Texas Instruments TPS61194xEVM User manual

Using the TPS61194xEVM Evaluation Module
User's Guide
Literature Number: SNVU492
January 2016

Contents
1 Preface ............................................................................................................................... 4
1.1 About this Manual........................................................................................................ 4
1.2 Related Documentation from Texas Instruments .................................................................... 4
1.3 FCC Warning ............................................................................................................. 4
1.4 If You Need Assistance ................................................................................................. 4
2 Introduction......................................................................................................................... 4
3 Description of the TPS61194 or TPS61194-Q1 Device............................................................... 5
3.1 Features................................................................................................................... 5
3.2 Applications ............................................................................................................... 5
4 Hardware Setup ................................................................................................................... 6
5 Board Layout....................................................................................................................... 7
6 Start-Up of the EVM and Power Sequences............................................................................. 8
6.1 PWM Input to Initiate Start-up Sequence............................................................................. 8
6.2 Shutdown Sequence..................................................................................................... 8
7 Boost Converter................................................................................................................... 9
7.1 Switching Frequency .................................................................................................... 9
7.2 Spread Spectrum and Synchronization ............................................................................... 9
7.3 Voltage Control.......................................................................................................... 10
8 LED Current Sinks.............................................................................................................. 11
8.1 Output Configuration ................................................................................................... 11
8.2 Current Setting.......................................................................................................... 11
8.3 Brightness Control...................................................................................................... 11
9 Fault Detection................................................................................................................... 11
9.1 Fault Indicator........................................................................................................... 11
10 Evaluation Board Schematic................................................................................................ 12
11 Bill of Materials .................................................................................................................. 13
12 Appendix A: LED Load Board .............................................................................................. 14
2Table of Contents SNVU492–January 2016
Submit Documentation Feedback
Copyright © 2016, Texas Instruments Incorporated

www.ti.com
List of Figures
1 Evaluation Board Connectors and Setup................................................................................. 6
2 Top Layer .................................................................................................................... 7
3 Bottom Layer (GND)......................................................................................................... 7
4 Evaluation Board Stackup .................................................................................................. 8
5 Switching Frequency vs RFSET .............................................................................................. 9
6 Converter Maximum Output Voltage vs R12 ........................................................................... 10
7 Output Current vs RISET ................................................................................................... 11
8 Evaluation Board Schematic.............................................................................................. 12
9 LED Load Board - Top Side .............................................................................................. 14
10 LED Load Board - Bottom View.......................................................................................... 14
11 LED Load Board - Schematic Diagram.................................................................................. 15
12 Forward Voltage for Cree Xlamp ML-B LEDs ......................................................................... 16
All trademarks are the property of their respective owners.
3
SNVU492–January 2016 List of Figures
Submit Documentation Feedback Copyright © 2016, Texas Instruments Incorporated

User's Guide
SNVU492–January 2016
TPS61194xEVM Evaluation Module
1 Preface
1.1 About this Manual
This user’s guide describes the module used to evaluate characteristics, operation, and use of the
TPS61194 high-performance 4-channel LED driver for industrial backlighting, test and measurement
equipment, and TPS61194-Q1 for automotive lighting. This document includes a schematic diagram, PCB
layout, and bill of materials (BOM).
1.2 Related Documentation from Texas Instruments
TPS61194 (SNVSAF5) and TPS61194-Q1 (SNVSAE9) data sheets.
1.3 FCC Warning
This equipment is intended for use in a laboratory test environment only. It generates, uses, and can
radiate radio frequency energy and has not been tested for compliance with the limits of computing
devices pursuant to subpart J of part 15 of FCC rules, which are designed to provide reasonable
protection against radio frequency interference. Operation of this equipment in other environments may
cause interference with radio communications, in which case the user, at their own expense, will be
required to take whatever measures may be required to correct this interference.
1.4 If You Need Assistance
Contact your local TI sales representative.
2 Introduction
The Texas Instruments TPS61194xEVM evaluation module (EVM) helps designers to evaluate the
operation and performance of the TPS61194 or TPS61194-Q1 device. The TPS61194xEVM uses the
TPS61194 or TPS61194-Q1 to drive up to 4 LED strings for LCD backlighting with high efficiency.
Information about output voltage and current ratings of the TPS61194 or TPS61194-Q1 can also be found
in the device data sheets (SNVSAF5 and SNVSAE9).
A power supply connection for the VIN and test points for each signal can be found on the evaluation
board. A separate LED board can be used as a load; it is also possible to connect LCD panel to the output
connectors.
For evaluation purposes, the EVMs have been tested over a 4.5-V to 40-V input range. This voltage range
is within the recommended operating range for input voltage of the TPS61194 or TPS61194-Q1. Users
are cautioned to evaluate their specific operating conditions and choose components with the appropriate
voltage ratings before designing this circuitry into a final product.
4TPS61194xEVM Evaluation Module SNVU492–January 2016
Submit Documentation Feedback
Copyright © 2016, Texas Instruments Incorporated

www.ti.com Description of the TPS61194 or TPS61194-Q1 Device
3 Description of the TPS61194 or TPS61194-Q1 Device
The TPS61194 or TPS61194-Q1 is an automotive high-efficiency LED driver with integrated boost/SEPIC
converter. It has 4 high-precision current sinks that can be controlled by a PWM input signal.
The boost converter has adaptive output voltage control based on the LED current sink headroom
voltages. This feature minimizes the power consumption by adjusting the voltage to lowest sufficient level
in all conditions. Boost controller supports spread spectrum for switching frequency and an external
synchronization with a dedicated pin. The high switching frequency allows the TPS61194 or TPS61194-
Q1 to avoid disturbance for AM radio band.
The input voltage range for the TPS61194 or TPS61194-Q1 is from 4.5 V to 40 V to support automotive
stop/start and load dump condition. The TPS61194 or TPS61194-Q1 device supports PWM brightness
dimming ratio up to 10 000:1 for input PWM frequency of 200 Hz. The device integrates extensive safety
and protection features.
3.1 Features
• Four High-Precision Current Sinks
– Current Matching 1% (typical)
– Output Current up to 100 mA/Channel
– Dimming Ratio 10 000:1 at 200-Hz PWM input
• Integrated Boost/SEPIC for LED String Power
– Output Voltage up to 45 V
– Switching Frequency 300 kHz to 2.2 MHz
– Boost Synchronization Input
– Spread Spectrum
• Input Voltage Operating Range 4.5 V to 40 V
• Power-Line FET Control for Inrush Current Protection and Standby Energy Saving
• Extensive Safety and Fault Tolerance Features
– Fault Output
– Input Voltage OVP and UVLO
– Open and Shorted LED Fault Detection
– Thermal Shutdown
• Minimum Number of External Components
3.2 Applications
• Industrial Backlighting Systems in Control Panels (TPS61194)
• Test and Measurement Equipment (TPS61194)
• Automotive Infotainment, Instrument Clusters, and Backlighting System (TPS61194-Q1)
5
SNVU492–January 2016 TPS61194xEVM Evaluation Module
Submit Documentation Feedback Copyright © 2016, Texas Instruments Incorporated

INPUT
VOLTAGE
OUTPUT
CONFIGURATION
LED
CONNECTOR
CONTROL
POINTS
FAULT LED
CONTROL POINTS
SHUNTS
CONTROL
POINTS
CONTROL
POINTS
Hardware Setup www.ti.com
4 Hardware Setup
Figure 1 shows connectors and main components on the TPS61194 or TPS61194-Q1 board.
Figure 1. Evaluation Board Connectors and Setup
6TPS61194xEVM Evaluation Module SNVU492–January 2016
Submit Documentation Feedback
Copyright © 2016, Texas Instruments Incorporated

www.ti.com Board Layout
5 Board Layout
Figure 2. Top Layer
Figure 3. Bottom Layer (GND)
See the TPS61194 (SNVSAF5) or TPS61194-Q1 (SNVSAE9) datasheet for PCB layout guidelines.
7
SNVU492–January 2016 TPS61194xEVM Evaluation Module
Submit Documentation Feedback Copyright © 2016, Texas Instruments Incorporated

Prepreg
Core
Prepreg
Top Layer
Bottom Layer
PGND
GND
Start-Up of the EVM and Power Sequences www.ti.com
Figure 4. Evaluation Board Stackup
• 4-layer board FR4
• Material thickness 1.616 ± 10% mm
• Surface finish immersion gold
6 Start-Up of the EVM and Power Sequences
The TPS61194xEVM is set up for easy start-up:
• Connect LEDs to OUT1 - OUT4 of connector J16. (Note: LED current default is 100 mA, and maximum
boost voltage default is 37 V. LED outputs that are not used must be grounded via jumpers J11 to
J14.)
• Connect input (BATTERY) voltage 12 V to connector J25.
The LEDs turn on immediately because the jumpers on the EVM are set up for PWM input of 100% duty
cycle. For connector and jumper positions, see Figure 1 and Figure 8.
Input (BATTERY) voltage range is 4.5 V to 40 V.
The TPS61194 or TPS61194-Q1 has a dual function VDDIO/EN pin. By default, VDDIO/EN = 3.3 V is
generated automatically on the EVM from battery input voltage via jumpers J1 and J26. VDDIO/EN acts
as enable for the device as well as supply/reference voltage for IO logic. The device starts when VIN
voltage is present and above the VIN UVLO voltage level (4 V), and the VDDIO/EN voltage is set above
threshold voltage (1.2 V).
By default, boost switching frequency is 400 kHz (jumper J4 connecting R3 = 160 kΩto FSET) and boost
maximum voltage is 37 V (R12 = 750 kΩand R13 = 130 kΩ). See Section 7.1 and Section 7.3 for
description on how to change boost settings.
By default, LED current is 100 mA per string (jumper J5 connecting R4 = 24 kΩto ISET). See Section 8.2
for the description on how to change LED current setting.
Alternatively to internal LDO, device circuitry can be powered from external power supply (4.4 V to 5.25 V)
connected to the LDO pin. Internal LDO are disabled in this case.
6.1 PWM Input to Initiate Start-up Sequence
The backlight is started by setting PWM input high. By default, the TPS61194xEVM has PWM input set
high (100% duty cycle), which is connected to VDDIO through jumper J2. Alternatively, an external PWM
signal can be connected by removing jumper J2 , shorting pins 3 and 4 on jumper J17, and connecting the
external PWM to connector J18.
6.2 Shutdown Sequence
The backlight is shut down (LEDs turned off) by setting PWM input low or when VDDIO/EN = 0. If
VDDIO/EN is set low, the TPS61194 or TPS61194-Q1 enters low-power mode with internal LDO disabled.
8TPS61194xEVM Evaluation Module SNVU492–January 2016
Submit Documentation Feedback
Copyright © 2016, Texas Instruments Incorporated

200
400
600
800
1000
1200
1400
1600
1800
2000
2200
20 40 60 80 100 120 140 160 180 200 220
fSW (kHz)
RFSET (k)
C010
www.ti.com Boost Converter
7 Boost Converter
7.1 Switching Frequency
Switching frequency for boost is defined as 300 kHz to 2.2 MHz. However, frequency from 250 kHz to 2.2
MHz can be set by the external resistor connected to the FSET pin, thus allowing the device to be
synchronized with the lowest external frequency of 300 kHz (see details in Section 7.2).
Switching frequency is defined by resistor R3 connected to FSET pin:
ƒSW = 67600 / (RFSET + 6.4)
where
• ƒSW: switching frequency, kHz
• RFSET: frequency setting resistor, kΩ(1)
Figure 5. Switching Frequency vs RFSET
By default, jumper J4 is installed on the board connecting R3 = 160 kΩto the FSET pin which sets the
boost at 400 kHz. An external resistor can be connected to change the switching frequency: remove
jumper J4, short pins 7 and 8 on jumper J17, and connect the external resistor to connector J18. Boost
internal parameters are adjusted automatically according to chosen frequency during start-up.
7.2 Spread Spectrum and Synchronization
The SYNC pin is used to enable boost spread spectrum or, alternatively, to synchronize boost switching
with an external frequency. To disable spread-spectrum functionality this pin should be connected to
ground; to enable spread spectrum SYNC should be connected to VDDIO/EN. Selection is done with
jumper J3. When spread spectrum is enabled, boost switching frequency is modulated ±3% from set
frequency with 1.875 kHz modulation frequency.
If an external frequency is detected at SYNC pin, the TPS61194 or TPS61194-Q1 starts to synchronize
boost with this frequency. Frequency must be higher than the switching frequency set by RFSET resistor
and be in range 1.2 V to 1.5 V × ƒSW SET.
9
SNVU492–January 2016 TPS61194xEVM Evaluation Module
Submit Documentation Feedback Copyright © 2016, Texas Instruments Incorporated

10
15
20
25
30
35
40
45
200 300 400 500 600 700 800 900 1000
Maximum converter output voltage (V)
R12 (k)
C011
VMAX BOOST = ( VBG
R13 + 0.0387 ) x R12 + VBG
Boost Converter www.ti.com
7.3 Voltage Control
Maximum boost converter voltage is defined by the feedback voltage divider R12 and R13.
Recommended value for R13 is 130 kΩ. R12 value can be calculated with the following equation:
where
• VBG = 1.2 V
• R12, R13 values are in kΩ(2)
Figure 6. Converter Maximum Output Voltage vs R12
Maximum voltage should be chosen based on the maximum voltage required for LED strings.
Recommended maximum voltage is about 30% higher than maximum LED string voltage. Initial boost
voltage is about 88% of maximum voltage. Boost output voltage is adjusted automatically based on LED
current sink headroom voltage.
Default setting for boost maximum voltage is 37 V (R12 is 750 kΩ).
10 TPS61194xEVM Evaluation Module SNVU492–January 2016
Submit Documentation Feedback
Copyright © 2016, Texas Instruments Incorporated