參數(shù)資料
型號(hào)： LT1725IGN
廠商： LINEAR TECHNOLOGY CORP
元件分類： 穩(wěn)壓器
英文描述： General Purpose Isolated Flyback Controller
中文描述： SWITCHING CONTROLLER, 125 kHz SWITCHING FREQ-MAX, PDSO16
封裝： 0.150 INCH, PLASTIC, SSOP-16
文件頁數(shù)： 20/28頁
文件大?。?/td> 241K
代理商： LT1725IGN
20
LT1725
1725f
APPLICATIOU
MAXIMUM LOAD/SHORT-CIRCUIT CONSIDERATIONS
The LT1725 is a current mode controller. It uses the V
C
node voltage as an input to a current comparator which
turns off the output switch on a cycle-by-cycle basis as
this peak current is reached. The internal clamp on the V
C
node, nominally 2.5V, then acts as an output switch peak
current limit.
This 2.5V at the V
C
pin corresponds to a value of 250mV
at the I
SENSE
pin, when the (ON) switch duty cycle is less
than 40%. For a duty cycle above 40%, the internal slope
compensation mechanism lowers the effective I
SENSE
voltage limit. For example, at a duty cycle of 80%, the
nominal I
SENSE
voltage limit is 220mV. This action be-
comes the switch current limit specification. Maximum
available output power is then determined by the switch
current limit, which is somewhat duty cycle dependent
due to internal slope compensation action.
Overcurrent conditions are handled by the same mecha-
nism. The output switch turns on, the peak current is
quickly reached and the switch is turned off. Because the
output switch is only on for a small fraction of the available
period, power dissipation is controlled.
Loss of current limit is possible under certain conditions.
Remember that the LT1725 normally exhibits a minimum
switch on time, irrespective of current trip point. If the duty
cycle exhibited by this minimum on time is greater than the
ratio of secondary winding voltage (referred-to-primary)
divided by input voltage, then peak current will not be
controlled at the nominal value, and will cycle-by-cycle
ratchet up to some higher level. Expressed mathemati-
cally, the requirement to maintain short-circuit control is:
(
W
U
U
t
f
V
I
R
V
N
ON
F
SC
SEC
IN
SP
<
+
)
where
t
ON
= output switch minimum on time
f = switching frequency
I
SC
= short-circuit output current
V
F
= output diode forward voltage at I
SC
R
SEC
= resistance of transformer secondary
V
IN
= input voltage
N
SP
= secondary-to-primary turns ratio ( N
SEC
/N
PRI
)
Trouble is typically only encountered in applications with
a relatively high product of input voltage times secondary-
to-primary turns ratio and/or a relatively long minimum
switch on time. (Additionally, several real world effects such
as transformer leakage inductance, AC winding losses, and
output switch voltage drop combine to make this simple
theoretical calculation a conservative estimate.)
THERMAL CONSIDERATIONS
Care should be taken to ensure that the worst-case input
voltage condition does not cause excessive die tempera-
tures. The 16-lead SO package is rated at 100
°
C/W, and
the 16-lead GN at 110
°
C/W.
Average supply current is simply the sum of quiescent
current given in the specifications section plus gate drive
current. Gate drive current can be computed as:
I
G
= f Q
G
where
Q
G
= total gate charge
f = switching frequency
(Note: Total gate charge is more complicated than C
GS
V
G
as it is frequently dominated by Miller effect of the C
GD
.
Furthermore, both capacitances are nonlinear in practice.
Fortunately, most MOSFET data sheets provide figures
and graphs which yield the total gate charge directly per
operating conditions.) Nearly all gate drive power is dissi-
pated in the IC, except for a small amount in the external
gate series resistor, so total IC dissipation may be com-
puted as:
P
D(TOTAL)
= V
CC
(I
Q
+ f Q
G
), where
I
Q
= quiescent current (from specifications)
Q
G
= total gate charge
f = switching frequency
V
CC
= LT1725 supply voltage
相關(guān)PDF資料
PDF描述
LT1725IS General Purpose Isolated Flyback Controller
LT1725 Monolithic Switching Regulator for Isolated Flyback Controller(單片開關(guān)穩(wěn)壓器(用于隔離回掃控制器))
LT1737CS High Power Isolated Flyback Controller
LT1737IS High Power Isolated Flyback Controller
LT1737CGN High Power Isolated Flyback Controller
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LT1725IGN#PBF 功能描述:IC REG CTRLR FLYBK ISO CM 16SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
LT1725IGN#TR 功能描述:IC REG CTRLR FLYBK ISO CM 16SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
LT1725IGN#TRPBF 功能描述:IC REG CTRLR FLYBK ISO CM 16SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
LT1725IS 功能描述:IC REG CTRLR FLYBK ISO CM 16SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
LT1725IS#PBF 功能描述:IC REG CTRLR FLYBK ISO CM 16SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*