参数资料
| 型号： | LT1738EG#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR PWM CM 20-SSOP |
| 标准包装： | 66 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 250kHz |
| 占空比： | 93.5% |
| 电源电压： | 2.55 V ~ 20 V |
| 降压： | 无 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 是 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 20-SSOP（0.209"，5.30mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1328 (CN2011-ZH PDF) |
LT1738
OPERATIO
The current slew feedback loop consists of the voltage
across the external sense resistor, which is internally
amplified and differentiated. The derivative is limited to a
value set by R CSL . The current slew rate is thus inversely
proportional to both the value of sense resistor and R CSL.
The two control loops are combined internally so that a
smooth transition from current slew control to voltage
slew control is obtained. When turning on, the driver
current will slew before voltage. When turning off, voltage
will slew before current. In general it is desirable to have
R VSL and R CSL of similar value.
Internal Regulator
Most of the control circuitry operates from an internal 2.4V
low dropout regulator that is powered from V IN . The
internal low dropout design allows V IN to vary from 2.7V
to 20V with stable operation of the controller. When SHDN
< 1.3V the internal regulator is completely disabled.
5V Regulator
A 5V regulator is provided for powering external circuitry.
This regulator draws current from V IN and requires V IN to
be greater than 6.5V to be in regulation. It can sink or
source 10mA. The output is current limited to prevent
against destruction from accidental short circuits.
Safety and Protection Features
There are several safety and protection features on the
chip. The first is overcurrent limit. Normally the gate driver
will go low when the output of the internal sense amplifier
exceeds the voltage on the V C pin. The V C pin is clamped
such that maximum output current is attained when the CS
pin voltage is 0.1V. At that level the outputs will be
immediately turned off (no slew). The effect of this control
is that the output voltage will foldback with overcurrent.
In addition, if the CS voltage exceeds 0.22V, the V C and SS
pins will be discharged to ground, resetting the soft-start
function. Thus if a short is present this will allow for faster
MOSFET turnoff and less MOSFET stress.
If the voltage on the FB pin exceeds regulation by approxi-
mately 0.22V, the outputs will immediately go low. The
implication is that there is an overvoltage fault.
The voltage on GCL determines two features. The first is
the maximum gate drive voltage. This will protect the
MOSFET gate from overvoltage.
With GCL tied to a zener or an external voltage source then
the maximum gate driver voltage is approximately
V GCL – 0.2V. If GCL is tied to V IN , then the maximum gate
voltage is determined by V IN and is approximately
V IN – 1.6V. There is an internal 19V zener on the GCL pin
that prevents the gate driver pin from exceeding approxi-
mately 19V.
In addition, the GCL voltage determines undervoltage
lockout of the gate drive. This feature disables the gate
driver if V IN is too low to provide adequate voltage to turn
on the MOSFET. This is helpful during start up to insure the
MOSFET has sufficient gate drive to saturate.
If GCL is tied to a voltage source or zener less than 6.8V,
the gate driver will not turn on until V IN exceeds GCL
voltage by 0.8V. For V GCL above 6.5V, the gate drive is
insured to be off for V IN < 7.3V and it will be turned on by
V GCL + 0.8V.
If GCL is tied to V IN , the gate driver is always on
(undervoltage lockout is disabled).
The gate drive has current limits for the drive currents. If
the sink or source current is greater than 300mA then the
current will be limited.
The V5 regulator also has internal current limiting that will
only guarantee ± 10mA output current.
There is also an on chip thermal shutdown circuit that will
turn off the output in the event the chip temperature rises
to dangerous levels. Thermal shutdown has hysteresis
that will cause a low frequency (<1kHz) oscillation to occur
as the chip heats up and cools down.
The chip has an undervoltage lockout feature that will
force the gate driver low in the event that V IN drops below
2.5V. This insures predictable behavior during start up and
shut down. SHDN can be used in conjuction with an
external resistor divider to completely disable the part if
the input voltage is too low. This can be used to insure
adequate voltage to reliably run the converter. See the
section in Applications Information.
Table 1 summarizes these features.
1738fa
10
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1738IG | 功能描述:IC REG CTRLR PWM CM 20-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 |
| LT1738IG#PBF | 功能描述:IC REG CTRLR PWM CM 20-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: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 |
| LT1738IG#PBF | 制造商:Linear Technology 功能描述:ICSMPS CONTROLLERCURRENT-MODESSOP20P 制造商:Linear Technology 功能描述:IC,SMPS CONTROLLER,CURRENT-MODE,SSOP,20P |
| LT1738IG#TR | 功能描述:IC REG CTRLR PWM CM 20-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 |
| LT1738IG#TRPBF | 功能描述:IC REG CTRLR PWM CM 20-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: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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