参数资料
型号: MAX1234ETI+
厂商: Maxim Integrated Products
文件页数: 26/44页
文件大小: 0K
描述: IC CNTRLR TOUCH 28-TQFN
其它有关文件: Automotive Product Guide
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 60
类型: 电阻
触摸面板接口: 4 线
输入数/键: 1,4 x 4 小键盘
分辨率(位): 8,10,12 b
数据接口: MICROWIRE?,QSPI?,串行,SPI?
数据速率/采样率 (SPS,BPS): 50k
电压基准: 内部
电源电压: 4.75 V ~ 5.25 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 28-TQFN 裸露焊盘
供应商设备封装: 28-TQFN-EP(5x5)
包装: 管件
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
32
______________________________________________________________________________________
Auxiliary Analog Inputs
Two auxiliary analog inputs (AUX1 and AUX2) allow the
MAX1233/MAX1234 to monitor analog input voltages
from zero to VREF. Figure 16 illustrates the process of
auxiliary input reading.
Temperature Measurements
The MAX1233/MAX1234 provide two temperature mea-
surement options: a single-ended conversion method
and a differential conversion method. Both temperature
measurement techniques rely on the semiconductor
junction’s operational characteristics at a fixed current
level. The forward diode voltage (VBE) vs. temperature is
a well-defined characteristic. The ambient temperature
can be predicted in applications by knowing the value
of the VBE voltage at a fixed temperature and then moni-
toring the delta of that voltage as the temperature
changes. Figure 17 illustrates the functional block of the
internal temperature sensor.
The single conversion method requires calibration at a
known temperature, but only requires a single reading to
predict the ambient temperature. First, the internal diode
forward bias voltage is measured by the ADC at a
known temperature. Subsequent diode measurements
provide an estimate of the ambient temperature through
extrapolation. This assumes a temperature coefficient of
-2.1mV/°C. The single conversion method results in a
resolution of 0.29°C/LSB (2.5V reference) and
0.12°C/LSB (1.0V reference) with a typical accuracy of
±2°C. Figure 18 shows the flowchart for the single tem-
perature measurement.
The differential conversion method uses two measure-
ment points. The first measurement is performed with a
fixed bias current into the internal diode. The second
measurement is performed with a fixed multiple of the
original bias current. The voltage difference between the
first and second conversion is proportional to the
absolute temperature and is expressed by the following
formula:
ΔVBE = (kT/q) ln(N)
where:
ΔVBE = difference in diode voltage
N = current ratio of the second measurement to the first
measurement
k = Boltzmann’s constant (1.38
× 10-23 eV/°Kelvin)
q = electron charge (1.60
× 10-19 C)
T = temperature in °Kelvin
The resultant equation solving for °K is:
T(°K) = q x
ΔV / (k × ln(N))
AUXILIARY INPUT 1 OR
AUXILIARY INPUT 2
DONE
NO
IS DATA
AVERAGING DONE?
STORE AUXILIARY INPUT 1 OR 2 IN
AUX1 OR AUX2 REGISTER
POWER DOWN
ADC
POWER UP
ADC
POWER UP REFERENCE
CONVERT
AUXILIARY INPUT 1 OR 2
POWER DOWN REFERENCE
TURN OFF CLOCK
HOST WRITES
ADC
CONTROL REGISTER
START CLOCK
IS ADC
REFERENCE IN
AUTO POWER-DOWN
MODE?
NO
YES
SET BUSY
LOW
YES
SET BUSY HIGH
Figure 16. Auxiliary Input Flowchart
TEMP1
TEMP2
A/D
CONVERTER
MUX
Figure 17. Internal Block Diagram of Temperature Sensor
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