ISL97687 Datasheet, PDF (1/24 Pages) Intersil Corporation – 4-Channel LED Driver with Phase Shift Control and 10-Bit Dimming Resolution

4-Channel LED Driver with Phase Shift Control and
10-Bit Dimming Resolution
ISL97687
The ISL97687 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.
The ISL97687’s current sources achieve typical current matching
to ±1%, while dynamically maintaining the minimum required
V_OUT necessary for regulation. This adaptive scheme
compensates for the non-uniformity of forward voltage variance
in the LED strings.
The ISL97687 can decode both an incoming PWM signal and an
analog input voltage, for DC-to-PWM dimming applications.
Modes include direct PWM and several modes where the PWM
frequency is synthesized on chip at 10-bit resolution. This can be
either free running, or synchronized with the frame rate to give
both a frequency and a phase lock, minimizing panel to panel
variation and display flicker. Phase shift is supported, reducing
flicker and audio noise, as is multiplication of the incoming
decoded analog and PWM values.
The ISL97687 has an advanced dynamic headroom control
function, which monitors the highest LED forward voltage string,
and regulates the output to the correct level to minimize power
loss. This proprietary regulation scheme also allows for
extremely linear PWM dimming from 0.02% to 100%. The LED
current can also be switched between two current levels, giving
support for 3D applications. The ISL97687 incorporates
extensive protections of string open and short circuit detections,
OVP, and OTP.
Features
• 4x160mA, 75V Rated Channels with Integrated Channel
Regulation FETs
• Channels can be Ganged for High Current
- 2x350mA
- 1x700mA
• 9V~32V Input Voltage
• Dimming Modes:
- Direct PWM Dimming from 100Hz~30kHz
- PWM Dimming with Adjustable Output Frequency
- 10-bit Dimming Resolution
- V_SYNC Function to Synchronize PWM Signal to Frame Rate
- Phase Shift
- Analog to PWM Dimming with 8-bit Resolution
• 2 Selectable Current Levels for 3D Applications
• Current Matching of ±1%
• Integrated Fault Protection Features such as String Open
Circuit Protection, String Short Circuit Protection, Overvoltage
Protection, and Over-Temperature Protection
• 28 Ld 5x5mm TQFN and 28 Ld 300mil SOIC Packages Available
Applications
• Monitor/TV LED Backlighting
• General/Industrial/Automotive Lighting
Related Literature
• See Apnote for “ISL97687IRTZ_LEVALZ” or
“ISL97687IRTZ_HEVALZ” for TQFN Application
• See Apnote for “ISL97687IBZ-EVAL1Z” for SOIC Application
VIN: 9V~32V
FUSE
VIN
VDC
VLOGIC
EN
STV
EN_VSYNC
EN_ADIM
PWMI
ACTL
EN_PS
SLEW
GD
CS
PGND
COMP
OVP
CSEL
ISET1
ISET2
OSC
PWM_SET/PLL
CH1
CH2
CH3
CH4
D1 ^{160mA MAX PER STRING}
Q1
RSENSE
FIGURE 1. ISL97687 APPLICATION DIAGRAM
110
100
90
80
70
60
50
40
30
20
10
0
0
I_CH2
I_CH3
I_CH1
I_CH4
20
40
60
80
100
DIMMING DUTY CYCLE (%)
FIGURE 2. PWM DIMMING LINEARITY
September 15, 2011
1
FN7714.0
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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