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| 型号： | LTC1649CS |
| 厂商： | Linear Technology |
| 文件页数： | 7/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 16-SOIC |
| 标准包装： | 50 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 260kHz |
| 占空比： | 93% |
| 电源电压： | 2.7 V ~ 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： | 0°C ~ 70°C |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1333 (CN2011-ZH PDF) |
LTC1649
APPLICATIO N S I N FOR M ATIO N
MOSFET Gate Drive
The LTC1649 is designed to operate from supplies as low
as 2.7V while using standard 5V logic-level N-channel
external MOSFETs. This poses somewhat of a challenge—
from as little as 2.7V, the LTC1649 must provide a 0V to
5V signal to the lower MOSFET, Q2, while the upper
MOSFET, Q1, requires a gate drive signal that swings from
0V to (V IN + 5V). The LTC1649 addresses this situation
with two specialized circuits. An onboard charge pump
boosts the input voltage at V IN to a regulated 5V at CP OUT .
This 5V supply is used to power the PV CC2 pin, which in
turn supplies 5V gate drive to Q2. This 5V supply is also
used to power the V CC pin, which allows the internal drive
circuitry to interface to the boosted driver supplies.
Gate drive for the top N-channel MOSFET, Q1, is supplied
by PV CC1 . This supply must reach V IN + 5V while Q1 is on.
Conveniently, the switching node at the source of Q1 rises
to V IN whenever Q1 is on. The LTC1649 uses this fact to
generate the required voltage at PV CC1 with a simple
external charge pump as shown in Figure 2. This circuit
charges the flying capacitor C2 to the 5V level at CP OUT
when the switching node is low. As the top MOSFET turns
on, the switching node begins to rise to V IN , and the PV CC1
is pulled up to V IN + 5V by C2. The 93% maximum duty
cycle (typical) means the switching node at the source of
Synchronous Operation
The LTC1649 uses a synchronous switching architecture,
with MOSFET Q2 taking the place of the diode in a classic
buck circuit (Figure 3). This improves efficiency by reduc-
ing the voltage drop and the resultant power dissipation
across Q2 to V ON = (I)(R DS(ON)(Q2) ), usually much lower
than V F of the diode in the classical circuit. This more than
offsets the additional gate drive required by the second
MOSFET, allowing the LTC1649 to achieve efficiencies in
the mid-90% range for a wide range of load currents.
Another feature of the synchronous architecture is that
unlike a diode, Q2 can conduct current in either direction.
This allows the output of a typical LTC1649 circuit to sink
current as well as sourcing it while remaining in regula-
tion. The ability to sink current at the output allows the
LTC1649 to be used with reactive or other nonconventional
loads that may supply current to the regulator as well as
drawing current from it.
V IN
Q1 will return to ground during at least 7% of each cycle,
CONTROLLER
Q1
ensuring that the charge pump will always provide ad-
equate gate drive to Q1.
D1
V OUT
1649 F03a
D CP
V IN
Figure 3a. Classical Buck Architecture
+
10 μ F CP OUT
PV CC2
PV CC1
G1
1 μ F
Q1
V IN
L1
V OUT
Q1
G2
Q2
+
C OUT
CONTROLLER
V OUT
Q2
LTC1649
Figure 2. PV CC1 Charge Pump
1649 F02
1649 F03b
Figure 3b. Synchronous Buck Architecture
7
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相关代理商/技术参数 |
参数描述 |
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| LTC1649CS#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 16-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 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:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LTC1649CS#TR | 功能描述:IC REG CTRLR BUCK PWM VM 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) |
| LTC1649CS#TRPBF | 功能描述:IC REG CTRLR BUCK PWM VM 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) |
| LTC1649IS | 功能描述:IC REG CTRLR BUCK PWM VM 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: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 |
| LTC1649IS#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 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 |
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