Renesas ISL97687IBZEV1Z User Manual

ISL97687IBZEV1Z
Evaluation Board
The ISL97687IBZEV1Z is a PWM controlled LED driver that
supports 4 channels of LED current, for Monitor and TV LCD
backlight applications. It is capable of driving 160mA per
channel from a 9V to 32V input supply, with current sources
rated up to 75V absolute maximum. Figure 1 shows a photo of
a 14 LED/Channel with a 120mA/Channel. The
ISL97687IBZEV1Z in Figure 2 is designed for a one layer PCB
with SOIC package.
Quick Start Guide
1. The ISL97687 provides many different PWM dimming
methods; the interface modes and its settings are
summarized in Table 2. Those interfaces can be selected
with switches and jumper settings of the ISL97687IBZEV1Z
evaluation board in Figures 2 and 4.
a. Direct PWM Dimming Mode
Connect jumper on right pin and middle pin of the
JP_PWM_SET by applying VDC to PWM_SET/PLL pin.
In this mode, all other inputs (ACTL, STV , EN_PS,
EN_VSYNC, EN_ADIM) will be neglected. The LED
dimming frequecy and phase of the LEDs will be the
same as the input of PWMI, as shown in Figures 5
and 6.
b. Decoded PWM Dimming Mode
Connect jumper of middle and left pin on the
JP_PWM_SET by applying POT resistor of R_PWM_SET
to adjust LED dimming frequency, as shown in Figures 7
and 8. The JP_CPLL should be opened.
c. VSYNC Mode
Connect jumper to the JP_CPLL and remove the jumper
of the JP_PWM_SET. Set switch SW_EN_VSYNC to be
ON(H). The LED dimming frequency will be selected by
frame signal coming to the STV pin (see Table 1 in the
ISL97687 datasheet). Figures 9 and 10 show the STV
and channel output waveforms at VSYNC mode.
d. Phase Shift Mode
Connect Jumper to the JP_PWM_SET for decoded PWM
dimming mode or JP_CPLL for VSYNC mode. Set the
switch SW_EN_PS to be ON(H) state. Figure 8 shows
phase shifted channel output. Figure 10 shows the
channel output waveforms in the phase shifted VSYNC
mode.
e. ACTL interface mode
Connect jumper JP_PWM_SET for decoded PWM
dimming mode or JP_CPLL for VSYNC mode. Set switch
SW_EN_ADIM to ON state. Apply analog control signal
0.3V(0% dimming) ~ 3.0V(100% dimming) to the ACTL
post (see Figure 5). In the ACTL or ACTL*PWMI mode,
the PWMI pin should not be floating or GND but tied to
VDC or applying PWM signal.
AN1706 Rev 1.00
November 26, 2012
USER'S MANUAL
2. The ISL97687IBZEV1Z evaluation board provides the
adjustments of Boost switching frequency, LED dimming
frequency, and LED peak with jumpers and potentiometers,
as shown in Figure 4. Follow the steps for the adjustment
and selection of the analog settings.
a. Boost switching frequency adjustment
Change the resistance of the potentiometer R_OSC for
the boost switching frequency adjustment.
b. Dimming frequency adjustment
Place jump JP_PWM_SET between middle and left pins
to connect PWM_SET pin to the potentiometer for the
dimming frequency adjustment.
c. LED peak current adjustment
For two step LED peak current settings, setup the
current levels with potentiometer of R_ISET1 and
R_ISET2 of fixed resistor R16 (36.5k populated for
80mA). The required current levels can be selected with
switch SW_CSEL.
d. OVP threshold setting
The OVP level can be set based on Equation 1. The
boost can regulate down to 30% of OVP. The OVP level
should be considered max forward voltage of strings
and margin of low temperature start-up.
 
OVP 1.21V R
=
UPPER
Please refer to the ISL97687
switching and regulation adjustment.
3. For power-up, set switch SW_nSHUT to right side position.
Apply input supply voltage to the PVIN and PGND pins
based on the load conditions according to Table 1.
4. Each LED string can be connected to the posts of CH1,
CH2, CH3, and CH4 with VOUT bias to the combined
anodes. The Max LEDs per strings can be up to 22 LEDs for
79.3V OVP. Make sure the minimum number of
LEDs/string will be limited by 30% ( 23.8V) of Boost OVP
level.
TABLE 1. LOAD CONDITION OF ISL97687 EVALUATION BOARD
EVALUATION BOARD
ISL97687IBZEV1Z
Max LEDs/Ch
OVP limit
Current limit
Typical input voltage range I
Typical input voltage range II
NOTE: Input voltage range, number of LEDs/Ch, and LED peak current
can be adjusted by the current sense and OVP settings but needs
careful attention on the Abs rating of the components.
AN1706
Rev 1.00
November 26, 2012
(EQ. 1)
 
R R
+
LOWER LOWER
datasheet for detailed
Driving up to 22 LEDs/Ch
79.3V (23.8V of 30% OVP)
4.25A (sense resistor 40mΩ)
20V to 30V for 12 to 22 LEDs with
120mA/Ch
10V to 20V for 10 to 14 LEDs with
120mA/Ch
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