- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄98002 > LT1111IS8-5#PBF (LINEAR TECHNOLOGY CORP) SWITCHING REGULATOR, PDSO8 PDF資料下載
參數(shù)資料
| 型號(hào)： | LT1111IS8-5#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING REGULATOR, PDSO8 |
| 封裝： | LEAD FREE, SOIC-8 |
| 文件頁(yè)數(shù)： | 4/16頁(yè) |
| 文件大?。?/td> | 237K |
| 代理商： | LT1111IS8-5#PBF |
第1頁(yè)第2頁(yè)第3頁(yè)當(dāng)前第4頁(yè)第5頁(yè)第6頁(yè)第7頁(yè)第8頁(yè)第9頁(yè)第10頁(yè)第11頁(yè)第12頁(yè)第13頁(yè)第14頁(yè)第15頁(yè)第16頁(yè)
12
LT1111
1111fd
U
S
A
O
PPLICATI
WU
U
I FOR ATIO
L1
LT1111 F08
GND
SW2
FB
SW1
LIM
I
IN
V
D1
A0
VOUT
R2
VOUT =
1.25V + 0.6V
( )
R1
R2
R1
2N3906
–VIN
C1
LT1111
C2
+
Figure 8. Negative-to-Positive Converter
Using the ILIM Pin
The LT1111 switch can be programmed to turn off at a set
switch current, a feature not found on competing devices.
This enables the input to vary over a wide range without
exceeding the maximum switch rating or saturating the
inductor. Consider the case wh
ere analysis shows the
LT1111 must operate at an 800mA peak switch current
with a 2V input. If VIN rises to 4V, the peak switch current
will rise to 1.6A, exceeding the maximum switch current
rating. With the proper resistor selected (see the “Maxi-
mum Switch Current vs ILIM” characteristic), the switch
current will be limited to 800mA, even if the input voltage
increases.
Another situation where the ILIM feature is useful occurs
when the device goes into continuous mode operation.
This occurs in step-up mode when:
V
VV
DC
OUT
DIODE
IN
SW
+
<
1
25
()
When the input and output voltages satisfy this relation-
ship, inductor current does not go to zero during the
switch OFF time. When the switch turns on again, the
current ramp starts from the non-zero current level in the
inductor just prior to switch turn-on. As shown in Figure
9, the inductor current increases to a high level before the
comparator turns off the oscillator. This high current can
cause excessive output ripple and requires oversizing the
output capacitor and inductor. With the ILIM feature,
however, the switch current turns off at a programmed
level as shown in Figure 10, keeping output ripple to a
minimum.
LT1111 F09
I
OFF
L
ON
SWITCH
Figure 9. No Current Limit Causes Large Inductor
Current Build-Up
LT1111 F10
I
ON
L
OFF
SWITCH
PROGRAMMED CURRENT LIMIT
Figure 10. Current Limit Keeps Inductor Current Under Control
Figure 11 details current limit circuitry. Sense transistor
Q1, whose base and emitter are paralleled with power
switch Q2, is ratioed such that approximately 0.5% of Q2’s
collector current flows in Q1’s collector. This current is
passed through internal 80
resistor R1 and out through
the ILIM pin. The value of the external resistor connected
between ILIM and VIN sets the current limit. When suffi-
cient switch current flows to develop a VBE across R1 +
RLIM, Q3 turns on and injects current into the oscillator,
turning off the switch. Delay through this circuitry is
approximately 1
s. The current trip point becomes less
accurate for switch ON times less than 3
s. Resistor
values programming switch ON time for 1
s or less will
cause spurious response in the switch circuitry although
the device will still maintain output regulation.
LT1111 F11
SW2
SW1
DRIVER
OSCILLATOR
VIN
ILIM
R1
80
(INTERNAL)
RLIM
(EXTERNAL)
Q1
Q2
Q3
Figure 11. LT1111 Current Limit Circuitry
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LT1172HVMK | 1.25 A SWITCHING REGULATOR, 100 kHz SWITCHING FREQ-MAX, MBFM2 |
| LT1307IS8#TR | 1.25 A SWITCHING REGULATOR, 750 kHz SWITCHING FREQ-MAX, PDSO8 |
| LT1508ISW#TR | POWER FACTOR CONTROLLER WITH POST REGULATOR, 115 kHz SWITCHING FREQ-MAX, PDSO20 |
| LT1513IT7-2#PBF | 5.4 A BATTERY CHARGE CONTROLLER, 580 kHz SWITCHING FREQ-MAX, PSFM7 |
| LT1513IR-2#PBF | 5.4 A BATTERY CHARGE CONTROLLER, 580 kHz SWITCHING FREQ-MAX, PSSO7 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT1111IS8PBF | 制造商:Linear Technology 功能描述:DC/DC Converter Adj Micropower 2-30V SO8 |
| LT1111M | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Micropower DC/DC Converter Adjustable and Fixed 5V, 12V |
| LT1111MJ8 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Micropower DC/DC Converter Adjustable and Fixed 5V, 12V |
| LT1111MJ8-12 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Micropower DC/DC Converter Adjustable and Fixed 5V, 12V |
| LT1111MJ8-5 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Micropower DC/DC Converter Adjustable and Fixed 5V, 12V |
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。