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| 型号： | LT3575EFE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 8/24页 |
| 文件大小： | 0K |
| 描述： | IC REG FLYBACK ISO ADJ 16TSSOP |
| 标准包装： | 95 |
| 类型： | 回扫，隔离 |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 可调至 60V |
| 输入电压： | 3 V ~ 40 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 1MHz |
| 电流 - 输出： | 2.5A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 16-TSSOP-EP |
| 配用： | 732-3306-ND - BOARD EVAL FOR LT3575 |
| 相关产品： | 732-2669-2-ND - TRANS FLYBACK LT3748 20UH SMD 732-2669-6-ND - TRANS FLYBACK LT3748 20UH SMD 732-2668-6-ND - TRANS FLYBACK LT3748 14UH SMD 732-2667-6-ND - TRANS FLYBACK LT3748 500UH SMD 732-2666-6-ND - TRANS FLYBACK LT3748 12UH SMD 732-2665-6-ND - TRANS FLYBACK LT3748 12UH SMD 732-2664-6-ND - TRANS FLYBACK LT3748 15UH SMD 732-2663-6-ND - TRANS FLYBACK LT3748 15UH SMD 732-2662-6-ND - TRANS FLYBACK LT3748 8UH SMD 732-2661-6-ND - TRANS FLYBACK LT3748 8UH SMD 更多... |
LT3575
APPLICATIONS INFORMATION
? R FB ? ? 1 ?
? ? V F SEC ( ES R )
V OUT BG ?
? ? ? α N
ERROR AMPLIFIER—PSEUDO DC THEORY
In the Block Diagram, the R REF (R4) and R FB (R3) resistors
can be found. They are external resistors used to program
the output voltage. The LT3575 operates much the same way
as traditional current mode switchers, the major difference
being a different type of error ampli?er which derives its
feedback information from the ?yback pulse.
Operation is as follows: when the output switch, Q1,
turns off, its collector voltage rises above the V IN rail. The
amplitude of this ?yback pulse, i.e., the difference between
it and V IN , is given as:
V FLBK = (V OUT + V F + I SEC ? ESR) ? N PS
V F = D1 forward voltage
I SEC = Transformer secondary current
ESR = Total impedance of secondary circuit
N PS = Transformer effective primary-to-secondary
turns ratio
The ?yback voltage is then converted to a current by
In combination with the previous V FLBK expression yields
an expression for V OUT , in terms of the internal reference,
programming resistors, transformer turns ratio and diode
forward voltage drop:
= V ? I
? R REF ? PS ?
Additionally, it includes the effect of nonzero secondary
output impedance (ESR). This term can be assumed to
be zero in boundary control mode. More details will be
discussed in the next section.
Temperature Compensation
The ?rst term in the V OUT equation does not have a tem-
perature dependence, but the diode forward drop has a
signi?cant negative temperature coef?cient. To compen-
sate for this, a positive temperature coef?cient current
source is connected to the R REF pin. The current is set by
a resistor to ground connected to the TC pin. To cancel the
temperature coef?cient, the following equation is used:
δ V F R FB
δ T
? R FB
δ V TC
δ V TC R FB
δ T
the action of R FB and Q2. Nearly all of this current ?ows
through resistor R REF to form a ground-referred voltage.
This voltage is fed into the ?yback error ampli?er. The
?yback error ampli?er samples this output voltage
information when the secondary side winding current is
=?
R TC
R TC =
N PS
?
1
? ?
N PS
1
δ V F / δ T
δ T
or ,
? ≈
N PS
zero. The error ampli?er uses a bandgap voltage, 1.23V,
as the reference voltage.
The relatively high gain in the overall loop will then cause
the voltage at the R REF resistor to be nearly equal to the
bandgap reference voltage V BG . The relationship between
V FLBK and V BG may then be expressed as:
( δ V F / δ T ) = Diode’s forward voltage temperature
coef?cient
( δ V TC / δ T) = 2mV
V TC = 0.55V
The resistor value given by this equation should also be
α ? FLBK ? =
? V ?
? R FB ?
V BG
R REF
or ,
veri?ed experimentally, and adjusted if necessary to achieve
optimal regulation overtemperature.
= V BG ?
? R FB ? ? 1 ?
? R REF ? ? ? ? α ? ?
? R FB ? ? 1 ?
? ? V F
V OUT BG ?
? ? ? N
? R REF ? PS α ?
? ? TC ? ? – I SEC ( ESR )
V FLBK
α = Ratio of Q1 I C to I E , typically ≈ 0.986
V BG = Internal bandgap reference
The revised output voltage is as follows:
= V
? V ? R FB
? R TC ? N PS α
3575f
8
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相关代理商/技术参数 |
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| LT3575IFE#PBF | 功能描述:IC REG FLYBACK ISO ADJ 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LT3575IFE#TRPBF | 功能描述:IC REG FLYBACK ISO ADJ 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT3579 | 制造商:LINER 制造商全称:Linear Technology 功能描述:6A Boost/Inverting DC/DC Converter with Fault Protection |
| LT3579-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:6A Boost/Inverting DC/DC Converter with Fault Protection |
| LT3579EFE#PBF | 功能描述:IC REG MULTI CONFIG SYNC 20TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
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