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MAX16929
Automotive TFT-LCD Power Supply with Boost
Converter and Gate Voltage Regulators
The number of positive charge-pump stages needed is
given by:
switching frequency of the boost converter, and V RIPPLE_
CP is the peak-to-peak value of the output ripple.
n CP =
V GH +V DROPOUT ? V SH
V SH +V SCHOTTKY ? 2 × V D
For the inverting charge pump connected to CN, use the
following equation to approximate the required output
capacitance:
n CN =
C OUT_CN ≥
and the number of negative charge-pump stages is
given by:
|V GL |+V DROPOUT
V SH + V SCHOTTKY ? 2 × V D
where n CP is the number of positive charge-pump stag-
es, n CN is the number of negative charge-pump stages,
V GH is the positive-gate voltage regulator output volt-
age, V GL is the negative-gate voltage regulator output
voltage, V SH is the boost converter’s output voltage, V D
is the forward-voltage drop of the charge-pump diode,
V SCHOTTKY is the forward drop of the Schottky diode
of the boost converter, and V DROPOUT is the dropout
margin for the regulator. Use V DROPOUT = 0.3V for the
negative voltage regulator and V DROPOUT = 2V at 20mA
for the positive-gate voltage regulator.
Flying Capacitors
Increasing the flying capacitor (C X ) value lowers the
effective source impedance and increases the output
current capability. Increasing the capacitance indefi-
nitely has a negligible effect on output current capability
because the internal switch resistance and the diode
impedance place a lower limit on the source impedance.
A 0.1 F F ceramic capacitor works well in most low-current
(1-D) × I LOAD_CN
f SW × V RIPPLE_CN
where C OUT_CN is the output capacitor of the charge
pump, D is the duty cycle of the boost converter,
I LOAD_CN is the load current of the charge pump, f SW
is the switching frequency of the boost converter, and
V RIPPLE_CN is the peak-to-peak value of the output
ripple.
Charge-Pump Rectifier Diodes
Use high-speed silicon switching diodes with a current
rating equal to or greater than two times the average
charge-pump input current. If it helps avoid an extra
stage, some or all of the diodes can be replaced with
Schottky diodes with an equivalent current rating.
Positive-Gate Voltage Regulator
Output-Voltage Selection
The output voltage of the positive-gate voltage regula-
tor can be adjusted by using a resistive voltage-divider
formed by R TOP and R BOTTOM . Connect R TOP between
the output and FBGH, and connect R BOTTOM between
FBGH and GND. Select R BOTTOM in the 10k I to 50k I
range. Calculate R TOP with the following equation:
applications. The voltage rating of the flying capacitors
for the positive charge pump should exceed V CP , and
that for the negative charge pump should exceed the
R TOP = R BOTTOM × (
V GH
V FBGH
? 1)
C OUT_CP ≥
magnitude of V CN .
Charge-Pump Output Capacitor
Increasing the output capacitance or decreasing the ESR
reduces the output-ripple voltage and the peak-to-peak
transient voltage. With ceramic capacitors, the output-
voltage ripple is dominated by the capacitance value.
Use the following equation to approximate the required
output capacitance for the noninverting charge pump
connected to CP:
D × I LOAD_CP
f SW × V RIPPLE_CP
where C OUT_CP is the output capacitor of the charge
pump, D is the duty cycle of the boost converter, I LOAD_
CP is the load current of the charge pump, f SW is the
where V GH is the desired output voltage and V FBGH = 1V
(the regulated feedback voltage for the regulator). Place
both resistors as close as possible to the device.
Avoid excessive power dissipation within the internal
pMOS device of the regulator by paying attention to the
voltage drop across the drain and source. The amount of
power dissipation is given by:
P GL = (V CP - V GH ) × I LOAD(MAX)
where V CP is the noninverting charge-pump output volt-
age applied to the drain, V GH is the regulated output
voltage, and I LOAD(MAX) is the maximum load current.
Stability Requirements
The positive-gate voltage regulator (GH) requires a
minimum output capacitance for stability. For an output
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MAX16929FGUI/V+
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功能描述:LCD 驱动器 18V 2MHz Auto TFT-LCD Pwr Supply RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube
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MAX16929GGUI/V+T
功能描述:LCD 驱动器 18V 2MHz Auto TFT-LCD Pwr Supply RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube
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功能描述:LCD 驱动器 18V 2MHz Auto TFT-LCD Pwr Supply RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube
MAX16929GUI/V+T
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MAX16929HGUI/V+
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MAX16929HGUI/V+T
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