参数资料
型号: LT1941EFE#PBF
厂商: Linear Technology
文件页数: 10/24页
文件大小: 0K
描述: IC REG MULTI CONFIG TRPL 28TSSOP
标准包装: 50
类型: 降压(降压),升压(升压),反相,Sepic
输出类型: 可调式
输出数: 3
输出电压: 1.25 V ~ 40 V
输入电压: 3.5 V ~ 25 V
PWM 型: 电流模式
频率 - 开关: 1.1MHz
电流 - 输出: 3A
同步整流器:
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 28-SOIC(0.173",4.40mm 宽)裸露焊盘
包装: 管件
供应商设备封装: 28-TSSOP 裸露焊盘
LT1941
APPLICATIONS INFORMATION
STEP-DOWN CONSIDERATIONS
FB Resistor Network
The output voltage is programmed with a resistor divider
(refer to the Block Diagram) between the output and the
FB pin. Choose the resistors according to
R1 = R2(V OUT /628mV – 1)
R2 should be 10k or less to avoid bias current errors.
where V F is the voltage drop of the catch diode (~0.4V) and
L is in μH. With this value the maximum load current will
be 2.1A for SW1 and 1.4A for SW2, independent of input
voltage. The inductor’s RMS current rating must be greater
than the maximum load current and its saturation current
should be at least 30% higher. For highest ef?ciency, the
series resistance (DCR) should be less than 0.1Ω. Table 1
lists several vendors and types that are suitable.
Table 1. Inductors
Input Voltage Range
PART NUMBER
VALUE
(μH)
I SAT
(A)
DCR
(Ω)
HEIGHT
(mm)
The minimum operating voltage is determined either by the
Sumida
LT1941’s undervoltage lockout of ~3.3V or by its maximum
duty cycle. The duty cycle is the fraction of time that the
internal switch is on and is determined by the input and
output voltages:
DC = (V OUT + V F )/(V IN – V SW + V F )
where V F is the forward voltage drop of the catch diode
(~0.4V) and V SW is the voltage drop of the internal switch
(~0.3V at maximum load). This leads to a minimum input
voltage of:
V IN(MIN) = (V OUT + V F )/DC MAX – V F + V SW
with DC MAX = 0.78.
The maximum operating voltage is determined by the
absolute maximum ratings of the V IN and BOOST pins
and by the minimum duty cycle DC MIN = 0.15:
V IN(MAX) = (V OUT + V F )/DC MIN – V F + V SW
This limits the maximum input voltage to ~14V with
V OUT = 1.8V and ~19V with V OUT = 2.5. Note that this is
a restriction on the operating input voltage; the circuit
will tolerate input voltage transients up to the Absolute
CR43-1R4
CR43-2R2
CDRH3D16-1R5
CDRH4D28-3R3
CDRH4D18-1R0
CDC5D23-2R2
CDRH5D28-2R6
Coilcraft
DO1606T-152
DO1606T-222
DO1608C-152
DO1608C-222
DO1608C-332
DO1608C-472
MOS6020-222
MOS6020-332
MOS6020-472
DO3314-222
Toko
(D62F)847FY-2R4M
(D73LF)817FY-2R2M
1.4
2.2
1.5
3.3
1.0
2.2
2.6
1.5
2.2
1.5
2.2
3.3
4.7
2.2
3.3
4.7
2.2
2.4
2.2
2.52
1.75
1.55
1.57
1.70
2.50
2.60
2.10
1.70
2.60
2.30
2.00
1.50
2.15
1.8
1.5
1.6
2.5
2.7
0.056
0.071
0.040
0.049
0.035
0.03
0.013
0.060
0.070
0.050
0.070
0.080
0.090
0.035
0.046
0.050
0.200
0.037
0.03
3.5
3.5
1.8
3.0
2.0
2.5
3.0
2.0
2.0
2.9
2.9
2.9
2.9
2.0
2.0
2.0
1.4
2.7
3.0
Maximum Rating.
Inductor Selection and Maximum Output Current
A good ?rst choice for the inductor value is
The optimum inductor for a given application may differ
from the one indicated by this simple design guide. A
larger value inductor provides a slightly higher maximum
load current and will reduce the output voltage ripple. If
L = (V OUT + V F )/1.6 for SW1
L = (V OUT + V F )/1.1 for SW2
1941fb
10
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