參數(shù)資料
型號(hào)： MAX1779
廠商： Maxim Integrated Products, Inc.
英文描述： 32-Bit Digital Signal Controller with ROM 100-LQFP -40 to 125
中文描述： 低功耗、三輸出TFT LCD DC-DC轉(zhuǎn)換器
文件頁(yè)數(shù)： 12/18頁(yè)
文件大?。?/td> 503K
代理商： MAX1779
M
Low-Power Triple-Output TFT LCD DC-DC
Converter
12
______________________________________________________________________________________
1.125V), the active-low ready signal (
RDY
) is pulled low
(see
Power Ready
section).
Power Ready
Power ready is an open-drain output. When the power-
up sequence is properly completed, the MOSFET turns
on and pulls
RDY
low with a typical 125
on-resis-
tance. If a fault is detected, the internal open-drain
MOSFET appears as a high impedance. Connect a
100k
pullup resistor between
RDY
and IN for a logic-
level output.
Fault Detection
Once
RDY
is low, if any output falls below its fault-
detection threshold, then
RDY
becomes high imped-
ance.
For the reference, the fault threshold is 1.05V. For the
main boost converter, the fault threshold is 88% of its
nominal value (V
FB
< 1.1V). For the negative charge
pump, the fault threshold is approximately 88% of its
nominal value (V
FBN
< 140mV). For the positive charge
pump, the fault threshold is 88% of its nominal value
(V
FBP
< 1.11V).
Once an output faults, all outputs later in the power
sequence shut down until the faulted output rises
above its power-up threshold. For example, if the nega-
tive charge-pump output voltage falls below the fault
detection threshold, the main boost converter remains
active while the positive charge pump stops switching
and its output voltage decays, depending on output
capacitance and load. The positive charge-pump out-
put will not power up until the negative charge-pump
output voltage rises above its power-up threshold (see
the
Power-Up Sequencing
section).
Voltage Reference
The voltage at REF is nominally 1.25V. The reference
can source up to 50μA with good load regulation (see
Typical Operating Characteristics
). Connect a 0.22μF
bypass capacitor between REF and GND.
Design Procedure
Main Boost Converter
Inductor Selection
Inductor selection depends upon the minimum required
inductance value, saturation rating, series resistance,
and size. These factors influence the converter
’
s effi-
ciency, maximum output load capability, transient
response time, and output voltage ripple. For most
applications, values between 10μH and 33μH work
best with the controller
’
s switching frequency.
The inductor value depends on the maximum output
load the application must support, input voltage, and
output voltage. With high inductor values, the MAX1779
sources higher output currents, has less output ripple,
and enters continuous-conduction operation with lighter
loads; however, the circuit
’
s transient response time is
slower. On the other hand, low-value inductors respond
faster to transients, remain in discontinuous-conduction
operation, and typically offer smaller physical size. The
maximum output current an inductor value will support
may be calculated by the following equations:
A. Continuous-conduction: if
then
B. Discontinuous-conduction: if
then
where I
LIM(MIN)
= 350mA and
= 250kHz (see the
Electrical Characteristics
).
The inductor
’
s saturation current rating should exceed
peak inductor current throughout the normal operating
range. Under fault conditions, the inductor current may
reach up to 600mA (I
LIM(MAX)
, see the
Electrical
Characteristics
). However, the MAX1779
’
s fast current-
limit circuitry allows the use of soft-saturation inductors
while still protecting the IC.
The inductor
’
s DC resistance significantly affects effi-
ciency due to the power loss in the inductor. The power
loss due to the inductor
’
s series resistance (P
LR
) may
be approximated by the following equation:
P
I
V
V
R
LR
MAIN
MAIN
IN
L
×
×
2
L
I
V
V
I
MAIN MAX
MAIN
IN MIN
(
LIM MIN
(
≥
(
)
2
1
2
(
)
)
)
-
I
V
V
I
MAIN MAX
IN MIN
(
MAIN
LIM MIN
(
(
)
)
)
<
1
2
L
V
V
IN MIN
(
MAIN
V
V
V
I
I
MAINVIN MIN
IN MIN
(
MAIN
LIM MIN
(
MAIN MAX
(
≥
1
2
1
2
)
(
)
)
)
)
-
-
I
V
V
I
MAIN MAX
IN MIN
(
MAIN
LIM MIN
(
(
)
)
)
≥
1
2
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1779EUE 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1779EUE+ 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 Triple-Output TFT LCD RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1779EUE+T 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 Triple-Output TFT LCD RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1779EUE-T 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX177C/D 功能描述:模數(shù)轉(zhuǎn)換器 - ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類(lèi)型:Differential 信噪比:107 dB 接口類(lèi)型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
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