参数资料
型号: MCP795W10-I/ST
厂商: Microchip Technology
文件页数: 5/13页
文件大小: 0K
描述: IC RTCC 64B SRAM WD/DET 14TSSOP
标准包装: 96
类型: 时钟/日历
特点: 警报,EEPROM,闰年,方波输出,SRAM,看门狗定时器
存储容量: 64B
时间格式: HH:MM:SS:hh(12/24 小时)
数据格式: YY-MM-DD-dd
接口: SPI
电源电压: 1.8 V ~ 5.5 V
电压 - 电源,电池: 1.3 V ~ 5.5 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 14-TSSOP(0.173",4.40mm 宽)
供应商设备封装: 14-TSSOP
包装: 管件
MCP4902/4912/4922
DS22250A-page 28
2010 Microchip Technology Inc.
6.4
Single-Supply Operation
The MCP4902/4912/4922 family of devices are rail-to-
rail voltage output DAC devices designed to operate
with a VDD range of 2.7V to 5.5V. Its output amplifier is
robust enough to drive small-signal loads directly.
Therefore, it does not require any external output buffer
for most applications.
6.4.1
DC SET POINT OR CALIBRATION
A common application for the DAC devices is
digitally-controlled set points and/or calibration of
variable parameters, such as sensor offset or slope.
For example, the MCP4922 provides 4096 output
steps. If the external voltage reference (VREF) is
4.096V, the LSb size is 1 mV. If a smaller output step
size is desired, a lower external voltage reference is
needed.
6.4.1.1
Decreasing Output Step Size
If the application is calibrating the bias voltage of a
diode or transistor, a bias voltage range of 0.8V may be
desired with about 200 V resolution per step. Two
common methods to achieve a 0.8V range is to either
reduce VREF to 0.82V or use a voltage divider on the
DAC’s output.
Using a VREF is an option if the VREF is available with
the
desired
output
voltage
range.
However,
occasionally, when using a low-voltage VREF, the noise
floor causes SNR error that is intolerable. Using a
voltage divider method is another option and provides
some advantages when VREF needs to be very low or
when the desired output voltage is not available. In this
case, a larger value VREF is used while two resistors
scale the output range down to the precise desired
level.
Example 6-1 illustrates this concept. Note that the
bypass capacitor on the output of the voltage divider
plays a critical function in attenuating the output noise
of the DAC and the induced noise from the
environment.
EXAMPLE 6-1:
EXAMPLE CIRCUIT OF SET POINT OR THRESHOLD CALIBRATION
VDD
SPI
3-wire
VTRIP
R1
R2
0.1 uF
Comparator
G = Gain selection (1x or 2x)
Dn = Digital value of DAC (0-255) for MCP4901/MCP4902
VOUT
VREF G
Dn
2
N
------
=
VCC+
VCC
VOUT
Vtrip
VOUT
R2
R1 R2
+
--------------------
=
VDD
RSENSE
DAC
= Digital value of DAC (0-1023) for MCP4911/MCP4912
= Digital value of DAC (0-4095) for MCP4921/MCP4922
N = DAC Bit Resolution
VREF
VO
MCP4901
MCP4911
MCP4921
(a) Single Output DAC:
(b) Dual Output DAC:
MCP4902
MCP4912
MCP4922
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MCP795W10T-I/ST 功能描述:实时时钟 1Kb EE 64B SRAM WD TED ID RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube
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MCP795W11-I/SL 功能描述:实时时钟 1Kb EE 64B SRAM WD TED EUI-48 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube
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