Prepreg
Core
Prepreg
Top Layer
Bottom Layer
PGND
GND
Start-Up of the EVM and Power Sequences
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
and
.
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 V
IN
voltage is present and above the V
IN
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 k
Ω
to FSET) and boost
maximum voltage is 37 V (R12 = 750 k
Ω
and R13 = 130 k
Ω
). See
and
for
description on how to change boost settings.
By default, LED current is 100 mA per string (jumper J5 connecting R4 = 24 k
Ω
to ISET). See
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.
8
TPS61194xEVM Evaluation Module
SNVU492 – January 2016
Copyright © 2016, Texas Instruments Incorporated