Datasheet

Basic Connections (see ) www.ti.com
The USB board can supply 3.3 V from an on board regulator or 5 V directly from the PC (see
documentation for the Texas Instruments USB interface board). When power from the USB is desired
connect a jumper across V
IN
/VUSB, if power is supplied from the IN header leave V
IN
/VUSB open. DO
NOT jumper V
IN
/VUSB while an external source is connected to IN as this will make a conflict between the
USB board and the external power supply.
The USB interface board interfaces directly with the LM3528.exe graphical interface via the PC, see
Section 7. If the LM3528.exe program is not used, control of the LM3528 evaluation board can be done by
connecting an external I
2
C compatible interface directly to the SCL and SDA headers. Both the SDA and
SCL lines have 10 kΩ pull-ups installed on the board.
6 Basic Connections (see Figure 1)
The LM3528 evaluation board is configured for two strings of six LEDs. There are two resistor pads on the
bottom side of the board, R1 and R2, that serve as feedback resistors for the operation of the LM3528 in
voltage output mode (OLED mode). When operating in OLED mode (with D1S – D6S installed), the
OLED/LED jumper must be installed in order to connect the center tap of the resistive divider (R1 and R2)
to the SUB/FB pin. Additionally (in OLED mode), the SOPEN header should be removed, otherwise, the
secondary LED string interferes with the feedback divider and causes erratic operation.
6.1 Jumper Connections/Component Descriptions
• J1 is a 3-pin, 3-position jumper. The leftmost pin (pin 1 in Figure 1) connects to the 3.3 V supply from
the USB board (pin 14 on the USBL connector). The rightmost pin (pin 3 in Figure 1) connects to IN.
The top middle pin (pin 2 in Figure 1) connects to VIO of the LM3528, the top side of the pull-up
resistors (RSDA, RSCL, RGPIO, RGPIO1), and the anode of the indicator diode D2.
• The SOPEN and MOPEN jumpers allow for the disconnection of the LEDs from the LM3528’s output.
SOPEN opens the SECONDARY (SUB/FB) LED string while MOPEN opens the MAIN LED string.
This is useful in testing OVP or disabling a string if OLED mode is required.
• The 5-pin, 5-position jumpers (2/3/4/5/6 LEDM and 2/3/4/5/6 LEDS) located above the MAIN and
SECONDARY LED strings, respectively, allow for shorting out of different LEDs in both the MAIN and
the SECONDARY strings. Both jumpers have their center pin (pin 5 in Figure 1) connected to the
cathode of the sixth LED in each string. Referring to jumper 2/3/4/5/6 LEDs, connecting pin 4 to pin 5
will short D6S, thus, making the SECONDARY string a five-LED configuration. Connect pin 3 to pin 5
to short D5S and D6S resulting in a four-LED configuration. Connect pin 2 to pin 5 for a three-LED
configuration (D4S – D6S shorted). Connect pin 1 to pin 5 for a two-LED configuration (D3S – D6S
shorted), and leave jumper 2/3/4/5/6 LEDS open for a six-LED configuration. The operation for jumper
2/3/4/5/6 LEDM is the same, only it applies to the MAIN LED string.
• Resistors R4 and R5 have 0 Ω’s across them. The 0 Ω resistors can be replaced with current sense
resistors for measuring LED current. Two vias have been placed at the terminals of each resistor,
which fit standard 0.1” headers.
• The OLED/LED jumper connects or disconnects the resistive divider from the SUB/FB node. In white
LED mode, the jumper should be open. In OLED mode, the jumper should be shorted so the SUB/FB
node can regulate V
OUT
at a constant voltage.
• D2 is a RED indicator diode that flashes the programmed pattern, programmed into the PGEN
registers (see the LM3528 High Efficiency, Multi Display LED Driver With 128 Exponential Dimming
Steps and Integrated OLED Power Supply in a 1.2mm × 1.6mm DSBGA Package Data Sheet
(SNVS513)). R3 is a 205 Ω current limiting resistor for D2. RGPIO is a 1 MΩ pull-up resistor for the
HWEN/PGEN/GPIO output. On power up, the HWEN/PGEN/GPIO output defaults as an active high
hardware enable (HWEN). RGPIO is installed to ensure that HWEN/PGEN/GPIO pulls high on start-
up.
7 LM3528–USB Interface Board and I
2
C Compatible Interface Program
In order to fully evaluate the LM3528, the use of an “I
2
C Compatible” interface must be used for any
functionality to occur. The detailed description regarding the interface control, the LM3528 registers, and
OLED mode is described in the LM3528 High Efficiency, Multi Display LED Driver With 128 Exponential
Dimming Steps and Integrated OLED Power Supply in a 1.2mm × 1.6mm DSBGA Package Data Sheet
(SNVS513).
6
AN-1823 LM3528 Evaluation Board SNVA336A–August 2008–Revised April 2013
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