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| 型号： | LTC1624CS8#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 19/28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
( ) ( )
where : I SW MAX = I OUT MAX ? ?
?
?
( V IN ) ( V OUT D V )
( ) ( )( ) L V + V
( IN OUT D V )
? V IN + V OUT + V D ?
? V IN ?
δ is the temperature dependency of R DS(ON) and k is a
constant inversely related to the gate drive current. The
maximum switch current occurs at V IN(MIN) and the peak
switch current is I SW(MAX) + ? I L /2. The maximum voltage
across the switch is V IN(MAX) + ? V OUT ? .
MOSFETs have I 2 R losses plus the P MAIN equation
includes an additional term for transition losses that are
highest at high total input plus output voltages. For
( ? V OUT ? + V IN ) < 20V the high current efficiency generally
improves with larger MOSFETs, while for ( ? V OUT ? + V IN )
> 20V the transition losses rapidly increase to the point
that the use of a higher R DS(ON) device with lower C RSS
actual provides higher efficiency. For additional informa-
tion refer to the Step-Down Converter: Power MOSFET
Selection in the Applications Information section.
Positive-to-Negative Converter: Inductor Selection
+
? I L P-P =
200 kHz +
Specify the maximum inductor current to safely handle
I L(PEAK) . Make sure the inductor’s saturation current rat-
ing (current when inductance begins to fall) exceeds the
maximum current rating set by R SENSE .
Positive-to-Negative Converter: R SENSE Selection for
Maximum Output Current
R SENSE is chosen based on the required output current.
Remember the LTC1624 current comparator has a maxi-
mum threshold of 160mV/R SENSE . The current compara-
tor threshold sets the peak of the inductor current, yielding
a maximum average output current I OUT(MAX) equal to
I L(PEAK) less half the peak-to-peak ripple current with the
remainder divided by the duty cycle.
Allowing a margin for variations in the LTC1624 (without
considering variation in R SENSE ) and assuming 30% ripple
current in the inductor, yields:
( )
? ?
100 mV ?
?
I OUT ( MAX ) ? V IN ( MIN ) OUT D ?
?
?
For most applications the inductor will fall in the range of
10 μ H to 100 μ H. Higher values reduce the input and output
ripple voltage (although not as much as step-down con-
verters) and also reduce core loss. Lower inductor values
are chosen to reduce physical size and improve transient
R SENSE =
V IN MIN
+ V + V
response but do increase output ripple.
Like the boost converter, the input current of the positive-
to-negative converter is calculated at full load current.
Peak inductor current can be significantly higher than
output current, especially with smaller inductors (with
Positive-to-Negative Converter: Output Diode
The output diode conducts current only during the switch
off-time. Peak reverse voltage for positive-to-negative
converters is equal to ? V OUT ? + V IN . Average forward
current in normal operation is equal to I D(PEAK) – ? I L /2.
? V IN + V OUT + V D ?
(
)
( )
? I L
?
?
V IN
?
?
( )
( ) ( )
I D PEAK = I OUT MAX ? + 1 ? +
?
?
high ? I L values). The following formula assumes continu-
ous mode operation and calculates maximum peak induc-
tor current at minimum V IN :
I L PEAK = I OUT MAX ? ? +
2
Peak diode current (occurring at V IN(MIN) ) is:
? V OUT + V D ?
? V IN ?
Positive-to-Negative Converter: Input and
? I L
2
The ripple current in the inductor ( ? I L ) is typically 20% to
50% of the peak inductor current occuring at V IN(MIN) and
I OUT(MAX) to minimize output ripple. Maximum ? I L occurs
at minimum V IN .
Output Capacitors
The output capacitor is normally chosen by its effective
series resistance (ESR), because this is what determines
output ripple voltage. Both input and output capacitors
need to be sized to handle the ripple current safely.
19
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相关代理商/技术参数 |
参数描述 |
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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 |
| LTC1624IS8#TRPBF | 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:- 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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