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| 型号： | LTC1435CG#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 7/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SSOP |
| 标准包装： | 77 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 138kHz |
| 占空比： | 99% |
| 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 ~ 70°C |
| 封装/外壳： | 16-SSOP（0.209"，5.30mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1333 (CN2011-ZH PDF) |
LTC1435
OPERATIO N
Main Control Loop
(Refer to Functional Diagram)
Low Current Operation
The LTC1435 uses a constant frequency, current mode
step-down architecture. During normal operation, the top
MOSFET is turned on each cycle when the oscillator sets
the RS latch, and turned off when the main current
comparator I1 resets the RS latch. The peak inductor
current at which I1 resets the RS latch is controlled by the
voltage on the I TH pin , which is the output of error amplifier
EA. The V OSENSE pin, described in the Pin Functions
section, allows EA to receive an output feedback voltage
V FB from an external resistive divider. When the load
current increases, it causes a slight decrease in V FB
relative to the 1.19V reference, which in turn causes the I TH
voltage to increase until the average inductor current
matches the new load current. While the top MOSFET is
off, the bottom MOSFET is turned on until either the
inductor current starts to reverse, as indicated by current
comparator I2, or the beginning of the next cycle.
The top MOSFET driver is biased from floating bootstrap
capacitor C B , which normally is recharged during each off
cycle. However, when V IN decreases to a voltage close to
V OUT , the loop may enter dropout and attempt to turn on
the top MOSFET continuously. The dropout detector counts
the number of oscillator cycles that the top MOSFET
remains on and periodically forces a brief off period to
allow C B to recharge.
The main control loop is shut down by pulling the RUN/SS
pin low. Releasing RUN/SS allows an internal 3 μ A current
source to charge soft start capacitor C SS . When C SS
reaches 1.3V, the main control loop is enabled with the I TH
voltage clamped at approximately 30% of its maximum
value. As C SS continues to charge, I TH is gradually re-
leased allowing normal operation to resume.
The LTC1435 is capable of Burst Mode operation in which
the external MOSFETs operate intermittently based on
load demand. The transition to low current operation
begins when comparator I2 detects current reversal and
turns off the bottom MOSFET. If the voltage across R SENSE
does not exceed the hysteresis of I2 (approximately 20mV)
for one full cycle, then on following cycles the top and
bottom drives are disabled. This continues until an induc-
tor current peak exceeds 20mV/R SENSE or the I TH voltage
exceeds 0.6V, either of which causes drive to be returned
to the TG pin on the next cycle.
Two conditions can force continuous synchronous opera-
tion, even when the load current would otherwise dictate
low current operation. One is when the common mode
voltage of the SENSE + and SENSE – pins is below 1.4V and
the other is when the SFB pin is below 1.19V. The latter
condition is used to assist in secondary winding regulation
as described in the Applications Information section.
INTV CC /EXTV CC Power
Power for the top and bottom MOSFET drivers and most
of the other LTC1435 circuitry is derived from the INTV CC
pin. The bottom MOSFET driver supply pin is internally
connected to INTV CC in the LTC1435. When the EXTV CC
pin is left open, an internal 5V low dropout regulator
supplies INTV CC power. If EXTV CC is taken above 4.8V,
the 5V regulator is turned off and an internal switch is
turned on to connect EXTV CC to INTV CC . This allows the
INTV CC power to be derived from a high efficiency
external source such as the output of the regulator itself
or a secondary winding, as described in the Applications
Information section.
Comparator OV guards against transient overshoots
> 7.5% by turning off the top MOSFET and keeping it off
until the fault is removed.
7
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| LTC1435CS | 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) |
| LTC1435CS#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:- 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 |
| LTC1435CS#TR | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Sync Step Down 3.5V to 36V Input 16-Pin SOIC N T/R |
| LTC1435CS#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) |
| LTC1435IG | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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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