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AAT3111IGU-3.6 参数 Datasheet PDF下载

AAT3111IGU-3.6图片预览
型号: AAT3111IGU-3.6
PDF下载: 下载PDF文件 查看货源
内容描述: [Analog Circuit,]
分类和应用:
文件页数/大小: 16 页 / 200 K
品牌: ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
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AAT3111
MicroPower Regulated Charge Pump
Functional Block Diagram
V
IN
S2
SHDN
CONTROL
S1
C+
C-
V
REF
S4
S3
V
OUT
-
+
GND
Functional Description
Operation
(Refer to block diagram)
The AAT3111 uses a switched capacitor charge
pump to boost an input voltage to a regulated output
voltage. Regulation is achieved by sensing the
charge pump output voltage through an internal
resistor divider network. A switched doubling circuit
is enabled when the divided output drops below a
preset trip point controlled by an internal comparator.
The charge pump switch cycling enables four inter-
nal switches at two non-overlapping phases. During
the first phase, switches S1 and S4 are switched on
(short) and switches S2 and S3 are off (open). The
flying capacitor C
FLY
is charged to a level approxi-
mately equal to input voltage V
IN
. On the second
phase, switches S1 and S4 are turned off (open),
and S2 and S3 are turned on (short). The low side of
the flying capacitor C
FLY
is connected to GND during
the first phase. During the second phase, the flying
capacitor C
FLY
is switched so that the low side is
connected to V
IN
. The voltage at the high side of the
flying capacitor C
FLY
is bootstrapped to 2
×
V
IN
and
is connected to the output through switch S3. For
each cycle phase, charge from input node V
IN
is
transported from a lower voltage to a higher voltage.
This cycle repeats itself until the output node voltage
is high enough to exceed the preset input threshold
of the control comparator. When the output voltage
exceeds the internal trip point level, the switching
cycle stops and the charge pump circuit is tem-
3111.2005.11.1.2
porarily placed in an idle state. When idle, the
AAT3111 has a quiescent current of 20µA or less.
The closed loop feedback system containing the
voltage sense circuit and control comparator allows
the AAT3111 to provide a regulated output voltage to
the limits of the input voltage and output load cur-
rent. The switching signal, which drives the charge
pump, is created by an integrated oscillator within
the control circuit block. The free-running charge
pump switching frequency is approximately 750kHz.
The switching frequency under a load is a function of
V
IN
, V
OUT
, C
OUT
, and I
OUT
.
For each phase of the switching cycle, the charge
transported from V
IN
to V
OUT
can be approximated
by the following formula:
V
PHASE
C
FLY
×
(2
×
V
IN
- V
OUT
)
The relative average current that the charge pump
can supply to the output may be approximated by
the following expression:
I
OUT(AVG)
α
C
FLY
×
(2
×
V
IN
- V
OUT
)
×
F
SW
The AAT3111 has complete output short-circuit and
thermal protection to safeguard the device under
extreme operating conditions. An internal thermal
protection circuit senses die temperature and will
shut down the device if the internal junction temper-
ature exceeds approximately 145°C. The charge
pump will remain disabled until the fault condition is
relieved.
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