TLC548C, TLC548I, TLC549C, TLC549I

8-BIT ANALOG-TO-DIGITAL CONVERTERS

WITH SERIAL CONTROL

SLAS067C – NOVEMBER 1983 – REVISED SEPTEMBER 1996

2

POST OFFICE BOX 655303

description (continued)

Operation of the TLC548 and the TLC549 is very similar to that of the more complex TLC540 and TLC541

devices; however, the TLC548 and TLC549 provide an on-chip system clock that operates typically at 4 MHz

and requires no external components. The on-chip system clock allows internal device operation to proceed

independently of serial input/output data timing and permits manipulation of the TLC548 and TLC549 as desired

for a wide range of software and hardware requirements. The I/O CLOCK together with the internal system clock

allow high-speed data transfer and conversion rates of 45 500 conversions per second for the TLC548, and

40 000 conversions per second for the TLC549.

Additional TLC548 and TLC549 features include versatile control logic, an on-chip sample-and-hold circuit that

can operate automatically or under microprocessor control, and a high-speed converter with differential

high-impedance reference voltage inputs that ease ratiometric conversion, scaling, and circuit isolation from

logic and supply noises. Design of the totally switched-capacitor successive-approximation converter circuit

allows conversion with a maximum total error of

±0.5 least significant bit (LSB) in less than 17 µs.

The TLC548C and TLC549C are characterized for operation from 0

°C to 70°C. The TLC548I and TLC549I are

characterized for operation from – 40

°C to 85°C.

functional block diagram

REF –

6

4

8

8

DATA

OUT

8-Bit

Analog-to

Digital

Converter

(Switched-

Capacitors)

8-to-1 Data

Selector

and

Driver

Output

Data

Regiser

Internal

System

Clock

Sample

and

Hold

7

5

2

3

1

ANALOG IN

REF +

CS

I/O CLOCK

Control

Logic and

Output Counter

typical equivalent inputs

INPUT CIRCUIT IMPEDANCE DURING SAMPLING MODE

INPUT CIRCUIT IMPEDANCE DURING HOLD MODE

1 k

Ω TYP

Ci = 60 pF TYP

(equivalent input

capacitance)

5 M

Ω TYP

ANALOG IN

ANALOG IN