參數(shù)資料
型號： LTC3856EFE#PBF
廠商： LINEAR TECHNOLOGY CORP
元件分類： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, PDSO38
封裝： 4.4 MM, LEAD FREE, PLASTIC, TSSOP-38
文件頁數(shù)： 13/40頁
文件大?。?/td> 2222K
代理商： LTC3856EFE#PBF
LTC3856
0
3856f
applicaTions inForMaTion
After determining the components for the temperature
compensation network, check the results by plotting
IMAX versus inductor temperature using the following
equations:
I
V
DCR
AT
C
MAX
SENSEMAX ADJ
SENSE
MAX
=
° +
(
)
2
25
1 ((
)
.
(
)
T
C
L MAX
°
25
0 4
100
where
V
V V
A
SENSEMAX ADJ
SENSE MAX
ITMP
(
)
(
)
.
=
1 8
1 3
VITMP = 10A (RS + RP||RNTC)
UsetypicalvaluesforVSENSE(MAX).Subtractingconstant A
willprovideaminimumvalueforVSENSE(MAX).Thesevalues
are summarized in Table 2.
Table 2. Values for VSENSE(MAX)
ILIM
GND
FLOAT
INTVCC
VSENSE(MAX) Typ
30mV
50mV
75mV
A
5mV
7mV
The resulting current limit should be greater than or
equal to IMAX for inductor temperatures between 25°C
and 100°C.
Typical values for the NTC compensation network are:
NTC RO = 100k, B-constant = 3000 to 4000
RS ≈ 20k
RP ≈ 50k
Another approach for generating the IMAX versus inductor
temperature curve plot is to first use the aforementioned
values as a starting point and then adjusting the RS and
RP values as necessary. Figure 6 shows a typical curve
of IMAX versus inductor temperature.
The same thermistor network can be used to correct for
temperatures less than 25°C. But, ensure that VITEMP is
greater than 0.2V for duty cycles of 25% or more, oth-
erwise temperature correction may not occur at elevated
ambients. For the most accurate temperature detection,
place the thermistor next to the inductors, as shown in
Figure 7. Take care to keep the ITEMP pins away from the
switch nodes.
Figure 6. Worst Case IMAX vs Inductor Temperature Curve
with and without NTC Temperature Compensation
Figure 7. Thermistor Location. Place Thermistor Next to
Inductor(s) for Accurate Sensing of the Inductor Temperature,
But Keep the ITEMP Pin Away from the Switch Nodes and
Gate Drive Traces.
3856 F07
VOUT
L1
SW1
L2
SW2
RNTC
Slope Compensation and Inductor Peak Current
Slopecompensationprovidesstabilityinconstant-frequen-
cy,currentmodearchitecturesbypreventingsubharmonic
oscillationathighdutycycles.Itisaccomplishedinternally
by adding a compensating ramp to the inductor current
signal at duty cycles in excess of 40%. Normally, this
results in a reduction of maximum inductor peak current
for duty cycles greater than 40%. However, the LTC3856
uses a scheme that counteracts this compensating ramp,
whichallowsthemaximuminductorpeakcurrenttoremain
unaffected throughout all duty cycles.
INDUCTOR TEMPERATURE (°C)
–40
I MAX
(A)
20
100
15
10
0
40
–20
20
60
80
120
5
0
25
3856 F06
NOMINAL
IMAX
RS = 20k
RP = 43.2k
NTC THERMISTOR:
RO = 100k
TO = 25°C
B = 4334
UNCORRECTED
IMAX
CORRECTED
IMAX
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
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LTC3856IFE#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 38TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標準包裝: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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