LX1991 EVAL KIT

LX1991 EVAL KIT Datasheet

LX1991 EVALUATION BOARD USER’S GUIDE

Part	Datasheet
LX1991 EVAL KIT	LX1991 EVAL KIT (pdf)

Related Parts	Information
LX1991-03EVAL	LX1991-03EVAL
LX1991-02EVAL	LX1991-02EVAL

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LX1991 EVALUATION BOARD USER’S GUIDE LX1991 Six Output Programmable LED Current Sink INTEGRATED PRODUCTS LX1991 EVALUATION BOARD USER GUIDE TABLE OF CONTENTS Overview Features Operation TABLES Evaluation Board Connections 3 Jumper 4 Test Point 4 FIGURES LX1991 Evaluation Board Component 5 LX1991 Evaluation Board Silk 5 LX1991 Evaluation Board Schematic 6 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax 714-893-2570 LX1991 EVALUATION BOARD USER GUIDE OVERVIEW The LX1991 six channel current sink driver is ideal for controlling brightness of high quality dimmable LED’s. The evaluation board 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 white surface mount LED’s whose cathodes are connected to each sink output of the LX1991. The anodes of the LED’s are 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. This 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. Use of a current probe will allow easy viewing of the current rise and fall times. A small rheostat Current Adjust in series with R8 1.02K which sets the maximum current at 30mA varies the RSET resistance such that the output LED currents will vary from about 1.5mA to 30mA. Two other jumpers are included, 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. Evaluation Board Features • 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 EVALUATION BOARD OPERATION 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. The LX1991 integrated circuit itself requires a input supply voltage EXT VDD in the range of 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 external control over dimming and 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 EXT_EN and RTN GND . Input EXT VDD VLOAD EXT_EN PWM_IN RTN/GND Allowable Range to 5.5V 3 to 40V 5V typ. 0 to VDD 0 to VDD 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 Table 1 Evaluation Board Connections Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax 714-893-2570 LX1991 EVALUATION BOARD USER GUIDE An external voltage signal or open collector logic can be applied to this point to disable the device. This external signal must be able to drive the 10K pull-up resistor low less than 0.8V .The PWM_IN header input allows an external PWM signal to control the output current by duty cycle dimming. This is accomplished by switching the device’s DIG_DIM input with a logic signal. The practical limit to this switching frequency is about 100Khz, at frequencies greater than this internal delays will add errors to the expected output duty cycle. The evaluation board comes with a 470pF CSLOPE capacitor. This value can be increased to vary the rise and fall times of the output current waveform. For greater detail see the LX1991 datasheet. Test Points SINK1 to SINK6 allow you to monitor the voltage drop across these pins to ground. This voltage will change to maintain the correct forward voltage across the LED’s for the programmed sink current. It can range from as low as 400mV to 40V when the outputs are off depending on the VLOAD supply voltage. The various jumper positions are summarized in table 2 and test points in table The factory installed active and passive components list can be found in table Following the two tables you will find the PCB silkscreen figure 1 and the circuit schematic in figure All necessary PCB traces and components are on the topside of the board. However there are PCB traces and silkscreen on the bottom side that when populated is used for a special version of the evaluation board that is used internally by Microsemi for training and demonstration purposes. Jumper PWM_IN EXT_EN

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LX1991 EVALUATION BOARD USER’S GUIDE

LX1991 Six Output Programmable LED Current Sink

INTEGRATED PRODUCTS

LX1991 EVALUATION BOARD

USER GUIDE

TABLE OF CONTENTS

Overview Features Operation

TABLES Evaluation Board Connections 3 Jumper 4 Test Point 4

FIGURES LX1991 Evaluation Board Component 5 LX1991 Evaluation Board Silk 5 LX1991 Evaluation Board Schematic 6

Microsemi

Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax 714-893-2570

LX1991 EVALUATION BOARD

USER GUIDE

OVERVIEW

The LX1991 six channel current sink driver is ideal for controlling brightness of high quality dimmable LED’s. The evaluation board 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 white surface mount LED’s whose cathodes are connected to each sink output of the LX1991. The anodes of the LED’s are 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. This 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. Use of a current probe will allow easy viewing of the current rise and fall times.

A small rheostat Current Adjust in series with R8 1.02K which sets the maximum current at 30mA varies the RSET resistance such that the output LED currents will vary from about 1.5mA to 30mA. Two other jumpers are included, 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.

Evaluation Board Features
• 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

EVALUATION BOARD OPERATION

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. The LX1991 integrated circuit itself requires a input supply voltage EXT VDD in the range of 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 external control over dimming and 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 EXT_EN and RTN GND .

Input EXT VDD

VLOAD

EXT_EN PWM_IN RTN/GND

Allowable Range to 5.5V
3 to 40V 5V typ.
0 to VDD 0 to VDD

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

Table 1 Evaluation Board Connections

Microsemi

Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax 714-893-2570

LX1991 EVALUATION BOARD

USER GUIDE

An external voltage signal or open collector logic can be applied to this point to disable the device. This external signal must be able to drive the 10K pull-up resistor low less than 0.8V .The PWM_IN header input allows an external PWM signal to control the output current by duty cycle dimming. This is accomplished by switching the device’s DIG_DIM input with a logic signal. The practical limit to this switching frequency is about 100Khz, at frequencies greater than this internal delays will add errors to the expected output duty cycle. The evaluation board comes with a 470pF CSLOPE capacitor. This value can be increased to vary the rise and fall times of the output current waveform. For greater detail see the LX1991 datasheet. Test Points SINK1 to SINK6 allow you to monitor the voltage drop across these pins to ground. This voltage will change to maintain the
correct forward voltage across the LED’s for the programmed sink current. It can range from as low as 400mV to 40V when the outputs are off depending on the VLOAD supply voltage.

The various jumper positions are summarized in table 2 and test points in table The factory installed active and passive components list can be found in table Following the two tables you will find the PCB silkscreen figure 1 and the circuit schematic in figure All necessary PCB traces and components are on the topside of the board. However there are PCB traces and silkscreen on the bottom side that when populated is used for a special version of the evaluation board that is used internally by Microsemi for training and demonstration purposes.

Jumper PWM_IN EXT_EN

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Datasheet ID: LX1991EVALKIT 649018