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| 型号： | LTC3727EG-1 |
| 厂商： | Linear Technology |
| 文件页数： | 25/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 28-SSOP |
| 标准包装： | 47 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 580kHz |
| 占空比： | 99% |
| 电源电压： | 4 V ~ 36 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： | 管件 |
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LTC3727/LTC3727-1
APPLICATIO S I FOR ATIO
I SC =
+ ?
? = 3 . 2 A
Design Example
As a design example for one channel, assume V IN =
24V(nominal), V IN = 30V(max), V OUT = 12V, I MAX = 5A and
f = 250kHz.
The inductance value is chosen first based on a 40% ripple
current assumption. The highest value of ripple current
occurs at the maximum input voltage. Tie the PLLFLTR pin
A short-circuit to ground will result in a folded back current
of:
45 mV 1 ? 200 ns ( 30 V ) ?
0 . 015 Ω 2 ? 14 μ H ?
with a typical value of R DS(ON) and δ = (0.005/ ° C)(20) = 0.1.
The resulting power dissipated in the bottom MOSFET is:
to the SGND pin for 250kHz operation. The minimum
inductance for 40% ripple current is:
P SYNC =
30 V – 12 V
30 V
( 3 . 2 A ) ( 2 1 . 1 ) ( 0 . 042 Ω )
V OUT ? V OUT ?
Δ I L = ? 1 – ?
( f )( L ) ? V IN ?
A 14 μ H inductor will result in 40% ripple current. The peak
inductor current will be the maximum DC value plus one
half the ripple current, or 6A, for the 14 μ H value.
The R SENSE resistor value can be calculated by using the
maximum current sense voltage specification with some
accommodation for tolerances:
= 284 mW
which is less than under full-load conditions.
C IN is chosen for an RMS current rating of at least 3A at
temperature assuming only this channel is on. C OUT is
chosen with an ESR of 0.02 Ω for low output ripple. The
output ripple in continuous mode will be highest at the
maximum input voltage. The output voltage ripple due to
ESR is approximately:
R SENSE ≤
90mV
6 A
≈ 0 . 015 Ω
V ORIPPLE = R ESR ( Δ I L ) = 0.02 Ω (2A) = 40mV P–P
PC Board Layout Checklist
( ) 5 [ ] )
P MAIN =
1 + ( 0 . 005 )( 50 ° C – 25 ° C
Choosing 1% resistors; R1 = 20k and R2 = 280k yields an
output voltage of 12V.
The power dissipation on the top side MOSFET can be
easily estimated. Choosing a Siliconix Si4412DY results
in: R DS(ON) = 0.042 Ω , C RSS = 100pF. At maximum input
voltage with T(estimated) = 50 ° C:
12 V 2
30 V
( 0 . 042 Ω ) + 1 . 7 ( 30 V ) ( 2 5 A )( 100 pF )( 250 kHz )
= 664 mW
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC3727. These items are also illustrated graphically in
the layout diagram of Figure 10; Figure 11 illustrates the
current waveforms present in the various branches of the
2-phase synchronous regulators operating in continuous
mode. Check the following in your layout:
1. Are the top N-channel MOSFETs M1 and M3 located
within 1cm of each other with a common drain connection
at C IN ? Do not attempt to split the input decoupling for the
two channels as it can cause a large resonant loop.
3727fc
25
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| LTC3727EG-1#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: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 |
| LTC3727EG-1#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:PolyPhase® 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 |
| LTC3727EG-1#TRPBF | 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:PolyPhase® 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 |
| LTC3727EG-1PBF | 制造商:Linear Technology 功能描述:DC-DC Controller Dual Step-Dn 36V SSOP28 |
| LTC3727EGPBF | 制造商:Linear Technology 功能描述:Dual Sync Buck Sw Vreg Controller SSOP28 |
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