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参数资料
| 型号： | LTC1909-8EG |
| 厂商： | Linear Technology |
| 文件页数： | 22/32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
APPLICATIO S I FOR ATIO
currents required by the MOSFET gate drivers. Applica-
tions using large MOSFETs with a high input voltage and
high frequency of operation may cause the LTC1909-8 to
exceed its maximum junction temperature rating or RMS
current rating. Most of the supply current drives the
LTC1693. Alternately, the external buffer circuit shown in
Figure 5 can be used. Note that the bipolar devices reduce
the signal swing at the MOSFET gate and benefit from an
increased EXTV CC voltage of about 6V.
MOSFET gates unless an external EXTV CC source is used.
BOOST
INTV CC
In continuous mode operation, this current is I GATECHG =
f(Q g(TOP) + Q g(BOT) ). The junction temperature can be
estimated from the equations given in Note 2 of the
TG
10 ?
Q1
FMMT619
GATE
OF M1
BG
10 ?
Q3
FMMT619
GATE
OF M2
Electrical Characteristics. For example, the LTC1909-8 is
limited to less than 14mA from a 30V supply:
Q2
FMMT720
Q4
FMMT720
T J = 70 ° C + (14mA)(30V)(130 ° C/W) = 125 ° C
SW
PGND
19098 F05
( )
t DELAY =
= 1 . 3 s / μ F C
1 . 2 μ A
Forlargercurrents,considerusinganexternalsupplywith
the EXTV CC pin.
EXTV CC Connection
The EXTV CC pin can be used to provide MOSFET gate drive
and control power from the output or another external
source during normal operation. Whenever the EXTV CC
pin is above 4.7V the internal 5V regulator is shut off and
an internal 50mA P-channel switch connects the EXTV CC
pin to INTV CC . INTV CC power is supplied from EXTV CC until
this pin drops below 4.5V. Do not apply more than 7V to
the EXTV CC pin and ensure that EXTV CC ≤ V IN . The follow-
ing list summarizes the possible connections for EXTV CC :
1. EXTV CC grounded. INTV CC is always powered from the
internal 5V regulator.
2. EXTV CC connected to an external supply. A high effi-
ciency supply compatible with the MOSFET gate drive
requirements (typically 5V) can improve overall efficiency.
3. EXTV CC connected to an output derived boost network.
The low voltage output can be boosted using a charge
pump or flyback winding to greater than 4.7V. The system
will start-up using the internal linear regulator until the
boosted output supply is available.
External Gate Drive Buffers
The LTC1909-8 drivers are adequate for driving up to
about 30nC into MOSFET switches with RMS currents of
50mA. Applications with larger MOSFET switches or oper-
ating at frequencies requiring greater RMS currents will
benefit from using external gate drive buffers such as the
Figure 5. Optional External Gate Driver
Soft-Start and Latchoff with the RUN/SS Pin
The RUN/SS pin provides a means to shut down the
LTC1909-8 as well as a timer for soft-start and overcurrent
latchoff. Pulling the RUN/SS pin below 0.8V puts the
LTC1909-8 into a low quiescent current shutdown
(I Q < 30 μ A). Releasing the pin allows an internal 1.2 μ A
current source to charge up the external timing capacitor
C SS . If RUN/SS has been pulled all the way to ground, there
is a delay before starting of about:
1 . 5 V
C SS SS
When the voltage on RUN/SS reaches 1.5V, the LTC1909-8
begins operating with a clamp on I TH of approximately
0.9V. As the RUN/SS voltage rises to 3V, the clamp on I TH
is raised until its full 2.4V range is available. This takes an
additional 1.3s/ μ F, during which the load current is folded
back until the output reaches 75% of its final value. The pin
can be driven from logic (Figures 6a or 6b) or from the
CPUON pin (Figures 6c and 6d). Diode D1 reduces the start
delay while allowing C SS to charge up slowly for the soft-
start function.
After the controller has been started and given adequate
time to charge up the output capacitor, C SS is used as a
short-circuit timer. After the RUN/SS pin charges above
4V, if the output voltage falls below 75% of its regulated
value, then a short-circuit fault is assumed. A 1.8 μ A
current then begins discharging C SS . If the fault condition
persists until the RUN/SS pin drops to 3.5V, then the
19098f
22
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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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