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参数资料
| 型号： | LTC1142CG#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 28-SSOP |
| 标准包装： | 2,000 |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 250kHz |
| 占空比： | 100% |
| 电源电压： | 3.5 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： | -40°C ~ 85°C |
| 封装/外壳： | 28-SSOP（0.209"，5.30mm 宽） |
| 包装： | 带卷 (TR) |
LTC1142/LTC1142L/LTC1142HV
APPLICATIO S I FOR ATIO
both track I MAX . Once R SENSE has been chosen, I BURST and
I SC(PK) can be predicted from the following:
A graph for selecting C T versus frequency including the
effects of input voltage is given in Figure 3.
I BURST ≈
15mV
R SENSE
As the operating frequency is increased the gate charge
losses will be higher, reducing efficiency (see Efficiency
Considerations section). The complete expression for
1 ? OUT ?
1 ? V ?
?
t OFF = 1 . 3 ? 10 4 ? C T ? ? REG ?
150mV
I SC(PK) =
R SENSE
The LTC1142 automatically extends t OFF during a short
circuit to allow sufficient time for the inductor current to
decay between switch cycles. The resulting ripple current
causes the average short-circuit current I SC(AVG) to be
reduced to approximately I MAX .
0.20
0.15
0.10
0.05
operating frequency of the circuit in Figure 1 is given by:
f =
t OFF ? V IN ?
where:
? V ?
? V OUT ?
V REG is the desired output voltage (i.e., 5V, 3.3V). V OUT
is the measured output voltage. Thus V REG / V OUT = 1 in
regulation.
Note that as V IN decreases, the frequency decreases.
When the input-to-output voltage differential drops below
1.5V for a particular section, the LTC1142 reduces t OFF in
that section by increasing the discharge current in C T . This
prevents audible operation prior to dropout.
0
0
1
2
3
4
5
1000
MAXIMUM OUTPUT CURRENT (A)
1142 F02
V SENSE = V OUT = 5V
Figure 2. Selecting R SENSE
L and C T Selection for Operating Frequency
800
600
Each regulator section of the LTC1142 uses a constant off-
time architecture with t OFF determined by an external
400
V IN = 12V
timing capacitor C T . Each time the P-channel MOSFET
switch turns on, the voltage on C T is reset to approximately
200
V IN = 7V
V IN = 10V
3.3V. During the off-time, C T is discharged by a current
which is proportional to V OUT . The voltage on C T is
analogous to the current in inductor L, which likewise
0
0
50
100 150 200
FREQUENCY (kHz)
250
300
1142 F03
decays at a rate proportional to V OUT . Thus the inductor
value must track the timing capacitor value.
The value of C T is calculated from the desired continuous
mode operating frequency:
Figure 3. Timing Capacitor Value
Once the frequency has been set by C T , the inductor L must
be chosen to provide no more than 25mV/R SENSE of peak-
to-peak inductor ripple current. This results in a minimum
C T =
1
2 . 6 ? 10 4 ? f
required inductor value of:
L MIN = 5.1 ? 10 5 ? R SENSE ? C T ? V REG
Assumes V IN = 2V OUT , Figure 1 circuit.
10
As the inductor value is increased from the minimum
value, the ESR requirements for the output capacitor are
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1142HV | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual High Efficiency Synchronous Step-Down Switching Regulators |
| LTC1142HV-ADJ | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual High Efficiency Synchronous Step-Down Switching Regulators |
| LTC1142HVCG | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP 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 |
| LTC1142HVCG#PBF | 功能描述:IC REG CTRLR BUCK 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 |
| LTC1142HVCG#TR | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP 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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