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| 型号： | LTC1735CGN#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 335kHz |
| 占空比： | 99.4% |
| 电源电压： | 4 V ~ 30 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | 0°C ~ 85°C |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
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LTC1735
OPERATIO
(Refer to Functional Diagram)
? 1 . 61 ( 10 7 ) ?
? Frequency ?
INTV CC /EXTV CC POWER
Power for the top and bottom MOSFET drivers and most
of the internal circuitry of the LTC1735 is derived from the
INTV CC pin. When the EXTV CC pin is left open, an internal
5.2V low dropout regulator supplies the INTV CC power
from V IN . If EXTV CC is raised above 4.7V, the internal
regulator is turned off and an internal switch connects
EXTV CC to INTV CC . This allows a high efficiency source,
such as the primary or a secondary output of the converter
itself, to provide the INTV CC power. Voltages up to 7V can
be applied to EXTV CC for additional gate drive capability.
APPLICATIO S I FOR ATIO
The basic LTC1735 application circuit is shown in Figure 1
on the first page. External component selection is driven
by the load requirement and begins with the selection of
R SENSE . Once R SENSE is known, C OSC and L can be chosen.
Next, the power MOSFETs and D1 are selected. The
operating frequency and the inductor are chosen based
largely on the desired amount of ripple current. Finally, C IN
is selected for its ability to handle the large RMS current
into the converter and C OUT is chosen with low enough
ESR to meet the output voltage ripple and transient speci-
fications. The circuit shown in Figure 1 can be configured
for operation up to an input voltage of 28V (limited by the
external MOSFETs).
R SENSE Selection for Output Current
R SENSE is chosen based on the required output current.
The LTC1735 current comparator has a maximum thresh-
old of 75mV/R SENSE and an input common mode range of
SGND to 1.1(INTV CC ). The current comparator threshold
sets the peak of the inductor current, yielding a maximum
average output current I MAX equal to the peak value less
half the peak-to-peak ripple current, ? I L .
Allowing a margin for variations in the LTC1735 and
external component values yields:
To provide clean start-up and to protect the MOSFETs,
undervoltage lockout is used to keep both MOSFETs off
until the input voltage is above 3.5V.
PGOOD (LTC1735F Only)
A window comparator monitors the output voltage and its
open-drain output is pulled low when the divided down
output voltage is not within ± 7.5% of the reference voltage
of 0.8V.
C OSC Selection for Operating Frequency and
Synchronization
The choice of operating frequency and inductor value is a
trade-off between efficiency and component size. Low
frequency operation improves efficiency by reducing
MOSFET switching losses, both gate charge loss and
transition loss. However, lower frequency operation re-
quires more inductance for a given amount of ripple
current.
The LTC1735 uses a constant frequency architecture with
the frequency determined by an external oscillator capaci-
tor C OSC . Each time the topside MOSFET turns on, the
voltage on C OSC is reset to ground. During the on-time,
C OSC is charged by a fixed current. When the voltage on the
capacitor reaches 1.19V, C OSC is reset to ground. The
process then repeats.
The value of C OSC is calculated from the desired operating
frequency assuming no external clock input on the FCB
pin:
C OSC ( pF ) = ? ? – 11
? ?
A graph for selecting C OSC versus frequency is shown in
R SENSE =
50mV
I MAX
Figure 2. The maximum recommended switching fre-
quency is 550kHz .
1735fc
11
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1735CS | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC 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) |
| LTC1735CS#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LTC1735CS#TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC 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) |
| LTC1735CS#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC 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) |
| LTC1735CS-1 | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC 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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