LT3513EUHF#PBF Linear Technology, LT3513EUHF#PBF Datasheet - Page 13

• Manufacturer Part Number: LT3513EUHF#PBF
• Description: IC REG 5-OUT FOR TFT-LCD 38QFN
• Manufacturer: Linear Technology

Specifications of LT3513EUHF#PBF

• Applications: Converter, TFT, LCD
• Voltage - Input: 4.5 ~ 30 V
• Number Of Outputs: 5
• Voltage - Output: 0.8 ~ 40 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 38-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

INDUCTOR SELECTION AND MAXIMUM OUTPUT
CURRENT
A good first choice for the inductor value is:
where V
and L is in µH. The inductor’s RMS current rating must be
greater than the maximum load current and its saturation
(~0.3V at maximum load). This leads to a minimum input
voltage of:
with DC
The user defined undervoltage is set by a resistor divider
connected to the UVLO pin. The comparator pulls 3µA
from the pin when the UVLO pin is higher than 1.25V.
The hysteresis and minimum input voltage equations are
as follows:
operaTion
L =
V
V
V
IN(MIN)
HYS
IN(MIN)
V
MAX
OUT
F
= R2 + 2k
is the voltage drop of the catch diode (~0.4V)
1.8
(
=
= 1.25V
= 0.75.
+ V
Dc
F
MAX
V
)
OUT
R1+ R2
• 3.9µA
V
– V
IN
R1
R2
R1
3513 A1
+ V
F
+ V
F
SW
UVLO
38
current should be at least 30% higher. For highest efficiency,
the series resistance (DCR) should be less than 0.1Ω.
Table 1 lists several vendors and types that are suitable.
Table 1. Inductor Vendors
The optimum inductor for a given application may differ
from the one indicated by this simple design guide. A larger
value inductor provides a higher maximum load current,
and reduces the output voltage ripple. If your load is lower
than the maximum load current, then you can relax the
value of the inductor and operate with higher ripple cur-
rent. This allows you to use a physically smaller inductor
or one with a lower DCR resulting in higher efficiency. Be
aware that the maximum load current depends on input
voltage. A graph in the Typical Performance Characteris-
tics section of this data sheet shows the maximum load
current as a function of input voltage and inductor value
for V
in discontinuous mode operation, which further reduces
maximum load current. For details of maximum output
current and discontinuous mode operation, see Linear
Technology’s Application Note 44. Finally, for duty cycles
greater than 50% (V
tance is required to avoid subharmonic oscillations, see
Application Note 19.
VENDOR
Coilcraft
Sumida
Murata
Toko
TDK
OUT
= 3.3V. In addition, low inductance may result
www.component.tdk.com
www.coilcraft.com
www.murata.com
www.sumida.com
www.toko.com
URL
OUT
/V
IN
> 0.5), a minimum induc-
PART SERIES
CDRH6D38
SLF10145
MSS7341
SLF7045
LQH55D
DC62CB
CDRH74
D63CB
D75C
CR54
CR75
D75F
LT3513
Shielded
Shielded
Shielded
Shielded
Shielded
Shielded
Shielded
Shielded
13
TYPE
Open
Open
Open
Open
3513fc