FAN5330SX Fairchild Semiconductor, FAN5330SX Datasheet - Page 7

• Manufacturer Part Number: FAN5330SX
• Description: IC LED DRVR WHITE BCKLGT SOT23-5
• Manufacturer: Fairchild Semiconductor
• Type: Backlight, White LED (Serial Interface)r

Specifications of FAN5330SX

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: General Purpose
• Frequency: 1.5MHz
• Voltage - Supply: 1.8 V ~ 5.5 V
• Voltage - Output: 30V
• Mounting Type: Surface Mount
• Package / Case: SOT-23-5, SC-74A, SOT-25
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 35mA
• Internal Switch(s): Yes
• Efficiency: 88%
• Operating Supply Voltage: 1.8 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

FAN5330 Rev. 1.0.1
Inductor Selection
The inductor parameters directly related to device performances
are saturation current and dc resistance. The FAN5330 oper-
ates with a typical inductor value of 10µH. The lower the dc
resistance, the higher the efficiency. Usually a trade-off between
inductor size, cost and overall efficiency is needed to make the
optimum choice.
The inductor saturation current should be rated around 1.5A,
which is the threshold of the internal current limit circuit. This
limit is reached only during the start-up and with heavy load
condition; when this event occurs the converter can shift over in
discontinuous conduction mode due to the automatic turn-off of
the switching transistor, resulting in higher ripple and reduced
efficiency.
Some recommended inductors are suggested in the table
below:
Capacitors Selection
For best performance, low ESR input and output capacitors are
required. Ceramic capacitors of C
placed close to the IC pins, are required for optimum perfor-
mance. The capacitances (C
higher ripple is acceptable. The output capacitor voltage rating
should be according to the V
suggested in the table below
Diode Selection
The external diode used for rectification is usually a Schottky
diode. Its average forward current and reverse voltage maxi-
mum ratings should exceed the load current and the voltage at
the output of the converter respectively. A barrier Schottky diode
such as BAT54 is preferred, due to its lower reverse current over
the temperature range.
Care should be taken to avoid any short circuit of V
even with the IC disabled, since the diode can be instantly dam-
aged by the excessive current.
Inductor
Capacitor
Value
10µH
10µH
10µH
Value
0.47µF
4.7µF
Table 2: Recommended Capacitors
Table 1: Recommended Inductors
COOPER
Vendor
MURATA
TDK
Panasonic
Vendor
Murata
SLF6025&-100M1R0
OUT
OUT
LQH66SN100M01C
Part Number
) may be reduced to 0.1µF, if
IN
setting. Some capacitors are
SD414-100
= 4.7µF and C
GRM21BR61A475K
ECJ-3YB1E474K
Part Number
OUT
OUT
Small Size
Efficiency
Highest
Com-
ment
= 0.47µF
to GND,
7
Brightness Control
1. Dimming Using PWM Logic Signal
A PWM signal applied to SHDN Table 5 on page 7 can control
the LED’s brightness in direct dependence with the duty cycle.
The maximum frequency should not exceed 1kHz to ensure a
linear dependence of the LED’s average current. The amplitude
of the PWM signal should be suitable to turn the FAN5333 ON
and OFF.
Alternatively, a PWM logic signal can be used to switch a FET
ON/OFF to change the resistance that sets the LED’s current
Table 6 on page 7. Adjusting the duty cycle from 0% to 100%
results in varying the LED’s current between I
Where
2. Dimming Using DC Voltage
An external adjustable DC voltage Table 7 on page 7 between
0V to 2V can control the LED’s current from 15mA to 0mA,
respectively.
Figure 6. Dimming Using a PWM Logic Signal
Figure 5. Dimming Using a PWM Signal
Figure 7. Dimming Using DC Voltage
I
MIN
=
FAN5330
R
-------------
R
MIN
5
V
MIN
FB
FB
and I
FAN5330
R
1.6K
SET
SHDN
FAN5330
MAX
FB
=
------------------------------- -
R
90K
MIN
V
V
DC
MIN
FB
R
SET
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and I
MAX
.