參數(shù)資料
型號(hào)： LTC3851EMSE-1#TRPBF
廠商： LINEAR TECHNOLOGY CORP
元件分類： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, PDSO16
封裝： 0.150 INCH, LEAD FREE, PLASTIC, MSOP-16
文件頁(yè)數(shù)： 4/28頁(yè)
文件大?。?/td> 337K
代理商： LTC3851EMSE-1#TRPBF
LTC3851-1
12
38511f
APPLICATIONS INFORMATION
The Typical Application on the rst page of this data sheet
is a basic LTC3851-1 application circuit. The LTC3851-1
can be congured to use either DCR (inductor resistance)
sensing or low value resistor sensing. The choice of the
two current sensing schemes is largely a design trade-off
between cost, power consumption and accuracy. DCR
sensing is becoming popular because it saves expensive
current sensing resistors and is more power efcient,
especially in high current applications. However, current
sensing resistors provide the most accurate current limits
for the controller. Other external component selection
is driven by the load requirement, and begins with the
selection of RSENSE (if RSENSE is used) and the inductor
value. Next, the power MOSFETs and Schottky diodes are
selected. Finally, input and output capacitors are selected.
The circuit shown on the rst page can be congured for
operation up to 40V at VIN.
SENSE+ and SENSE– Pins
The SENSE+ and SENSE– pins are the inputs to the current
comparators. The common mode input voltage range of
the current comparators is 0V to 5.5V. Both SENSE pins
are high impedance inputs with small base currents of
less than 1μA. When the SENSE pins ramp up from 0V to
1.4V, the small base currents ow out of the SENSE pins.
When the SENSE pins ramp down from 5V to 1.1V, the
small base currents ow into the SENSE pins. The high
impedance inputs to the current comparators allow ac-
curate DCR sensing. However, care must be taken not to
oat these pins during normal operation.
Low Value Resistors Current Sensing
A typical sensing circuit using a discrete resistor is shown
in Figure 1. RSENSE is chosen based on the required output
current.
The current comparator has a maximum threshold, VMAX
= 50mV. The current comparator threshold sets the maxi-
mum peak of the inductor current, yielding a maximum
average output current, IMAX, equal to the peak value less
half the peak-to-peak ripple current,
ΔIL.Allowingamargin
of 20% for variations in the IC and external component
values yields:
R
V
II
SENSE
MAX
L
=
+
0 8
2
.
/
Δ
Inductor DCR Sensing
For applications requiring the highest possible efciency,
the LTC3851-1 is capable of sensing the voltage drop
across the inductor DCR, as shown in Figure 2. The
DCR of the inductor represents the small amount of
DC winding resistance of the copper, which can be less
than 1m
Ω for today’s low value, high current inductors.
If the external R1||R2 C1 time constant is chosen to
be exactly equal to the L/DCR time constant, the voltage
drop across the external capacitor is equal to the voltage
drop across the inductor DCR multiplied by R2/(R1 + R2).
Therefore, R2 may be used to scale the voltage across the
sense terminals when the DCR is greater than the target
sense resistance. Check the manufacturer’s data sheet
for specications regarding the inductor DCR, in order
to properly dimension the external lter components.
The DCR of the inductor can also be measured using a
good RLC meter.
Figure 1. Using a Resistor to Sense Current with the LTC3851-1
VIN
INTVCC
BOOST
TG
SW
BG
GND
FILTER COMPONENTS
PLACED NEAR SENSE PINS
SENSE+
SENSE–
LTC3851-1
VOUT
RSENSE
38511 F01
相關(guān)PDF資料
PDF描述
LTC3851EUD-1#TRPBF SWITCHING CONTROLLER, PQCC16
LTCEMSE-1#PBF SWITCHING CONTROLLER, PDSO16
LTC3851IUD-1#TRPBF SWITCHING CONTROLLER, PQCC16
LTC3859IUHF#TRPBF SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PQCC38
LTC3859EFE#PBF SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PDSO38
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
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LTC3851EUD-1#PBF 功能描述:IC REG CTRLR BUCK PWM CM 16-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
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