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PDF ISL97671 Data sheet ( Hoja de datos )
| Número de pieza | ISL97671 | |
| Descripción | 6-Channel SMBus/I2C or PM Dimming LED Driver | |
| Fabricantes | Intersil | |
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6-Channel SMBus/I2C or PWM Dimming LED Driver
with Phase Shift Control
ISL97671
The ISL97671 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 ISL97671 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 ISL97671 VIN pin.
The ISL97671 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 ISL97671 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.
The ISL97671 has a full range of dimming capabilities
that include SMBus/I2C controlled PWM dimming or DC
dimming. It can also do direct PWM dimming with as low
as 350nS pulse on PWM pin which translates to a duty-
cycle of 0.007% at a 200Hz dimming frequency.
Features
• 6 Channels
• 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*(see page 27)
• Notebook Displays WLED or RGB LED Backlighting
• LCD Monitor LED Backlighting
• Automotive Displays LED Backlighting
• Automotive or Traffic Lighting
Typical Application Circuit
VIN = 4.5~26.5V
VOUT = 45V*, 40mA PER STRING
ISL97671
1 FAULT
2 VIN
4 VDC
LX 20
OVP 16
PGND 19
7 SMBCLK/SCL
6 SMBDAT/SDACH0 10
5 PWM
3 EN
CH1 11
CH2 12
CH3 13
17 RSET
CH4 14
8 FPWM
CH5 15
9 AGND
COMP 18
*VIN > 12V
June 24, 2010
FN7631.0
FIGURE 1. ISL97671 TYPICAL APPLICATION DIAGRAM WITH SMBus/I2C CONTROL
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  
ISL97671
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Absolute Maximum Ratings (TA = +25°C)
VIN, EN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 28V
FAULT . . . . . . . . . . . . . . . . . . . . . . . VIN-8.5V to VIN+0.3V
VDC, COMP, RSET. . . . . . . . . . . . . . . . . . . . . -0.3V to 5.5V
SMBCLK/SCL*, SMBDAT/SDA*, FPWM, PWM . . -0.3V to 5.5V
EN, OVP . . . . . . . . . . . . . . . . . . . . . . . . . . . -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 = 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
VIN Shutdown Current
Output Voltage
VUVLO
Undervoltage Lockout Threshold
VUVLO_HYS Undervoltage Lockout Hysteresis
REGULATOR
4.5V < VIN ≤ 26V,
FSW = 600kHz
8.55V < VIN ≤ 26V,
FSW = 1.2MHz
4.5V < VIN ≤ 8.55V,
FSW = 1.2MHz
10 µA
45 V
45 V
VIN/0.19 V
2.6
275
3.3
V
mV
VDC
IVDC_STBY
IVDC
VLDO
ENLow
LDO Output Voltage
Standby Current
VIN ≥ 6V
EN = 0V
Active Current
EN = 5V
VDC LDO Droop Voltage
VIN > 5.5V, 20mA
Guaranteed Range for EN Input Low Voltage
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
5 FN7631.0
June 24, 2010
5 Page 
ISL97671
www.DataSheet4U.com
For example, if 10 LEDs are used with the worst case
VOUT of 35V. If R1 and R2 are chosen such that the OVP
level is set at 40V, then the VOUT is allowed to operate
between 25.6V and 40V. If the requirement is changed to
a 6 LEDs 21V VOUT application, then the OVP level must
be reduced and users should follow VOUT = (64%
~100%) OVP requirement. Otherwise, the headroom
control will be disturbed such that the channel voltage
can be much higher than expected and sometimes it can
prevent the driver from operating properly.
The ratio of the OVP capacitors should be the inverse of
the OVP resistors. For example, if RUPPER/RLOWER = 33/1,
then CUPPER/CLOWER = 1/33 with CUPPER = 100pF and
CLOWER = 3.3nF.
Current Matching and Current Accuracy
Each channel of the LED current is regulated by the
current source circuit, as shown in Figure 20.
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. On the
other hand, the absolute accuracy is additionally
determined by the external RSET, and therefore, additional
tolerance will be contributed by the current setting
resistor. A 1% tolerance resistor is therefore
recommended.
boost makes the output to the correct level such that the
lowest channel pin 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
programmed current. The output voltage will regulate
cycle-by-cycle and is always referenced to the highest
forward voltage string in the architecture.
Dimming Controls
The ISL97671 provides SMBus/I2C controlled PWM or DC
dimming where the users need to turn the LEDs on
through the SMBus/I2C communications (see the
“SMBus/I2C Communications” section). On the other
hand, the ISL97671 also provides PWM dimming by
external PWM signal where the SMBCLK and SMBDAT
pins need to pull low or grounded.
The ISL97671 allows 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.
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
=
-4---0---1----.--8-
RSET
(EQ. 2)
Once RSET is fixed, the LED DC current can be adjusted
through Register 0x07 (BRTDC) as follows:
ILED = 1.58x(BRTDC ⁄ RSET)
(EQ. 3)
+- REF
RSET
+
-
PWM DIMMING
DC DIMMING
+
-
FIGURE 20. SIMPLIFIED CURRENT SOURCE CIRCUIT
Dynamic Headroom Control
The ISL97671 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. When this 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
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 2 yields
Equation 4:
RSET = 401.8 ⁄ 0.02 = 20.1kΩ
(EQ. 4)
If BRTDC is set to 200 then:
ILED = 1.58 • 200 ⁄ 20100 = 15.7mA
(EQ. 5)
PWM CONTROL
The ISL97671 provides three 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 6channels 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
11 FN7631.0
June 24, 2010
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet ISL97671.PDF ] | |
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