参数资料
型号: PCA9507DP,118
厂商: NXP Semiconductors
文件页数: 17/20页
文件大小: 0K
描述: IC I/O EXPANDER I2C 24B 8TSSOP
产品培训模块: I²C Bus Fundamentals
特色产品: NXP - I2C Interface
标准包装: 1
接口: I²C,SM 总线
输入/输出数: 2 输入,2 输出
中断输出:
频率 - 时钟: 400kHz
电源电压: 2.7 V ~ 5.5 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 8-TSSOP,8-MSOP(0.118",3.00mm 宽)
供应商设备封装: 8-TSSOP
包装: 标准包装
其它名称: 568-5924-6
PCA9507_1
NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 — 7 February 2008
6 of 20
NXP Semiconductors
PCA9507
2-wire serial bus extender for HDMI DDC I2C-bus and SMBus
6.3.2 Port B (SDAB and SCLB)
SDAB and SCLB are standard I2C-bus with static level offset that has no rise time
accelerator. The static level offset produces an output LOW of 0.5 V (typical) at 6 mA. As
with the standard I2C-bus system, pull-up resistors are required to provide the logic HIGH
levels. The size of these pull-up resistors depends on the system requirement, and should
meet the current sinking capability of the device that drives the buffer, as well as that of
the buffer. The minimum and maximum pull-up resistors are determined and the pull-up
resistor’s value is chosen to be within the minimum and maximum range.
Using Equation 1, calculate the minimum pull-up resistor value:
(1)
Where:
RPU(min) is the minimum pull-up resistor value for the open-drain SCLB and SDAB.
VCC(B)(max) is the maximum supply rail of the pull-up resistor.
0.4 V is the maximum VOL of the device that drives the buffer on logic LOW.
IOL(max) at VOL = 0.4 V is the maximum sink current of the device that drives the buffer
on logic LOW.
The maximum pull-up resistor should also be sized such that the RC time constant meets
the standard I2C-bus rise time, which is 1
s for Standard-mode (100 kHz) or 300 ns for
Fast-mode (400 kHz). DDC bus complies with the I2C-bus Standard-mode and operates
below 100 kHz, and maximum rise time is 1
s using a simplied RC equation.
Using Equation 2, calculate the maximum pull-up resistor value:
(2)
Where:
RPU(max) is the maximum allowable pull-up resistor on the SCLB and SDAB in order to
meet the I2C-bus rise time specication.
CL(max) is the maximum allowable capacitance load (include the capacitance of driver,
the line, and the buffer) in order to meet the rise time specication.
tr is the rise time specied as 1 s (for bus speed 100 kHz or lower) and 300 ns (for bus
speed 400 kHz or lower).
The chosen pull-up resistor RPU is: RPU(min) ≤ RPU ≤ RPU(max).
R
PU min
()
V
CC B
() max
()
0.4 V
I
OL max
()
-------------------------------------------------
=
R
PU max
()
C
L max
()
×
1.2
t
r
×
=
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