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参数资料
| 型号： | LTC3789EGN#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 0.1 A SWITCHING CONTROLLER, 710 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封装： | 0.150 INCH, LEAD FREE, PLASTIC, SSOP-28 |
| 文件页数： | 10/28页 |
| 文件大小： | 486K |
| 代理商： | LTC3789EGN#TRPBF |
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LTC3789
18
3789f
applicaTions inForMaTion
In the boost region, the discontinuous current shifts
from the input to the output, so COUT must be capable
of reducing the output voltage ripple. The effects of ESR
(equivalent series resistance) and the bulk capacitance
must be considered when choosing the right capacitor
for a given output ripple voltage. The steady ripple due to
charging and discharging the bulk capacitance is given by:
Ripple (Boost,Cap) =
IOUT(MAX) VOUT – VIN(MIN)
(
)
COUT VOUT f
V
Ripple (Buck,Cap) =
IOUT(MAX) VIN(MAX) – VOUT
(
)
COUT VIN(MAX) f
V
where COUT is the output filter capacitor.
The steady ripple due to the voltage drop across the ESR
is given by:
VBOOST,ESR = IL(MAX,BOOST) ESR
VBUCK,ESR = IL(MAX,BUCK) ESR
Multiple capacitors placed in parallel may be needed to
meet the ESR and RMS current handling requirements.
Dry tantalum, special polymer, aluminum electrolytic and
ceramic capacitors are all available in surface mount
packages. Ceramic capacitors have excellent low ESR
characteristics but can have a high voltage coefficient.
Capacitors are now available with low ESR and high ripple
current ratings, such as OS-CON and POSCAP.
Power MOSFET Selection and
Efficiency Considerations
The LTC3789 requires four external N-channel power
MOSFETs, two for the top switches (switches A and
D, shown in Figure 1) and two for the bottom switches
(switches B and C, shown in Figure 1). Important param-
eters for the power MOSFETs are the breakdown voltage
VBR,DSS,thresholdvoltageVGS,TH,on-resistanceRDS(ON),
reverse transfer capacitance CRSS and maximum current
IDS(MAX).
The drive voltage is set by the 5.5V INTVCC supply. Con-
sequently, logic-level threshold MOSFETs must be used
in LTC3789 applications.
InordertoselectthepowerMOSFETs,thepowerdissipated
by the device must be known. For switch A, the maximum
power dissipation happens in the boost region, when it
remains on all the time. Its maximum power dissipation
at maximum output current is given by:
PA,BOOST =
VOUT
VIN
IOUT(MAX)
2
ρt RDS(ON)
where ρt is a normalization factor (unity at 25°C) ac-
counting for the significant variation in on-resistance
with temperature, typically about 0.4%/°C, as shown in
Figure 11. For a maximum junction temperature of 125°C,
using a value ρt = 1.5 is reasonable.
JUNCTION TEMPERATURE (°C)
–50
ρ T
NORMALIZED
ON-RESISTANCE
()
1.0
1.5
150
3789 F11
0.5
0
50
100
2.0
Figure 11. Normalized RDS(ON) vs Temperature
Switch B operates in the buck region as the synchronous
rectifier. Its power dissipation at maximum output current
is given by:
PB,BUCK =
VIN VOUT
VIN
IOUT(MAX)2 ρt RDS(ON)
SwitchCoperatesintheboostregionasthecontrolswitch.
Its power dissipation at maximum current is given by:
PC,BOOST =
VOUT – VIN
(
)V
OUT
VIN 2
IOUT(MAX)2 ρt
RDS(ON) + k VOUT3
IOUT(MAX)
VIN
CRSS f
相关PDF资料 |
PDF描述 |
|---|---|
| LTC3789EUFD#TRPBF | 0.1 A SWITCHING CONTROLLER, 710 kHz SWITCHING FREQ-MAX, PQCC28 |
| LTC3789EGN#PBF | 0.1 A SWITCHING CONTROLLER, 710 kHz SWITCHING FREQ-MAX, PDSO28 |
| LTC3789IUFD#PBF | 0.1 A SWITCHING CONTROLLER, 710 kHz SWITCHING FREQ-MAX, PQCC28 |
| LTC3789IGN#TRPBF | 0.1 A SWITCHING CONTROLLER, 710 kHz SWITCHING FREQ-MAX, PDSO28 |
| LTC3803HS6-3#TRPBF | 1 A SWITCHING CONTROLLER, 330 kHz SWITCHING FREQ-MAX, PDSO6 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3789EUFD#PBF | 功能描述:IC REG CTRLR BST PWM CM 28-QFN 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 |
| LTC3789EUFD#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 28-QFN 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 |
| LTC3789IGN#PBF | 功能描述:IC REG CTRLR BST 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 |
| LTC3789IGN#TRPBF | 功能描述:IC REG CTRLR BST 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 |
| LTC3789IUFD#PBF | 功能描述:IC REG CTRLR BST PWM CM 28-QFN 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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