EL7513IY Intersil, EL7513IY Datasheet - Page 9

• Manufacturer Part Number: EL7513IY
• Description: IC LED DRIVR WHITE BCKLGT 8-MSOP
• Manufacturer: Intersil
• Type: Backlight, White LEDr

Specifications of EL7513IY

• Constant Current: Yes
• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 800kHz ~ 1.2MHz
• Voltage - Supply: 2.6 V ~ 13.2 V
• Voltage - Output: 18V
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 75mA
• Internal Switch(s): Yes
• Efficiency: 91%
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Waveforms
All performance curves and waveforms are taken with C
series; unless otherwise specified.
Detailed Description
The EL7513 is a constant current boost regulator specially
designed for driving white LEDs. It can drive up to 4 LEDs in
series or 12 LEDs in parallel/series configuration and
achieves efficiency up to 91%.
The brightness of the LEDs is adjusted through a voltage
level on the CNTL pin. When the level falls below 0.1V, the
chip goes into shut-down mode and consumes less than
1µA of current for V
Steady-State Operation
EL7513 is operated in constant frequency PWM. The
switching is around 1MHz. Depending on the input voltage,
the inductance, the type of LEDs driven, and the LED’s
current, the converter operates at either continuous
conduction mode or discontinuous conduction mode (see
waveforms). Both are normal.
Brightness Control
LED’s current is controlled by the voltage level on CNTL pin
(V
with frequency less than 200Hz (for C
higher frequency PWM is used, an RC filter is recommended
before the CNTL pin (see Figure 20).
CNTL
ΔV
ΔV
V
LX
IN
I
O
FIGURE 18. DISCONTINUOUS CONDUCTION MODE
L
). This voltage can be either a DC or a PWM signal
V
CTRL
FIGURE 20. PWM BRIGHTNESS CONTROL
SIGNAL
= 0.34V, I
PWM
(Continued)
IN
LED
less than 5.5V.
0.1µF
100k
= 5mA
1µs/DIV
9
3
CNTL
COMP
= 4700pF). When a
1
10mV/DIV
100mA/DIV
10V/DIV
50mV/DIV
= 4.7µF, C
EL7513
2
= 1µF, C
The relationship between the LED current and CNTL voltage
level is as follows:
When R
15mA. The range of V
Shut-Down
When V
down mode. The max current consumed by the chip is less
than 1µA for V
Over-Voltage Protection
When an LED string is disconnected from the output, V
continue to rise because of no current feedback. When V
reaches 18V (nominal), the chip will shut down. The output
voltage will drop. When V
chip will boost output voltage again until it reaches 18V. This
hiccough continues until LED is applied or converter is shut
down.
When designing the converter, caution should be taken to
ensure the highest operating LED voltage does not exceed
17V, the minimum shut-down voltage. There is no external
component required for this function.
Component Selection
The input and output capacitors are not very important for
the converter to operate normally. The input capacitance
is normally 0.22µF - 4.7µF and output capacitance
0.22µF - 1µF. Higher capacitance is allowed to reduce the
voltage/current ripple, but at added cost. Use X5R or X7R
type (for its good temperature characteristics) of ceramic
capacitors with correct voltage rating and maximum height.
3
I
LED
FIGURE 19. OVER VOLTAGE PROTECTION (LED
= 0.1µF, L = 33µF, V
=
----------------------------
13.33 R
CNTL
1
V
is 5Ω, 1V of V
CNTL
×
DISCONNECTED)
is less than 100mV, the converter is in shut-
IN
1
less than 5.5V.
IN
CNTL
= 3.3V, V
CNTL
O
drops below 16V (nominal), the
is 250mV to 5.5V.
conveniently sets I
CNTL
= 1V, R
1
= 5Ω, 4 LEDs in a
V
V
December 22, 2008
O
COMP
LED
(5V/DIV)
(1V/DIV)
to
(EQ. 1)
FN7112.5
O
will
O