- 您现在的位置：买卖IC网 > PDF目录15307 > LT1725IGN#TRPBF (Linear Technology)IC REG CTRLR FLYBK ISO CM 16SSOP PDF资料下载
参数资料
| 型号： | LT1725IGN#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 18/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBK ISO CM 16SSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 125kHz |
| 占空比： | 90% |
| 电源电压： | 最高 22V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页当前第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页
LT1725
APPLICATIO S I FOR ATIO
Capacitor C1 should then be made large enough to avoid
the relaxation oscillatory behavior described above. This
is complicated to determine theoretically as it depends on
the particulars of the secondary circuit and load behavior.
Empirical testing is recommended. (Use of the optional
soft-start function will lengthen the power-up timing and
require a correspondingly larger value for C1.)
A further note—certain users may wish to utilize the
general functionality of the LT1725, but may have an
available input voltage significantly lower than, say, 48V.
If this input voltage is within the allowable V CC range, i.e.,
perhaps 20V maximum, the internal wide hysteresis range
UVLO function becomes counterproductive. In such cases
it is simply better to operate the LT1725 directly from the
available DC input supply. The LT1737 is identical to the
LT1725, with the exception that it lacks the internal wide
hysteresis UVLO function. It is therefore designed to
operate directly from DC input supplies in the range of
4.5V to 20V. See the LT1737 data sheet for further
information.
FREQUENCY COMPENSATION
Loop frequency compensation is performed by connect-
ing a capacitor from the output of the error amplifier (V C
pin) to ground. An additional series resistor, often re-
quired in traditional current mode switcher controllers, is
usually not required and can even prove detrimental. The
phase margin improvement traditionally offered by this
extra resistor will usually be already accomplished by the
nonzero secondary circuit impedance, which adds a “zero”
to the loop response.
In further contrast to traditional current mode switchers,
V C pin ripple is generally not an issue with the LT1725. The
dynamic nature of the clamped feedback amplifier forms
an effective track/hold type response, whereby the V C
voltage changes during the flyback pulse, but is then “held”
during the subsequent “switch on” portion of the next
cycle. This action naturally holds the V C voltage stable
during the current comparator sense action (current mode
switching).
OUTPUT VOLTAGE ERROR SOURCES
Conventional nonisolated switching power supply ICs
typically have only two substantial sources of output
voltage error: the internal or external resistor divider
network that connects to V OUT and the internal IC refer-
ence. The LT1725, which senses the output voltage in both
a dynamic and an isolated manner, exhibits additional
potential error sources to contend with. Some of these
errors are proportional to output voltage, others are fixed
in an absolute millivolt sense. Here is a list of possible
error sources and their effective contribution.
Internal Voltage Reference
The internal bandgap voltage reference is, of course,
imperfect. Its error, both at 25 ° C and over temperature is
already included in the specifications.
User Programming Resistors
Output voltage is controlled by the user-supplied feedback
resistor divider ratio. To the extent that the resistor ratio
differs from the ideal value, the output voltage will be
proportionally affected. Highest accuracy systems will
demand 1% components.
Schottky Diode Drop
The LT1725 senses the output voltage from the trans-
former primary side during the flyback portion of the cycle.
This sensed voltage therefore includes the forward drop,
V F , of the rectifier (usually a Schottky diode). The nominal
V F of this diode should therefore be included in feedback
resistor divider calculations. Lot to lot and ambient tem-
perature variations will show up as output voltage shift/
drift.
Secondary Leakage Inductance
Leakage inductance on the transformer secondary re-
duces the effective secondary-to-third winding turns ratio
(N S /N T ) from its ideal value. This will increase the output
voltage target by a similar percentage. To the extent that
secondary leakage inductance is constant from part to
part, this can be accommodated by adjusting the feedback
resistor ratio.
1725fa
18
相关PDF资料 |
PDF描述 |
|---|---|
| LT1737IGN#TRPBF | IC REG CTRLR FLYBK ISO CM 16SSOP |
| UCY2G220MPD | CAP ALUM 22UF 400V 20% RADIAL |
| LTC3778EF#TRPBF | IC REG CTRLR BUCK PWM CM 20TSSOP |
| URS2A331MHD | CAP ALUM 330UF 100V 20% RADIAL |
| SEK330M250ST | CAP ALUM 33UF 250V 20% RADIAL |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1725IS | 功能描述:IC REG CTRLR FLYBK ISO CM 16SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LT1725IS#PBF | 功能描述:IC REG CTRLR FLYBK ISO CM 16SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LT1725IS#TR | 功能描述:IC REG CTRLR FLYBK ISO CM 16SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LT1725IS#TRPBF | 功能描述:IC REG CTRLR FLYBK ISO CM 16SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LT1737 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Power Isolated Flyback Controller |
发布紧急采购，3分钟左右您将得到回复。