TLC1542C, TLC1542I, TLC1542M, TLC1542Q, TLC1543C, TLC1543I, TLC1543Q
10-BIT ANALOG-TO-DIGITAL CONVERTERS WITH
SERIAL CONTROL AND 11 ANALOG INPUTS
SLAS052E – MARCH 1992 – OCTOBER 1998
Terminal Functions
TERMINAL
NAME
ADDRESS
NO.
17
I/O
I
DESCRIPTION
Serial address input. A 4-bit serial address selects the desired analog input or test voltage that is to
be converted next. The address data is presented with the MSB first and shifts in on the first four rising
edges of I/O CLOCK. After the four address bits have been read into the address register, this input
is ignored for the remainder of the current conversion period.
Analog signal inputs. The 11 analog inputs are applied to these terminals and are internally multiplexed.
The driving source impedance should be less than or equal to 1 kΩ.
Chip select. A high-to-low transition on this input resets the internal counters and controls and enables
DATA OUT, ADDRESS, and I/O CLOCK within a maximum of a setup time plus two falling edges of
the internal system clock. A low-to-high transition disables ADDRESS and I/O CLOCK within a setup
time plus two falling edges of the internal system clock.
The 3-state serial output for the A/D conversion result. This output is in the high-impedance state when
CS is high and active when CS is low. With a valid chip select, DATA OUT is removed from the
high-impedance state and is driven to the logic level corresponding to the MSB value of the previous
conversion result. The next falling edge of I/O CLOCK drives this output to the logic level corresponding
to the next most significant bit, and the remaining bits shift out in order with the LSB appearing on the
ninth falling edge of I/O CLOCK. On the tenth falling edge of I/O CLOCK, DATA OUT is driven to a low
logic level so that serial interface data transfers of more than ten clocks produce zeroes as the unused
LSBs.
End of conversion. This output goes from a high to a low logic level on the trailing edge of the tenth I/O
CLOCK and remains low until the conversion is complete and data are ready for transfer.
The ground return terminal for the internal circuitry. Unless otherwise noted, all voltage measurements
are with respect to this terminal.
Input/output clock. This terminal receives the serial I/O CLOCK input and performs the following four
functions:
1) It clocks the four input address bits into the address register on the first four rising edges of the I/O
CLOCK with the multiplex address available after the fourth rising edge.
2) On the fourth falling edge of I/O CLOCK, the analog input voltage on the selected multiplex input
begins charging the capacitor array and continues to do so until the tenth falling edge of
I/O CLOCK.
3) It shifts the nine remaining bits of the previous conversion data out on DATA OUT.
4) It transfers control of the conversion to the internal state controller on the falling edge of the tenth
clock.
The upper reference voltage value (nominally VCC) is applied to this terminal. The maximum input
voltage range is determined by the difference between the voltage applied to this terminal and the
voltage applied to the REF – terminal.
The lower reference voltage value (nominally ground) is applied to this terminal.
Positive supply voltage
A0 – A10
CS
1 – 9, 11, 12
15
I
I
DATA OUT
16
O
EOC
GND
I/O CLOCK
19
10
18
O
I
I
REF +
14
I
REF –
VCC
13
20
I
I
detailed description
With chip select (CS) inactive (high), the ADDRESS and I/O CLOCK inputs are initially disabled and DATA OUT
is in the high-impedance state. When the serial interface takes CS active (low), the conversion sequence begins
with the enabling of I/O CLOCK and ADDRESS and the removal of DATA OUT from the high-impedance state.
The serial interface then provides the 4-bit channel address to ADDRESS and the I/O CLOCK sequence to I/O
CLOCK. During this transfer, the serial interface also receives the previous conversion result from DATA OUT.
I/O CLOCK receives an input sequence that is between 10 and 16 clocks long from the host serial interface.
The first four I/O clocks load the address register with the 4-bit address on ADDRESS, selecting the desired
analog channel, and the next six clocks providing the control timing for sampling the analog input.
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•
DALLAS, TEXAS 75265
3
TI [ TEXAS INSTRUMENTS ]
