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參數(shù)資料
| 型號(hào)： | MAX8740 |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類(lèi)： | DC/DC變換器 |
| 英文描述： | TFT-LCD Step-Up DC-DC Converter |
| 中文描述： | TFT-LCD升壓型DC-DC轉(zhuǎn)換器 |
| 文件頁(yè)數(shù)： | 6/12頁(yè) |
| 文件大?。?/td> | 341K |
| 代理商： | MAX8740 |
M
TFT-LCD Step-Up DC-DC Converter
6
_______________________________________________________________________________________
Detailed Description
The MAX8740 is a highly efficient power supply that
employs a current-mode, fixed-frequency, PWM archi-
tecture for fast transient response and low-noise opera-
tion. The device regulates the output voltage through a
combination of an error amplifier, two comparators, and
several signal generators (Figure 2). The error amplifier
compares the signal at FB to 1.24V and varies the
COMP output. The voltage at COMP determines the
current trip point each time the internal MOSFET turns
on. As the load changes, the error amplifier sources or
sinks current to the COMP output to command the
inductor peak current necessary to service the load. To
maintain stability at high duty cycles, a slope-compen-
sation signal is summed with the current-sense signal.
At light loads, this architecture allows the MAX8740 to
“skip” cycles to prevent overcharging the output voltage.
In this region of operation, the inductor ramps up to a
peak value of approximately 150mA, discharges to the
output, and waits until another pulse is needed again.
Output Current Capability
The output current capability of the MAX8740 is a func-
tion of current limit, input voltage, operating frequency,
and inductor value. Because of the slope compensa-
tion used to stabilize the feedback loop, the inductor
current limit depends on the duty cycle. The current
limit is determined by the following equation:
I
LIM
= (1.26 - 0.35 x D) x I
LIM_EC
where I
LIM
_
EC
is the current limit specified at 71% duty
cycle (see the
Electrical Characteristics
table) and D is
the duty cycle.
The output current capability depends on the current-
limit value and is governed by the following equation:
where I
LIM
is the current limit calculated above,
η
is the
regulator efficiency (85% nominal), and D is the duty
cycle. The duty cycle when operating at the current
limit is:
where V
DIODE
is the rectifier diode forward voltage and
R
ON
is the on-resistance of the internal MOSFET.
D
V
V
×
V
V
I
R
V
OUT
IN
DIODE
+
OUT
LIM
ON
DIODE
+
=
I
I
D
V
f
L
V
V
OUT MAX
(
LIM
IN
OSC
IN
OUT
)
0.
×
×
×
=
×
η
GND
LX
IN
FREQ
FB
COMP
4
μ
A
5
μ
A
N
ERROR
COMPARATOR
ERROR
AMPLIFIER
SKIP
COMPARATOR
SS
CLOCK
SKIP
BIAS
SHDN
MAX8740
Σ
CURRENT
SENSE
CONTROL
AND DRIVER
LOGIC
SOFT-
START
SLOPE
COMPEN-
SATION
OSCILLATOR
∞
1.24V
Figure 2. Functional Diagram
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX8740ETB | TFT-LCD Step-Up DC-DC Converter |
| MAX878LCPA | Analog IC |
| MAX8710 | LCD display panel power supply TFT Monitor TV |
| MAX8711 | LCD display panel power supply TFT Monitor TV |
| MAX8712 | LCD display panel power supply TFT Monitor TV |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX8740ETB | 制造商:Maxim Integrated Products 功能描述:LOW COST LCD MONITOR PANEL POWER SU - Rail/Tube |
| MAX8740ETB+ | 制造商:Maxim Integrated Products 功能描述:- Rail/Tube |
| MAX8740ETB+T | 功能描述:LCD 驅(qū)動(dòng)器 TFT-LCD Step-Up DC/DC Converter RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時(shí)鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| MAX8740ETB-T | 功能描述:LCD 驅(qū)動(dòng)器 RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時(shí)鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| MAX8740EUB+ | 制造商:Maxim Integrated Products 功能描述:- Rail/Tube |
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