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參數(shù)資料
| 型號： | LT1680ISW#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 200 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 0.300 INCH, PLASTIC, SOP-16 |
| 文件頁數(shù)： | 4/16頁 |
| 文件大?。?/td> | 217K |
| 代理商： | LT1680ISW#TRPBF |
12
LT1680
S1 + SX is greater than S2, this condition for subharmonic
oscillation no longer exists.
For boost topologies, the required additional current wave-
form slope, or “Slope Compensation,” follows the relation:
S
SDC
DC
X ≥
()(
)
()
12
1
–
For duty cycles less than 50% (DC < 0.5), SX is negative and
is not required. For duty cycles greater than 50%, SX takes
on values dependent on S1 and duty cycle. S1 is simply VIN/
L. This leads to a minimum inductance requirement for a
given VIN, duty cycle and slope compensation (SX) of:
L
V
S
DC
MIN
IN
X
=
()
21
1
–
The LT1680 contains an internal slope compensation
ramp that has an equivalent current referred value of:
S = 0.084
f
R
X
O
SENSE
Amp/s
where fO is oscillator frequency and RSENSE is the external
current sense resistor. This yields a minimum inductance
requirement of:
L
VR
DC
fDC
MIN
IN
SENSE
O
≥ ( )()()
()( )
()
[]
21
0 084
1
–
.
A down side of slope compensation is that, since the IC
servo loop senses an increase in perceived inductor cur-
rent, the internal current limit functions are affected such
that the maximum current capability of a regulator is
reduced by the same amount as the effective current
referred slope compensation. The LT1680, however, uses
a current limit scheme that is independent of the slope
compensation effects (Average Current Limiting). This
provides operation at any duty cycle with no reduction in
current sourcing capability, provided ripple current peak
amplitude is less than 15% of the current limit value. For
example, if the converter is set up to average current limit
at 10A, as long as the peak inductor current is less than
11.5A, duty cycles up to 90% can be achieved without
compromising the average current limit value.
OSCILLATOR
PERIOD
TIME
0
5a
5b
I
T1
I2
I1
S1
S2
S1 + SX
1680 F05
Figure 5. Inductor Current at DC > 50% and
Slope Compensation Adjusted Signal
APPLICATIO S I FOR ATIO
WU
UU
Figure 6. Maximum Peak Ripple Current (Normalized)
vs Duty Cycle for Average Current Limit
DUTY CYCLE
0
1.10
MAXIMUM
PEAK
RIPPLE
CURRENT
(I
PK
/I
AVG
)
1.15
1.25
1.30
1.35
0.2 0.3 0.4 0.5 0.6 0.7 0.8
1680 F06
1.20
0.1
0.9
1.40
1.45
If an inductor smaller than the minimum required for
internal slope compensation (calculated above as LMIN) is
desired, additional slope compensation is necessary. The
LT1680 provides this capability through the SL/ADJ pin.
This feature is implemented by referencing this pin via a
resistor divider from the 5VREF pin to ground. The addi-
tional slope compensation will be affected at the point in
the oscillator waveform (at pin CT) corresponding to the
voltage set by the resistor divider. Additional slope com-
pensation can be calculated using the relation:
S
f
RR
X
O
TH
SENSE
= ()( )
()(
)
2500
Amp/s
where RTH is the Thevenin resistance of the resistor
divider. Actual compensation will actually be somewhat
greater due to internal curvature correction circuitry that
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相關代理商/技術參數(shù) |
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|---|---|
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| LT1681ESW#TR | 功能描述:IC SYNCHRONOUS FWRD CTRLR 20SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 電源控制器，監(jiān)視器 系列:- 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:- 應用:多相控制器 輸入電壓:- 電源電壓:9 V ~ 14 V 電流 - 電源:- 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:40-WFQFN 裸露焊盤 供應商設備封裝:40-TQFN-EP（5x5） 包裝:帶卷 (TR) |
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