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TPS61043
SLVS465C – DECEMBER 2003 – REVISED FEBRUARY 2016
TPS61043 Constant Current LED Driver
1 Features
3 Description
•
•
•
•
•
•
The TPS61043 is a high-frequency boost converter
with constant current output that drives white LEDs or
similar. The LED current is set with the external
sense resistor (RS) and is directly regulated by the
feedback pin (FB) that regulates the voltage across
the sense resistor RS to 252 mV (typical). To control
LED brightness, the LED current can be pulsed by
applying a PWM (pulse width modulated) signal with
a frequency range of 100 Hz to 50 kHz to the control
pin (CTRL). To allow higher flexibility, the device can
be configured so that the brightness is controlled by
an analog signal as well, as described in Application
Information. To avoid possible leakage currents
through the LEDs during shutdown, the control pin
(CTRL) disables the device and disconnects the
LEDs from ground. For maximum safety during
operation, the output has integrated overvoltage
protection that prevents damage to the device by
limiting the output voltage to typically 18 V in case of
a high-impedance output (for example, faulty LED).
The TPS61043 device provides a solution for
applications where higher LED currents or more than
four LEDs in series must be powered.
1
•
•
•
•
•
•
•
Current Source With 18-V Overvoltage Protection
Powers up to 4 LEDs in Series
Input Voltage Range: 1.8 V to 6 V
Internal 30-V Switch
Up to 85% Efficiency
Precise Brightness Control Using PWM Signal or
Analog Signal
Switching Frequency up to 1 MHz
Internal Power MOSFET Switch 400 mA
Operates With Small Output Capacitors Down to
100 nF
Disconnects LEDs During Shutdown
No Load Quiescent Current 38 µA Typical
Shutdown Current 0.1 µA Typical
Available in a Small 3-mm × 3-mm QFN Package
2 Applications
•
White LED Supply for Display Backlight and
Sidelight in
– PDAs, Pocket PCs, Smart Phones
– Handheld Devices
– Cellular Phones
Device Information(1)
PART NUMBER
TPS61043
PACKAGE
VSON (8)
BODY SIZE (NOM)
3.00 mm × 3.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application
L1
4.7 µH
VIN
1.8 V to 6 V
CIN
4.7 µF
Enable/PWM Brightness
Control 100 Hz to 50 kHz
3
5
VIN
SW
CTRL OVP
D1
(A)
CO
100 nF
25 V
8
7
6 GND LED 1
4 FB
RS 2
RS
13 Ω
(A) Output capacitor values like 1 µF and larger, reduce the LED ripple current and improve line regulation.
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.
TPS61043
SLVS465C – DECEMBER 2003 – REVISED FEBRUARY 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
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
4
4
4
4
6
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Parameter Measurement Information .................. 7
Detailed Description .............................................. 8
8.1
8.2
8.3
8.4
Overview ................................................................... 8
Functional Block Diagram ......................................... 8
Feature Description................................................... 9
Device Functional Modes........................................ 10
9
Application and Implementation ........................ 12
9.1 Application Information............................................ 12
9.2 Typical Application .................................................. 15
9.3 System Examples ................................................... 19
10 Power Supply Recommendations ..................... 22
11 Layout................................................................... 22
11.1 Layout Guidelines ................................................. 22
11.2 Layout Example .................................................... 22
11.3 Thermal Considerations ........................................ 22
12 Device and Documentation Support ................. 23
12.1
12.2
12.3
12.4
12.5
12.6
Device Support......................................................
Documentation Support ........................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
23
23
23
23
23
23
13 Mechanical, Packaging, and Orderable
Information ........................................................... 23
4 Revision History
Changes from Revision B (May 2015) to Revision C
Page
•
Changed image object in Figure 25. ................................................................................................................................... 22
•
Added Community Resources section. ................................................................................................................................ 23
Changes from Revision A (December 2003) to Revision B
•
2
Page
Added Pin Configuration and Functions section, 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
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SLVS465C – DECEMBER 2003 – REVISED FEBRUARY 2016
5 Pin Configuration and Functions
DRB Package
8-PIN VSON
Top View
LED 1
8 SW
Exposed
Thermal
†
Die Pad
RS 2
VIN 3
7 OVP
6 GND
FB 4
†
5 CTRL
The exposed thermal die pad
is connected to GND.
Pin Functions
PIN
I/O
DESCRIPTION
NAME
NO.
CTRL
5
I
Combined enable and PWM control pin. If CTRL is constantly pulled high, the device is enabled and the internal
LED switch (Q2) is constantly turned on. When CTRL is pulled to GND, the device is disabled. Apply a PWM
signal (100 Hz to 50 kHz) to this pin to control the brightness of the LEDs
FB
4
I
Feedback. FB regulates the LED current through the sense resistor by regulating the voltage across RS to
252 mV.
GND
6
LED
1
I
Input of the LED switch (Q2). Connect the LEDs to this pin.
OVP
7
I
Overvoltage protection. OVP is connected to the output capacitor of the converter.
RS
2
O
Output of the internal LED switch. The sense resistor that programs the LED current is connected to RS.
SW
8
I
Drain of the integrated switch (Q1)
VIN
3
I
Input supply pin.
GND
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
MIN
Supply Voltages, v(VIN)
(2)
Voltages, V(Rs), V(CTRL), V(FB)
Voltages, V(SW), V(LED)
MAX
UNIT
–0.3
7
V
–0.3
Vin + 0.3
V
30
V
(2)
Voltage, V(OVP)
30
V
Operating junction temperature
–40
150
°C
Lead temperature (soldering, 10 sec)
260
260
°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, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltage values are with respect to network ground terminal.
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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 JESD22C101 (2)
±750
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.
6.3 Recommended Operating Conditions
MIN
NOM
MAX
UNIT
VI
Input voltage
1.8
6
V
TA
Operating ambient temperature
–40
85
°C
TJ
Operating junction temperature
–40
125
°C
6.4 Thermal Information
TPS61043
THERMAL METRIC (1)
DRB (VSON)
UNIT
8 PINS
RθJA
Junction-to-ambient thermal resistance
48.6
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
66.9
°C/W
RθJB
Junction-to-board thermal resistance
23.8
°C/W
ψJT
Junction-to-top characterization parameter
1.5
°C/W
ψJB
Junction-to-board characterization parameter
23.9
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
5.2
°C/W
(1)
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
6.5 Electrical Characteristics
VI = 3.6 V, CTRL= VI, TA = –40°C to + 85°C, typical values are at TA= 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
SUPPLY CURRENT
VI
Input voltage range
1.8
6
V
I(Q)
Operating quiescent current into VIN
IO = 0 mA, not switching
IO(sd)
Shutdown current
CTRL = GND
38
65
µA
0.1
1
VUVLO
Under-voltage lockout threshold
VI falling
1.5
µA
1.7
V
CTRL
VIH
CTRL high level input voltage
VIL
CTRL low level input voltage
1.3
IIkg
CTRL input leakage current
CTRL = GND or VIN
ton
Minimim CTRL pulse witdh to enable
CTRL = low to high
500
toff
Minimum CTRL pulse width to disable
CTRL = high to low
f(CTRL)
D(CTRL)
V
0.3
V
0.1
µA
10
32
ms
PWM switching frequency applied to CTRL
0.1
50
kHz
PWM duty cycle applied to CTRL
1%
100%
us
POWER SWITCH AND CURRENT LIMIT (SW)
VS
Maximum switch voltage
rds(ON)
MOSFET ON-resistance
V I = 3.6 V; I(SW) = 200 mA
Ilkg
MOSFET leakage current
V(SW) = 28 V
ILIM
MOFSET current limit
TON
Power switch maximum on-time
TOFF
Power switch minimum off-time
4
320
VO = 15 V
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30
V
300
600
mΩ
0.1
10
µA
400
480
mA
4.5
µs
400
ns
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Electrical Characteristics (continued)
VI = 3.6 V, CTRL= VI, TA = –40°C to + 85°C, typical values are at TA= 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
LED SWITCH AND CURRENT LIMIT (LED)
VS
Maximum switch voltage
30
V
I (LED)
Maximum LED switch current
60
mA
rds(ON)
MOSFET ON-resistance
VI = 3.6 V; ISW = 20 mA
Ilkg
MOSFET leakage current
V(LED)= 28 V
1
2
Ω
0.1
10
µA
16.9
V
OUTPUT
VO
Output voltage range
OVP connected
(1)
I(FB)
Feedback input bias current
VFB
Feedback trip point voltage
1.8 V ≤ VI ≤ 6.0 V
V(OVP)
Output overvoltage protection
VO rising
Vhys(OVP)
Output overvoltage protection hysteresis
I(OVP)
OVP input current
(1)
VI
V(FB) = 0.252 V
100
nA
244
252
260
mV
17
18
19
V
23
µA
3.65
VO = 15 V
17
V
The feedback input is high-impedance MOSFET Gate input.
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6.6 Typical Characteristics
Table 1. Table of Graphs
FIGURE
V(FB)
Feedback voltage
vs Temperature
Figure 1
I(FB)
Feedback current
vs Temperature
Figure 2
rds(on)
Main switch Q1
vs Temperature
Figure 3
vs Input voltage
Figure 4
vs Temperature
Figure 5
vs Input voltage
Figure 6
vs PWM duty cycle on CTRL pin
Figure 7
LED switch Q2
ILED
Average LED current
60
258
VCC = 3.7 V
I(fb) - Feedback Current - nA
V(fb) - Feedback Voltage - mV
260
256
254
252
250
248
246
244
242
240
40
VCC = 3.6 V
20
0
- 20
VCC = 5 V
- 60
- 40
- 15
10
35
60
85
- 40
- 15
TA - Free-Air Temperature - °C
60
85
rds(on) − On-State Resistance − mΩ
600
VCC = 3.6 V
450
400
350
300
250
200
TA = 27°C
500
400
300
200
100
0
−40
−15
10
35
60
85
1.8
2.4
3.0
TA − Free-Air Temperature − °C
3.6
4.2
4.8
5.4
6.0
VI − Input Voltage − V
Figure 3. rds(on) Main Switch (Q1) vs Temperature
Figure 4. rds(ON) Main Switch (Q1) vs Input Voltage
3.0
1.5
rds(on) - On-State Resistance - Ω
1.6
rds(on) - On-State Resistance - Ω
35
Figure 2. Feedback Current vs Temperature
500
rds(on) − On-State Resistance − mΩ
10
TA - Free-Air Temperature - °C
Figure 1. Feedback Voltage vs Temperature
VCC = 3.6 V
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
TA = 25°C
2.5
2.0
1.5
1.0
0.5
0.0
- 40
- 15
10
35
60
85
1.8
TA - Free-Air Temperature - °C
2.4
3.0
3.6
4.2
4.8
5.4
6.0
VI - Input Voltage - V
Figure 5. rds(on) LED Switch (Q2) vs Temperature
6
VCC = 2.4 V
- 40
Figure 6. rds(on) LED Switch (Q2) vs Input Voltage
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IO - Output Current - mA
20
15
10
fPWM = 50 kHz
fPWM = 100 Hz
5
fPWM = 25 kHz
0
0
20
40
60
80
100
Duty Cycle - %
Figure 7. Average LED Current vs PWM Duty Cycle on CTRL Pin
7 Parameter Measurement Information
L1
4.7 µH
VIN
1.8 V to 6 V
CIN
4.7 µF
Enable/PWM Brightness
Control 100 Hz to 50 kHz
3
5
VIN
SW
CTRL OVP
D1
CO
1 µF
25 V
8
7
6 GND LED 1
4 FB
RS 2
RS
13 Ω
L1 = Murata LQH32CN4R7 (4.7 µH)
D1 = Zetex Schottky ZHCS400
CIN = 4.7 µF X5R 20% JMK212BJ475MG-T
COUT = 1 µF X7R 10% TMK316BJ105KL-T
Figure 8. Schematic
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8 Detailed Description
8.1 Overview
The TPS61043 operates like a standard boost converter but regulates the voltage across the sense resistor (RS)
instead of the output voltage. This gives an accurate regulated LED current independent of the input voltage and
number of LEDs connected. With integrated overvoltage protection (OVP) the TPS61043 is configured as a
current source with overvoltage protection ideally suited to drive LEDs. The device can generate output voltages
of up to 18 V and has an internal 400mA MOSFET switch (Q1). This allows several LEDs to be connected in
series to the output. The internal LED switch (Q2) in series with the LEDs has a maximum current rating of 60
mA and disconnects the LEDs from ground during shutdown. The LED switch is driven by a PWM signal applied
to the control pin (CTRL), which directly controls the LED brightness. With this control method the LED
brightness depends on the PWM duty cycle only and is independent of the PWM frequency and amplitude.
8.2 Functional Block Diagram
EN
SW
EN
VIN
UVLO
Bias
VREF
0.252 V
Control
Logic
Q1
Gate
Driver
Thermal
Shutdown
OVP
CTRL
Enable
Control
Logic
R1
1080 kΩ
Current
Limit
Softstart
EN
R2
25 kΩ
4.5 µs Max
On Time
GND
PWM
Gate
Drive
Overvoltage Protection
+
-
VREF
8
+
LED
Q2
Error
Comparator
FB
0.4 V
400 ns Min
Off Time
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RS
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8.3 Feature Description
8.3.1 Operation
The TPS61043 operates like a standard boost converter but regulates the voltage across the sense resistor (RS)
instead of the output voltage. This gives an accurate regulated LED current independent of the input voltage and
number of LEDs connected. With integrated overvoltage protection (OVP) the TPS61043 is configured as a
current source with overvoltage protection ideally suited to drive LEDs. The device can generate output voltages
of up to 16.9 V if the OVP-function is used and has an internal 400 mA MOSFET switch (Q1). This allows up to
four LEDs to be connected in series to the output. The internal LED switch (Q2) in series with the LEDs has a
maximum current rating of 60 mA and disconnects the LEDs from ground during shutdown. The LED switch is
driven by a PWM signal applied to the control pin (CTRL), which directly controls the LED brightness. With this
control method the LED brightness depends on the PWM duty cycle only and is independent of the PWM
frequency and amplitude. If the OVP-function is not needed, the device can be used to generate output voltages
up to 28V.
8.3.2 Boost Converter
The boost converter operates in a pulse frequency modulation (PFM) scheme with constant peak current control.
This control scheme maintains high efficiency over the entire load current range and with a switching frequency
of up to 1 MHz, enables the use of small external components. The converter monitors the sense voltage across
RS with the feedback pin (FB) and, when the feedback voltage falls below the reference voltage (252 mV typ),
the main switch turns on and the current ramps up. The main switch turns off when the inductor current reaches
the internally set peak current of 400 mA (typ). Refer to the Peak Current Control (Boost Converter) section for
more information. The second criteria that turns off the main switch is the maximum on-time of 4.5 µs (typ). This
limits the maximum on-time of the converter in extreme conditions. As the switch is turned off the external
Schottky diode is forward biased, delivering the stored inductor energy to the output. The main switch remains off
until the minimum off time of 400 ns (typ) has passed and the feedback voltage is below the reference voltage
again. Using this PFM peak current control scheme, the converter operates in discontinuous conduction mode
(DCM) where the switching frequency depends on the inductor, input and output voltage, and LED current. Lower
LED currents reduce the switching frequency, which results in high efficiency over the entire LED current range.
This regulation scheme is inherently stable, allowing a wide range for the selection of the inductor and output
capacitor.
8.3.3 Peak Current Control (Boost Converter)
The internal switch is turned on until the inductor current reaches the DC current limit (ILIM) of 400 mA (typ) . Due
to the internal current limit delay of 100 ns (typ) the actual current exceeds the DC current limit threshold by a
small amount. The typical peak current limit can be calculated:
V
I
+I
) I 100 ns
P(typ)
(LIM)
L
(1)
IP = 400mA +
VI
´ 100ns
L
(2)
The higher the input voltage and the lower the inductor value, the greater the current limit overshoot.
8.3.4 Softstart
All inductive step-up converters exhibit high in-rush current during start-up if no special precautions are taken.
This can cause voltage drops at the input rail during start-up, which may result in an unwanted or premature
system shutdown.
The TPS61043 limits this in-rush current during start-up by increasing the current limit in two steps starting from
ILIM/4 for 256 switch cycles to ILIM/2 for the next 256 switch cycles and then full current limit. See Figure 16 for
typical start-up behavior.
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Feature Description (continued)
8.3.5 Control (CTRL)
The CTRL pin serves two functions. One is the enable and disable of the device. The other is the PWM control of
the internal LED switch (Q2). The CTRL pin can be used as a standard enable pin for the device if no PWM
signal is applied to the CTRL pin. To enable the device, the CTRL pin must be pulled high for a time period of at
least 500 µs. The device starts with the Softstart cycle. Pulling the CTRL pin to GND for a time period ≥32 ms
disables the device, disconnecting the LEDs from GND by opening the LED switch (Q2) to avoid any LED
leakage current. See Figure 9 for the CTRL pin timing.
toff
tp
ton
ton
High
Low
Minimum
On-Time
to Enable
the Device
(50 µs)
t
D = tp/t
Minimum
Off-Time
to Disable
the Device
(32 ms)
Figure 9. CTRL Timing Diagram
To enable the device, the CTRL signal must be high for 500 µs (see Figure 9). The PWM signal can then be
applied with a pulse width (tp) greater or smaller than tON. To force the device into shutdown mode, the CTRL
signal must be low for at least 32 ms. Requiring the CTRL pin to be low for 32 mS before the device enters
shutdown allows for PWM dimming frequencies as low as 100 Hz. The device is enabled again when a CTRL
signal is high for a period of 500 µs minimum. See Figure 7 for the PWM duty cycle versus LED current
characteristic.
The internal LED switch (Q2) is driven by the PWM signal when applied to the CTRL pin. Applying a PWM signal
in the range of 100 Hz to 50 kHz allows the LED current to be pulsed with the duty cycle of the PWM signal. The
CTRL pin accepts a PWM duty cycle from D = 1% to 100%. Duty cycles below 1% are also possible with the
restriction that the device is forced into shutdown as the off time of the applied PWM signal exceeds 10 ms.
When a PWM signal is applied to the CTRL pin the LED switch (Q2) turns on immediately. The internal error
comparator is disabled for 400 ns. This 400 ns delay time is required to establish the correct voltage level across
the sense resistor RS after the LED switch (Q2) is closed.
To achieve good LED current accuracy and linearity, the switching frequency of the converter must be higher
than the PWM frequency applied to the CTRL pin. This CTRL pin must be terminated.
8.4 Device Functional Modes
8.4.1 Overvoltage Protection (OVP)
As with any current source, the output voltage rises as the output impedance increases as for example with a
disconnected load. To prevent the output voltage from exceeding the maximum main switch (Q1) voltage rating,
an overvoltage protection (OVP) circuit is integrated. With an OVP threshold voltage of 19 V maximum, up to 4
LEDs can be connected in series. This allows the use of a cheaper output capacitor with a 25 V voltage rating.
When the output voltage exceeds the OVP threshold voltage, (Q1) turns off. The converter switch remains off
until the output voltage falls below the OVP threshold voltage. As long as the output voltage is below the OVP
threshold the converter continues its normal operation, until the output voltage exceeds the OVP threshold again.
If overvoltage protection is not needed, then the OVP pin should be connected to GND. In this case the
TPS61043 can be used to generate output voltages up to 28 V.
10
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Device Functional Modes (continued)
8.4.2 Undervoltage Lockout
An undervoltage lockout feature prevents mis-operation of the device at input voltages below 1.5 V (typical). As
long as the input voltage is below the undervoltage threshold the device remains off, with the main MOSFET
switch (Q1) and the LED switch (Q2) open.
8.4.3 Thermal Shutdown
An internal thermal shutdown is implemented in the TPS61043 that shuts down the device if the typical junction
temperature of 160°C is exceeded. If the device is in thermal shutdown mode, the main MOSFET switch (Q1)
and the LED switch (Q2) are open.
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
Table 2. Possible Diodes (or Equivalent)
COMPONENT SUPPLIER
REVERSE VOLTAGE
ON Semiconductor MBR0530
30 V
ON Semiconductor MBR0520
20 V
Toshiba CRS02
30 V
Zetex ZHCS400
40 V
9.1.1 Efficiency
The overall efficiency of the application depends on the specific application conditions and mainly on the
selection of the inductor. A lower inductor value increases the switching frequency and switching losses yielding
in a lower efficiency. A lower inductor dc resistance has lower copper losses, giving a higher efficiency.
Therefore, the efficiency can typically vary ±5% depending on the selected inductor. and can be used as a
guideline for the application efficiency. These curves show the typical efficiency powering four LEDs using a 4.7µH inductor with just 1,2 mm height. The efficiency curve in and show the efficiency delivering the power to the
LEDs rather than the overall converter efficiency and is calculated as:
V
I
LED
h + LED
V
I
I
I
(3)
9.1.2 Setting the LED Current
The converter regulates the LED current by regulating the voltage across the current sense resistor (RS). The
voltage across the sense resistor is regulated to the internal reference voltage of V(FB) = 252 mV.
PWM
100 Hz to 50 kHz
3 VIN
SW 8
5
7
CTRL OVP
6
1
GND LED
4 FB
RS 2
Rs
Figure 10. Setting the LED Current
The LED current can be calculated:
V
0.252V
ILED = FB =
RS
RS
12
(4)
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The current programming method is used when the brightness of the LEDs is fixed or controlled by a PWM
signal applied to the CTRL pin. When using a PWM signal on the CTRL pin, the LED brightness is only
dependent on the PWM duty cycle, independent of the PWM frequency, or amplitude, which simplifies the
system.
9.1.3 Analog Control Signal for Brightness Control
Alternatively, an analog voltage can be used as well to control the LED brightness.
3
Enable: CTRL = High
Disable: CTRL = Low
5
VIN
SW
CTRL OVP
6
GND
4
LED
FB
RS
8
7
1
2
R1
PWM
Signal
VADJ
(Brightness Control)
R
I1
Rs
Vs
R2
C
Optional Filter for the
use of a PWM Signal
Figure 11. Setting the LED Current Using an Analog Control Signal
In Figure 11 the LED current is determined by the voltage applied to R2 (VADJ) and the selection of R1, R2 and
the sense resistor (RS). In this configuration, the LED current is linear controlled instead of pulsed as in the
configuration before. To select the resistor values following steps are required.
1. Select the voltage VADJ(max) to turn the LEDs off, for example, 3.3 V
2. Select the voltage VADJ(min) to turn the LEDs fully on, for example, 0 V
3. Select the maximum and minimum LED current IO(max) and IO(min), for example, IO(max) = 20 mA, IO(min) = 0 mA
4. Calculate R2 to achieve a feedback current in the range of I1 = 3 µA to 10 µA as the LEDs are fully turned
on:
Vref - VADJ(min)
R2 =
I1
(5)
5. Calculate R1
R1 = Vref ´
IO(max) ´ R 2 + VADJ(min) - IO(min) ´ R 2 - VADJ(max)
VADJ(max) ´ IO(max) + Vref ´ IO(min) - VADJ(min) ´ IO(min) - Vref ´ IO(max)
(6)
6. Calculate the sense voltage (VS) at maximum LED current
R1 R1
VS = Vref ´ (1 +
)´ VADJ(min)
R2 R2
7. Calculate the required sense resistor (RS)
VS
RS =
IO(max)
(7)
(8)
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9.1.4 PWM Control With Separate Enable
The control pin (CTRL) combines the enable function as well as the PWM brightness control function in one pin.
For some systems an independent enable function is required. One way to implement this is to use the
brightness control configuration as shown in the previous section Figure 11.
Other possible solutions are shown in Figure 12, Figure 13, Figure 14.
PWM Brightness Control
100 Hz to 50 kHz
Enable (EN)
3 VIN
SW 8
5
7
CTRL OVP
6
1
GND LED
4
FB
RS
2
Figure 12. Separate Enable and PWM Control Using a Schottky Diode
PWM Brightness Control
100 Hz to 50 kHz
3 VIN
SW 8
5
CTRL OVP 7
6
1
GND LED
4 FB
RS 2
Enable (EN)
Figure 13. Separate Enable and PWM Control Using a Transistor
PWM Brightness Control
100 Hz to 50 kHz
Enable (EN)
3 VIN
SW 8
5
CTRL OVP 7
6
GND LED 1
4
2
FB
RS
Figure 14. Separate Enable and PWM Control Using an AND Gate
14
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9.2 Typical Application
L1
4.7 µH
VIN
1.8 V to 6 V
3
5
CIN
4.7 µF
Enable/PWM Brightness
Control 100 Hz to 50 kHz
VIN
SW
CTRL OVP
D1
(A)
CO
100 nF
25 V
8
7
6 GND LED 1
4 FB
RS 2
RS
13 Ω
(A) Output capacitor values like 1 µF and larger, reduce the LED ripple current and improve line regulation.
Figure 15. Typical Application Schematic
9.2.1 Design Requirements
For this design example, use the parameters listed in Table 3 as the input parameters.
Table 3. Design Parameters
DESIGN PARAMETER
TYPICAL VALUE
Input Voltage
1.8 V to 6 V
Output Voltage
VIN to 16 V
Dimming frequency
0.1 to 50 kHz
9.2.2 Detailed Design Procedure
9.2.2.1 Inductor Selection, Maximum Load Current, and Switching Frequency
The PFM peak current control scheme of the TPS61043 is inherently stable. The inductor value does not affect
the stability of the regulator. The selection of the inductor together with the nominal LED current, input, and
output voltage of the application determines the switching frequency of the converter.
The first step is to calculate the maximum load current the converter can support using the selected inductor.
The inductor value has less effect on the maximum available load current and is only of secondary order. A good
inductor value to start with is 4.7 µH. Depending on the application, inductor values down to 1 µH can be used.
The maximum inductor value is determined by the maximum on time of the switch of 4.5 µs (typical). The peak
current limit of 400 mA (typical) must be reached within this 4.5 µs for proper operation. The maximum load
current of the converter is determined at the operation point where the converter starts to enter the continuous
conduction mode. The converter must always operate in discontinuous conduction mode to maintain regulation.
Depending on the time period of the inductor current fall time being larger or smaller compared to the minimum
off time of the converter (400 ns typ), the maximum load current can be calculated.
Inductor fall time:
Ip ´ L
tf =
VO - VI
where
•
tf ≥ 400 ns
ILOAD(max)
(9)
I ´ VI
= h´ P
2 ´ VO
(10)
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ILOAD(max) = h ´
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IP2 ´ L ´ VI
(VO - VI ) ´ (2 ´ IP ´ L + 2 ´ 400ns ´ VI )
where
•
•
L = selected inductor value
η = expected converter efficiency. Typically between 70% to 85%
(11)
V
IP = 400mA + I ´ 100ns
L
(12)
(Peak inductor current as described in the Peak Current Control (Boost Converter) section)
The above formula contains the expected converter efficiency that allows calculating the expected maximum load
current the converter can support. The efficiency can be taken out of the efficiency graphs shown in and or 80%
can be used as an accurate estimation.
If the converter can support the desired LED current, the next step is to calculate the converter switching
frequency at the operation point, which must be ≤1 MHz. Also the converter switching frequency should be much
higher than the applied PWM frequency at the CTRL pin to avoid nonlinear brightness control. Assuming the
converter shows no double pulses or pulse bursts (Figure 17 and Figure 18) on the switch node (SW) the
switching frequency at the operation point can be calculated as:
ƒs +
2
ǒ
I
ǒV O * V I ) V F Ǔ
O
V
I
LIM
) I
L
100 ns
Ǔ
v 1MHz
2
L
where
•
•
•
•
ILIM = minimum switch current limit (320 mA typical)
L = selected inductor value
IO = nominal load or LED current
VF = Rectifier diode forward voltage (typically 0.3 V)
(13)
The smaller the inductor value, the higher the switching frequency of the converter but the lower the efficiency.
The selected inductor must have a saturation current that meets the maximum peak current of the converter as
calculated in Peak Current Control (Boost Converter). Use the maximum value for ILIM (480 mA) for this
calculation. Another important inductor parameter is the DC resistance. The lower the DC resistance the higher
the efficiency of the converter. See Table 4 and Figure 20 to Figure 24 for a selection of inductors.
Table 4. Possible Inductors (or Equivalent)
INDUCTOR VALUE
16
COMPONENT SUPPLIER
SIZE
10 µH
muRata LQH43CN100K01
4.5 mm × 3.2 mm × 2.6 mm
4.7 µH
muRata LQH32CN4R7M11
3.2 mm × 2.5 mm × 2 mm
10 µH
Coilcraft DO1605T-103MX
5.5 mm × 4.1 mm × 1.8 mm
4.7 µH
Sumida CDRH3D16-4R7
3.8 mm × 3.8 mm × 1.8 mm
3.3 µH
Sumida CMD4D11-3R3
3.5 mm × 5.3 mm × 1.2 mm
4.7 µH
Sumida CMD4D11-4R7
3.5 mm × 5.3 mm × 1.2 mm
3.3 µH
Sumida CMD4D11-3R3
3.5 mm × 5.3 mm × 1.2 mm
4.7 µH
Coiltronics SD12-4R7
5.2 mm × 5.2 mm × 1.2 mm
3.3 µH
Coilcraft LPO1704-332M
6.6 mm × 5.5 mm × 1 mm
4.7 µH
Coilcraft LPO1704-472M
6.6 mm × 5.5 mm × 1 mm
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9.2.2.2 Output Capacitor Selection and Line Regulation
For better output voltage filtering, a low ESR output capacitor is recommended. Ceramic capacitors have a low
ESR value, but depending on the application, tantalum capacitors can be used.
The selection of the output capacitor value directly influences the output voltage ripple of the converter which
also influences line regulation. The larger the output voltage ripple, the larger the line regulation, which means
that the LED current changes if the input voltage changes. If a certain change in LED current gives a noticeable
change in LED brightness, depends on the LED manufacturer and on the application. Applications requiring good
line regulation ≤1%/V (typ) must use output capacitor values ≥1 µF.
See Table 5 and Figure 20 to Figure 24 for the selection of the output capacitor.
Assuming the converter does not show double pulses or pulse bursts (see Figure 17 and Figure 18) on the
switch node (SW), the output voltage ripple is calculated as:
DV
I
+ O
O
C
O
V
ȡ ǒI
) I 100 nsǓ
ȧ 1 * LIM(min) L
ȧƒs
V )V *V
O
F
I
ȧ
Ȣ
ȣ
ȧ) I
ȧ P
ȧ
Ȥ
L
ESR
where
•
•
•
•
•
•
•
ILIM(min) = minimum switch current limit (320 mA typical)
L = selected inductor value
IO = nominal load current
fS = switching frequency at the nominal load current as calculated with Equation 13.
VF = rectifier diode forward voltage (0.3 V typical)
CO = selected output capacitor
ESR = output capacitor ESR value
(14)
9.2.2.3 Input Capacitor Selection
For good input voltage filtering, low ESR ceramic capacitors are recommended. A 4.7-µF ceramic input capacitor
is sufficient for most applications. For better input voltage filtering the capacitor value can be increased. Refer to
Table 5 and Figure 20 to Figure 24 for input capacitor selection.
Table 5. Possible Input and Output Capacitors (or Equivalent)
CAPACITOR
VOLTAGE RATING
COMPONENT SUPPLIER
COMMENTS
4.7 µF/X5R/0805
6.3 V
Tayo Yuden JMK212BY475MG
10 µF/X5R/0805
6.3 V
Tayo Yuden JMK212BJ106MG
CI
CI
100 nF
Any
CO
220 nF
Any
CO
470 nF
Any
CO
1.0 µF/X7R/1206
25 V
Tayo Yuden TMK316BJ105KL
CO
1.0 µF/X7R/1206
35 V
Tayo Yuden GMK316BJ105KL
CO
4.7 µF/X5R/1210
25 V
Tayo Yuden TMK325BJ475MG
CO
9.2.2.4 Diode Selection
To achieve high efficiency a Schottky diode must be used. The current rating of the diode must meet the peak
current rating of the converter as it is calculated in the peak current control section. Use the maximum value for
ILIM for this calculation. See Table 6 and Figure 20 to Figure 24 for the Schottky diode selection.
Table 6. Possible Diodes (or Equivalent)
COMPONENT SUPPLIER
REVERSE VOLTAGE
ON Semiconductor MBR0530
30 V
ON Semiconductor MBR0520
20 V
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Table 6. Possible Diodes (or Equivalent) (continued)
COMPONENT SUPPLIER
REVERSE VOLTAGE
Toshiba CRS02
30 V
Zetex ZHCS400
40 V
9.2.3 Application Curves
Vsw
5V/Div
Vout
10V/Div
Vout
500mV/Div
CTRL
1V/Div
LED Current
20mA/Div
Input Current
100mA/Div
50µs/Div
2.5µs/Div
Figure 16. Soft-Start
Figure 17. PFM Operation
Vsw
5V/Div
Vsw
5V/Div
Vout
50mV/Div
Vout
500mV/Div
LED Current
20mA/Div
LED Current
20mA/Div
2.5µs/Div
25µs/Div
Figure 18. Bust Mode Operation
18
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9.3 System Examples
9.3.1 TPS61043 With 1-mm Total System Height
TPS61043 is designed from 3 V to 6 V input for driving LED with 1-mm total system height.
L1
4.7 µH
Coilcraft LPO1704-472
D1
ZHCS400
CO
1 µF
VIN
3 V to 6 V
3 VIN
SW 8
5
CTRL OVP 7
C(IN)
4.7 µF
6 GND
4 FB
LED 1
RS
2
RS
13 Ω
Enable/PWM Brightness
Control 100 HZ to 50 kHz
Figure 20. TPS61043 With 1-mm Total System Height
9.3.2 TPS61043 With Low LED Ripple Current and Higher Accuracy Using a 4.7-µF Output Capacitor
TPS61043 is designed from 3 V to 6 V input for driving LED with low LED ripple current and higher accuracy
using a 4.7-µF output capacitor.
L1
4.7 µH
SUMIDA CMD4D11
D1
ZHCS400
CO
4.7 µF
VIN = 3 V to 6 V
3
5
C(IN)
4.7 µF
6
4
Enable/PWM Brightness
Control 100 HZ to 50 kHz
VIN
SW
CTRL
OVP
GND
LED
FB
RS
8
7
1
2
RS
13 Ω
Figure 21. TPS61043 With Low LED Ripple Current and Higher Accuracy Using a 4.7-µF Output Capacitor
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System Examples (continued)
9.3.3 TPS61043 Powering 3 LEDs
TPS61043 is designed from 3 V to 6 V input for driving 3 LEDs in series.
L1
4.7 µH
Coilcraft LPO1704-472
D1
ZHCS400
CO
1 µF
VIN = 2.7 V to 6 V
3 VIN
5
CIN
4.7 µF
6
CTRL
SW 8
OVP 7
GND
LED
4 FB
1
RS 2
RS
13 Ω
Enable/PWM Brightness
Control 100 Hz to 50 kHz
Figure 22. TPS61043 Powering 3 LEDs
9.3.4 Adjustable Brightness Control Using an Analog Voltage
TPS61043 is designed from 3 V to 6 V input for driving LED with adjustable brightness control using an analog
voltage.
D1
ZHCS400
L1
4.7 µH
CO
100 nF
VIN = 3 V to 6 V
3 VIN
5 CTRL
C(IN)
4.7 µF
6
4
Analog Brightness Control
3.3 V = LED Off
0 V = ILED = 20 mA
GND
SW
8
OVP 7
1
LED
FB
R1
10 kΩ
RS 2
RS
13 Ω
R2
120 kΩ
Figure 23. Adjustable Brightness Control Using an Analog Voltage
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System Examples (continued)
9.3.5 Alternative Adjustable Brightness Control Using PWM Signal
TPS61043 is designed for driving LED with adjustable brightness control using an analog voltage.
L1
4.7 µH
D1
ZHCS400
CO
100 nF
VIN = 3 V to 6 V
CTRL
SW 8
OVP 7
GND
LED
3 VIN
5
CIN
4.7 µF
6
4 FB
3.3 V PWM Signal
0 % LEDs on
100 % LEDs Off
R1
10 kΩ
R
C
1
RS 2
RS
13 Ω
R2
120 kΩ
Figure 24. Alternative Adjustable Brightness Control Using PWM Signal
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10 Power Supply Recommendations
The device is designed to operate from an input voltage supply range between 1.8 V and 6 V. The input power
supply’s output current needs to be rated according to the supply voltage, output voltage and output current of
TPS61043.
11 Layout
11.1 Layout Guidelines
In all switching power supplies the layout is an important step in the design, especially at high peak currents and
switching frequencies. If the layout is not carefully done, the regulator might show noise problems and duty cycle
jitter.
The input capacitor should be placed as close as possible to the input pin for good input voltage filtering. The
inductor and diode must be placed as close as possible to the switch pin to minimize noise coupling into other
circuits. It is important to connect the output capacitor directly across the diode cathode pin and ground rather
than connecting the output capacitor across the LEDs. This minimizes EMI. Because the feedback pin and
network is a high-impedance circuit, the feedback network should be routed away from the inductor.
11.2 Layout Example
GND
VIN
CIN
FB
VIN
RS
LED
4
3
2
1
RSENSE
TPS61043
L
5
6
7
8
CTRL
GND
OVP
SW
COUT
LED
DIODE
Figure 25. Layout Example
11.3 Thermal Considerations
The TPS61043 comes in a thermally enhanced QFN package. The package includes a thermal pad improving
the thermal capabilities of the package. See QFN/SON PCB Attachment (SLUA271).
The thermal resistance junction to ambient RΘJA of the QFN package greatly depends on the PCB layout. Using
thermal vias and wide PCB traces improves the thermal resistance R ΘJA. Under normal operation conditions no
PCB vias are required for the thermal pad. However, the thermal pad must be soldered to the PCB.
22
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12 Device and Documentation Support
12.1 Device Support
12.1.1 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.
12.2 Documentation Support
12.2.1 Related Documentation
For related documentation see the following:
QFN/SON PCB Attachment, SLUA271
12.3 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.
12.4 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
12.5 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.
12.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
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14-Oct-2022
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)
Samples
(4/5)
(6)
TPS61043DRBR
ACTIVE
SON
DRB
8
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
AQN
Samples
TPS61043DRBT
ACTIVE
SON
DRB
8
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
AQN
Samples
(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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