Datasheet
TLC548C, TLC548I, TLC549C, TLC549I
8-BIT ANALOG-TO-DIGITAL CONVERTERS
WITH SERIAL CONTROL
SLAS067C – NOVEMBER 1983 – REVISED SEPTEMBER 1996
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
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 kΩ TYP
C
i
= 60 pF TYP
(equivalent input
capacitance)
5 MΩ TYP
ANALOG IN
ANALOG IN