icl8068cdd Intersil Corporation, icl8068cdd Datasheet - Page 19
![no-image](/images/manufacturer_photos/0/3/342/intersil_corporation_sml.jpg)
icl8068cdd
Manufacturer Part Number
icl8068cdd
Description
14-bit/16-bit, Microprocessor- Compatible, 2-chip, A/d Converter
Manufacturer
Intersil Corporation
Datasheet
1.ICL8068CDD.pdf
(21 pages)
Initial Clear Circuitry
The internal logic of the 7104 is supplied by an internal
regulator between V++ and Digital Ground. The regulator
includes a low-voltage detector that will clear various
registers. This is intended to ensure that on initial power-up,
the control logic comes up in Auto-Zero, with the 2nd, 3rd,
and 4th MSB bits cleared, and the “mode” F/F cleared (i.e.,
in “direct” mode). This, however, will also clear these regis-
ters if the supply voltage “glitches” to a low enough value.
Additionally, if the supply voltage comes up too fast, this
clear pulse may be too narrow for reliable clearing. In gen-
eral, this is not a problem, but if the UART internal “MODE”
F/F should come up set, the byte and chip ENABLE lines will
become active outputs. In many systems this could lead to
bus conflicts, especially in non-handshake systems. In any
case, SEN should be high (held high for non-handshake sys-
tems) to ensure that the MODE F/F will be cleared as fast as
possible (see Figure 11 for timing). For these and other
reasons, adequate supply bypass is recommended.
Oscillator
The ICL7104-14 is provided with a versatile three terminal
oscillator to generate the internal clock. The oscillator may
be overdriven, or may be operated as an RC or crystal
oscillator.
Figure 14 shows the oscillator configured for RC operation.
The internal clock will be of the same frequency and phase
as the voltage on the CLOCK 3 pin. The resistor and
capacitor should be connected as shown. The circuit will
oscillate at a frequency given by f = 0.45/RC. A 50 - 100k
resistor is recommended for useful ranges of frequency. For
optimum 60Hz line rejection, the capacitor value should be
chosen such that 32768 (-16), 8192 (-14) clock periods is
close to an integral multiple of the 60Hz period.
AS OUTPUT
BYTE DATA
HIGH BYTE
SEN INPUT
LOW BYTE
INTERNAL
INTERNAL
INTERNAL
CE/LOAD
POSITIVE TRANSITION
CAUSES ENTRY INTO
UART MODE
OUTPUT
STATUS
MIDDLE
CLOCK
LATCH
MODE
INPUT
MODE
MBEN
HBEN
LBEN
DATA
DATA
xxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxx
xxxxxx
xxxxxx
UART
NORM
xxxx
xxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
DON’T CARE
ICL8052/ICL7104, ICL8068/ICL7104
FIGURE 13. HANDSHAKE TRIGGERED BY MODE
DATA VALID
LATCH PULSE INHIBITED
THREE-STATE HIGH IMPEDANCE
IN UART MODE
DEINT PHASE III
5-24
NOTE: Clock 3 has the same output drive as the bit outputs.
As a result of pin count limitations, the ICL7104-16 has only
CLOCK 1 and CLOCK 2 available, and cannot be used as
an RC oscillator. The internal clock will correspond to the
inverse of the signal on CLOCK 2. Figure 15 shows a crystal
oscillator circuit, which can be used with both 7104 versions.
If an external clock is to be used, it should be applied to
CLOCK 1. This internal clock will correspond to the signal
applied to this pin.
DATA VALID
ZERO-CROSSING OCCURS
FIGURE 14. RC OSCILLATOR (ICL7104-14 ONLY)
CLOCK
CLOCK
V+
FIGURE 15. CRYSTAL OSCILLATOR
1
†
ZERO-CROSSING DETECTED
25
1
STATUS OUTPUT UNAFFECTED
BY UART MODE
25
THREE-STATE WITH PULLUP
f
CRYSTAL
CLOCK
OSC
CLOCK
= 0.45/RC
2
DATA VALID
26
2
R
26
C
†
CLOCK
CAPACITOR VALUE
DEPENDS ON CRYSTAL
TYP 0-30pF
3
xxxxxxxx
xxxxxxxx
24