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參數(shù)資料
| 型號： | MAX1518B |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類： | DC/DC變換器 |
| 英文描述： | TFT-LCD DC-DC Converter with Operational Amplifiers |
| 中文描述： | TFT-LCD DC-DC轉(zhuǎn)換器，帶有運算放大器 |
| 文件頁數(shù)： | 21/25頁 |
| 文件大?。?/td> | 1308K |
| 代理商： | MAX1518B |
M
TFT-LCD DC-DC Converter with
Operational Amplifiers
______________________________________________________________________________________
21
Adjust the gate-off linear-regulator REG N output volt-
age by connecting a resistive voltage-divider from
V
GOFF
to REF with the center tap connected to FBN
(Figure 1). Select R8 in the range of 20k
to 50k
.
Calculate R7 with the following equation:
where V
FBN
= 250mV, V
REF
= 1.25V. Note that REF can
only source up to 50μA; using a resistor less than 20k
for R8 results in higher bias current than REF can supply.
Pass-Transistor Selection
The pass transistor must meet specifications for current
gain (h
FE
), input capacitance, collector-emitter saturation
voltage and power dissipation. The transistor’s current
gain limits the guaranteed maximum output current to:
where I
DRV
is the minimum guaranteed base-drive cur-
rent, V
BE
is the transistor’s base-to-emitter forward volt-
age drop, and R
BE
is the pullup resistor connected
between the transistor’s base and emitter. Furthermore,
the transistor’s current gain increases the linear regula-
tor’s DC loop gain (see the
Stability Requirements
sec-
tion), so excessive gain destabilizes the output.
Therefore, transistors with current gain over 100 at the
maximum output current can be difficult to stabilize and
are not recommended unless the high gain is needed to
meet the load-current requirements.
The transistor’s saturation voltage at the maximum out-
put current determines the minimum input-to-output
voltage differential that the linear regulator can support.
Also, the package’s power dissipation limits the usable
maximum input-to-output voltage differential. The maxi-
mum power-dissipation capability of the transistor’s
package and mounting must exceed the actual power
dissipated in the device. The power dissipated equals
the maximum load current (I
LOAD(MAX)_LR
) multiplied
by the maximum input-to-output voltage differential:
where V
IN(MAX)_LR
is the maximum input voltage of the
linear regulator, and V
OUT
_
LR
is the output voltage of
the linear regulator.
Stability Requirements
The MAX1518B linear-regulator controllers use an inter-
nal transconductance amplifier to drive an external
pass transistor. The transconductance amplifier, the
pass transistor, the base-emitter resistor, and the out-
put capacitor determine the loop stability. The following
applies to both linear-regulator controllers in the
MAX1518B.
P I
V
V
LOAD MAX
LR
IN MAX
(
LR
OUT LR
×
(
)_
)_
_
(
)
I
I
V
R
h
LOAD MAX
DRV
BE
BE
FE MIN
(
(
)
)
=
×
R
R
V
V
V
V
FBN
REF
GOFF
FBN
7
8
=
×
POSITIVE CHARGE-PUMP
OUTPUT VOLTAGE vs. V
MAIN
V
MAIN
(V)
G
12
10
8
6
4
10
20
30
40
50
60
0
2
14
2-STAGE CHARGE PUMP
3-STAGE CHARGE PUMP
V
D
= 0.3V TO 1V
1-STAGE CHARGE PUMP
Figure 9. Positive Charge-Pump Output Voltage vs. V
MAIN
NEGATIVE CHARGE-PUMP
OUTPUT VOLTAGE vs. V
MAIN
V
MAIN
(V)
G
12
10
8
6
4
-40
-35
-30
-25
-20
-15
-10
-5
-0
-45
2
14
1-STAGE
CHARGE PUMP
2-STAGE
CHARGE PUMP
3-STAGE
CHARGE PUMP
V
D
= 0.3V TO 1V
Figure 10. Negative Charge-Pump Output Voltage vs. V
MAIN
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1518BETJ+ | 功能描述:LCD 驅(qū)動器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率: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 |
| MAX1518BETJ+T | 功能描述:LCD 驅(qū)動器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率: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 |
| MAX1518ETJ | 功能描述:LCD 驅(qū)動器 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 |
| MAX1518ETJ+ | 功能描述:LCD 驅(qū)動器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率: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 |
| MAX1518ETJ+T | 功能描述:LCD 驅(qū)動器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率: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 |
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