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PDF ISL97687 Data sheet ( Hoja de datos )
| Número de pieza | ISL97687 | |
| Descripción | 4-Channel LED Driver | |
| Fabricantes | Intersil | |
| Logotipo |  |
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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
VOUT 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
- VSYNC 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
Applicationswww.DataSheet.co.kr
• 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
DIMMING DUTY CYCLE (%)
FIGURE 2. PWM DIMMING LINEARITY
100
September 15, 2011
FN7714.0
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Copyright Intersil Americas Inc. 2011. All Rights Reserved
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
Datasheet pdf - http://www.DataSheet4U.net/
1 page  
ISL97687
Table of Contents
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Thermal Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Typical Performance Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Theory of Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
PWM Boost Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
OVP and VOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Current Matching and Current Accuracy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Dynamic Headroom Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Dimming Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
LED DC Current Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
PWM Dimming Frequency Adjustment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Phase Shift Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
VOUT Control when LEDs are Off. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Switching Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5V and 2.4V Low Dropout Regulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Soft-Start and boost current limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Fault Protection and Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Short Circuit Protection (SCP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Open Circuit Protection (OCP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Undervoltage Lock-out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Over-Temperature Protection (OTP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Component Selections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
www.DataSheet.co.kr
Input Capacitor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Inductor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Output Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Channel Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Schottky Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
High Current Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
PCB Layout Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Two Layers PCB Layout with TQFN Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
General Power PAD Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
One Layer PCB Layout with SOIC Package. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Equivalent Circuit Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Package Outline Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5 FN7714.0
September 15, 2011
Datasheet pdf - http://www.DataSheet4U.net/
5 Page 
ISL97687
and cheaper solution, as well as keeping the maximum voltages
and currents that can be seen in the system during fault
conditions at less extreme levels.
Parallel capacitors should be placed across the OVP resistors
such that RUPPER /RLOWER = CLOWER /CUPPER . Using a CUPPER
value of at least 30pF is recommended. These capacitors reduce
the AC impedance of the OVP node, which is important when
using high value resistors. The ratio of the OVP capacitors should
be the inverse of the OVP resistors. For example, if
RUPPER/RLOWER = 33/1, then CUPPER /C LOWER = 1/33 with
CUPPER = 100pF and CLOWER = 3.3nF. These components are not
always needed, but it is highly recommended to include
replacements to populate them if necessary.
Current Matching and Current Accuracy
The LED current in each channel is regulated using an active
current source circuit, as shown in Figure 20. The peak LED
current is set by translating the RISET current to the output with a
scaling factor of 2919/RISET. The drain terminals of the current
source MOSFETs are designed to run at 750mV to optimize
power loss versus accuracy requirements. The sources of
channel-to-channel current matching error come from the
op amp offsets, reference voltage, and current source sense
resistors. These parameters are optimized for current matching
and absolute current accuracy. However, the absolute accuracy is
additionally determined by the external RISET. A 0.1% tolerance
resistor is therefore recommended.
+- REF
RSET
+-
PWM DIMMING
+-
and is updated as needed, to allow for temperature and aging
affects in the LEDs.
Dimming Controls
The ISL97687 provides two basic ways to control the LED current,
and therefore, the brightness. These are described in detail in
subsequent sub-sections, but can be broadly divided into the
following two types of dimming:
Step 1. LED DC current adjustment
Step 2. PWM chopping of the LED current defined in Step 1.
LED DC Current Setting
The initial brightness should be set by choosing an appropriate
value for the resistor on the ISET1/2 pins. This resistor must
connect to AGND, and should be chosen to fix the maximum
possible LED current:
ILEDmax = -R2----9I-S--1--E--9-T-
(EQ. 2)
The ISL97687 includes two built-in levels of current, individually
set by the resistors on ISET1 and ISET2, according to Equation 2,
which can be switched between by using the CSEL pin.
CSEL = 0: The current setting is based on ISET1
CSEL = 1: The current setting is based on ISET2
This is typically used in 3D systems to provide a higher current
level in 3D modes, but is not restricted to this application. CSEL
can be switched in operation and updates immediately in direct
PWM mode, and at the start of the next PWM dimming cycle in
other modes.www.DataSheet.co.kr
LED DC DIMMING
It is possible to control the LED current by applying a DC voltage
VDIM to the ISET1/2 pin via a resistor as in Figure 21.
ISET
VISET: 1.21V
RISET
RDIM
VDIM
FIGURE 20. SIMPLIFIED CURRENT SOURCE CIRCUIT
Dynamic Headroom Control
The ISL97687 features a proprietary dynamic headroom control
circuit that detects the highest forward voltage string, or
effectively the lowest voltage from any of the CH pins. The
system will regulate the output voltage to the correct level to
allow the channel with the lowest voltage to have just sufficient
headroom to correctly regulate the LED current. Since all LED
strings are connected to the same output voltage, the other CH
pins will have a higher voltage, but the regulated current source
circuit on each channel will ensure that each channel has the
correct current level. The output voltage regulation is dynamic,
FIGURE 21. LED CURRENT CONTROL WITH VDIM
If the VDIM is above VISET 1.21V, the brightness will reduce, and
vice versa. In this configuration, it is important that the control
voltage be set to the maximum brightness (minimum voltage)
level when the ISL97687 is enabled, even if the LEDs are not lit
at this point. This is necessary to allow the chip to calibrate to the
maximum current level that will need to be supported.
Otherwise, on-chip power dissipation will be higher at current
levels above the start-up level. Dimming with this technique
should be limited to a minimum of 10~20% brightness, as LED
current accuracy is increasingly degraded at lower levels.
11
FN7714.0
September 15, 2011
Datasheet pdf - http://www.DataSheet4U.net/
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet ISL97687.PDF ] | |
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