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参数资料
| 型号： | LTC3785EUF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 3 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC24 |
| 封装： | 4 X 4 MM, PLASTIC, MO-220WGGD, QFN-24 |
| 文件页数： | 20/20页 |
| 文件大小： | 275K |
| 代理商： | LTC3785EUF |
LTC3785
3785fc
operaTion
the buck-boost range, approximately 0.7V, the AC switch
pair completely phase out the BD pair, and the boost phase
begins at duty cycle, D4(SW).
The input voltage, VIN,wherethefourswitchregionbegins
is given by:
VIN =
VOUT
1– 300ns f
(
)
V
the point at which the four switch region ends is given
by:
VIN = VOUT(1 – D) = VOUT(1 – 300ns f) V
Boost Region (VIN < VOUT)
Switch A is always on and switch B is always off during
boost mode. When the error amp output voltage, VC,isap-
proximately above 0.7V, switch pair C and D will alternately
switch to provide a boosted output voltage. This operation
is typical to a synchronous boost regulator. The maximum
duty cycle of the converter is limited to 90% typical.
Burst Mode OPERATION
DuringBurstModeoperation,theLTC3785deliversenergy
to the output until it is regulated and then goes into a sleep
state where the outputs are off and the IC is consuming
only 86A. In Burst Mode operation, the output ripple
has a variable frequency component, which is dependent
upon load current.
During the period where the converter is delivering en-
ergy to the output, the inductor will reach a peak current
determined by an on time, tON, and will terminate at zero
current for each cycle. The on time is given by:
tON =
2.4
VIN f
where f is the oscillator frequency.
The peak current is given by:
IPEAK =
VIN
L
tON
IPEAK =
2.4
f L
So the peak current is independent of VIN and inversely
proportional to the f L product optimizing the energy
transfer for various applications.
In Burst Mode operation the maximum output current is
given by:
IOUT(MAX,BURST) ≈
1.2 VIN
f L VOUT + VIN
(
)
A
Burst Mode operation is user-controlled by driving the
MODE pin high to enable and low to disable.
VCC REGULATOR
An internal P-channel low dropout regulator produces
4.35V at the VCC pin from the VIN supply pin. VCC powers
the drivers and internal circuitry of the LTC3785. The VCC
pin regulator can supply a peak current of 100mA and
must be bypassed to ground with a minimum of 4.7F
placed directly adjacent to the VCC and GND pins. Good
bypassing is necessary to supply the high transient cur-
rent required by the MOSFET gate drivers and to prevent
interaction between channels. If desired, the VCCregulator
can be connected to VOUT through a Schottky diode to
provide higher gate drive in low input voltage applications.
The VCC regulator can also be driven with an external 5V
source directly (without a Schottky diode).
TOPSIDE MOSFET DRIVER SUPPLY (VBST1, VBST2)
The external bootstrap capacitors connected to the VBST1
and VBST2 pins supply the gate drive voltage for the top-
side MOSFET switches A and D. When the top MOSFET
switch A turns on, the switch node SW1 rises to VIN and
the VBST2 pin rises to approximately VIN + VCC. When the
bottom MOSFET switch B turns on, the switch node SW1
drops low and the boost capacitor is charged through the
diode connected to VCC. When the top MOSFET switch D
turns on, the switch node SW2 rises to VOUT and the VBST2
pin rises to approximately VOUT + VCC. When the bottom
MOSFET switch C turns on, the switch node SW2 drops
low and the boost capacitor is charged through the diode
connectedtoVCC.Theboostcapacitorsneedtostoreabout
100 times the gate charge required by the top MOSFET
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相关代理商/技术参数 |
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| LTC3785EUF#PBF | 功能描述:IC REG CTRLR BST PWM VM 24-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 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 |
| LTC3785EUF#TRPBF | 功能描述:IC REG CTRLR BST PWM VM 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) |
| LTC3785EUF-1#PBF | 功能描述:IC REG CTRLR BST PWM VM 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) |
| LTC3785EUF-1#TRPBF | 功能描述:IC REG CTRLR BST PWM VM 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: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 |
| LTC3785EUFPBF | 制造商:Linear Technology 功能描述:10V Synch Buck-Boost Controller LTC3785 |
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