SC7106 데이터 시트보기 (PDF) - Silan Microelectronics
부품명
상세내역
제조사
SC7106 Datasheet PDF : 21 Pages
| |||
SC7106/7107
3. SIGNAL INTEGRATE PHASE
During signal integrate, the auto-zero loop is opened, the internal short is removed, and the internal input high
and low are connected to the external pins. The converter then integrates the differential voltage between IN HI
and IN LO for a fixed time. This differential voltage can be within a wide common mode range: up to 1V from
either supply. If, on the other hand, the input signal has no return with respect to the converter power supply, IN
LO can be tied to analog COMMON to establish the correct common mode voltage. At the end of this phase, the
polarity of the integrated signal is determined.
4. DE-INTEGRATE PHASE
The final phase is de-integrate, or reference integrate. Input low is internally connected to analog COMMON
and input high is connected across the previously charged reference capacitor. Circuitry within the chip ensures
that the capacitor will be connected with the correct polarity to cause the integrator output to return to zero. The
time required for the output to return to zero is proportional to input signal. Specifically the digital reading
displayed is: DISPLAY COUNT=1000 (VIN/VREF).
5. DIFFERENTIAL INPUT
The input can accept differential voltages anywhere within the common mode range of the input amplifier, or
specifically from 0.5V below the positive supply to 1V above the negative supply. In this range, the system has a
CMRR of 86dB typical. However, care must be exercised to assure the integrator output does not saturate. A
worst case condition would be a large positive common mode voltage with a near full-scale negative differential
input voltage. The negative input signal drives the integrator positive when most of its swing has been used up by
the positive common mode voltage. For these critical applications the integrator output swing can be reduced to
less than the recommended 2V full-scale swing with little loss of accuracy. The integrator output can swing to
within 0.3V of either supply without loss of linearity.
6. DIFFERENTIAL REFERENCE
The reference voltage can be generated anywhere within the power supply voltage of the converter. The main
source of common mode error is a roll-over voltage caused by the reference capacitor losing or gaining charge to
stray capacity on its nodes. If there is a large common mode voltage, the reference capacitor can gain charge
(increase voltage) when called up to de-integrate a positive signal but lose charge (decrease voltage) when
called up to de-integrate a negative input signal. This difference in reference for positive or negative input voltage
will give a roll-over error. However, by selecting the reference capacitor such that it is large enough in
comparison to the stray capacitance, this error can be held to less than 0.5 count worst case. (See Component
Value Selection.)
7. ANALOG COMMON
This pin is included primarily to set the common mode voltage for battery operation (SC7106) or for any system
where the input signals are floating with respect to the power supply. The COMMON pin sets a voltage that is
approximately 2.8V more negative than the positive supply. This is selected to give a minimum end-of -life battery
voltage of about 6V. However, analog COMMON has some of the attributes of a reference voltage. When the
total supply voltage is large enough to cause the zener to regulate (>7V), the COMMON voltage will have a low
voltage coefficient (0.001%/V), low output impedance (≈15Ω), and a temperature coefficient typically less than
80ppm/°C.
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http: www.silan.com.cn
REV:1.2 2006.02.27
Page 8 of 22
Share Link: 