参数资料
型号: PCA85132U/2DB/Q1,0
厂商: NXP Semiconductors
文件页数: 41/62页
文件大小: 0K
描述: IC LCD DRIVER 32 UNCASED
标准包装: 600
显示器类型: LCD
配置: 多重
接口: I²C
数字或字符: 任何数字类型
电流 - 电源: 60µA
电源电压: 1.8 V ~ 5.5 V
工作温度: -40°C ~ 95°C
封装/外壳: 模具
供应商设备封装: 模具
包装: 散装
NXP Semiconductors
PCA85132
LCD driver for low multiplex rates
14. Application information
14.1 Pull-up resistor sizing on I 2 C-bus
14.1.1 Max value of pull-up resistor
The bus capacitance (C b ) is the total capacitance of wire, connections, and pins. This
capacitance on pin SDA limits the maximum value of the pull-up resistor (R PU ) due to the
specified rise time.
According to the I 2 C-bus specification the rise time (t r ) is defined between the V DD -related
input threshold of V IL = 0.3V DD and V IH = 0.7V DD . The value for t r(max) is 300 ns.
t r is calculated with Equation 7 :
t r = t2 – t1
whereas t1 and t2 are the time since the charging started. The values for t1 and t2 are
derivatives of the functions V(t1) and V(t2):
(7)
V ? t1 ? = 0.3V DD = V DD ? 1 – e
V ? t2 ? = 0.7V DD = V DD ? 1 – e
-t1 ? R PU C b
-t2 ? R PU C b
?
?
(8)
(9)
with the results of
t1 = – R PU C b ? ln ( 0.7 )
t2 = – R PU C b ? ln ( 0.3 )
t r = – R PU C b ? ln ( 0.3 ) + R PU C b ? ln ( 0.7 )
(10)
(11)
(12)
R PU(max) is a function of the rise time (t r ) and the bus capacitance (C b ) and is calculated
R PU ? max ? = ----------------------- = --------------------------
0.8473C b 0.8473C b
t r 300 ? 10 – 9
(13)
14.1.2 Min value of pull-up resistor
The supply voltage limits the minimum value of resistor R PU due to the specified minimum
sink current (see value of I OL on pin SDAACK in Table 21 on page 35 ). R PU(min) as a
function of V DD is calculated with Equation 14 :
R PU ? min ? = --------------------------
V DD – V OL
I OL
(14)
The designer now has the minimum and maximum value of R PU . The values for R PU(max)
and R PU(min) are shown in Figure 30 and Figure 31 .
PCA85132
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 11 July 2013
? NXP B.V. 2013. All rights reserved.
41 of 62
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