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参数资料
| 型号： | LT1725CGN#TR |
| 厂商： | Linear Technology |
| 文件页数： | 17/28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： | 0°C ~ 100°C |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 相关产品： | 732-2262-6-ND - TRANS FLYBACK LT1725 20.4UH 732-2262-1-ND - TRANS FLYBACK LT1725 20.4UH 732-2262-2-ND - TRANS FLYBACK LT1725 20.4UH |
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LT1725
APPLICATIO S I FOR ATIO
V IN
R1/2
V IN
V IN
R1
UVLO
R1
UVLO
C2
R1/2
UVLO
R2
C1
100pF
R2
C1
100pF
R2
1725 F06
(6a) “Standard” UVLO
Divider Topology
(6b) Filter Capacitor
Directly On UVLO Node
Figure 6
(6c) Recommended Topology to
Filter High Frequency Ripple
speed supply ripple, while leaving the UVLO pin node
impedance relatively unchanged at high frequency.
V IN
R1
INTERNAL WIDE HYSTERESIS
UNDERVOLTAGE LOCKOUT
The LT1725 is designed to implement isolated DC/DC
converters operating from input voltages of typically 48V
+
C1
PGND
I VCC
V CC
LT1725 GATE
SGND
V IN
or more. The standard operating topology utilizes a third
transformer winding on the primary side that provides
both feedback information and local power for the LT1725
via its V CC pin. However, this arrangement is not inherently
self-starting. Start-up is effected by the use of an external
“trickle-charge” resistor and the presence of an internal
wide hysteresis undervoltage lockout circuit that monitors
V CC pin voltage (see Figure 7). Operation is as follows:
“Trickle charge” resistor R1 is connected to V IN and
supplies a small current, typically on the order of a single
mA, to charge C1. At first, the LT1725 is off and draws only
its start-up current. After some time, the voltage on C1
(V CC ) reaches the V CC turn-on threshold. The LT1725 then
turns on abruptly and draws its normal supply current.
Switching action commences at the GATE pin and the
MOSFET begins to deliver power. The voltage on C1
begins to decline as the LT1725 draws its normal supply
current, which greatly exceeds that delivered by R1. After
some time, typically tens of milliseconds, the output
voltage approaches its desired value. By this time, the
third transformer winding is providing virtually all the
supply current required by the LT1725.
One potential design pitfall is undersizing the value of
capacitor C1. In this case, the normal supply current
1725 F07
V ON THRESHOLD
V VCC
I VCC
0
V GATE
Figure 7
drawn by the LT1725 will discharge C1 too rapidly; before
the third winding drive becomes effective, the V CC turn-off
threshold will be reached. The LT1725 turns off, and the
V CC node begins to charge via R1 back up to the turn-on
threshold. Depending upon the particular situation, this
may result in either several on-off cycles before proper
operation is reached, or, permanent relaxation oscillation
at the V CC node.
Component selection is as follows:
Resistor R1 should be selected to yield a worst-case
minimum charging current greater than the maximum
rated LT1725 start-up current, and a worst-case maxi-
mum charging current less than the minimum rated
LT1725 supply current.
1725fa
17
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1725CS | 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) |
| LT1725CS#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) |
| LT1725CS#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) |
| LT1725CS#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) |
| LT1725IGN | 功能描述:IC REG CTRLR FLYBK ISO CM 16SSOP 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) |
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