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参数资料
| 型号： | LTC3789EUFD#PBF |
| 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, PQCC28 |
| 封装： | 4 X 5 MM, LEAD FREE, PLASTIC, MO-220, QFN-28 |
| 文件页数： | 15/28页 |
| 文件大小： | 486K |
| 代理商： | LTC3789EUFD#PBF |
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LTC3789
22
3789f
applicaTions inForMaTion
Design Example
VIN = 5V to 18V
VOUT = 12V
IOUT(MAX) = 5A
f = 400kHz
Maximum ambient temperature = 60°C
Set the frequency at 400kHz by applying 1.2V on the FREQ
pin (see Figure 7). The 10A current flowing out of the
FREQ pin will give 1.2V across a 120k resistor to GND. The
inductance value is chosen first based on a 30% ripple cur-
rent assumption. In the buck region, the ripple current is:
IL,BUCK =
VOUT
f L
1–
VOUT
VIN
IRIPPLE,BUCK =
IL,BUCK 100
IOUT
%
The highest value of ripple current occurs at the maximum
input voltage. In the boost region, the ripple current is:
IL,BOOST =
VIN
f L
1 –
VIN
VOUT
IRIPPLE,BOOST =
IL,BOOST 100
IIN
%
The highest value of ripple current occurs at VIN =
VOUT/2.
A6.8Hinductorwillproduce11%rippleintheboostregion
(VIN = 6V) and 29% ripple in the buck region (VIN = 18V).
The RSENSE resistor value can be calculated by using the
maximum current sense voltage specification with some
accommodation for tolerances.
RSENSE =
2 140mV VIN(MIN)
2 IOUT(MAX,BOOST) VOUT + IL,BOOST VIN(MIN)
Select an RSENSE of 10mΩ.
Output voltage is 12V. Select R1 as 20k. R2 is:
R2 =
VOUT R1
0.8
– R1
Select R2 as 280k. Both R1 and R2 should have a toler-
ance of no more than 1%.
Selecting MOSFET Switches
The MOSFETs are selected based on voltage rating and
RDS(ON)value.Itisimportanttoensurethatthepartisspeci-
fiedforoperationwiththeavailablegatevoltageamplitude.
In this case, the amplitude is 5.5V and MOSFETs with an
RDS(ON) value specified at VGS = 4.5V can be used.
Select QA and QB. With 18V maximum input voltage
MOSFETs with a rating of at least 30V are used. As we do
not yet know the actual thermal resistance (circuit board
design and airflow have a major impact) we assume that
the MOSFET thermal resistance from junction to ambient
is 50°C/W.
If we design for a maximum junction temperature, TJ(MAX)
= 125°C, the maximum RDS(ON) value can be calculated.
First, calculate the maximum power dissipation:
PD(MAX) =
TJ(MAX) TA(MAX)
R(ja)
PD(MAX) =
(125 60)
50
= 1.3W
The maximum dissipation in QA occurs at minimum input
voltage when the circuit operates in the boost region and
QA is on continuously. The input current is then:
VOUT IOUT(MAX)
VIN(MIN)
, OR 12A
We calculate a maximum value for RDS(ON):
RDS(ON) (125°C) <
PD(MAX)
IIN(MAX) 2
RDS(ON) (125°C) <
1.3W
(12A)2
= 0.009
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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 |
| LTC3789IUFD#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 |
| LTC3789IUFDPBF | 制造商:Linear Technology 功能描述:4-Switch Buck-Boost Controller QFN28EP |
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