Datasheet 搜索 > 微控制器 > Microchip（微芯） > PIC18F97J94-I/PT 数据手册 > PIC18F97J94-I/PT 数据手册 263/696 页
器件3D模型￥ 41.064
PIC18F97J94-I/PT 数据手册 - Microchip（微芯）
制造商:
Microchip（微芯）
分类:
微控制器
封装:
TQFP-100
描述:
MICROCHIP PIC18F97J94-I/PT 微控制器, 8位, 闪存, PIC18FxxJxx, 64 MHz, 128 KB, 3.7714 KB, 100 引脚, TQFP
Pictures:
3D模型
符号图
焊盘图
引脚图
产品图
页面导航:
引脚图在P3P4P5P32P40P264P321P322P324P344P346Hot
典型应用电路图在P357P521
原理图在P11P14P15P16P53P60P85P221P236P245P255P282
封装尺寸在P665
标记信息在P663
封装信息在P663P665P666P667P669P671P673P675
功能描述在P489
技术参数、封装参数在P76P488P551P636P637P638P639P641P642P643
应用领域在P62P72P76P326P333P505
电气规格在P11P33P49P76P90P92P461P485P488P492P497P499
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PIC18F97J94-I/PT数据手册
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若手册格式错乱，请下载阅览PDF原文件
2012 Microchip Technology Inc. DS30575A-page 263
PIC18F97J94 FAMILY
13.7 Design Considerations for the
LCD Charge Pump
When designing applications that use the LCD regula-
tor with the charge pump enabled, users must always
consider both the dynamic current and RMS (static)
current requirements of the display, and what the
charge pump can deliver. Both dynamic and static
current can be determined by Equation 13-1:
EQUATION 13-1: LCD STATIC, DYNAMIC
CURRENT
For dynamic current, C, is the value of the capacitors
attached to LCDBIAS3 and LCDBIAS2. The variable,
dV, is the voltage drop allowed on C2 and C3 during a
voltage switch on the LCD display, and dt is the duration
of the transient current after a clock pulse occurs.
For practical design purposes, it will be assumed to be
0.047 µF for C, 0.1V for dV and 1 µs for dt. This yields
a dynamic current of 4.7 mA for 1 µs.
RMS current is determined by the value of C
FLY for C,
the voltage across V
LCAP1 and VLCAP2 for dV and the
regulator clock period (TPER) for dt. Assuming a C
FLY
value of 0.047 µF, a value of 1.02V across CFLY and
TPER of 30 µs, the maximum theoretical static current
will be 1.8 mA. Since the charge pump must charge five
capacitors, the maximum current becomes 360 µA.
For a real-world assumption of 50% efficiency, this
yields a practical current of 180 µA. Users should com-
pare the calculated current capacity against the
requirements of the LCD. While dV and dt are relatively
fixed by device design, the values of C
FLY and the
capacitors on the LCDBIAS pins can be changed to
increase or decrease current. As always, any changes
should be evaluated in the actual circuit for their impact
on the application.
I = C x
dV
dt
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