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| 型号： | LTC1624CS8#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST FLYBK INV 8SOIC |
| 标准包装： | 100 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 225kHz |
| 占空比： | 95% |
| 电源电压： | 3.5 V ~ 36 V |
| 降压： | 是 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 是 |
| 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： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1333 (CN2011-ZH PDF) |
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LTC1624
APPLICATIO N S I N FOR M ATIO N
? I L = IN OUT ? OUT D ?
( )( ) ? V IN + V D ?
100 ? resistor in series with the SENSE – pin. This offset
cancels the internal offset in current comparator I 2 (refer
to Functional Diagram). This comparator in conjunction
with the voltage on the I TH /RUN pin determines when to
enter into Burst Mode operation (refer to Low Current
Operation in Operation section). With the additional exter-
nal offset present, the drive to the topside MOSFET is
always enabled every cycle and constant frequency opera-
tion occurs for I OUT > I OUT(MIN) .
Step-Down Converter: Design Example
As a design example, assume V IN = 12V(nominal),
V IN = 22V(max), V OUT = 3.3V and I MAX = 2A. R SENSE can
immediately be calculated:
R SENSE = 100mV/2A = 0.05 ?
Assume a 10 μ H inductor. To check the actual value of the
ripple current the following equation is used:
V ? V ? V + V ?
f L
The highest value of the ripple current occurs at the
With the 0.05 ? sense resistor I SC(AVG) = 2A will result,
increasing the 0.5V Schottky diode dissipation to 0.98W.
C IN is chosen for an RMS current rating of at least 1.0A at
temperature. C OUT is chosen with an ESR of 0.03 ? for low
output ripple. The output ripple in continuous mode will be
highest at the maximum input voltage. The output voltage
ripple due to ESR is approximately:
V ORIPPLE = R ESR ( ? I L ) = 0.03 ? (1.58A P-P ) = 47mV P-P
Step-Down Converter: Duty Cycle Limitations
At high input to output differential voltages the on-time
gets very small. Due to internal gate delays and response
times of the internal circuitry the minimum recommended
on-time is 450ns. Since the LTC1624’s frequency is inter-
nally set to 200kHz a potential duty cycle limitation exists.
When the duty cycle is less than 9%, cycle skipping may
occur which increases the inductor ripple current but does
not cause V OUT to lose regulation. Avoiding cycle skipping
imposes a limit on the input voltage for a given output
voltage only when V OUT < 2.2V using 30V MOSFETs.
(Remember not to exceed the absolute maximum voltage
of 36V.)
maximum input voltage:
V IN(MAX) = 11.1V OUT + 5V
For DC > 9%
? = 1 . 58 A P-P
( )
200 kHz 10 μ H ? 22 V + 0 . 5 V ?
? I L =
22 V ? 3 . 3 V ? 3 . 3 V + 0 . 5 V ?
?
Boost Converter Applications
The LTC1624 is also well-suited to boost converter appli-
The power dissipation on the topside MOSFET can be
easily estimated. Choosing a Siliconix Si4412DY results
in: R DS(ON) = 0.042 ? , C RSS = 100pF. At maximum input
voltage with T(estimated) = 50 ° C:
cations. A boost converter steps up the input voltage to a
higher voltage as shown in Figure 6.
V IN
( ) [ ( ) ( ) ] ( )
3 . 3 V + 0 . 5 V
1 + 0 . 005 50 ° C ? 25 ° C 0 . 042 ?
+ 2 . 5 ( ) ( )( )( ) = 62 mW
+
P MAIN =
2
2 A
22 V + 0 . 5 V
1 . 85
22 V 2 A 100 pF 200 kHz
The most stringent requirement for the Schottky diode
occurs when V OUT = 0V (i.e. short circuit) at maximum V IN .
V IN
SENSE –
BOOST
LTC1624
TG
SW
GND
C B
R SENSE
L1
D1
M1
V FB
+
C IN
R2
R1
V OUT
C OUT
In this case the worst-case dissipation rises to:
( ) ( )
+ V ?
P D = I SC AVG V D ?
? V IN ?
? V IN D ?
Figure 6. Boost Converter
1624 F06
13
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| LTC1624IS8 | 功能描述:IC REG CTRLR BST FLYBK INV 8SOIC 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 |
| LTC1624IS8#PBF | 功能描述:IC REG CTRLR BST FLYBK INV 8SOIC 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 |
| LTC1624IS8#PBF | 制造商:Linear Technology 功能描述:DC/DC Converter IC |
| LTC1624IS8#TR | 功能描述:IC REG CTRLR BST FLYBK INV 8SOIC 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 |
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