Intersil ISL97684 User Manual

ISL97684 LED Driver Evaluation Board User Manual
Introduction
The ISL97684 Evaluation Board provides a complete testing
platform for ISL97684, a four channel LED driver. Please refer
to the product datasheet for detailed information, including
pinout, pin function descriptions, electrical specifications and
applications related information.
Instructions
Please follow the steps described below to start your
evaluation.
1. Set Switch #1 and Switch #2 (SW1 and SW2) to position 3
(left side).
2. For the enable control jumper, JP1, set the shunt to the
"ON" position (right side) to connect the EN pin to VIN.
When the shunt is in the "OFF" position, it will disable the
chip by pulling the EN pin to ground.
3. Connect JP14 so the VIN pin is connected to PVIN.
4. For JP20, connect the shunt to the upper position.
5. Connect WR and JP2-JP6.
6. Apply 1.5V~5.5V PWM signal between the PWMI pin and
AGND.
7. Apply 4V~26.5V between PVIN and PGND and the LEDs
should be lit. You may start the evaluation.
Note:
• In Step #1 above, the SW1, SW2 position can be adjusted to
different positions for different configurations. Details are
provided in the following:
TABLE 1.
SW1 SW2
POSITION POSITION
1 1 LX switching frequency = 600kHz, PFM
CH1-CH4
3 3 LX switching frequency = 1MHz, PFM
CH1-CH4
3 1 LX switching frequency = 600kHz, No PFM
CH1-CH4
1 3 LX switching frequency = 1MHz, No PFM
CH1-CH4
• The LED maximum DC current adjustment
For each channel, the maximum DC current is set by
resistance connected to the RSET pin. The current for each
channel can be calculated as follows:
⁄ 〈 〉
I_LED(mA) 402 RSET kΩ
=
On the board, a potentiometer R5 and a few other resistors
are provided for easily adjusting the LED maximum DC
current; please refer to the evaluation board schematic on
page 2 for more details.
December 13, 2011
AN1668.0
DESCRIPTION
(EQ. 1)
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
• LED dimming frequency and duty cycle
1. As mentioned in Step #4, when the shunt on JP20 is
connected to the upper position and the FPWM/DPWM pin
is connected to VDC, the device enters direct PWM mode,
which means both the LED dimming frequency and the
duty cycle are synchronized with the external PWM signal
applied on the PWMI pin.
2. When the shunt on JP20 is connected to the lower position,
the FPWM/DPWM pin is connected to a resistor. Under
such conditions, the LED dimming frequency of the chip is
programmed by the resistance connected on the
FPWM/DPWM pin per the following equation:
( )
FPWM Hz 12.4
=
The duty cycle is still modulated by the external PWM signal
applied on the PWMI pin. On board, a potentiometer R11
and a few other resistors are provided for easily adjusting
the LED dimming frequency under such configuration.
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Application Note 1668
7
×10 ⁄ R_FPWM Ω ( )
Copyright Intersil Americas Inc. 2011. All Rights Reserved
(EQ. 2)