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| 型号： | LTC1735CS-1#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 16/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SOIC |
| 标准包装： | 50 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 335kHz |
| 占空比： | 99.4% |
| 电源电压： | 3.5 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-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
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LTC1735-1
APPLICATIO S I FOR ATIO
When adjusting the gate drive level, the final arbiter is the
total input current for the regulator. If you make a change
capacitor C SS. If RUN/SS has been pulled all the way to
ground there is a delay before starting of approximately:
and the input current decreases, then you improved the
efficiency. If there is no change in input current, then there
is no change in efficiency.
T DELAY =
1 . 5 V
1 . 2 μ A
C SS = ( 1 . 25 s / μ F ) C SS
SENSE + / SENSE – Pins
The common mode input range of the current comparator
is from 0V to 1.1(INTV CC ). Continuous linear operation is
guaranteed throughout this range allowing output volt-
ages anywhere from 0.8V to 7V. A differential NPN input
stage is used and is biased with internal resistors from an
internal 2.4V source as shown in the Functional Diagram.
This causes current either to be sourced or sunk by these
pins depending on the output voltage. If the output voltage
is below 2.4V, current will flow out of both SENSE pins to
the main output. This forces a minimum load current that
can be fulfilled by the V OUT resistive divider. The maxi-
mum current flowing out of the SENSE pins is:
I SENSE+ + I SENSE– = (2.4V – V OUT )/24k
When the voltage on RUN/SS reaches 1.5V the
LTC1735-1 begins operating with a current limit at ap-
proximately 25mV/R SENSE . As the voltage on RUN/SS
increases from 1.5V to 3V, the internal current limit is
increased from 25mV/R SENSE to 75mV/R SENSE . The out-
put current limit ramps up slowly, taking an additional
1.25s/ μ F to reach full current. Ramping the output cur-
rent slowly reduces the starting surge current
required from the input supply.
Diode D1 in Figure 4 and Figure 5 reduces the start delay
while allowing C SS to charge up slowly for the soft-start
function. This diode and C SS can be deleted if soft-start is
not needed. The RUN/SS pin has an internal 6V zener
clamp (see Functional Diagram).
3.3V OR 5V RUN/SS RUN/SS
Since V OSENSE is servoed to the 0.8V reference voltage, we
can choose R1 in Figure 3 to have a maximum value to
absorb this current:
D1
C SS
C SS
R 1 ( Max ) = 24 k ?
? 2 . 4 V – V OUT ?
? 0 . 8 V ?
?
Figure 4. RUN/SS Pin Interfacing
1735-1 F04
Regulating an output voltage of 1.8V, the maximum value
of R1 should be 32k. Note that for output voltages above
2.4V no maximum value of R1 is necessary to absorb the
3.3V OR 5V
D1
V IN
R SS
RUN/SS
INTV CC
R SS
D1
RUN/SS
sense currents; however, R1 is still bounded by the
V OSENSE feedback current.
Soft-Start/Run Function
C SS
C SS
The RUN/SS pin is a multipurpose pin that provides a soft-
(a)
(b)
1735-1 F05
start function and a means to shut down the LTC1735-1.
Soft-start reduces surge currents from V IN by gradually
increasing the controller’s current limit I TH(MAX) . This pin
can also be used for power supply sequencing.
Pulling the RUN/SS pin below 1.5V puts the LTC1735-1
into a low quiescent current shutdown (I Q < 25 μ A). This
pin can be driven directly from logic as shown in Figures
4 and 5. Releasing the RUN/SS pin allows an internal
1.2 μ A current source to charge up the external soft-start
16
Figure 5. RUN/SS Pin Interfacing with Latchoff Defeated
Fault Conditions: Overcurrent Latchoff
The RUN/SS pin also provides the ability to shut off the
controller and latchoff when an overcurrent condition is
detected. The RUN/SS capacitor C SS is used initially to
turn on and limit the inrush current of the controller. After
the controller has been started and given adequate time to
charge up the output capacitor and provide full load
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| LTC1735EGN#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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) |
| LTC1735EGN#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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) |
| LTC1735IF | 功能描述:IC REG CTRLR BUCK PWM CM 20TSSOP 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1735IF#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 20TSSOP 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1735IF#TR | 功能描述:IC REG CTRLR BUCK PWM CM 20TSSOP 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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