TC850 datasheet(2/26 Pages) MICROCHIP

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TC850

DS21479C-page 2

General Description:

The TC850 is a monolithic CMOS A/D converter (ADC)

with resolution of 15-bits plus sign. It combines a

chopper-stabilized buffer and integrator with a unique

multiple-slope integration technique that increases

conversion speed. The result is 16 times improvement

in speed over previous 15-bit, monolithic integrating

ADCs (from 2.5 conversions per second up to 40 per

second).

Faster

conversion

speed

especially

welcome in systems with human interface, such as

digital scales.

The TC850 incorporates an ADC and a

μP-compatible

digital interface. Only a voltage reference and a few,

noncritical, passive components are required to form a

complete 15-bit plus sign ADC. CMOS processing

provides the TC850 with high-impedance, differential

inputs. Input bias current is typically only 30 pA, permit-

ting direct interface to sensors. Input sensitivity of 100

μV per Least Significant bit (LSb) eliminates the need

for precision external amplifiers. The internal amplifiers

are auto-zeroed, ensuring a zero digital output, with 0V

analog input. Zero adjustment potentiometers or

calibrations are not required.

The TC850 outputs data on an 8-bit, 3-state bus. Digital

inputs are CMOS compatible while outputs are TTL/

CMOS compatible. Chip-enable and byte-select inputs,

combined with an end-of-conversion output, ensures

easy interfacing to a wide variety of microprocessors.

Conversions can be performed continuously or on

command. In Continuous mode, data is read as three

consecutive bytes and manipulation of address lines is

not required.

Operating from ±5V supplies, the TC850 dissipates

only 20 m

Ω. The TC850 is packaged in a 40-pin plastic

or ceramic dual-in-line package (DIPs) and in a 44-pin

plastic leaded chip carrier (PLCC), surface-mount

package.

Functional Block Diagram

÷4

BUF

INT IN

Buffer

Pinout of 40-Pin Package

Integrator

Comparator

DB7

TC850

REF-

RINT

CINT

INT OUT

IN+

6-Bit

Up/Down

Counter

REF2+

REF1+

DB0

9-Bit

Up/Down

Counter

. . . .

CONT/

DEMAND

Analog

Mux

IN-

COMMON

+5V

–5V

OSC2

L/H

OVR/

POL

OSC1

A/D

Control

Sequencer

Data Latch

Octal 2-Input Mux

3-State Data Bus

Clock

Oscillator

Bus Interface

Decode Logic

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