- 您现在的位置：买卖IC网 > PDF目录20516 > 750105 (Wurth Electronics Inc)BOARD EVAL FOR LT3574 PDF资料下载
参数资料
| 型号： | 750105 |
| 厂商： | Wurth Electronics Inc |
| 文件页数： | 8/24页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR LT3574 |
| 标准包装： | 1 |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，隔离 |
| 功率 - 输出： | 2.5W |
| 输出电压： | 5V |
| 电流 - 输出： | 500mA（最小值） |
| 输入电压： | 10 ~ 30 V |
| 稳压器拓扑结构： | 回扫 |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | LT3574 |
| 其它名称： | 732-3309 |
LT3574
APPLICATIONS INFORMATION
? ? V F ? I SEC ( ES R )
V OUT = V BG ?
A ? FLBK ? =
? V ? V BG
= V BG ?
? R FB ? ? 1 ?
? R REF ? ? ? ? A ? ?
= ? FB ? ?
D V F R 1 D V TC
? R FB 1 D V TC R FB
D V F / D T
D T
? ? V F
? R FB ? ? 1 ?
V OUT BG ?
? ? ? N
? R REF PS A ?
? ? TC ? ? – I SEC ( ESR )
ERRORAMPLIFIER—PSEUDODCTHEORY
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 LT3574 operates much the same way
as traditional current mode switchers, the major difference
being a different type of error amplifier which derives its
feedback information from the flyback pulse.
Operation is as follows: when the output switch, Q1, turns
off, its collector voltage rises above the V IN rail. The am-
plitude of this flyback 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 flyback voltage is then converted to a current by
the action of R FB and Q2. Nearly all of this current flows
through resistor R REF to form a ground-referred voltage.
This voltage is fed into the flyback error amplifier. The
flyback error amplifier samples this output voltage infor-
mation when the secondary side winding current is zero.
The error amplifier 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:
or ,
? R FB ? R REF
V FLBK
A = Ratio of Q1 I C to I E , typically ≈ 0.986
V BG = Internal bandgap reference
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:
? R FB ? ? 1 ?
? ?
? R REF ? ? A N 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 first term in the V OUT equation does not have a tem-
perature dependence, but the diode forward drop has a
significant negative temperature coefficient. To compen-
sate for this, a positive temperature coefficient current
source is connected to the R REF pin. The current is set by
a resistor to ground connected to the T C pin. To cancel the
temperature coefficient, the following equation is used:
or ,
D T R TC N PS D T
R TC = ? ? ≈
N PS N PS
( D V F / D T ) = Diode’s forward voltage temperature
coefficient
( D V TC / D T) = 2mV
V TC = 0.55V
The resistor value given by this equation should also be
verified experimentally, and adjusted if necessary to achieve
optimal regulation over temperature.
The revised output voltage is as follows:
= V
?
? V ? R FB
? R TC ? N PS A
3574f
相关PDF资料 |
PDF描述 |
|---|---|
| 396-062-540-804 | CARD EDGE 62POS DL .125X.250 BLK |
| BAV99WT1 | DIODE SWITCH SS DUAL 70V SOT323 |
| 396-062-540-802 | CARD EDGE 62POS DL .125X.250 BLK |
| BAV99RWT1 | DIODE SWITCH SS DUAL 70V SOT323 |
| 396-062-540-204 | CARD EDGE 62POS DL .125X.250 BLK |
相关代理商/技术参数 |
参数描述 |
|---|---|
| 75010531 | 制造商:PHILIPS 功能描述:STARTER FLUORESCENT TUBE 70-125W 制造商:Philco/Philips 功能描述:STARTER, FLUORESCENT TUBE, 70-125W 制造商:NXP Semiconductors 功能描述:STARTER, FLUORESCENT TUBE, 70-125W; Accessory Type:Starter; For Use With:Fluorescent; SVHC:No SVHC (18-Jun-2012); Power Rating:125W; Supply Voltage:240V ;RoHS Compliant: Yes |
| 750-105-R220/270 | 制造商:CTS Corporation 功能描述: |
| 750-105-R220/330 | 制造商: 功能描述: 制造商:undefined 功能描述: 制造商:CTS Corporation 功能描述:S10-R220/330 |
| 750106 | 功能描述:BOARD EVAL FOR LT3575 RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:- 标准包装:1 系列:- 主要目的:DC/DC，步降 输出及类型:1，非隔离 功率 - 输出:- 输出电压:3.3V 电流 - 输出:3A 输入电压:4.5 V ~ 28 V 稳压器拓扑结构:降压 频率 - 开关:250kHz 板类型:完全填充 已供物品:板 已用 IC / 零件:L7981 其它名称:497-12113STEVAL-ISA094V1-ND |
| 750-106 | 制造商:GLENAIR 制造商全称:Glenair, Inc. 功能描述:Pre-Terminated Assemblies |
发布紧急采购，3分钟左右您将得到回复。