LX1991-02EVAL Microsemi Analog Mixed Signal Group, LX1991-02EVAL Datasheet - Page 3

• Manufacturer Part Number: LX1991-02EVAL
• Description: BOARD EVAL LED DRIVER 6CHANNEL
• Manufacturer: Microsemi Analog Mixed Signal Group

Specifications of LX1991-02EVAL

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LX1991 E
O
The LX1991 six channel current sink driver is
ideal for controlling brightness of high quality
dimmable
demonstrates how this low cost bipolar IC
enables precise current regulation in LED
display lighting applications, yet requires far
fewer parts than discrete solutions.
The evaluation board ships with six (Microsemi
UBLED470A)
cathodes are connected to each sink output of
the LX1991.
connected together to a test point called VLOAD
which the user can connect to an external
voltage source (typically 5V, maximum is 40V)
LED6 requires an external jumper between TP7
and TP8 to allow current to flow.
demonstrates that one or more channels can be
left open without effecting the other channels. In
addition these test points allow the easy addition
of a application specific load or a current probe
loop.
viewing of the current rise and fall times.
R8 (1.02K which sets the maximum current at
30mA) varies the R
output LED currents will vary from about 1.5mA
to 30mA.
EXT_EN which enables/disables the LX1991,
and PWM_IN which allows an externally
supplied PWM signal to toggle the DIG_DIM
input to allow duty cycle dimming.
Copyright © 2002
Rev. 1.0 1/8/03
A small rheostat (Current Adjust) in series with
RTN/GND
EXT VDD
VERVIEW
PWM_IN
EXT_EN
VLOAD
Input
Use of a current probe will allow easy
LED’s.
Two other jumpers are included,
VALUATION
white surface mount LED’s whose
Allowable Range
3 to 40V (5V typ.)
The anodes of the LED’s are
4.5 to 5.5V
0 to VDD
0 to VDD
SET
0V
The
resistance such that the
B
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
evaluation
OARD
Table 1 – Evaluation Board Connections
LX1991 power supply. Quiescent current draw is between 4 and
13mA depending on voltage and temperature and the programmed
output sink currents
LED voltage supply. Required voltage depends on forward voltage
requirements of LED’s and 700-1000mV chip overhead. This
current will vary between 9 and 180mA depending on the
programmed output sink current and if all six LED are connected.
Input for external enable control, board ships with 10K pull-up to
EXT VDD
Input to allow duty cycle dimming of output 150hz to 100Khz logic
signal, active high
Common ground reference
board
This
Integrated Products
Microsemi
Evaluation Board Features
E
The evaluation board has four possible inputs of
which at least two must be used to operate the
circuit. In the simplest configuration connect 5V
to both EXT VDD and VLOAD and the common
(ground return) to RTN. With power connected
to these two pins and the a jumper (factory
installed) between PWM_IN and PULL-UP the
evaluation board should be operational.
LX1991 integrated circuit itself requires a input
supply voltage (EXT VDD) in the range of 4.5 to
5.5V. When using the included white LED’s a
supply voltage of at least 4V is required on the
VLOAD input depending on the current setting
(current adjust). All inputs are described in table
1 below.
The other two inputs PWM_IN and ENABLE
allow
shutdown. The evaluation board comes with a
built in 10K pull-up resistor R1 that is connected
between the ENABLE input and EXT VDD. R1
will enable the device unless a jumper is placed
between
VALUATION
•
•
•
One channel is left open for application
specific loads to be added or current
probe loop
Included rheostat allows output current to
be set from 1 to 30mA
Jumpers allow external PWM signal to
burst dim the LED’s and an external
enable control
Description
external
B
EXT_EN
OARD
control
O
PERATION
and
over
U
RTN
dimming
SER
G
(GND).
UIDE
Page 3
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and