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参数资料
| 型号： | LTC1909-8EG |
| 厂商： | Linear Technology |
| 文件页数： | 17/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 28-SSOP |
| 标准包装： | 47 |
| 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： | 管件 |
| 其它名称： | LTC19098EG |
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LTC1909-8
OPERATIO
(Refer to Functional Diagram)
long time for the output of the DC/DC converter to de-
crease to the new voltage under light load conditions. To
reduce this time needed, the PGTMR pin can be connected
to the FCB (force continuous bar) pin of the converter.
When the SEL pin is toggled to select a new code, the FCB
pin is forced low for 50 μ s. This forces the DC/DC converter
out of Burst Mode TM operation and into continuous mode.
The PGTMR pin may be tied to the same pull-up resistor
as the PGOOD pin.
SMBus Controller Supply
If the EXTV CC pin is tied to ground, the V CC pin of the
SMBus controller should be tied to an external 5V supply.
It should not be tied to the INTV CC pin because the internal
5V regulator at the INTV CC pin is shut down while V RUN/SS
is below 1.5V and the SMBus controller will not be pow-
ered up. If the EXTV CC pin is tied to an external 5V supply,
APPLICATIO S I FOR ATIO
the V CC pin can be tied to the same supply or to the INTV CC
pin since the INTV CC pin is connected to the EXTV CC pin by
an internal switch when V EXTVCC >4.7V. The EXTV CC and
V CC voltages should be kept below the absolute maximum
rating of 7V.
Power-Up Reset
On power-up, the internal POR circuit generates a low
reset pulse, which stays low until V CC rises above approxi-
mately 2.2V. The reset pulse forces the SMBus interface
into an idle state in which it listens for a start bit. At the
same time the outputs of both Register 0 and Register 1
are set to 11111B. The DCON bit is pulled high so that the
CPUON pin is pulled low to shut down the DC/DC con-
verter. PGTMR is also pulled low as the converter is shut
down and therefore not in regulation.
Burst Mode is a trademark of Linear Technology Corporation.
The basic LTC1909-8 application circuit is shown in
Figure 1. External component selection is primarily deter-
mined by the maximum load current and begins with the
R SENSE =
V RNG
10 ? I OUT ( MAX )
selection of the sense resistance and power MOSFET
switches. The LTC1909-8 uses either an external sense
resistor or the on-resistance of the synchronous power
MOSFET for determining the inductor current. The desired
amount of ripple current and operating frequency largely
determines the inductor value. Finally, C IN is selected for
its ability to handle the large RMS current into the con-
verter and C OUT is chosen with low enough ESR to meet
the output voltage ripple and transient specification.
Maximum Sense Voltage and V RNG Pin
Inductor current is determined by measuring the voltage
across a sense resistance that appears between the PGND
and SENSE + pins. The maximum sense voltage is set by
the voltage applied to the V RNG pin and is equal to
approximately (0.133) ? V RNG . The current mode control
loop will not allow the inductor current valleys to exceed
(0.133) ? V RNG /R SENSE . In practice, one should allow some
margin for variations in the LTC1909-8 and external com-
ponent values and a good guide for selecting the sense
An external resistive divider from INTV CC can be used to
set the voltage of the V RNG pin between 0.5V and 2V
resulting in nominal sense voltages of 50mV to 200mV.
Additionally, the V RNG pin can be tied to SGND or INTV CC
in which case the nominal sense voltage defaults to 70mV
or 140mV, respectively. The maximum allowed sense
voltage is about 1.33 times this nominal value.
Connecting the SENSE + Pin
The LTC1909-8 can be used with or without a sense
resistor. When using a sense resistor, it is placed between
the source of the bottom MOSFET M2 and ground. Con-
nect the SENSE + pin to the source of the bottom MOSFET
so that the resistor appears between the SENSE + and
PGND pins. Using a sense resistor provides a well defined
current limit, but adds cost and reduces efficiency. Alter-
natively, one can eliminate the sense resistor and use the
bottom MOSFET as the current sense element by simply
connecting the SENSE + pin to the switch node SW at the
drain of the bottom MOSFET. This improves efficiency, but
resistance is:
19098f
17
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| LTC1909-8EG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-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 |
| LTC1909-8EG#TR | 功能描述:IC REG CTRLR BUCK PWM CM 28-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 |
| LTC1909-8EG#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-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 |
| 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 |
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