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PDF ISL97674 Data sheet ( Hoja de datos )
| Número de pieza | ISL97674 | |
| Descripción | 6-Channel LED Driver | |
| Fabricantes | Intersil | |
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6-Channel LED Driver with Phase Shift Control and
Frame Rate to Dimming Frequency
Synchronization
ISL97674
The ISL97674 is a 6-Channel 45V dual dimming capable
LED driver that can be used with either SMBus/I2C or
PWM signal for dimming control. The ISL97674 drives 6
channels of LED to support 78 LEDs from 4.5V to 26V or
48 LEDs from a boost supply of 2.7V to 26V and a
separate 5V bias on the ISL97674 VIN pin.
The ISL97674 compensates for non-uniformity of the
forward voltage drops in the LED strings with its 6 voltage
controlled-current source channels. Its headroom control
monitors the highest LED forward voltage string for output
regulation, to minimize the voltage headroom and power
loss in a typical multi string operation.
The ISL97674 features optional channel phase shift
control to minimize the input, output ripple
characteristics and load transients as well as spreading
the light output to help reduce the video and audio
interference from the backlight driver operation. The
phase shift can be programmed with equal phase angle
or adjustable in 7-bit resolution. In addition, the
ISL97674 also has a unique VSYNC function that accepts
30Hz ~ 120Hz frame signal and synchronizes it to the
dimming frequency to minimize panel to panel visual
interference variation. The dimming frequencies are
available from 200Hz to 30kHz and can be synchronized
from 140Hz to 1085Hz.
Features
• 6 Channels
• Frame Rate to Dimming Frequency Synchronization
• 4.5V to 26.5V Input
• 45V Output Max
• Up to 40mA LED Current per channel
• Extensive Dimming Control
- PWM/DPST Dimming, I2C 8-bit with equal phase
shift, and 0.007% Direct PWM dimming at 200Hz
• Optional Master Fault Protection
• PWM Dimming Linearity 0.4%~100% <30kHz
• 600kHz/1.2MHz selectable switching frequency
• Dynamic Headroom Control
• Protections with Flag Indication
- String Open/Short Circuit, VOUT Short Circuit,
Overvoltage and Over-Temperature Protections
- Optional Master Fault Protection
• Current Matching ±0.7%
• 20 Ld 4mmx3mm QFN Package
Applications
• Notebook Displays WLED or RGB LED Backlighting
• LCD Monitor LED Backlighting
• Automotive Displays LED Backlighting
Typical Application Circuit
VIN = 4.5~26.5V
VOUT = 45V*, 40mA PER STRING
June 25, 2010
FN7634.0
ISL97674
1 FAULT
2 VIN
4 VDC
LX 20
OVP 16
18 COMP
7 SCL
PGND 19
6 SDA
3 EN/PWM
5 VSYNC
8 PLLC
17 RSET
CH0 10
CH1 11
CH2 12
CH3 13
CH4 14
CH5 15
AGND 9
*VIN > 12V
FIGURE 1. ISL97674 TYPICAL APPLICATION DIAGRAM
1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2010. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
1 page  
ISL97674
www.DataSheet4U.com
Absolute Maximum Ratings (TA = +25°C)
VIN, EN/PWM. . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 28V
FAULT . . . . . . . . . . . . . . . . . . . . . VIN - 8.5V to VIN + 0.3V
VDC, COMP, RSET, OVP . . . . . . . . . . . . . . . . . -0.3V to 5.5V
SCL, SDA, VSYNC, PLLC . . . . . . . . . . . . . . . . -0.3V to 5.5V
CH0 - CH5, LX . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 45V
PGND, AGND . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +0.3V
Above voltage ratings are all with respect to AGND pin
ESD Rating
Human Body Model (Tested per JESD22-A114E) . . . . . 3kV
Machine Model (Tested per JESD22-A115-A) . . . . . . . 300V
Charged Device Model . . . . . . . . . . . . . . . . . . . . . . . 1kV
Thermal Information
Thermal Resistance (Typical)
θJA (°C/W) θJC (°C/W)
20 Ld QFN Package (Notes 4, 5, 7). 40
2.5
Thermal Characterization (Typical)
PSIJT (°C/W)
20 Ld QFN Package (Note 6) . . . . . . . . . . . . 1
Maximum Continuous Junction Temperature . . . . . . +125°C
Storage Temperature . . . . . . . . . . . . . . . -65°C to +150°C
Pb-Free Reflow Profile . . . . . . . . . . . . . . . . . .see link below
http://www.intersil.com/pbfree/Pb-FreeReflow.asp
Operating Conditions
Temperature Range . . . . . . . . . . . . . . . . . . -40°C to +85°C
IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless
otherwise noted, all tests are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact
product reliability and result in failures not covered by warranty.
NOTES:
4. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach”
features. See Tech Brief TB379.
5. For θJC, the “case temp” location is the center of the exposed metal pad on the package underside.
6. PSIJT is the PSI junction-to-top thermal characterization parameter. If the package top temperature can be measured with this
rating then the die junction temperature can be estimated more accurately than the θJC and θJC thermal resistance ratings.
7. Refer to JESD51-7 high effective thermal conductivity board layout for proper via and plane designs.
Electrical Specifications
All specifications below are tested at TA = +25°C; VIN = 12V, EN/PWM = 5V, RSET = 20.1kΩ,
unless otherwise noted. Boldface limits apply over the operating temperature range,
-40°C to +85°C.
PARAMETER
DESCRIPTION
CONDITION
MIN
MAX
(Note 8) TYP (Note 8) UNIT
GENERAL
VIN (Note 9) Backlight Supply Voltage
≤13 LEDs per channel (3.2V/20mA
type)
4.5
26.5
V
IVIN_STBY
VOUT
VUVLO
VUVLO_HYS
REGULATOR
VIN Shutdown Current
Output Voltage
Undervoltage Lock-out Threshold
Undervoltage Lock-out Hysteresis
4.5V < VIN ≤ 26V,
FSW = 600kHz
8.55V < VIN ≤ 26V,
FSW = 1.2MHz
4.5V < VIN ≤ 8.55V, FSW = 1.2MHz
2.6
10 µA
45 V
45 V
VIN/0.19
3.3
V
V
275 mV
VDC
IVDC_STBY
IVDC
VLDO
ENLow
LDO Output Voltage
Standby Current
VIN > 6V
EN/PWM = 0V
Active Current
EN/PWM = 5V
VDC LDO Droop Voltage
Guaranteed Range for EN Input Low
Voltage
VIN > 5.5V, 20mA
4.55
4.8
5
20
5
5
200
0.5
V
µA
mA
mV
V
ENHi
Guaranteed Range for EN Input High
Voltage
1.8 V
tENLow
EN/PWM low time before shut-down
30.5
ms
5 FN7634.0
June 25, 2010
5 Page 
ISL97674
www.DataSheet4U.com
MAXIMUM DC CURRENT SETTING
The initial brightness should be set by choosing an
appropriate value for RSET. This should be chosen to fix
the maximum possible LED current:
ILEDmax = -(--R4---0-S---1-E--.--8T----)
(EQ. 1)
+- REF
+-
DC CURRENT ADJUSTMENT
Once RSET is fixed, the LED DC current can be adjusted
through Register 0x07 (BRTDC) as follows:
RSET
PWM DIMMING
DC DIMMING
+-
FIGURE 19. SIMPLIFIED CURRENT SOURCE CIRCUIT
The LED peak current is set by translating the RSET
current to the output with a scaling factor of 401.8/RSET.
The source terminals of the current source MOSFETs are
designed to run at 500mV to optimize power loss versus
accuracy requirements. The sources of errors of the
channel-to-channel current matching come from the
op amps offset, internal layout, reference, and current
source resistors. These parameters are optimized for
current matching and absolute current accuracy.
However, the absolute accuracy is additionally
determined by the external RSET. A 1% tolerance resistor
is recommended.
Dynamic Headroom Control
The ISL97674 features a proprietary Dynamic Headroom
Control circuit that detects the highest forward voltage
string or effectively the lowest voltage from any of the
CH0-CH5 pins digitally. When the lowest channel voltage
is lower than the short circuit threshold, VSC, such
voltage will be used as the feedback signal for the boost
regulator. The boost makes the output to the correct
level such that the lowest channel is at the target
headroom voltage. Since all LED stacks are connected to
the same output voltage, the other channel pins will have
a higher voltage, but the regulated current source circuit
on each channel will ensure that each channel has the
same current. The output voltage will regulate cycle-by-
cycle and it is always referenced to the highest forward
voltage string in the architecture.
Dimming Controls
The ISL97674 allow two ways of controlling the LED
current, and therefore, the brightness. They are:
1. DC current adjustment
2. PWM chopping of the LED current defined in Step 1.
There are various ways to achieve DC or PWM current
control, which will be described in the following.
where BRT is the PWM brightness level programmed in
the Register 0x00. BRT ranges from 0 to 255 in decimal
ILED = 1.58x(BRTDC ⁄ RSET)
(EQ. 2)
BRTDC can be programmed from 0 to 255 in decimal and
defaults to 255 (0xFF). If left at the default value, LED
current will be fixed at ILEDmax. BRTDC can be adjusted
dynamically on the fly during operation. BRTDC = 0
disconnects all channels.
For example, if the maximum required LED current
(ILED(max)) is 20mA, rearranging Equation 1 yields
Equation 3:
RSET = 401.8 ⁄ 0.02 = 20.1kΩ
(EQ. 3)
If BRTDC is set to 200 then:
ILED = 1.58 • 200 ⁄ 20100 = 15.7mA
(EQ. 4)
PWM Control
The ISL97674 provides two different PWM dimming
methods, as described in the following. Each of these
methods results in PWM chopping of the current in the
LEDs for all 6 channels to provide an average LED
current. During the On periods, the LED current will be
defined by the value of RSET and BRTDC, as described in
Equations 1 and 2. The source of the PWM signal can be
described as follows:
1. SMBus/I2C generated 256 level duty cycle
programmed through the SMBus/I2C.
2. External signal from PWM.
The default PWM dimming is in SMBus/I2C mode. In both
methods, the average LED current of each channel is
controlled by ILED and the PWM duty cycle in percent as:
ILED(ave) = ILED × PWM
(EQ. 5)
Method 1 (SMBus/I2C controlled PWM)
To use this mode, users need to set Register0x01 to 0x05
with EN/PWM in logic high.
The average LED current of each channel is controlled
by the SMBus/I2C setting as
ILED(ave) = ILED × (BRT ⁄ 255)
(EQ. 6)
and defaults to 255 (0xFF). BRT = 0 disconnects all
channels.
11 FN7634.0
June 25, 2010
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet ISL97674.PDF ] | |
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