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| 型号： | LTC3852EUDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 28/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR DOUBLER PWM 24-QFN |
| 标准包装： | 73 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 810kHz |
| 占空比： | 99% |
| 电源电压： | 2.7 V ~ 38 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 是 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 24-WFQFN 裸露焊盘 |
| 包装： | 管件 |
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LTC3852
APPLICATIONS INFORMATION
will improve performance and ensure proper regulation
under all conditions. Figure 15 shows an example layout
for the charge pump.
sensing pins needs to be placed immediately adjacent to
the pins of the IC. This capacitor helps to minimize the
effects of differential noise injection due to high frequency
capacitive coupling. If problems are encountered with
high current output loading at lower input voltages, look
C FLY
0603
C +
LTC3852EUDD
V PUMP
for inductive coupling between C IN , the Schottky and the
top MOSFET to the sensitive current and voltage sensing
C –
GND1
V IN1
C PUMP
0603
traces. In addition, investigate common ground path
voltage pickup between these components and the GND
pin of the IC.
C IN
Design Example
0603
As a design example, assume V IN = 3.3V (nominal), V IN =
5.5V (maximum), V OUT = 1.5V, I MAX = 15A, and f = 400kHz
3852 F15
Figure 15. Recommended Charge Pump Layout
PC Board Layout Debugging
It is helpful to use a DC-50MHz current probe to monitor
the current in the inductor while testing the circuit. Monitor
(refer to Figure 16).
The inductance value is chosen ?rst based on a 30%
ripple current assumption. The highest value of ripple
current occurs at the maximum input voltage. Connect
a 68.1k resistor between the FREQ/PLLFLTR and GND
pins, generating 400kHz operation. The inductance for
30% ripple current is:
V OUT ? 1 ? OUT ?
L =
1.5V ? 1 ?
=
the output switching node (SW pin) to synchronize the
oscilloscope to the internal oscillator and probe the actual
output voltage as well. Check for proper performance
over the operating voltage and current range expected
in the application. The frequency of operation should be
maintained over the input voltage range down to dropout
Δ I L ( f ) ? V IN ?
1 ? V ?
1 ? 1.5V ?
?
4.5A ( 400kHz ) ? 3.3V ?
= 454nH
and until the output load drops below the low current
operation threshold—typically 10% of the maximum
designed current level in Burst Mode operation.
The duty cycle percentage should be maintained from cycle
A 400nH inductor will produce 34% ripple current.The peak
inductor current will be the maximum DC value (15A) plus
one-half the ripple current (2.5A), or 17.5A. The minimum
on-time occurs at maximum V IN :
to cycle in a well designed, low noise PCB implementation.
Variation in the duty cycle at a subharmonic rate can suggest
noise pick-up at the current or voltage sensing inputs or
t ON(MIN) =
V OUT
V IN(MAX) ( f )
=
1.5V
5.5V ( 400kHz )
= 6 8 2ns
inadequate loop compensation. Overcompensation of the
loop can be used to tame a poor PC layout if regulator
bandwidth optimization is not required.
Investigate whether any problems exist only at higher out-
which is greater than the 90ns minimum on-time.
The R SENSE resistor value can be calculated by using the
minimum current sense voltage speci?cation with a 20%
increase for current limit.
put currents or only at higher input voltages. If problems
coincide with high input voltages and low output currents,
look for capacitive coupling between the BOOST, SW, TG
R SENSE ≤
V SENSE(MIN)
I PEAK ? 1.2
≤
40mV
17.5A ? 1.2
= 1.9m Ω
and possibly BG connections and the sensitive voltage
and current pins. The capacitor placed across the current
Choosing 1% resistors: R1 = 20k and R2 = 37.4k yields
an output voltage of 1.496V.
3852f
28
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| LTC3852IUDD#PBF | 功能描述:IC REG CTRLR DOUBLER PWM 24-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:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3852IUDD#TRPBF | 功能描述:IC REG CTRLR DOUBLER PWM 24-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:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3853EUJ#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 40-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC3853EUJ#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 40-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC3853EUJPBF | 制造商:Linear Technology 功能描述:DC-DC Controller Triple Buck 24V QFN40 |
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