参数资料
型号: LT3471EDD#TRPBF
厂商: Linear Technology
文件页数: 10/16页
文件大小: 0K
描述: IC REG MULTI CONFIG ADJ DL 10DFN
标准包装: 2,500
类型: 升压(升压),反相,回扫,Sepic
输出类型: 可调式
输出数: 2
输出电压: 1 V ~ 40 V
输入电压: 2.4 V ~ 16 V
PWM 型: 电流模式
频率 - 开关: 1.2MHz
电流 - 输出: 1.3A
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: 10-WFDFN 裸露焊盘
包装: 带卷 (TR)
供应商设备封装: 10-DFN(3x3)
LT3471
APPLICATIONS INFORMATION
DIODE SELECTION
A Schottky diode is recommended for use with the
LT3471. For high ef ?ciency, a diode with good thermal
characteristics at high currents should be used such as
the On Semiconductor MBRM120. This is a 20V diode.
Where the switch voltage exceeds 20V, use the MBRM140,
a 40V diode. These diodes are rated to handle an average
forward current of 1.0A. In applications where the average
forward current of the diode is less than 0.5A, use the
Philips PMEG 2005, 3005, or 4005 (a 20V, 30V or 40V
diode, respectively).
LAYOUT HINTS
The high speed operation of the LT3471 demands care-
ful attention to board layout. You will not get advertised
performance with careless layout. Figure 5 shows the
recommended component placement.
Compensation—Theory
Like all other current mode switching regulators, the
LT3471 needs to be compensated for stable and ef ?cient
operation. Two feedback loops are used in the LT3471: a
fast current loop which does not require compensation,
and a slower voltage loop which does. Standard Bode
plot analysis can be used to understand and adjust the
voltage feedback loop.
As with any feedback loop, identifying the gain and phase
contribution of the various elements in the loop is critical.
Figure 6 shows the key equivalent elements of a boost con-
verter. Because of the fast current control loop, the power
stage of the IC, inductor and diode have been replaced by
the equivalent transconductance ampli?er g mp . g mp acts as
a current source where the output current is proportional
to the V C voltage. Note that the maximum output current
of g mp is ?nite due to the current limit in the IC.
CONTROL 1
C SS1
C SS2
CONTROL 2
GND
R SS1
GND
R SS2
GND
g mp
V OUT
C4
C PL
R ESR
R L
V OUT1 D1
L1
V CC
C1
?
L2
C5
V OUT2
L3
?
V C
R C
C C
R O
g ma
+
1.00V
REFERENCE
R1
R2
C OUT
SW1
SW2
3471 F06
C3
10
9
SHDN /SS1
8
7
SHDN /SS2
6
D2
C C : COMPENSATION CAPACITOR
C OUT : OUTPUT CAPACITOR
C PL : PHASE LEAD CAPACITOR
GND
LT3471
PIN 11 GND
GND
g ma : TRANSCONDUCTANCE AMPLIFIER INSIDE IC
g mp : POWER STAGE TRANSCONDUCTANCE AMPLIFIER
R C : COMPENSATION RESISTOR
R L : OUTPUT RESISTANCE DEFINED AS V OUT DIVIDED BY I LOAD(MAX)
R O : OUTPUT RESISTANCE OF g ma
R1, R2: FEEDBACK RESISTOR DIVIDER NETWORK
R ESR : OUTPUT CAPACITOR ESR
R4
FB1N
1
R3
FB1P
2
V REF
3
R2
FB2P
4
R1
FB2N
5
Figure 6. Boost Converter Equivalent Model
V OUT1
V OUT2
C2
3471 F05
Figure 5. Suggested Layout Showing a Boost on SW1 and
an Inverter on SW2. Note the Separate Ground Returns for
All High Current Paths (Using a Multilayer Board)
3471fb
10
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