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參數(shù)資料
| 型號： | LTC3731HUH#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 5 A SWITCHING CONTROLLER, 750 kHz SWITCHING FREQ-MAX, PQCC32 |
| 封裝： | 5 X 5 MM, LEAD FREE, PLASTIC, MO-220WHHD, QFN-32 |
| 文件頁數(shù)： | 9/34頁 |
| 文件大小： | 427K |
| 代理商： | LTC3731HUH#PBF |
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LTC3731H
3731Hfb
applicaTions inForMaTion
availableincaseheightsrangingfrom2mmto4mm.Other
capacitor types include Sanyo POS-CAP, Sanyo OS-CON,
Nichicon PL series and Sprague 595D series. Consult the
manufacturer for other specific recommendations.
RSENSE Selection for Output Current
Once the frequency and inductor have been chosen,
RSENSE1, RSENSE2, RSENSE3 are determined based on the
required peak inductor current. The current comparator
has a typical maximum threshold of 75mV/RSENSE and
an input common mode range of SGND to (1.1) VCC.
The current comparator threshold sets the peak inductor
current, yielding a maximum average output current IMAX
equal to the peak value less half the peak-to-peak ripple
current, IL.
Allowing a margin for variations in the IC and external
component values yields:
R
N
mV
I
SENSE
MAX
=
50
The IC works well with values of RSENSE from 0.002Ω to
0.02Ω.
VCC Decoupling
The VCC and VDR pins supply power to the internal cir-
cuits of the controller and to the top and bottom gate
drivers. Therefore, they must be bypassed very carefully
to ground with ceramic capacitors, type X7R or X5R (de-
pending upon the operating temperature environment)
of at least 1F immediately next to the IC and preferably
an additional 10F placed very close to the IC due to the
extremely high instantaneous currents involved. The total
capacitance, taking into account the voltage coefficient
of ceramic capacitors, should be 100 times as large as
the total combined gate charge capacitance of ALL of the
MOSFETs being driven. Good bypassing close to the IC is
necessary to supply the high transient currents required
by the MOSFET gate drivers while keeping the 5V supply
quiet enough so as not to disturb the very small-signal
high bandwidth of the current comparators.
Topside MOSFET Driver Supply (CB, DB)
External bootstrap capacitors, CB, connected to the
BOOST pins, supply the gate drive voltages for the top-
side MOSFETs. Capacitor CB in the Functional Diagram
is charged though diode DB from VCC when the SW pin
is low. When one of the topside MOSFETs turns on, the
driver places the CB voltage across the gate-source of the
desired MOSFET. This enhances the MOSFET and turns
on the topside switch. The switch node voltage, SW,
rises to VIN and the BOOST pin follows. With the topside
MOSFET on, the boost voltage is above the input supply
(VBOOST = VCC + VIN). The value of the boost capacitor CB
needs to be 30 to 100 times that of the total gate charge
capacitance of the topside MOSFET(s) as specified on the
manufacturer’s data sheet. The reverse breakdown of DB
must be greater than VIN(MAX).
The output voltage is set by an external resistive divider
according to the following formula:
V
R
OUT =
+
0 6 1
1
2
.
The resistive divider is connected to the output as shown
in Figure 2.
Soft-Start/Run Function
The RUN/SS pin provides three functions: 1) ON/OFF, 2)
soft-start and 3) a defeatable short-circuit latch off timer.
Soft-startreducestheinputpowersources’surgecurrents
by gradually increasing the controller’s current limit (pro-
portional to an internal buffered and clamped VITH). The
latchoff timer prevents very short, extreme load transients
from tripping the overcurrent latch. A small pull-up cur-
rent (>5A) supplied to the RUN/SS pin will prevent the
overcurrent latch from operating. A maximum pull-up cur-
rent of 200A is allowed into the RUN/SS pin even though
the voltage at the pin may exceed the absolute maximum
rating for the pin. This is a result of the limited current
and the internal protection circuit on the pin. The following
explanation describes how this function operates.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3731IG | 制造商:Linear Technology 功能描述:LDO Cntrlr SYNC BUCK REG 0.6V to 6V 36-Pin SSOP |
| LTC3731IG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC3731IG#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC3731IUH | 制造商:Linear Technology 功能描述:LDO Cntrlr SYNC BUCK REG 0.6V to 6V 32-Pin QFN EP |
| LTC3731IUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
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