参数资料
型号: LT1913IDD#PBF
厂商: Linear Technology
文件页数: 11/24页
文件大小: 0K
描述: IC REG BUCK ADJ 3.5A 10DFN
标准包装: 121
类型: 降压(降压)
输出类型: 可调式
输出数: 1
输出电压: 0.79 V ~ 25 V
输入电压: 3.6 V ~ 25 V
PWM 型: 电流模式
频率 - 开关: 200kHz ~ 2.4MHz
电流 - 输出: 3.5A
同步整流器:
工作温度: -40°C ~ 125°C
安装类型: 表面贴装
封装/外壳: 10-WFDFN 裸露焊盘
包装: 管件
供应商设备封装: 10-DFN(3x3)
LT1913
APPLICATIONS INFORMATION
operating input voltage. Conversely, a lower switching
frequency will be necessary to achieve safe operation at
high input voltages.
If the output is in regulation and no short-circuit, start-
up, or overload events are expected, then input voltage
transients of up to 25V are acceptable regardless of the
switching frequency. In this mode, the LT1913 may enter
pulse skipping operation where some switching pulses
are skipped to maintain output regulation. In this mode
the output voltage ripple and inductor current ripple will
be higher than in normal operation.
The minimum input voltage is determined by either the
ripple current. The LT1913’s switch current limit (I LIM ) is
5.5A at low duty cycles and decreases linearly to 4.5A at
DC = 0.8. The maximum output current is a function of
the inductor ripple current:
I OUT(MAX) = I LIM – Δ I L /2
Be sure to pick an inductor ripple current that provides
suf?cient maximum output current (I OUT(MAX) ).
The largest inductor ripple current occurs at the highest
V IN . To guarantee that the ripple current stays below the
speci?ed maximum, the inductor value should be chosen
according to the following equation:
LT1913’s minimum operating voltage of ~3.6V or by its
maximum duty cycle (see equation in previous section).
The minimum input voltage due to duty cycle is:
L =
V OUT + V D
f SW I L
1–
V OUT + V D
V IN(MAX)
V IN ( MIN ) =
V OUT + V D
1– f SW t OFF ( MIN )
– V D + V SW
where V D is the voltage drop of the catch diode (~0.4V),
V IN(MAX) is the maximum input voltage, V OUT is the output
voltage, f SW is the switching frequency (set by RT), and
where V IN(MIN) is the minimum input voltage, and t OFF(MIN)
is the minimum switch off time (150ns). Note that higher
switching frequency will increase the minimum input
voltage. If a lower dropout voltage is desired, a lower
switching frequency should be used.
Inductor Selection
For a given input and output voltage, the inductor value
L is in the inductor value.
The inductor’s RMS current rating must be greater than the
maximum load current and its saturation current should be
about 30% higher. To keep the ef?ciency high, the series
resistance (DCR) should be less than 0.05 , and the core
material should be intended for high frequency applications.
Table 1 lists several vendors and suitable types.
Table 1. Inductor Vendors
and switching frequency will determine the ripple current.
The ripple current Δ I L increases with higher V IN or V OUT
and decreases with higher inductance and faster switch-
ing frequency. A reasonable starting point for selecting
the ripple current is:
Δ I L = 0.4(I OUT(MAX) )
where I OUT(MAX) is the maximum output load current. To
guarantee suf?cient output current, peak inductor current
must be lower than the LT1913’s switch current limit (I LIM ).
VENDOR
Murata
TDK
Toko
Sumida
NEC
URL
www.murata.com
www.componenttdk.com
www.toko.com
www.sumida.com
www.nec.com
PART SERIES
LQH55D
SLF10145
D75C
D75F
CDRH74
CR75
CDRH8D43
MPLC073
MPBI0755
TYPE
Open
Shielded
Shielded
Open
Shielded
Open
Shielded
Shielded
Shielded
The peak inductor current is:
I L(PEAK) = I OUT(MAX) + Δ I L /2
where I L(PEAK) is the peak inductor current, I OUT(MAX) is
the maximum output load current, and Δ I L is the inductor
Of course, such a simple design guide will not always re-
sult in the optimum inductor for your application. A larger
value inductor provides a slightly higher maximum load
current and will reduce the output voltage ripple. If your
1913f
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