- 您现在的位置：买卖IC网 > PDF目录15270 > LTC1909-8EG#TRPBF (Linear Technology)IC REG CTRLR BUCK PWM CM 28-SSOP PDF资料下载
参数资料
| 型号： | LTC1909-8EG#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 28-SSOP |
| 标准包装： | 2,000 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 200kHz |
| 占空比： | 90% |
| 电源电压： | 4 V ~ 36 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 ~ 85°C |
| 封装/外壳： | 28-SSOP（0.209"，5.30mm 宽） |
| 包装： | 带卷 (TR) |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页当前第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页
LTC1909-8
OPERATIO
(Refer to Functional Diagram)
The LTC1909-8 consists of two independent sections: a
current mode controller for the DC/DC step-down con-
verter and a SMBus VID voltage programmer. It simplifies
the design of SMBus controlled power supplies.
Current Mode Controller
In normal operation, the top MOSFET of the current mode
controller is turned on for a fixed interval determined by a
one-shot timer OST. When the top MOSFET is turned off,
the bottom MOSFET is turned on until the current com-
parator I CMP trips, restarting the one-shot timer and initi-
ating the next cycle. Inductor current is determined by
sensing the voltage between the PGND and SENSE + pins
using either the bottom MOSFET on-resistance or a sepa-
rate sense resistor. The voltage on the I TH pin sets the
comparator threshold corresponding to inductor valley
current. The error amplifier EA adjusts this voltage by
comparing the feedback signal V FB from the output voltage
with an internal 0.8V reference. The feedback voltage is
derived from the output voltage by a resistive divider in the
SMBus VID programmer. If the load current increases, it
causes a drop in the feedback voltage relative to the
reference. The I TH voltage then rises until the average
inductor current again matches the load current.
At low load currents, the inductor current can drop to zero
and become negative. This is detected by current reversal
comparator I REV which then shuts off M2, resulting in
discontinuous operation. Both switches will remain off
with the output capacitor supplying the load current until
the I TH voltage rises above the zero current level (0.8V) to
initiate another cycle. Discontinuous mode operation is
disabled by comparator F when the FCB pin is brought
below 0.8V, forcing continuous synchronous operation.
The operating frequency is determined implicitly by the
top MOSFET on-time and the duty cycle required to
maintain regulation. The one-shot timer generates an on-
time that is proportional to the ideal duty cycle, thus
holding frequency approximately constant with changes
in V IN . The nominal frequency can be adjusted with an
external resistor R ON .
Overvoltage and undervoltage comparators OV and UV
pull the PGOOD output low if the output feedback voltage
exits a ± 7.5% window around the regulation point. Fur-
thermore, in an overvoltage condition, M1 is turned off and
M2 is turned on and held on until the overvoltage condition
clears.
Foldback current limiting is provided if the output is
shorted to ground. As V FB drops, the buffered current
threshold voltage I THB is pulled down by clamp Q3 to a 1V
level set by Q4 and Q6. This reduces the inductor valley
current level to one sixth of its maximum value as V FB
approaches 0V.
Pulling the RUN/SS pin low forces the controller into its
shutdown state, turning off both M1 and M2. Releasing
the pin allows an internal 1.2 μ A current source to charge
up an external soft-start capacitor C SS . When this voltage
reaches 1.5V, the controller turns on and begins switch-
ing, but with the I TH voltage clamped at approximately
0.6V below the RUN/SS voltage. As C SS continues to
charge, the soft-start current limit is removed. Shorting
the RUN/SS pin to the CPUON pin of the SMBus VID
programmer puts the regulator under software control.
The open-drain CPUON pin does not interfere with the
soft-start cycle.
INTV CC /EXTV CC Power
Power for the top and bottom MOSFET drivers and most
of the internal controller circuitry is derived from the
INTV CC pin. The top MOSFET driver is powered from a
floating bootstrap capacitor C B . This capacitor is re-
charged from INTV CC through an external Schottky diode
D B when the top MOSFET is turned off. When the EXTV CC
pin is grounded and V RUN/SS >1.5V, an internal 5V low
dropout regulator supplies the INTV CC power from V IN . If
EXTV CC rises 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 connected to EXTV CC ,
such as an external 5V supply or a secondary output from
the converter, to provide the INTV CC power. Voltages up to
7V can be applied to EXTV CC for additional gate drive. If the
input voltage is low and INTV CC drops below 3.5V,
undervoltage lockout circuitry prevents the power switches
from turning on.
SMBus VID Voltage Programmer
The SMBus interface is used to program the divider (to set
the output voltage of the DC/DC converter) and to shut
down the current mode controller or allow it to soft-start.
19098f
14
相关PDF资料 |
PDF描述 |
|---|---|
| LTC1435CG#TRPBF | IC REG CTRLR BUCK PWM CM 16-SSOP |
| HCM12DSAI | CONN EDGECARD 24POS R/A .156 SLD |
| HSM06DRKF | CONN EDGECARD 12POS DIP .156 SLD |
| GBM30DTKT | CONN EDGECARD 60POS DIP .156 SLD |
| GBM36DTKS | CONN EDGECARD 72POS DIP .156 SLD |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1911EMS8-1.5#PBF | 功能描述:IC REG BUCK 1.5V 0.25A 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LTC1911EMS8-1.5#TR | 功能描述:IC REG BUCK 1.5V 0.25A 8MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LTC1911EMS8-1.5#TRPBF | 功能描述:IC REG BUCK 1.5V 0.25A 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LTC1911EMS8-1.8 | 功能描述:IC REG BUCK 1.8V 0.25A 8MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LTC1911EMS8-1.8#PBF | 功能描述:IC REG BUCK 1.8V 0.25A 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
发布紧急采购，3分钟左右您将得到回复。