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TC500ACPE View Datasheet(PDF) - Microchip Technology

Part NameTC500ACPE Microchip
Microchip Technology Microchip
DescriptionPrecision Analog Front Ends with Dual Slope ADC
TC500ACPE Datasheet PDF : 38 Pages
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TC500/A/510/514
8.6 Integrator Output Zero Phase
The comparator delay and the controller’s response
latency may result in overshoot, causing charge
buildup on the integrator at the end of a conversion.
This charge must be removed or performance will
degrade. The integrator output zero phase should be
activated (AB = 00) until CMPTR goes high. It is
absolutely critical that this phase be terminated
immediately so that overshoot is not allowed to occur in
the opposite direction. At this point, it can be assured
that the integrator is near zero. Auto-zero should be
entered (AB = 01) and the TC5XX held in this state until
the next cycle is begun (see Figure 8-2).
Integrator
Output
Zero
Crossing
Comparator
Output Comp
Integrate
Phase
FIGURE 8-2:
Overshoot
De-integrate Phase
Integrator
Zero Phase
Overshoot.
8.7 Using the TC510/TC514
8.7.1
NEGATIVE SUPPLY VOLTAGE
CONVERTER (TC510, TC514)
A capacitive charge pump is employed to invert the
voltage on VDD for negative bias within the TC510/
TC514. This voltage is also available on the VOUT– pin
to provide negative bias elsewhere in the system. Two
external capacitors are required to perform the
conversion.
Timing is generated by an internal state machine driven
from an on-board oscillator. During the first phase,
capacitor CF is switched across the power supply and
charged to VS+. This charge is transferred to capacitor
COUT– during the second phase. The oscillator
normally runs at 100 kHz to ensure minimum output
ripple. This frequency can be reduced by placing a
capacitor from OSC to VDD. The relationship between
the capacitor value is shown in Section 2.0 “Typical
Performance Curves”.
8.7.2
ANALOG INPUT MULTIPLEXER
(TC514)
The TC514 is equipped with a four-input differential
analog multiplexer. Input channels are selected using
select inputs (A1, A0). These are high-true control
signals (i.e., channel 0 is selected when (A1, A0 = 00).
DS21428E-page 18
© 2008 Microchip Technology Inc.
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General Description:
TheTC500/A/510/514 family are precision analog front ends that implement dual slope A/D converters having a maximum resolution of 17 bits plus sign. As a minimum, each device contains the integrator, zero crossing comparator and processor interface logic. The TC500 is the base (16-bit max) device and requires both positive and negative power supplies. The TC500A is identical to the TC500 with the exception that it has improved linearity, allowing it to operate to a maximum resolution of 17 bits. The TC510 adds an on board negative power supply converter for single supply operation. The TC514 adds both a negative power supply converter and a 4-input differential analog multiplexer.

Features:
• Precision (up to 17 bits) A/D Converter “Front End”
• 3-Pin Control Interface to Microprocessor
• Flexible: User Can Trade-off Conversion Speed for Resolution
• Single-Supply Operation (TC510/TC514)
• 4 Input, Differential Analog MUX (TC514)
• Automatic Input Voltage Polarity Detection
• Low Power Dissipation:
   - (TC500/TC500A): 10 mW
   - (TC510/TC514): 18 mW
• Wide Analog Input Range:
   - ±4.2V (TC500A/TC510)
• Directly Accepts Bipolar and Differential Input Signals

Applications:
• Precision Analog Signal Processor
• Precision Sensor Interface
• High Accuracy DC Measurements

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