Datasheet

TLC2543C, TLC2543I, TLC2543M
12-BIT ANALOG-TO-DIGITAL CONVERTERS
WITH SERIAL CONTROL AND 11 ANALOG INPUTS
SLAS079F – DECEMBER 1993 – REVISED NOVEMBER 2001
17
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
data format and pad bits (continued)
When CS
is held low continuously, the first data bit of the newly completed conversion occurs on DATA OUT
on the rising edge of EOC. When a new conversion is started after the last falling edge of I/O CLOCK, EOC goes
low and the serial output is forced to a setting of 0 until EOC goes high again.
When CS
is negated between conversions, the first data bit occurs on DATA OUT on the falling edge of CS.
On each subsequent falling edge of I/O CLOCK after the first data bit appears, the data is changed to the next
bit in the serial conversion result until the required number of bits has been output.
chip-select input (CS)
CS
enables and disables the device. During normal operation, CS should be low. Although the use of CS is not
necessary to synchronize a data transfer, it can be brought high between conversions to coordinate the data
transfer of several devices sharing the same bus.
When CS is brought high, the serial-data output is immediately brought to the high-impedance state, releasing
its output data line to other devices that may share it. After an internally generated debounce time, I/O CLOCK
is inhibited, thus preventing any further change in the internal state.
When CS
is subsequently brought low again, the device is reset. CS must be held low for an internal debounce
time before the reset operation takes effect. After CS
is debounced low, I/O CLOCK must remain inactive (low)
for a minimum time before a new I/O cycle can start.
CS
can interrupt any ongoing data transfer or any ongoing conversion. When CS is debounced low long enough
before the end of the current conversion cycle, the previous conversion result is saved in the internal output
buffer and shifted out during the next I/O cycle.
power-down features
When a binary address of 1110 is clocked into the input data register during the first four I/O CLOCK cycles,
the power-down mode is selected. Power down is activated on the falling edge of the fourth I/O CLOCK pulse.
During power down, all internal circuitry is put in a low-current standby mode. No conversions are performed,
and the internal output buffer keeps the previous conversion cycle data results provided that all digital inputs
are held above V
CC
– 0.5 V or below 0.5 V. The I/O logic remains active so the current I/O cycle must be
completed even when the power-down mode is selected. Upon power-on reset and before the first I/O cycle,
the converter normally begins in the power-down mode. The device remains in the power-down mode until a
valid input address (other than 1110) is clocked in. Upon completion of that I/O cycle, a normal conversion is
performed with the results being shifted out during the next I/O cycle.