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TPS54200, TPS54201
SLUSCO8B – NOVEMBER 2016 – REVISED JUNE 2018
TPS54200, TPS54201 4.5-V to 28-V Input Voltage, 1.5-A Output Current,
Synchronous Buck Mono-Color or IR LED Driver
1 Features
3 Description
•
•
The TPS54200 and TPS54201 devices are 1.5-A
synchronous buck mono-color or IR drivers with 28-V
maximum input voltage. Current-mode operation
provides fast transient response and eases loop
stabilization.
1
•
•
•
•
•
•
•
•
•
•
•
4.5-V to 28-V Wide Input Range
Integrated 150-mΩ and 70-mΩ MOSFETs for
1.5‑A, Continuous Output Current
Low, 2-μA Shutdown Current
Fixed 600-kHz Frequency
Peak Current Mode With Internal Compensation
200-mV and 100-mV Sense Voltage During
Analog and PWM Dimming Modes
Precision Analog Dimming (ADIM) by PWM Input
LED-Open and -Short Protection
Sense-Resistor-Open and -Short Protection
Shutdown-and-Latch Mode Protection
(TPS54200)
Auto-Retry Mode Protection (TPS54201)
Thermal Shutdown
6-Pin SOT-23-THIN Package
The TPS54200 and TPS54201 can be used to drive
single-string or multi-string mono-color or Infrared (IR)
LED arrays as in the case of night vision cameras.
By integrating the MOSFETs and employing the SOT23-THIN package, the TPS54200 and TPS54201
devices provide high power density and only require
a small footprint on the PCB.
The TPS54200 and TPS54201 devices implement
analog dimming by changing the internal reference
voltage proportional to the duty cycle of the PWM
signal input in analog dimming mode. This devices
also support PWM dimming mode, in which the
internal reference voltage is halved to 100 mV for
higher efficiency.
2 Applications
•
•
Device Information(1)
IR LED for Day or Night Vision
– IP Network Camera
– Analog Security Camera
– Video Doorbell
– Embedded Camera System
LED Display and Lighting
– Refrigerators and Freezers
– Electronic Smart Lock
– General-Purpose LED Driver
– Architecture Lighting
PART NUMBER
SOT-23-THIN (6)
1.6 mm x 2.9 mm
TPS54201
SOT-23-THIN (6)
1.6 mm x 2.9 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Excellent Deep Dimming in ADIM
CBOOT
2
SW
BOOT
6
PWM
5
CO
PWM Input
RF
VIN
3
CIN
VIN
FB
4
CF
RSENSE
Copyright © 2016, Texas Instruments Incorporated
ILED/ILED_Full (at 100% PWM duty cycle)
LO
GND
BODY SIZE (NOM)
TPS54200
Simplified Schematic
1
PACKAGE
6%
5.5%
5%
4.5%
4%
3.5%
Unit 1
Unit 2
Unit 3
Unit 4
Unit 5
Unit 6
Unit 7
Unit 8
3%
2.5%
2%
1.5%
1%
1%
1.5%
2%
2.5%
3%
3.5%
PWM duty cycle
4%
4.5%
5%
D001
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.
TPS54200, TPS54201
SLUSCO8B – NOVEMBER 2016 – REVISED JUNE 2018
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Description (continued).........................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
4
4
5
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
5
5
5
5
6
7
7
8
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Timing Requirements ................................................
Switching Characteristics ..........................................
Typical Characteristics ..............................................
Detailed Description ............................................ 11
8.1 Overview ................................................................. 11
8.2 Functional Block Diagram ....................................... 12
8.3 Feature Description................................................. 13
8.4 Device Functional Modes........................................ 17
9
Application and Implementation ........................ 20
9.1 Application Information............................................ 20
9.2 Typical Application ................................................. 20
10 Power Supply Recommendations ..................... 30
11 Layout................................................................... 30
11.1 Layout Guidelines ................................................. 30
11.2 Layout Example .................................................... 31
12 Device and Documentation Support ................. 32
12.1
12.2
12.3
12.4
12.5
12.6
12.7
Device Support......................................................
Documentation Support .......................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
32
32
32
32
32
32
32
13 Mechanical, Packaging, and Orderable
Information ........................................................... 33
4 Revision History
Changes from Revision A (March 2017) to Revision B
Page
•
Changed "Hiccup Mode" to "Auto-Retry Mode" in the Features section and throughout the data sheet ............................. 1
•
Changed the package description .......................................................................................................................................... 1
•
Changed the Applications section .......................................................................................................................................... 1
•
Changed "WLED" to "mono-color or IR LED" in the first sentence of the Description section .............................................. 1
•
Changed package descriptor from SOT23 to SOT-23-THIN in the Device Information table................................................ 1
•
Changed pinout diagram and associated text ........................................................................................................................ 4
•
Changed "PWM duty input" to "PWM input duty cycle" in the Pin Functions table................................................................ 4
•
Changed "free-air" to "ambient" in the Absolute Maximum Ratings condition statement ...................................................... 5
•
Changed "free-air" to "ambient" in the Recommended Operating Conditions condition statement ....................................... 5
•
Changed the package description in the Thermal Information table header.......................................................................... 5
•
Changed "Rising" and "Falling" to "Rising VPWM" and "Falling VPWM" for the VADIM, VPDIM, and VPWM Electrical
Characteristics table entries ................................................................................................................................................... 6
•
Changed "SW" to "VSW" in the Test Conditions column for the RHSD entry in the Electrical Characteristics table................. 6
•
Changed "dim mode" to "dimming mode" in the Test Conditions column for the ILIM_HS1 entry in the Electrical
Characteristics table ............................................................................................................................................................... 6
•
Changed the symbol for switching frequency from FSW to fSW .............................................................................................. 7
•
Changed VIN to VVIN in the Typical Characteristics condition statement ................................................................................ 8
•
Changed "hiccup up mode" to "auto-retry mode" ................................................................................................................ 11
•
Changed "duty" to "duty cycle" in multiple locations throughout the data sheet .................................................................. 13
•
Changed "PWM duty" to "PWM duty cycle" in the Figure 16 image .................................................................................... 13
•
Changed "floating driver" to "boot regulator" in the Bootstrap Voltage (BOOT) section ..................................................... 14
•
Changed VIN to VVIN in multiple locations throughout the data sheet................................................................................... 14
•
Changed various wording in the
Added the Device Support and Documentation Support sections section for clarity, and changed "512 switching
cycles " to "tSHUTDOWN_DELAY" ....................................................................................................................................... 14
•
Changed "hiccup up" to "auto-retry mode" in the Fault Protection section .......................................................................... 15
2
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SLUSCO8B – NOVEMBER 2016 – REVISED JUNE 2018
Revision History (continued)
•
Changed "hiccup" to "auto-retry" or "shuddown -and-restart," and deleted "programmed for XXX switching cycles" text.. 15
•
Changed "will be clamped by low" to "is clamped at the low-"............................................................................................. 15
•
Changed "hiccup" to "auto-retry" or "shuddown -and-restart," and deleted "programmed for XXX switching cycles" text.. 15
•
Changed "hiccup" to "auto-retry" or "shuddown -and-restart," and deleted "programmed for XXX switching cycles" text.. 15
•
Changed "hiccup" to "auto-retry" or "shuddown -and-restart," and deleted "programmed for XXX switching cycles" text.. 15
•
Changed "Recycle VIN can reset" to "Cycling VIN resets".................................................................................................... 16
•
Changed "once the device shuts down, it starts" to "a device shutdown starts".................................................................. 16
•
Changed "hiccup" to "auto-retry" or "shuddown -and-restart," and deleted "programmed for XXX switching cycles" text.. 16
•
Changed "hiccup" to "auto-retry" or "shuddown -and-restart," and deleted "programmed for XXX switching cycles" text.. 16
•
Changed "Vin at" to "VVIN" .................................................................................................................................................... 17
•
Changed "VADIM" to "VADIM" and "VPDIM" to "VPDIM" .......................................................................................................... 17
•
Changed "it's" to "the output is"............................................................................................................................................ 17
•
Changed "VIN" to "VIN" and "recycled" to "cycled" at the end of the Mode Detection ......................................................... 17
•
Changed "a little big" to "excessive" in the Analog Dimming Mode Operation section........................................................ 18
•
Changed "PWM duty cycle" to "PWM state" ........................................................................................................................ 19
•
Changed "12-VIN" to "12-V VVIN"........................................................................................................................................... 20
•
Changed "FSW" to "fSW" and "VIN(max)" to "VVIN(max)" in Equation 3 from F to f ....................................................................... 21
•
Changed "FSW" to "fSW" and "VIN(ripple)" to "VVIN(ripple)" in Equation 8 from F to f .................................................................... 21
•
Changed the symbol for frequency in Equation 11 from F to f............................................................................................. 22
•
Changed "RF" to "RF" and "CF" to "CF"................................................................................................................................ 22
•
Changed "VOUT" to "VOUT" in the conditions of multiple application curves........................................................................ 24
•
Changed the wording of the second and third paragraphs of the Inductor Selection section for clarity.............................. 27
•
Changed the symbol for frequency in Equation 14 from F to f............................................................................................. 27
•
Changed "wide areas advantages" to "added width also".................................................................................................... 30
•
Changed "reduce the possibility" to "minimize" .................................................................................................................... 30
•
Added the Device Support and Documentation Support sections ....................................................................................... 32
Changes from Original (November 2016) to Revision A
Page
•
Added initial release of the TPS54201 device........................................................................................................................ 1
•
Changed description to include protection modes. ................................................................................................................ 4
•
Changed ILIM_HS1 and ILIM_HS2 CURRENT LIMIT. .................................................................................................................... 6
•
Changed the low-side source-current limit from (2.4/3.4/4.4) to (2.3/3.3/4.4), ...................................................................... 6
•
Added TPS54201 tHIC_THERMAL, tHIC_OV and tHIC_WAIT Timing Requirements. ........................................................................... 7
•
Added TPS54201 LED Short Protection image. .................................................................................................................. 25
•
Added TPS54201 LED Open Protection image. ................................................................................................................. 25
•
Added TPS54201 Sense Resistor Short Protection image. ................................................................................................ 25
Copyright © 2016–2018, Texas Instruments Incorporated
Product Folder Links: TPS54200 TPS54201
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5 Description (continued)
Cycle-by-cycle current limit in the high-side MOSFET protects the converter in an overload condition and is
enhanced by a low-side MOSFET freewheeling current limit which prevents current runaway. There is a lowside MOSFET sinking current limit to prevent excessive reverse current. For safety and protection, the
TPS54200 and TPS54201 devices include LED-open and -short protection, sense-resistor-open and -short
protection, and device thermal protection. The TPS54200 device implements shutdown-and-latch mode
protection, whereas the TPS54201 device adopts auto-retry mode protection.
6 Pin Configuration and Functions
DDC Package
6-Pin SOT-23-THIN
Top View
GND
1
6
BOOT
SW
2
5
PWM
VIN
3
4
FB
Not to scale
Pin Functions
PIN
NAME
NO.
TYPE (1)
DESCRIPTION
BOOT
6
O
A bootstrap capacitor is required between BOOT and SW.
FB
4
I
LED current-detection feedback
GND
1
G
Power ground
PWM
5
I
Dimming input. Default low (internally pulled low). In analog dimming mode, the internal reference is
proportional to the PWM input duty cycle. In PWM dimming mode, LED current is ON during the PWM
high period in each PWM cycle.
SW
2
O
Switching node to the external inductor
VIN
3
P
Input supply voltage
(1)
4
I = Input, O = Output, P = Supply, G = Ground
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SLUSCO8B – NOVEMBER 2016 – REVISED JUNE 2018
7 Specifications
7.1 Absolute Maximum Ratings
over operating ambient temperature range (unless otherwise noted) (1)
MIN
MAX
VIN
–0.3
30
PWM
–0.3
7
FB
–0.3
7
BOOT–SW
–0.3
7
SW
–0.3
30
–5
30
Operating junction temperature, TJ
–40
150
°C
Storage temperature range, Tstg
–65
150
°C
Input voltage range, VI
Output voltage range, VO
SW (20 ns transient)
(1)
UNIT
V
V
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.
7.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic
discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001
(1)
UNIT
±4000
Charged-device model (CDM), per JEDEC specification JESD22-C101 (2)
V
±1500
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.
7.3 Recommended Operating Conditions
over operating ambient temperature range (unless otherwise noted)
MIN
MAX
4.5
28
PWM
–0.1
6
FB
–0.1
6
BOOT-SW
VIN
VI
Input voltage range
VO
Output voltage range
–0.1
6.5
SW
–0.1
28
TJ
Operating junction temperature
–40
125
UNIT
V
V
°C
7.4 Thermal Information
TPS5420x
THERMAL METRIC (1)
DDC (SOT-23-THIN)
UNIT
6 PINS
RθJA
Junction-to-ambient thermal resistance
89.2
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
39.5
°C/W
RθJB
Junction-to-board thermal resistance
14.7
°C/W
ψJT
Junction-to-top characterization parameter
1.2
°C/W
ψJB
Junction-to-board characterization parameter
14.7
°C/W
(1)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
Copyright © 2016–2018, Texas Instruments Incorporated
Product Folder Links: TPS54200 TPS54201
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7.5 Electrical Characteristics
The electrical ratings specified in this section apply to all specifications in this document, unless otherwise noted. These
specifications are interpreted as conditions that do not degrade the device parametric or functional specifications for the life of
the product containing it. TJ = –40°C to 125°C, VVIN = 4.5 V to 28 V, (unless otherwise noted).
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
INPUT SUPPLY
VVIN
Input voltage range
IOFF
Shutdown current
VVIN_UVLO
4.5
PWM = GND
VIN undervoltage lockout
28
V
µA
2
8.6
Rising VVIN
3.83
4.2
4.47
Falling VVIN
3.4
3.7
3.95
Hysteresis
470
V
mV
DIMMING (PWM PIN)
VADIM
Analog dimming-mode threshold
VPDIM
PWM dimming-mode threshold
VPWM
Threshold to identify PWM duty cycle
VPWM_SHUTDOWN
Shutdown threshold
Rising VPWM
1.97
Falling VPWM
2.07
2.17
1.8
Rising VPWM
0.9
Falling VPWM
1
1.1
0.8
Rising VPWM
0.91
1
1.12
Falling VPWM
0.5
0.63
0.72
0.35
0.55
V
V
V
V
FEEDBACK AND ERROR AMPLIFIER
VFB1
Feedback voltage in analog dimming
mode
PWM = 3.3 V, SW duty cycle > 90%
201
205
210
mV
VFB2
Feedback voltage in PWM dimming mode PWM = 1.5 V, SW duty cycle > 90%
96
100
104
mV
Rising
2.1
2.33
Falling
2
2.2
150
259
mΩ
70
120
mΩ
2.4
3
3.6
A
1
1.4
1.8
A
BOOT PIN
VBOOT_UVLO
BOOT-SW UVLO threshold
V
POWER STAGE
RHSD
High-side FET on-resistance
VBOOT – VSW= 6 V
RLSD
Low-side FET on-resistance
VVIN > 6 V
ILIM_HS1
High-side current limit 1
Either one of the following conditions:
1. PWM dimming mode
2. Analog dimming mode and PWM duty
cycle >25%
ILIM_HS2
High-side current limit 2
Analog dimming mode and PWM duty
cycle 6 V
2.3
3.3
4.4
A
ILIM_LS_SINK
Low-side sink current limit
VVIN > 6 V
1.25
1.7
2.2
A
150
160
170
°C
CURRENT LIMIT
FAULT PROTECTION
Thermal
shutdown (1)
Rising temperature
VOVP
VOCP
(1)
6
Hysteresis
10
°C
Overvoltage protection
1
V
Overcurrent protection
120%
Not production tested
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SLUSCO8B – NOVEMBER 2016 – REVISED JUNE 2018
7.6 Timing Requirements
MIN
TYP
MAX
UNIT
THERMAL SHUTDOWN
tHIC_THERMAL
TPS54200 and TPS54201 thermal shutdown auto-retry time
32 768
Cycles
32 768
Cycles
OVERVOLTAGE PROTECTION
tHIC_OV
TPS54201 auto-retry time for overvoltage protection
OVERCURRENT AND OPEN-LOOP PROTECTION
tSHUTDOWN_DELAY
TPS54200 shutdown delay time for open-loop and overcurrent
protection
512
Cycles
tHIC_WAIT
TPS54201 auto-retry wait time for open-loop and overcurrent
protection
512
Cycles
tHIC_OC
TPS54201 auto-retry time for open-loop and overcurrent protection
16 384
Cycles
SOFT START
tSS
Internal soft-start time
0.6
ms
7.7 Switching Characteristics
TJ = –40°C to 125°C, VVIN = 4.5 V to 28 V, (unless otherwise noted).
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
480
600
700
kHz
90
105
ns
OSCILLATOR
fsw
Switching frequency
ON-TIME CONTROL
tMIN_ON
Measured at 90% to 90% and 1-A
loading
Minimum on-time
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7.8 Typical Characteristics
VVIN = 12 V, unless otherwise specified
240
220
2.5
+LJK VLGH )(7 5GV RQ P
Shutdown Quiescent Current (uA)
3
2
1.5
1
0.5
200
180
160
140
120
0
-50
-25
0
25
50
75
Junction Temperature (°C)
100
100
-50
125
Figure 1. Shutdown Quiescent Current vs Junction
Temperature
100
125
D002
207
206.5
FB Voltage in ADIM (mV)
100
/RZ VLGH )(7 5GV RQ P
0
25
50
75
Junction Temperature (°C)
Figure 2. High-Side FET On-Resistance vs Junction
Temperature
110
90
80
70
60
206
205.5
205
204.5
204
203.5
50
-50
-25
0
25
50
75
Junction Temperature (°C)
100
203
-50
125
-25
D003
Figure 3. Low-Side FET On-Resistance vs Junction
Temperature
0
25
50
75
Junction Temperature (°C)
100
125
D004
Figure 4. FB Voltage in ADIM vs Junction Temperature
610
Switching Frequency (kHz)
101
FB Voltage in PDIM (mV)
-25
D001
100.5
100
99.5
605
600
595
590
585
99
-50
-25
0
25
50
75
Junction Temperature (°C)
100
125
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-25
0
25
50
75
Junction Temperature (°C)
D005
Figure 5. FB Voltage in PDIM vs Junction Temperature
8
580
-50
100
125
D006
Figure 6. Switching Frequency vs Junction Temperature
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Typical Characteristics (continued)
VVIN = 12 V, unless otherwise specified
1.65
3.3
High Side Current Limit 2 (A)
High Side Current Limit 1 (A)
3.25
3.2
3.15
3.1
3.05
3
1.6
1.55
1.5
1.45
2.95
2.9
-50
-25
0
25
50
75
Junction Temperature (°C)
100
1.4
-50
125
Figure 7. High-Side Source Current Limit 1 Threshold vs
Junction Temperature
100
125
D008
1.85
Low Side Sink Current Limit (A)
Low Side Source Current Limit (A)
0
25
50
75
Junction Temperature (°C)
Figure 8. High-Side Source Current Limit 2 Threshold vs
Junction Temperature
3.6
3.5
3.4
3.3
3.2
3.1
3
-50
-25
0
25
50
75
Junction Temperature (°C)
100
1.8
1.75
1.7
1.65
1.6
-50
125
-25
D009
Figure 9. Low-Side Source Current Limit Threshold vs
Junction Temperature
0
25
50
75
Junction Temperature (°C)
100
125
D010
Figure 10. Low-Side Sink Current Limit Threshold vs
Junction Temperature
2.2
4.2
Rising
Falling
2.15
4.1
VIN UVLO Threshold (V)
BOOT UVLO Threshold (V)
-25
D007
2.1
2.05
2
1.95
4
Rising
Falling
3.9
3.8
3.7
1.9
-50
-25
0
25
50
75
Junction Temperature (°C)
100
125
3.6
-50
-25
D011
Figure 11. BOOT-SW UVLO Threshold vs Junction
Temperature
0
25
50
75
Junction Temperature (°C)
100
125
D012
Figure 12. VIN UVLO Threshold vs Junction Temperature
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Typical Characteristics (continued)
VVIN = 12 V, unless otherwise specified
1.1
PWM Dimming Mode Threshold (V)
Analog Dimming Mode Threshold (V)
2.1
2.05
2
Rising
Falling
1.95
1.9
1.85
1.8
-50
-25
0
25
50
75
Junction Temperature (°C)
100
125
1.05
1
0.95
Rising
Falling
0.9
0.85
0.8
0.75
-50
-25
0
25
50
75
Junction Temperature (°C)
D013
Figure 13. Analog Dimming Mode Threshold vs Junction
Temperature
100
125
D014
Figure 14. PWM Dimming Mode Threshold vs Junction
Temperature
PWM Shutdown Threshold (V)
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
-50
-25
0
25
50
75
Junction Temperature (°C)
100
125
D015
Figure 15. PWM Shutdown Threshold vs Junction Temperature
10
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8 Detailed Description
8.1 Overview
The TPS5420x device is a 1.5-A synchronous buck LED driver up to 28-V input. Current-mode operation
provides fast transient response. The optimized internal compensation network minimizes the external
component count and simplifies the control loop design.
The TPS5420x device has a fixed 600-kHz switching frequency for a good tradeoff between efficiency and size.
The integrated 150-mΩ high-side MOSFET and 70-mΩ low-side MOSFET allow for a high-efficiency LED driver
with continuous output current up to 1.5 A.
The TPS5420x device supports deep dimming in both analog and PWM dimming modes. In analog dimming
mode, the internal reference voltage is changed in proportion to the duty cycle of the PWM signal in the 1% to
100% range. In the PWM dimming mode, the LED turns on and off periodically according to the PWM duty cycle.
For higher efficiency, the internal reference is halved to 100 mV.
Cycle-by-cycle current limit in the high-side MOSFET protects the converter in overload conditions and is
enhanced by a low-side MOSFET freewheeling current limit which prevents current runaway. There is a low-side
MOSFET sinking-current limit to prevent excessive reverse current.
For safety and protection, the TPS5420x includes LED-open and -short protection, sense-resistor-open and short protection, and device thermal protection. The TPS54200 device implements shutdown-and-latch mode
protection, whereas the TPS54201 device implements auto-retry mode protection.
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8.2 Functional Block Diagram
Enable
PWM
VIN
5
3
Peak
Detector
Delay
Thermal
Shutdown
+
VTH
PWM
DIM Mode
Selection
Enable
Timer
and Logic
UVLO
Shutdown
Logic
Boot
Charge
OVP Shutdown
Open Loop Shutdown
Mode
VIN
Bandgap
SS
OCP Shutdown
Maximum
Clamp
VBGP
BOOT
2
SW
Boot
UVLO
PWM
Dimming
Control and
Error Amp
6
HS MOSFET
Current
Comparator
Mode
Power Stage
and Deadtime
Control Logic
Comp
Slope
Compensation
Mode
FB
Oscillator
4
+
OVP
Shutdown
+
OCP
Shutdown
PWM
VIN
1V
VOCP
Regulator
Current
Sense
LS MOSFET
Current Limit
1
GND
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8.3 Feature Description
8.3.1 Fixed-Frequency PWM Control
The device uses a fixed-frequency and peak-current-mode control. The LED current is sensed by a resistor in
series with the LED string. The sensed voltage is fed to the FB pin through an RC filter, and then compared to an
internal voltage reference by an error amplifier. An internal oscillator initiates the turnon of the high-side power
switch. The error amplifier output is compared to the current of the high-side power switch. When the powerswitch current reaches the error-amplifier output-voltage level, the high-side power switch is turned off and the
low-side power switch is turned on. Thus, the error amplifier output voltage regulates inductor peak current, and
in turn the LED current, to a target value. The device implements a current limit by clamping the error amplifier
voltage to a maximum level and also implements a minimum clamp for improved transient-response
performance.
8.3.2 Error Amplifier
The device has a transconductance amplifier as the error amplifier. The error amplifier compares the FB voltage
to the lower of the internal soft-start voltage or the internal voltage reference. The transconductance of the error
amplifier is 240 μA/V typically. The frequency compensation components are placed internally between the
output of the error amplifier and ground.
8.3.3 Slope Compensation and Output Current
The device adds a compensating ramp to the signal of the switch current. This slope compensation prevents
subharmonic oscillations as the duty cycle increases. The available peak inductor current remains constant over
the full duty-cycle range.
8.3.4 Input Undervoltage Lockout
The device implements internal undervoltage-lockout (UVLO) circuitry on the VIN pin. The device is disabled
when the VIN pin voltage falls below the internal VIN UVLO threshold, which is 3.7 V typical. The internal VIN
UVLO threshold has a hysteresis of 470 mV.
8.3.5 Voltage Reference
The voltage reference system produces a precise ±2.5% voltage reference over temperature by scaling the
output of a temperature-stable band-gap circuit when the PWM duty cycle is 100%. In PWM dimming mode, the
voltage reference, VREF, is fixed at 100 mV. In analog dimming mode, VREF, is proportional to the duty cycle of
PWM as shown in Figure 16.
VREF (mV)
200
100
PWM duty cycle (%)
Figure 16. VREF vs PWM Duty Cycle in Analog Dimming Mode
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Feature Description (continued)
8.3.6 Setting LED Current
Once the voltage reference, VREF, is chosen, one can set the LED current by choosing the proper sensing
resistor according to Equation 1:
VREF
RSENSE
ILED
(1)
8.3.7 Internal Soft Start
The TPS5420x device uses an internal soft-start function. The internal soft-start time is set to 0.6 ms typically.
8.3.8 Bootstrap Voltage (BOOT)
The TPS5420x has an integrated boot regulator and requires a 0.1-μF ceramic capacitor between the BOOT and
SW pins to provide the gate drive voltage for the high-side MOSFET. A ceramic capacitor with an X7R or X5R
grade dielectric is recommended because of the stable characteristics over temperature and voltage. This boot
regulator has its own UVLO protection. This UVLO rising threshold is 2.1 V with a hysteresis of 100 mV. A 6-V
bootstrap voltage is maintained between BOOT and SW when VVIN > 6 V.
8.3.9 Overcurrent Protection
The device is protected from overcurrent conditions by cycle-by-cycle current limiting on both the high-side
MOSFET and the low-side MOSFET.
8.3.9.1 High-Side MOSFET Overcurrent Protection
The device implements current-mode control, which uses the internal COMP voltage to control the turnoff of the
high-side MOSFET and the turnon of the low-side MOSFET on a cycle-by-cycle basis. During each cycle, the
switch current and the current reference generated by the internal COMP voltage are compared. When the peak
switch current intersects the current reference, the high-side switch turns off. During overcurrent conditions, such
as when the sensing resistor is shorted, or an open circuit occurs in the feedback-filter RC network that drives FB
low, the error amplifier responds by driving the COMP pin high, increasing the switch current. The error amplifier
output is clamped internally. This clamp functions as a switch-current limit. This current limit is fixed at 3.1 A
typical in PWM dimming mode. In analog dimming mode with the PWM duty cycle >25%, this limit is also 3.1 A.
If the PWM duty cycle is below 25%, this limit is halved to 1.5 A typical. Furthermore, if an output overcurrent
condition occurs for more than the shutdown delay time, tSHUTDOWN_DELAY, the device shuts down and latches off
to protect the LED from overcurrent damage.
8.3.9.2 Low-Side MOSFET Overcurrent Protection
While the low-side MOSFET is turned on, the conduction current is monitored by the internal circuitry. During
normal operation, the low-side MOSFET sources current to the load. At the end of every clock cycle, the low-side
MOSFET sourcing current is compared to the internally set low-side sourcing current-limit. If the low-side
sourcing-current limit is exceeded, the high-side MOSFET does not turn on and the low-side MOSFET stays on
for the next cycle. The high-side MOSFET turns on again when the low-side current is below the low-side
sourcing current-limit at the start of a cycle.
8.3.9.3 Low-Side MOSFET Reverse Overcurrent Protection
The TPS5420x device implements low-side reverse-current protection by detecting the voltage across the lowside MOSFET. When the converter sinks current through its low-side FET, the control circuit turns off the lowside MOSFET if the reverse current is more than 1.7 A typical. By implementing this additional protection
scheme, the converter is able to protect itself from excessive sink current during fault conditions.
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Feature Description (continued)
8.3.10 Fault Protection
The device is protected from several kinds of fault conditions, such as LED open and short, sense-resistor open
and short, and thermal shutdown. The only difference between the TPS54200 and TPS54201 devices is the
different protection mode used. The TPS54200 device implements shutdown-and-latch mode protection, whereas
the TPS54201 device implements auto-retry mode protection.
8.3.10.1 LED-Open Protection
When the LED load is open, the FB voltage is low, and the internal COMP voltage is driven high and clamped.
This action triggers a shutdown delay counter (TPS54200) or auto-retry wait counter (TPS54201). For the
TPS54200 device, once the shutdown delay time tSHUTDOWN_DELAY expires, the device shuts down and latches off.
Both FETs are kept off. This is a latched shutdown. The device can be reset by recycling VIN. For TPS54201,
once the auto-retry wait time tHIC_WAIT expires, the device shuts down and starts auto-retry timer tHIC_OC. During
the shutdown period, both FETs are kept off. Once the auto-retry timer expires, the TPS54201 device restarts
again. If the failure still exists, the TPS54201 device repeats the foregoing shutdown-and-restart process.
8.3.10.2 LED Short Protection
When the LED load is shorted, the FB voltage is higher than VREF, and the internal COMP voltage is driven low
and clamped, and the high-side MOSFET is commanded on for a minimum on-time each cycle. In this condition,
if the output voltage is too low, the inductor current may not be able to balance in a cycle, causing current
runaway. Finally, the inductor current is clamped at the low-side MOSFET sourcing-current limit, which is much
higher than target LED current. If the FB voltage is higher than the OCP threshold, which is 250 mV typical in
analog dimming mode, or 120 mV typical in PWM dimming mode, the shutdown delay counter (TPS54200) or
auto-retry wait counter (TPS54201) is triggered. For the TPS54200 device, once the shutdown delay time
tSHUTDOWN_DELAY expires, the device shuts down and latches off. Both FETs are kept off. This is a latched
shutdown. The device can be reset by recycling VIN. For the TPS54201 device, once the auto-retry wait time
tHIC_WAIT expires, the device shuts down and starts auto-retry timer tHIC_OC. During the shutdown period, both
FETs are kept off. Once the auto-retry timer expires, the TPS54201 device restarts again. If the failure still exists,
the TPS54201 device repeats the foregoing shutdown-and-restart process.
8.3.10.3 Sense-Resistor Short Protection
When the sense resistor is shorted, the FB voltage is low, and the internal COMP voltage is driven high and
clamped. This action triggers the shutdown delay counter (TPS54200) or auto-retry wait counter (TPS54201). For
the TPS54200 device, once the shutdown delay time tSHUTDOWN_DELAY expires, the device shuts down and latches
off. Both FETs are kept off. This is a latched shut-down. The device can be reset by recycling VIN. For the
TPS54201 device, once the auto-retry wait time tHIC_WAIT expires, the device shuts down and starts auto-retry
timer tHIC_OC. During the shutdown period, both FETs are kept off. Once the auto-retry timer expires, the
TPS54201 device restarts again. If the failure still exists, the TPS54201 device repeats the foregoing shutdownand-restart process.
8.3.10.4 Sense-Resistor Open Protection
When the sense resistor is open before the device powers on, the device charges the BOOT capacitor at the
power-on moment. The charging current flows through the inductor, the output capacitor, and the RC filter at the
FB pin to charge up the FB pin voltage. Once the device detects an FB voltage higher than the 1-V OVP
threshold, the device shuts down immediately. For the TPS54200 device, this is a latched shutdown, and the
device can be reset by cycling VIN. For the TPS54201 device, once the device shuts down, it starts the
overvoltage auto-retry timer tHIC_OV. During the shutdown period, both FETs are kept off. Once the overvoltage
auto-retry timer expires, the TPS54201 device restarts again. If the failure still exists, the TPS54201 device
repeats the foregoing auto-retry shutdown-and-restart process.
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Feature Description (continued)
8.3.10.5 Overvoltage Protection
When the FB pin, for some reason, has a voltage higher than 1 V applied, the device shuts down immediately.
Both FETs are kept off. This is called overvoltage protection. For the TPS54200 device, this is a latched
shutdown. Cycling VIN resets the device. For the TPS54201 device, a device shutdown starts the overvoltage
auto-retry timer tHIC_OV. During the shutdown period, both FETs are kept off. Once the overvoltage auto-retry
timer expires, the TPS54201 device restarts again. If the failure still exists, the TPS54201 device repeats the
foregoing auto-retry shutdown-and-restart process.
8.3.10.6 Thermal Shutdown
The internal thermal-shutdown circuitry forces the device to stop switching if the junction temperature exceeds a
typical value of 160°C. When the junction temperature drops below a typical value of 150°C, the internal thermalauto-retry timer tHIC_THERMAL begins to count. The device reinitiates the power-up sequence once the thermalauto-retry timer expires.
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8.4 Device Functional Modes
8.4.1 Enable and Disable Device
The PWM pin performs not only the dimming function, but also the enable-and-disable function. When the VIN
voltage is above the UVLO threshold, the TPS5420x device can be enabled by driving the PWM pin higher than
the threshold voltage, 0.56 V typical. To disable the device, keep the PWM pin lower than the threshold voltage,
0.55 V typical, for 40 ms or longer. The PWM pin has an internal pulldown resistor, so floating this pin disables
the device.
The suggested power-on sequence is applying VVIN first, followed by the PWM signal.
8.4.2 Mode Detection
The magnitude of the PWM signal is used to determine which dimming mode the device enters. The internal
peak detector at the PWM pin holds the magnitude of the PWM signal. Once the device is enabled, after 300-µs
delay, the output of the peak detector is compared with two voltage thresholds, VADIM and VPDIM, which are 1 V
and 2.07 V, respectively. If the output of the peak detector is higher than 2.07 V, analog dimming mode is
chosen and locked. If the output is between 1 V and 2.07 V, PWM dimming mode is chosen and locked. If the
output is less than 1 V, the device waits another 300 µs and compares again, and this process repeats until at
least one mode is chosen and locked. See Figure 17 and Table 1 for reference. After the mode is detected and
locked, soft start begins, the output voltage ramps up, and the LED current is regulated at the target value. The
dimming mode cannot be changed unless VIN or PWM is cycled. section
PWM
+
EN
VTH
PWM
Peak
Detector
VADIM
VPDIM
VPWM
+
+
A
+
B
Internal
PWM
Figure 17. Mode Detection Circuit
Table 1. Mode Detection Condition
A
B
MODE
H
H
Enter analog dimming mode
L
H
Enter PWM dimming mode
L
L
Keep detecting until one dimming mode is locked
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8.4.3 Analog Dimming Mode Operation
Once the analog dimming mode is chosen, the internal voltage reference for the FB pin is approximately 200 mV
at full scale, and proportional to the PWM duty cycle as shown in Figure 16. LED current is continuous in this
mode, and the current magnitude can be adjusted by changing PWM duty cycle, see Figure 18. Because the
internal voltage reference is filtered from the PWM signal, a too-low PWM frequency may cause excessive ripple
at the voltage reference. To minimize this ripple, the suggested PWM signal frequency is 10 kHz or higher, such
as 50 kHz.
200 mV/RSENSE
LED current
100 mV/RSENSE
50 kHz/50%
PWM
t
3V
t
Figure 18. Analog Dimming Operation
A comparator with 400-mV hysteresis is used to generate the internal PWM signal, see Figure 17. This internal
PWM duty cycle determines the voltage reference. To make sure the PWM pin signal is correctly identified, the
high level of the PWM signal should be higher than 1 V, and the low level should be lower than 0.6 V. Figure 19
shows the relationship between the external PWM and internal PWM signals.
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8.4.4 PWM Dimming-Mode Operation
Once the PWM dimming mode is chosen, the internal voltage reference for the FB pin is fixed at 100 mV. The
LED current is on or off corresponding to the PWM state, see Figure 19. Due to the limited control-loop
response, to get a relatively linear dimming performance, the suggested PWM signal frequency should be less
than 1 kHz.
1V
0.6 V
PWM Pin Signal
Internal PWM
100 mV/RSENSE
0
LED Current
Figure 19. PWM Dimming Operation
In some application where dimming is not needed, one can just connect a resistor divider from VVIN to the PWM
pin as Figure 20 shows.
LO
CBOOT
1
GND
BOOT
6
2
SW
PWM
5
3
VIN
FB
4
CO
RF
VIN
CIN
RTOP
CF
RSENSE
RBOT
Figure 20. Application Without Dimming
RTOP and RBOT should be sized to make sure the PWM pin voltage is higher than 1 V when VVIN reaches its
steady voltage. It is best to make sure the PWM pin voltage is less than 2 V, thus one can have 100 mV at the
FB pin for better efficiency. Use 10 kΩ as a good starting point for RBOT, then choose RTOP according to
Equation 2:
§ V
·
R TOP ¨ IN
1¸ u RBOT
V
© PWM
¹
(2)
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The TPS5420x device is typically used as a buck converter to drive one or more LEDs from a 4.5-V to 28-V
input. The TPS5420x device supports both analog dimming mode and PWM dimming mode.
9.2 Typical Application
3
2
9.2.1 TPS5420x 12-V Input, 1.5-A, 3-Piece IR LED Driver With Analog Dimming
U1
VIN
C2
10µF
C3
0.1µF
3
VIN
5
PWM
BOOT
6
SW
2
FB
4
0.1µF
D1
SFH 4715A
Infrared
L1
R1
0
1
C1
10µH
3
2
VIN = 10.8V ~ 13.2V
D2
SFH 4715A
Infrared
C4
10µF
PWM
GND
TP1
1
3.3V, 50kHz, 1% to 100% duty
1
R2
TPS54200DDCR
910
GND
3
2
GND
R3
0.033
D3
SFH 4715A
Infrared
C5
0.082µF
1
R4
0.1
GND
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GND
Figure 21. 12-V VVIN, 1.5-A, 3-Piece IR LED, Analog Dimming Reference Design
9.2.1.1 Design Requirements
For this design example, use the parameters in Table 2.
Table 2. Design Parameters
20
PARAMETER
VALUE
Input voltage range
10.8 V to 13.2 V
LED string forward voltage
5.4-V stack
Output voltage
5.6 V
LED current at 100% PWM duty cycle
1.5 A
LED current ripple
30 mA or less
Input voltage ripple
400 mV or less
PWM dimming range
1% to 100%, 3.3 V, 50 kHz
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9.2.1.2 Detailed Design Procedure
9.2.1.2.1 Inductor Selection
Use Equation 3 to calculate the minimum value of the output inductor (LMIN).
VOUT ´ (VVIN(max) - VOUT )
L MIN =
VVIN(max) ´ KIND ´ ILED ´ fSW
where
•
•
•
KIND is a coefficient that represents the amount of inductor ripple current relative to the maximum LED current.
ILED is the maximum LED current.
VOUT is the sum of the voltage across LED load and the voltage across the sense resistor.
(3)
In general, the suggested value of KIND is between 0.2 and 0.4. For an application that can tolerate higher LED
current ripple or use larger output capacitors, one can choose 0.4 for KIND. Otherwise, a smaller KIND like 0.2 can
be chosen to get low-enough LED current ripple.
With the chosen inductor value the user can calculate the actual inductor current ripple using Equation 4.
VOUT ´ (VVIN(max) - VOUT )
IL(ripple) =
VVIN(max) ´ L ´ fSW
(4)
The inductor rms-current and saturation-current ratings must be greater than the rms current and saturation
current seen in the application. This ensures that the inductor does not overheat or saturate. During power up,
transient conditions, or fault conditions, the inductor current can exceed its normal operating current. For this
reason, the most conservative approach is to specify an inductor with a saturation current rating equal to or
greater than the converter current limit. This is not always possible due to application size limitations. The peakinductor-current and rms-current equations are shown in Equation 5 and Equation 6.
IL(ripple)
IL(peak) ILED
(5)
2
IL(rms)
ILED2
IL(ripple)2
12
(6)
In this design, choose KIND = 0.3. According to the LED manufacturer’s data sheet, the IR LED has 1.75-V
forward voltage at 1.5-A current, so VOUT = 1.75 V × 3 + 0.2 V = 5.45 V and the calculated inductance is 11.9 µH.
A 10-µH inductor (part number is 744066100 from Wurth) is chosen. With this inductor, the ripple, peak, and rms
currents of the inductor are 0.53 A, 1.77 A, and 1.51 A, respectively. The chosen inductor has ample margin.
9.2.1.2.2 Input Capacitor Selection
The device requires an input capacitor to reduce the surge current drawn from the input supply and the switching
noise from the device. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their
low ESR and small temperature coefficients. For most applications, a 10-μF capacitor is enough. An additional
0.1-μF capacitor from VIN to GND is optional to provide additional high-frequency filtering. The input capacitor
must have a voltage rating greater than the maximum input voltage and have a ripple-current rating greater than
the maximum input-current ripple of the converter. The rms input-ripple current is calculated in Equation 7, where
D is the duty cycle (output voltage divided by input voltage).
ICIN(rms)
ILED u D u 1 D
(7)
Use Equation 8 to calculate the input ripple voltage, where ESRCIN is the ESR of input capacitor. Ceramic
capacitance tends to decrease as the applied dc voltage increases. This depreciation must be accounted for
when calculating input ripple voltage.
ILED ´ D ´ (1 - D)
+ ILED ´ ESR CIN
VVIN(ripple) =
CIN ´ fSW
(8)
In this design, a 10-µF, 35-V X7R ceramic capacitor, part number GRM32ER7YA106KA12L from muRata, is
chosen. This yields around 70-mV input ripple voltage. The calculated rms input ripple current is 0.75 A, well
below the ripple-current rating of the capacitor.
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9.2.1.2.3 Output Capacitor Selection
The output capacitor reduces the high-frequency ripple current through the LED string. Various guidelines
disclose how much high-frequency ripple current is acceptable in the LED string. Excessive ripple current in the
LED string increases the rms current in the LED string, and therefore the LED temperature increases.
1. Look up the total dynamic resistance of the LED string (RLED) using the LED manufacturer’s data sheet.
2. Calculate the required impedance of the output capacitor (ZOUT), given the acceptable peak-to-peak ripple
current through the LED string, ILED(ripple). IL(ripple) is the peak-to-peak inductor ripple current as calculated
previously in the Inductor Selection section.
3. Calculate the minimum effective output capacitance required.
4. Increase the output capacitance appropriately due to the derating effect of applied dc voltage.
See Equation 9, Equation 10 and Equation 11.
'VF
RLED
u # of LEDs
'IF
ZCOUT
COUT =
(9)
RLED u ILED(ripple)
IL(ripple) ILED(ripple)
(10)
1
2p ´ fSW ´ Z COUT
(11)
Once the output capacitor is chosen, Equation 12 can be used to estimate the peak-to-peak ripple current
through the LED string.
ZCOUT u IL(ripple)
ILED(ripple)
ZCOUT RLED
(12)
An OSRAM IR LED, SFH4715A, is used here. The dynamic resistance of this LED is 0.25 Ω at 1.5-A forward
current. In this design, a 10-µF, 35-V X7R ceramic capacitor is chosen, the part number is
GRM32ER7YA106KA12L, from muRata. The calculated ripple current of the LED is about 20 mA.
9.2.1.2.4 FB Pin RC Filter Selection
The RC filter comprising RF and CF and connected between the sense resistor and the FB pin is used to
generate a pole for loop stability purposes. Moving this pole can adjust loop bandwidth. The suggested frequency
of the pole is 2 kHz in analog dimming mode and 4 kHz in PWM dimming mode. Use Equation 13 to choose RF
and CF. Due to the dc offset current of the internal amplifier, the suggested value of RF is less than 1 kΩ to
minimize the effect on LED current-regulation accuracy.
1
CF
2S u RF u fPOLE
(13)
Analog dimming mode is implemented in this design. Choose the pole at around 2 kHz, with 910 Ω as the filter
resistor; then the calculated filter capacitance is 87 nF. An 82 nF capacitor is chosen for this filter.
9.2.1.2.5 Sense Resistor Selection
The maximum target LED current at 100% PWM duty is 1.5 A, and the corresponding VREF is 200 mV. Using
Equation 1, calculate the needed sense resistance at 133 mΩ. Pay close attention to the power consumption of
the sense resistor in this design at 300 mW, and make sure the chosen resistor has enough margin in its power
rating.
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9.2.1.3 Application Curves
100%
CH2
95%
90%
Efficiency
85%
CH3
80%
75%
70%
65%
CH4
60%
Efficiency_LED
Efficiency_Vout
55%
50%
0
10
20
30
40
50
60
PWM duty %
70
80
90
100
D001
CH2: SW
CH3: LED current
(AC-coupled)
CH4: Inductor current
Figure 22. Efficiency
Figure 23. LED Current Ripple at 1% PWM Duty Cycle
CH2
CH1
CH3
CH2
CH4
CH4
CH2: SW
CH3: LED current
CH4: Inductor
current
(AC-coupled)
CH1: VVIN
CH2: SW
CH4: Inductor
current
(AC-coupled)
Figure 24. LED Current Ripple at 100% PWM Duty Cycle
Figure 25. Input Voltage Ripple at 100% PWM Duty Cycle
CH1
CH1
CH3
CH3
CH4
CH4
CH1: PWM
CH3: Inductor
current
CH4: LED current
Figure 26. LED Current Transient as PWM Duty Cycle
Changes From 1% to 99%
CH1: PWM
CH3: Inductor
current
CH4: LED current
Figure 27. LED Current Transient as PWM Duty Cycle
Changes From 50% to 99%
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1600
CH1
1400
1200
LED current (mA)
CH3
CH4
1000
800
600
400
200
0
0
CH1: PWM
CH3: Inductor
current
20%
40%
60%
PWM duty %
80%
100%
D002
CH4: LED current
Figure 29. LED Current vs PWM Duty Cycle
Figure 28. LED Current Transient as PWM Duty Cycle
Changes From 99% to 1%
CH1
CH1
CH2
CH2
CH3
CH3
CH4
CH4
CH1: PWM
CH2: SW
CH3: VOUT
CH4: LED
current;
Figure 30. Start-Up at 1% PWM Duty Cycle and 50 kHz
CH1: PWM
CH2: SW
CH3: VOUT
CH4: LED
current;
Figure 31. Shutdown at 1% PWM Duty Cycle and 50 kHz
CH1
CH1
CH2
CH2
CH3
CH4
CH3
CH4
CH1: PWM
CH2: SW
CH3: VOUT
CH4: LED
current
Figure 32. Start-Up at 100% PWM Duty Cycle
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CH1: PWM
CH2: SW
CH3: VOUT
CH4: LED
current
Figure 33. Shutdown at 100% PWM Duty Cycle
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CH1
CH2
CH3
CH4
CH1: VOUT
CH2: SW
CH3: FB
CH4: Inductor
current
Figure 34. LED Short Protection (100% PWM Duty Cycle)
of TPS54200
CH1: VOUT
CH2: SW
CH3: FB
CH4: Inductor
current
Figure 35. LED Short Protection (100% PWM Duty Cycle)
of TPS54201
CH1
CH2
CH3
CH4
CH1: VOUT
CH2: SW
CH3: FB
CH4: Inductor
current
Figure 36. LED Open Protection (100% PWM Duty Cycle)
of TPS54200
CH1: VOUT
CH2: SW
CH3: FB
CH4: Inductor
current
Figure 37. LED Open Protection (100% PWM Duty Cycle)
of TPS54201
CH1
CH2
CH3
CH4
CH1: VOUT
CH2: SW
CH3: FB
CH4:Inductor
current
Figure 38. Sense Resistor Short Protection (100% PWM
Duty Cycle) of TPS54200
CH1: VOUT
CH2: SW
CH3: FB
CH4: Inductor
current
Figure 39. Sense-Resistor Short Protection (100% PWM
Duty Cycle) of TPS54201
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1
9.2.2 TPS5420x 24-V Input, 1-A, 4-Piece WLED Driver With PWM Dimming
U1
C2
10µF
C3
0.1µF
VIN
BOOT
6
0.1µF
5
PWM
SW
R1
2
3
C1
3
0
GND
10µH
1
VIN = 21.6V ~ 26.4V
VIN
D1
Cool White
L1
2
D2
Cool White
GND
4
GND
TP1
1
1
PWM
FB
R2
TPS54200DDCR
D3
Cool White
200
GND
2
3
GND
1.5V, 250Hz, 1% to 100% duty
2
3
C4
10µF
C5
0.082µF
GND
1
R3
0.1
D4
Cool White
2
3
GND
GND
GND
Copyright © 2016, Texas Instruments Incorporated
Figure 40. 24-V Input, 1-A, 4-Piece WLED Driver With PWM Dimming Reference Design
9.2.2.1 Design Requirements
For this design example, use the parameters in Table 3.
Table 3. Design Parameters
26
PARAMETER
VALUE
Input voltage range
21.6 V to 26.4 V
LED string forward voltage
11.6-V stack
Output voltage
11.7 V
LED current at 100% PWM duty cycle
1A
LED current ripple
30 mA or less
Input voltage ripple
400 mV or less
PWM dimming range
1% to 100%, 1.5 V, 250 Hz
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9.2.2.2 Detailed Design Procedure
The detailed design process in this example is basically the same with that shown in the previous design
example. Following are the design results.
9.2.2.2.1 Inductor Selection
A Cree white LED XLampXML is used. According to the LED manufacturer’s data sheet, this LED has 2.9-V
forward voltage at 1-A current, so VOUT = 2.9 V × 4 + 0.1 V = 11.7 V. Choose KIND = 0.3, which gives a 36-µH
inductance. With this inductance, the ripple current on the inductor is only 0.3-A peak-to-peak, which is too
conservative and increases total system cost and size.
For this application, with concerns about system cost and size taken into account, decide the inductance by
choosing a larger peak-to-peak inductor ripple current. To choose a proper peak-to-peak inductor ripple, the lowside FET sink current limit should not be exceeded when the converter works in a no-load condition. To meet this
requirement, half of the peak-to-peak inductor ripple must be lower than that limit. Another consideration with this
larger peak-to-peak ripple current is the increased core loss and copper loss in the inductor, which is also
acceptable. Once this peak-to-peak inductor ripple current is chosen, Equation 14 can be used to calculate the
required inductance.
VOUT ´ (VIN(max) - VOUT )
L MIN =
VIN(max) ´ IL(ripple) ´ fSW
where
•
IL(RIPPLE) is the peak-to-peak inductor ripple current.
(14)
Choose 1-A peak-to-peak inductor ripple current, and half of the current is 0.5 A, much lower than the minimum
low-side sink current limit of 1.25 A. The calculated inductance is 10.9 µH. Choose a 10-µH inductor with part
number 744066100 from Wurth. The ripple, peak, and rms currents of the inductor are 1.09 A, 1.54 A, and 1.05
A, respectively. The chosen inductor has ample margin in this design.
9.2.2.2.2 Input Capacitor Selection
In this design, a 10-µF, 35-V X7R ceramic capacitor, part number GRM32ER7YA106KA12L from muRata, is
chosen. This yields around 70-mV input-ripple voltage. The calculated rms input ripple current is 0.5 A, well
below the ripple-current rating of the capacitor.
9.2.2.2.3 Output Capacitor Selection
The dynamic resistance of this LED is 0.184 Ω at 1-A forward current. In this design, choose a 10-µF, 35-V X7R
ceramic capacitor, part number GRM32ER7YA106KA12L from muRata. The calculated ripple current of the LED
is about 40 mA.
9.2.2.2.4 FB Pin RC Filter Selection
PWM dimming mode is implemented in this design. Choose the pole at around 4 kHz, and choose 475 Ω as the
filter resistor. With those values, an 82 nF capacitor should be chosen for this filter. To get a faster loop
response, choose a smaller filter resistor. In this design, 200 Ω was chosen to get a pole at approximately 10
kHz.
9.2.2.2.5 Sense Resistor Selection
The maximum target LED current at 100% PWM duty cycle is 1 A, and the corresponding VREF is 100 mV. By
using Equation 1, one can calculate the needed sense resistance of 100 mΩ. Pay close attention to the power
consumption of the sense resistor in this design at 100 mW. Make sure the chosen resistor has enough margin
in the power rating.
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9.2.2.3 Application Curves
CH1
CH1
CH2
CH2
CH3
CH3
CH4
CH4
CH1: PWM
CH2: SW
CH3: VOUT
CH4: LED
current
Figure 41. Start-Up at 1% PWM Duty Cycle and 250 Hz
CH1: PWM
CH2: SW
CH3: VOUT
CH4: LED
current
Figure 42. Shutdown at 1% PWM Duty Cycle and 250 Hz
CH1
CH1
CH2
CH2
CH3
CH3
CH4
CH4
CH1: PWM
CH2: SW
CH3: VOUT
CH4: LED
Current
Figure 43. Start-Up at 100% PWM Duty Cycle
CH1: PWM
CH2: SW
CH3: VOUT
CH4: LED
current
Figure 44. Shutdown at 100% PWM Duty Cycle
CH1
CH1
CH4
CH4
CH1 PWM
CH4: LED
current
CH1: PWM
Figure 45. PWM Dimming With 2% Duty Cycle and 250 Hz
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CH4: LED
current
Figure 46. PWM Dimming With 50% Duty Cycle and 250 Hz
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CH2
CH1
CH3
CH4
CH4
CH1: PWM
CH4: LED
current
CH2: SW
Figure 47. PWM Dimming With 99% Duty Cycle and 250 Hz
CH3: LED
current
(AC-coupled)
CH4: Inductor
current
Figure 48. LED Current Ripple at 100% PWM Duty Cycle
CH1
CH2
CH4
CH1: VVIN
(AC-coupled)
CH2: SW
CH4: Inductor current
Figure 49. Input Voltage Ripple at 100% PWM Duty Cycle
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10 Power Supply Recommendations
The devices are designed to operate from an input voltage supply range between 4.5 V and 28 V. This input
supply must be well regulated. If the input supply is located more than a few inches from the device or converter,
additional bulk capacitance may be required in addition to the ceramic bypass capacitors.
11 Layout
The TPS5420x requires a proper layout for optimal performance. The following section gives some guidelines to
help ensure a proper layout.
11.1 Layout Guidelines
An example of a proper layout for the TPS5420x is shown in Figure 50.
• Creating a large GND plane for good electrical and thermal performance is important.
• The VIN and GND traces should be as wide as possible to reduce trace impedance. The added width also
provides excellent heat dissipation.
• Thermal vias can be used to connect the topside GND plane to additional printed-circuit board (PCB) layers
for heat dissipation and grounding.
• The input capacitors must be located as close as possible to the VIN pin and the GND pin.
• The SW trace must be kept as short as possible to minimize radiated noise and EMI.
• Do not allow switching current to flow under the device.
• The FB trace should be kept as short as possible and placed away from the high-voltage switching trace and
the ground shield.
• In higher-current applications, routing the load current of the current-sense resistor to the junction of the input
capacitor and GND node may be necessary.
30
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11.2 Layout Example
LED LOAD
VSENSE
OUTPUT
CAPACITOR
SENSE RESISTOR
VOUT
GND
CONNECTED TO
POWER GND ON
INTERNAL OR
BOTTOM LAYER
BOOT
CAPACITOR
OUTPUT
INDUCTOR
GND
BOOT
SW
PWM
VIN
FB
TO PWM
CONTROL
SW
RC FILTER
GND
VIN
INPUT
CAPACITOR
CONNECTED TO
POWER GND ON
INTERNAL OR
BOTTOM LAYER
VIA to Ground Plane
Figure 50. Layout Example
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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 Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to order now.
Table 4. Related Links
PARTS
PRODUCT FOLDER
ORDER NOW
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
TPS54200
Click here
Click here
Click here
Click here
Click here
TPS54201
Click here
Click here
Click here
Click here
Click here
12.3 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
12.4 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.
12.5 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
12.6 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
12.7 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
32
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13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the mostcurrent data available for the designated devices. This data is subject to change without notice and without
revision of this document. For browser-based versions of this data sheet, see the left-hand navigation pane.
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PACKAGE OPTION ADDENDUM
www.ti.com
23-Dec-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)
TPS54200DDCR
ACTIVE
SOT-23-THIN
DDC
6
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
4200
Samples
TPS54200DDCT
ACTIVE
SOT-23-THIN
DDC
6
250
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
4200
Samples
TPS54201DDCR
ACTIVE
SOT-23-THIN
DDC
6
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
4201
Samples
TPS54201DDCT
ACTIVE
SOT-23-THIN
DDC
6
250
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
4201
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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