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参数资料
| 型号： | LTC3859IUHF#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PQCC38 |
| 封装： | 5 X 7 MM, LEAD FREE, PLASTIC, MO-220WHKD, QFN-38 |
| 文件页数： | 18/42页 |
| 文件大小： | 624K |
| 代理商： | LTC3859IUHF#PBF |
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LTC3859
25
3859fa
APPLICATIONS INFORMATION
The total RMS power lost is lower when both controllers
are operating due to the reduced overlap of current pulses
required through the input capacitor’s ESR. This is why
the input capacitor’s requirement calculated above for the
worst-case controller is adequate for the dual controller
design. Also, the input protection fuse resistance, battery
resistance, and PC board trace resistance losses are also
reduced due to the reduced peak currents in a 2-phase
system. The overall benet of a multiphase design will
only be fully realized when the source impedance of the
power supply/battery is included in the efciency testing.
The drains of the top MOSFETs should be placed within
1cm of each other and share a common CIN (s). Separat-
ing the drains and CIN may produce undesirable voltage
and current resonances at VIN.
A small (0.1μF to 1μF) bypass capacitor between the chip
VIN pin and ground, placed close to the LTC3859, is also
suggested. A small (1Ω to 10Ω) resistor placed between
CIN (C1) and the VIN pin provides further isolation between
the two channels.
The selection of COUT is driven by the effective series
resistance (ESR). Typically, once the ESR requirement
is satised, the capacitance is adequate for ltering. The
output ripple (
DVOUT) is approximated by:
ΔV
OUT ≈ΔIL ESR +
1
8fC
OUT
where f is the operating frequency, COUT is the output
capacitance and
DIL is the ripple current in the inductor.
The output ripple is highest at maximum input voltage
since
DIL increases with input voltage.
Setting Output Voltage
The LTC3859 output voltages are each set by an external
feedback resistor divider carefully placed across the output,
as shown in Figure 5. The regulated output voltages are
determined by:
V
OUT, BUCK = 0.8V 1 +
R
B
R
A
V
OUT, BOOST = 1.2V 1 +
R
B
R
A
To improve the frequency response, a feedforward ca-
pacitor, CFF, may be used. Great care should be taken to
route the VFB line away from noise sources, such as the
inductor or the SW line.
Tracking and Soft-Start
(TRACK/SS1, TRACK/SS2, SS3 Pins)
The start-up of each VOUT is controlled by the voltage on
the respective TRACK/SS pin (TRACK/SS1 for channel 1,
TRACK/SS2 for channel 2, SS3 for channel 3). When the
voltage on the TRACK/SS pin is less than the internal
0.8V reference (1.2V reference for the boost channel), the
LTC3859 regulates the VFB pin voltage to the voltage on the
TRACK/SS pin instead of the internal reference. Likewise,
the TRACK/SS pin for the buck channels can be used to
program an external soft-start function or to allow VOUT
to track another supply during start-up.
Figure 5. Setting Output Voltage
3859 F05
1/3 LTC3859
VFB
RB
CFF
RA
VOUT
Figure 6. Using the TRACK/SS Pin to Program Soft-Start
3859 F06
1/3 LTC3859
TRACK/SS
SGND
CSS
Soft-start is enabled by simply connecting a capacitor
from the TRACK/SS pin to ground, as shown in Figure 6.
An internal 1μA current source charges the capacitor,
providing a linear ramping voltage at the TRACK/SS pin.
The LTC3859 will regulate the VFB pin (and hence VOUT)
according to the voltage on the TRACK/SS pin, allowing
VOUT to rise smoothly from 0V to its nal regulated value.
The total soft-start time will be approximately:
tSS_BUCK = CSS
0.8V
1A
tSS_BOOST = CSS
1.2V
1A
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3860EUH#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 32-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 |
| LTC3860EUH#PBF | 制造商:Linear Technology 功能描述:BUCK DC/DC CONVERTER IC |
| LTC3860EUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM VM 32-QFN 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: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) |
| LTC3860IUH#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 32-QFN 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:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 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:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
| LTC3860IUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM VM 32-QFN 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: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) |
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