assembly Layer
Figure 3−2.Top Layer Routing
3-2
Figure 3−3.Bottom Layer Routing
Board Layout
Board Layout
3-3
This page intentionally left blank
3-4
Chapter 4
This chapter provides the TPS61040EVM-002 schematic and bill of materials.
Topic Page
4.1 Schematic 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Bill of Materials 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Schematic and Bill of Materials
4-1
Schematic
4.1 Schematic
VIN
GND
L1
10 µ H
U1
On
Off
DIM1
DIM2
GND
TPS61040DBV
5
SW
VIN
GND
4
EN
FB
J3
1
2
3
10 kΩ
1
2
3
R1
J1
1
2
C1
4.7µ F
J2
1
2
1
Open
1
JP1
D1
MBR0530
R3
147 kΩ
R2
249 kΩ
C2
1µ F
R4
100Ω
D2
D3
D4
D5
J4
1
2
LED ANODE
1
C3
0.1µF
1
D6
1
1
MMBZ5254BLT1
J5
1
LED CATHODE
2
J6
1
GND
2
4.2 Bill of Materials
Qty Reference
Designator
1 C2 Capacitor, ceramic, 1.0 µF, 6.3 V,
1 C3 Capacitor, ceramic, 0.1 µF, 16 V,
1 D1 Diode, Schottky, 350 mA, 40V SOD−123 OnSemi MBR0530T1
D2, D3, D4, D5 Unpopulated (open)
1 D6 Diode, Zener, 27 V, 94 mA, 225 mW,5%SOT23 Motorola MMBZ5254BLT1
Description Size MFR Part Number
603 Murata GRM188R60J105KA01
X5R, 15%
603 Murata GRM188R71C104KA01
X7R, 10%
5 J1, J2, J4, J5, J6 Header, 2 pin, 100 -mil spacing,
(36-pin strip)
1 J3 Header, 3 pin, 100-mil spacing,
(36-pin strip)
1 JP1 Header, 3 pin, 100-mil spacing,
(36-pin strip)
1 L1 Inductor, SMT, 10 µH, 0.76 A,
0.23 mΩ
1 R1 Resistor, chip, 10.0 kΩ, 1/16 W, 1% 603 Std Std
1 R2 Resistor, chip, 249 kΩ, 1/16 W, 1% 603 Std Std
1 R3 Resistor, chip, 147 kΩ, 1/16 W, 1% 603 Std Std
1 R4 Resistor, chip, 100 Ω, 1/16 W, 1% 603 Std Std
1 U1 IC, High-efficiency boost converter SOT23−5
1 −− PCB, 1.6 In x 1.1 In x 0.062 In Any SLVP210
1 −− Shunt, 100 mil, black 0.100 3M 929950−00
4-2
0.100 x 2” Sullins PTC36SAAN
0.100 x 3” Sullins PTC36SAAN
0.100 x 3” Sullins PTC36SAAN
0.150 x 0.162 Sumida CR32−100
TI TPS61040DBV
(DBV)
Mouser Electronics
Authorized Distributor
Click to View Pricing, Inventory, Delivery & Lifecycle Information:
Texas Instruments:
TPS61040EVM-002
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