參數(shù)資料
型號(hào)： LT1111M
廠商： Linear Technology Corporation
英文描述： Dual 4-Input Positive-NAND Gates 14-SO 0 to 70
中文描述： 微功率DC / DC轉(zhuǎn)換可調(diào)和固定5V，12V的
文件頁(yè)數(shù)： 6/16頁(yè)
文件大?。?/td> 337K
代理商： LT1111M
6
LT1111
Gain block A2 can serve as a low-battery detector. The
negative input of A2 is the 1.25V reference. A resistor
divider from V
IN
to GND, with the mid-point connected to
the SET pin provides the trip voltage in a low-battery
detector application. AO can sink 300
μ
A (use a 22k
resistor pull-up to 5V).
A resistor connected between the I
LIM
pin and V
IN
sets
maximum switch current. When the switch current ex-
ceeds the set value, the switch cycle is prematurely
terminated. If current limit is not used, I
LIM
should be tied
directly to V
IN
. Propagation delay through the current limit
circuitry is approximately 1
μ
s.
In step-up mode the switch emitter (SW2) is connected to
ground and the switch collector (SW1) drives the induc-
tor; in step-down mode the collector is connected to V
IN
and the emitter drives the inductor.
The LT1111-5 and LT1111-12 are functionally identical to
the LT1111. The -5 and -12 versions have on-chip voltage
setting resistors for fixed 5V or 12V outputs. Pin 8 on the
fixed versions should be connected to the output. No
external resistors are needed.
U
LT11
O
ATI
11OPER
The LT1111 is a gated oscillator switcher. This type
architecture has very low supply current because the
switch is cycled when the feedback pin voltage drops
below the reference voltage. Circuit operation can best be
understood by referring to the LT1111 block diagram.
Comparator A1 compares the feedback (FB) pin voltage
with the 1.25V reference signal. When FB drops below
1.25V, A1 switches on the 72kHz oscillator. The driver
amplifier boosts the signal level to drive the output NPN
power switch. The switch cycling action raises the output
voltage and FB pin voltage. When the FB voltage is suffi-
cient to trip A1, the oscillator is gated off. A small amount
of hysteresis built into A1 ensures loop stability without
external frequency compensation. When the comparator
output is low, the oscillator and all high current circuitry is
turned off, lowering device quiescent current to just 300
μ
A.
The oscillator is set internally for 7
μ
s ON time and 7
μ
s OFF
time, optimizing the device for circuits where V
OUT
and V
IN
differ by roughly a factor of 2. Examples include a 3V to 5V
step-up converter or a 9V to 5V step-down converter.
W
IAGRA
BLOCK
S
LT1111 BD01
IN
V
GND
SET
A0
A2
1.25V
REFERENCE
A1
OSCILLATOR
DRIVER
SW1
SW2
LIM
I
GAIN BLOCK/
ERROR AMP
COMPARATOR
+
–
+
–
FB
LT1111-5/LT1111-12
LT1111
LT1111 BD02
IN
V
GND
SET
A0
A2
1.25V
REFERENCE
A1
OSCILLATOR
DRIVER
R1
SW1
SW2
LIM
I
R2
220k
SENSE
LT1111-5:
LT1111-12:
R1 = 73.5k
R1 = 25.5k
GAIN BLOCK/
ERROR AMP
COMPARATOR
+
–
+
–
相關(guān)PDF資料
PDF描述
LT1111MJ8-5 Micropower DC/DC Converter Adjustable and Fixed 5V, 12V
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
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
LT1112 制造商:LINEAR 制造商全稱:LINEAR 功能描述:Dual/Quad Low Power Precision, Picoamp Input Op Amps
LT1112_1 制造商:LINEAR 制造商全稱:LINEAR 功能描述:Dual/Quad Low Power Precision, Picoamp Input Op Amps
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