DATASHEET
ISL97678
8-Channel 45V, 50mA LED Driver
The
ISL97678
is an 8-channel PWM dimming LED driver for
LCD backlight applications. The ISL97678 is capable of driving
up to 96 pieces of 3.4V/50mA LEDs but larger numbers of
LEDs are possible if the LED forward voltage combined is less
than 45V. The ISL97678 has 8 channels of voltage controlled
current sources with typical currents matching to ±1%, which
compensate for the non-uniformity effect of forward voltages
variance in the LED strings. To minimize the voltage headroom
and power loss in the typical multi-string operation, the
ISL97678 features dynamic headroom control that monitors
the highest LED forward voltage string and uses its feedback
signal for output regulation.
The ISL97678 features PWM dimming up to 30kHz with
0.4%~100% duty cycle and maintains ±1% current matching
across all ranges. The PWM dimming frequency can be
adjusted between 100Hz and 30kHz. The boost switching
frequency can also be adjusted between 600kHz and 1.5MHz.
The ISL97678 features extensive protection functions that
include string open and short circuit detections, OVP, and OTP.
The ISL97678 is available in the 32 Ld QFN 5mmx5mm and
operate from -40°C to +85°C with input voltage ranges from
4.75V to 26V.
FN6998
Rev.3.00
Sep 8, 2017
Features
• 8 channels
• 4.75V ~ 26V input
• 45V maximum output
• Drive typically 96 LEDs (3.4V/50mA each)
• External PWM input up to 20kHz dimming
• Dimming range 0.4%~100% up to 30kHz
• Current matching ±0.7% typical
• Protections
- String open circuit and short circuit detections, OVP, and
OTP
• Adjustable dimming frequency
• Adjustable switching frequency
• 32 Ld (5mmx5mm) QFN package
Applications
• Notebook displays WLED or RGB LED backlighting
• LCD monitor LED backlighting
Related Literature
• For a full list of related documents, visit our website
-
ISL97678
product page
V
IN
4.75V~26V
45V*, 50mA per String
96 (8x12) LEDs
C
IN
10µF
VIN
EN
LX
OVP
C
LOWER
R
LOWER
10µH/3A
3x4.7µF/50V
C
OUT
C
UPPER
R
UPPER
PROCESSOR
PWM
ISL97678
R
SET
R
FPWM
R
FSW
RSET
FPWM
CH1
CH2
CH8
LED
BACKLIGHT
FSW
AGND
PGND
FIGURE 1. TYPICAL APPLICATION CIRCUIT: TFT-LCD NOTEBOOK DISPLAY
FN6998 Rev.3.00
Sep 8, 2017
Page 1 of 17
ISL97678
Typical Application Circuit
V
IN
* = 4.75V~26V
C
IN
Optional fuse
10µF
16
VIN
L1
10µH/3A
20
LX
21
LX
D1
C
OUT
45V*, 50mA per String
96 (8x12) LEDs
3x4.7µF/50V
R
UPPER
806k
C
UPPER
100pF
17 EN
1µF
18
1µF
10
50k
11
333k
12
14.2k
13
3.3nF
14 COMP
15k
4
2
PWM
AGND
AGND
AGND
AGND
RSET
FPWM
FSW
VLOGIC
VDC
ISL97678
OVP
23
C
LOWER
3.3nF
R
LOWER
22k
CH1
CH2
CH3
25
26
27
28
29
30
31
32
THERMAL
PAD
CH4
CH5
CH6
CH7
CH8
PGND
3
5
1
PGND 19
AGND
AGND
AGND
PGND
AGND
6
7
8
9
15
22
Note: V
IN
* ≥ 12V for 45V/50mA Applications
FIGURE 2. ISL97678 TYPICAL APPLICATION DIAGRAM
FN6998 Rev.3.00
Sep 8, 2017
Page 2 of 17
ISL97678
Block Diagram
V
IN
= 4.75V~26V
C
IN
10µF
Optional fuse
45V*, 50mA per String
96 (8x12) LEDs
VIN
10µH/3A
EN
O/P SHORT
LX
2x4.7µF/50V
C
OUT
C
UPPER
R
UPPER
VDC
VLOGIC
REG1
REG
OSC &
RAMP
COMP
ANALOG BIAS
LOGIC BIAS
FAULT
FSW
LOGIC
Imax
ILIMIT
OVP
OVP
C
LOWER
R
LOWER
FSW
R
FSW
FET
DRIVER
PGND
FAULT CONTROL
COMP
GM
AMP
HIGHEST VF
STRING DETECT
VSET
+
-
Open Ckt, Short Ckt
Detection
CH1
CH2
RSET
R
SET
REF
GEN
REF_
VSC
REF_
OVP
+
-
1
2
CH8
AGND
PWM
FPWM
R
FPWM
TEMP
SENSOR
PWM DIMMING
CONTROLLER
+
-
8
FAULT
CONTROL
ISL97678
FIGURE 3. ISL97678 BLOCK DIAGRAM
Ordering Information
PART NUMBER
(Notes
1, 2)
ISL97678IRZ
NOTES:
1. Add “-T” suffix for 6k unit or “-TK” for 1k unit tape and reel options. Refer to
TB347
for details on reel specifications.
2. These Intersil Pb-free plastic packaged products employ special Pb-free material sets, molding compounds/die attach materials, and 100% matte
tin plate plus anneal (e3 termination finish, which is RoHS compliant and compatible with both SnPb and Pb-free soldering operations). Intersil Pb-
free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
3. For Moisture Sensitivity Level (MSL), please see the product information page for
ISL97678.
For more information on MSL, see
TB363.
PART MARKING
ISL9767 8IRZ
PACKAGE
(RoHS Compliant)
32 Ld 5x5 QFN
L32.5x5B
PKG.
DWG. #
FN6998 Rev.3.00
Sep 8, 2017
Page 3 of 17
ISL97678
Pin Configuration
ISL97678
(32 LD 5X5 QFN)
TOP VIEW
CH8
CH7
CH6
CH5
CH4
CH3
CH2
26
CH1
25
24 NC
23 OVP
22 PGND
21 LX
EXPOSED THERMAL PAD
AGND
AGND
AGND
AGND
5
6
7
8
9
AGND
10
VLOGIC
11
FSW
12
FPWM
13
RSET
14
COMP
15
AGND
16
VIN
20 LX
19 PGND
18 VDC
17 EN
32
PGND
AGND
AGND
PWM
1
2
3
4
31
30
29
28
27
Pin Descriptions
(I = Input, O = Output, S = Supply)
PIN
1, 19, 22
2, 3, 5, 6, 7,
8, 9, 15
4
10
11
12
13
14
16
17
18
20, 21
23
24
25 ~ 32
NAME
PGND
AGND
PWM
VLOGIC
FSW
FPWM
RSET
COMP
VIN
EN
VDC
LX
OVP
NC
CH1 ~ CH8
TYPE
S
S
I
O
I
I
I
O
S
I
S
O
I
I/O
I
Power Ground.
Analog Ground.
PWM Brightness Control.
Internal 2.5V Logic Bias Regulator. Need Decoupling Capacitor for Regulation.
When R
FSW
is 100k, f
SW
is 500kHz.
When R
FSW
is 33k, f
SW
is 1.5MHz.
When R
FPWM
is 333k, FPWM is 200Hz.
When R
FPWM
is 3.3k, FPWM is 20kHz.
Resistor Connection for Setting LED Current.
Boost compensation.
Main Power.
Enable
Internal 5V Analog Bias Regulator. Needs Decoupling Capacitor for Regulation.
Boost MOSFET Drain Terminal Switching Node.
Overvoltage Protection Input as well as Output Voltage FB Monitoring.
No Connect
LED Driver PWM Dimming Monitoring.
DESCRIPTION
FN6998 Rev.3.00
Sep 8, 2017
Page 4 of 17
ISL97678
Absolute Maximum Ratings
Voltage ratings are all with respect to AGND pin
VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 27V
EN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 27V
VLOGIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 2.75V
VDC, PWM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 5.75V
COMP, RSET, FPWM, FSW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to min
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .(VDC + 0.3V, 5.75V)
CH1 - CH8, LX, OVP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 45V
PGND, AGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +0.3V
Thermal Information
Thermal Resistance (Typical)
JA
(°C/W)
32 Ld QFN (Notes
4, 5).
. . . . . . . . . . . . . . . . 31
Thermal Characterization (Typical, Note
6)
JC
(°C/W)
3
PSI
JT
(°C/W)
Recommended Operating Conditions
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40°C to +85°C
32 Ld QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0.2
Maximum Continuous Junction Temperature . . . . . . . . . . . . . . . . .+125°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C
Power Dissipation
T
A
< +25°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2W
T
A
< +70°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8W
T
A
< +85°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3W
T
A
< +100°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.8W
Pb-Free Reflow Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see
TB493
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.
JA
is measured with the component mounted on a high-effective thermal conductivity test board in free air. See
TB379
for details.
5. For
JC
, the “case temp” location is the center of the exposed metal pad on the package underside.
6. PSI
JT
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
JA
and
JC
thermal resistance ratings.
Electrical Specifications
5.
All specifications below are characterized at T
A
= -40°C to +85°C; V
IN
= 12V, EN = 5V, R
SET
= 36kΩ, unless
otherwise noted. Boldface limits apply over the operating temperature range, -40°C to +85°C.
PARAMETER
GENERAL
V
IN
I
VIN_SHDN
V
OUT
V
UVLO
V
UVLO_HYS
LINEAR REGULATOR
V
DC
V
DC_DROP
I
VDC
V
LOGIC
V
LOGIC_DROP
5V Analog Bias Regulator
VDC LDO Dropout Voltage
Active Current
2.5V Logic Bias Regulator
V
LOGIC
LDO Dropout Voltage
V
IN
> 6V
I
VDC
= 30mA
EN = 5V, R = 33kΩ
V
IN
> 6V
I
VLOGIC
= 30mA
2.3
4.8
5
71
10
2.4
31
2.5
100
5.1
100
V
mV
mA
V
mV
Backlight Supply Voltage
VIN Shutdown Current
Output Voltage
Undervoltage Lockout Threshold
Undervoltage Lockout Hysteresis
2.9
300
EN = 0
4.75
26
(Note
8)
5
45
3.3
V
µA
V
V
mV
DESCRIPTION
TEST CONDITIONS
MIN
(Note
7)
TYP
MAX
(Note
7)
UNITS
BOOST SWITCHING REGULATOR
SS
SW
ILimit
r
DS(ON)
VFSW
Soft-Start
Boost FET Current Limit
Internal Boost Switch ON-Resistance
f
SW
Voltage
R
FSW
= 33kΩ
1.18
T
A
= +25°C to +85°C
3.0
130
1.21
1.24
16
4.7
ms
A
mΩ
V
FN6998 Rev.3.00
Sep 8, 2017
Page 5 of 17
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