ÓMacroblock, Inc. 2003
Floor 6-4, No. 18, Pu-Ting Rd., Hsinchu, Taiwan 30077, ROC.
TEL: +886-3-579-0068, FAX: +886-3-579-7534 E-mail: info@mblock.com.tw
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Macroblock Preliminary Datasheet MBI1008
LED Backlight Driver
Typical Application Circuit
General Description
MBI1008 is a CMOS constant current driver
that
provides four regulated current sources.
It is
designed to drive LEDs with matched
currents
(within 5 %) to produce balanced light sources for
backlights.
MBI1008 is simple and easy to use. It accepts
an
input voltage range from 2.7V to 8V and maintains
a constant current determined
by an external
resistor, R1. Neither a capacitor, an inductor, nor
Schottky diode is needed. MBI1008
delivers up to
25mA of load current. In addition, customers
can
get very high efficiency (up t
o 92%) by well
matching V
LED
input supply voltage and LED
forward voltages, Vf.
MBI1008 features low cost, high efficiency, easy
to use, and space-saving 6-
pin SOT26 package
for applications that need uniform LEDs
illumination.
Features
n 4 constant-current output channels
n High efficiency, up to 92%
n Adjustable output current :15-25 mA
n Very small size – neither an inductor,
a capacitor nor Schottky diode is
needed.
n
Small
6
-
p
in SOT2
6
p
ackage
Application
s
n LED Backlight
n Cellular Phones
n PDAs
n Digital Cameras
n Portable MP3 Players
n Pagers
VLED
GND
RSET
5
6 4 3 1
OUT0 OUT1 OUT2 OUT3
IOUT
R1
3.8 K
2
VOUT
ISET
4.5V
※Neither a capacitor, an inductor
nor Schottky diode is needed.
MBI1008
February, 2003, V1.2
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LED Backlight Driver
Pin Description
Electrical Characteristics
(Ta = 25°C, unless otherwise noted)
PARAMETER SYMBOL
CONDITIONS MIN TYP MAX UNITS
Output Voltage V
OUT Current matching between
any two outputs less than 5
%
0.5 - 1.6 V
IOUT = 15mA - 1.11 -
IOUT = 20mA - 1.17 -
RSET Pin Voltage VRSET
IOUT = 25mA - 1.22 -
V
Output Current I
OUT Input Voltage VLED = 4.5V,
R1= 3.8KΩ
19.5 20.0 20.5 mA
Efficiency η Input Voltage VLED = 7.8V,
VOUT = 0.6V
- 92 - %
Output Current
vs.Temperature
Variation
I
OUT = 20 mA 0.0625
mA/°C
Absolute Maximum Ratings
VOUT Voltage ...................................................... 8V
VRSET Voltage .................................................... 8V
ILED Current ................................................. 60 mA
Junction Temperature ................................. 125°C
Operating Temperature Range ...... –20°C to 85°C
Storage Temperature Range ....... –65°C to 150°C
Package/Order Information
ORDER PART
NUMBER
MBI1008
PACKAGE
6-LEAD SOT26
OUT3
1
2
3
4
5
6
GND
OUT2
OUT1
R
SET
OUT0
1008
ZXX
OUT3 (P
in 1):
Current output Pin. LED’s cathode
is connected to it.
GND (Pin 2): Ground Pin. Tie this pin directly to
local ground plane.
OUT2 (Pin 3): Current output Pin. LED’s cathode
is connected to it.
OUT1 (Pin 4):
Current output Pin. LED’s cathode
is connected to it.
RSET (Pin 5): A resistor between this pin and VLED
regulates the LED current flowing into the LED pin.
This pin is also used to provide LED dimming.
OUT0 (Pin 6): Current output Pin. LED’s cathode
is connected to it.
MBI1008
February, 2003, V1.2
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LED Backlight Driver
Typical Operating Characteristics
12.5
15
17.5
20
22.5
25
27.5
0.30.50.70.91.11.31.5
OUT0
OUT1
OUT2
OUT3
I
OUT
vs. V
OUT
IOUT (mA)
V
OUT
(V)
Fig. 1 (@ VLED = 7.5V, Ta = 25°C)
0
10
20
30
40
50
345678910111213
R1 (Kohm)
IOUT (mA)
I
OUT
vs. R1
GND
2
R
SET
5
6 4 3 1
OUT0 OUT1 OUT2 OUT3
V
LED
7.5V
R1
7K
V
OUT
I
OUT
Test Circuit for IOUT vs. VOUT
GND
2
R
SET
5
6 4 3 1
OUT0 OUT1 OUT2 OUT3
I
OUT
R1
VOUT
1V
Test Circuit for IOUT vs. R1
V
LED
7.5V
Fig. 2 (@ VLED = 7.5V, Ta = 25°C)
MBI1008
February, 2003, V1.2
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LED Backlight Driver
12.5
15
17.5
20
22.5
25
27.5
0.30.50.70.91.11.31.5
OUT0
OUT1
OUT2
OUT3
IOUT (mA)
V
OUT
(V)
I
OUT
vs. V
OUT
Fig. 3 (@ VLED = 4V, Ta = 25°C)
0
10
20
30
40
50
60
11.522.533.544.555.566.57
I
OUT
(mA)
R1
(Kohm)
I
OUT
vs. R1
GND
2
R
SET
5
6 4 3 1
OUT0 OUT1 OUT2 OUT3
I
OUT
R1
VOUT
1V
Test Circuit for IOUT vs. R1
V
LED
4V
Fig. 4 (@ VLED = 4V, Ta = 25°C)
GND
2
R
SET
5
6 4 3 1
OUT0 OUT1 OUT2 OUT3
V
LED
4V
R1
3.2K
V
OUT
I
OUT
Test Circuit for IOUT vs. VOUT
MBI1008
February, 2003, V1.2
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LED Backlight Driver
Application Information
Resistor Selection
R1 is used to regulate the LED current. For the best accuracy, a resistor with ±1% precision
should be used.
Regulating Output Current
LED current is regulated by a single resistor connected to the R
SET pin (see Typical
Application Circuits). The voltage of RSET pin, VRSET, is internally regulated to around 1.17V,
which sets the current, I
SET, flowing into this pin to equal to (VLED –VRSET) / R1. MBI1008
regulates the current into the LED pin, IOUT, to 22.85 times the value of ISET. A typical operating
characteristic of I
OUT vs. R1 is shown (see Fig. 2). For other LED current values, use the
following equation to choose R1.
IOUT ≈ 22.85 x (VLED – VRSET) / R1
Efficiency Consideration
Except the output driver stage, the control parts of MBI1008 consume very little power (typical
value ≤ 8 mW). According to Fig. 1 and Fig. 5 (IOUT vs. VOUT), when VOUT is between 0.5V to
1.6V, the variations of I
OUT would be within 5﹪. Moreover, V
OUT = V
LED - Vf , and thus V
LED
should be high enough to let V
OUT be between 0.5V to 1.6V. On the other hand, the power
efficiency can be estimated as (VLED - VOUT) / VLED; thus ensuring to get higher efficiency, VLED
should be as low as possible.
The following example shows how to achieve high power efficiency. (see Fig. 5).
For white LEDs, the forward voltage, Vf, ranges from 3.0V to 4.0V.
If Vf1 + Vf2 = 7.2 V
V
LED = Vf1 + Vf2 + VOUT = 7.8V, (let VOUT = 0.6V)
then Efficiency = (VLED - VOUT) / VLED = 7.2V / 7.8V = 92.3%
Therefore, a proper design of V
LED is strongly recommended in order to always let VOUT be its
minimum specification value, 0.6V, that is the key to get the high efficiency.
GND
2
RSET
5
6 4 3 1
OUT0 OUT1 OUT2 OUT3
V
LED
I OUT
R1
Vf1
Vf2
VOUT
Fig. 5
MBI1008
February, 2003, V1.2
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LED Backlight Driver
Outline Drawings
Dimension In Millimeters
Symbol Min. Nom. Max.
A 1.00 1.10 1.30
A1 0.00 --- 0.10
A2 0.70 0.80 0.90
b 0.35 0.40 0.50
C 0.10 0.15 0.25
D 2.70 2.90 3.10
E 1.40 1.60 1.80
e --- 1.90 (typ.) ---
H 2.60 2.80 3.00
L 0.37 --- ---
Θ1 1° 5° 9°
NOTE
1. PACKAGE BODY SIZES EXCLUDE MOLD FLASH PROTRUSIONS
OR GATE BURRS
2. TOLERANCE ± 0.1000 mm (4mil) UNLESS OTHERWISE SPECIFIED
3. COPLANARITY: 0.1000 mm
4. DIMENSION L IS MEASURED IN GAGE PLANE
