HI-8020 Ver la hoja de datos (PDF) - Holt Integrated Circuits
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HI-8020 Datasheet PDF : 7 Pages
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HI-8020/HI-8120 Series
FUNCTIONAL DESCRIPTION
Whenever a Logic "0" is applied to the Chip Select (CS)
input, one bit of data is clocked into the shift register from the
serial data input (DIN) with each negative transition of the
Clock (CL) input. A Logic "1" present at the Load (LD) input
will cause a parallel transfer of data from the shift register to
the data latch. If the Load (LD) input is held high while data
is clocked into the shift register, the latch will be transparent.
All four logic inputs are TTL compatible on the HI-8020 and
CMOS compatible on the HI-8120.
on the rising edge of the Clock (CL). Clock (CL), Load (LD)
and Chip Select (CS) should be tied in common with each
other, respectively, between all cascaded display drivers.
INTERNAL OSCILLATOR CIRCUIT
To display segments, a Logic "1" is stored in the appropriate
shift register bit position, and the segment output is out-of-
phase with the backplane.
The backplane output functions in 1 of 2 modes; externally
driven or self-oscillating. When the LCDØ input is externally
driven with the LCDØOPT input open circuit (Figure 2), the
backplane output will be in-phase with LCDØ. Utilizing the
self-oscillating mode, inputs LCDØ and LCDØOPT are tied
together and connected to an RC circuit (Figure 3).
A 150KW resistor with a 470pF capacitor generates an
approximate backplane frequency of 100Hz. The
LCDØ/LCDØOPT oscillator frequency is divided by 256 to
determine the backplane output frequency. The resistor
value (R) must be at least 30KW for proper self-oscillator
operation.
LCDØ
LCDØ
OPT
R
C
÷ 256
Q
For displays having a number of segments greater than 38,
two or more of the display drivers may be cascaded together
by connecting the serial data output (DOUT) from the first
driver, to the serial data input (DIN) of the following driver,
etc.(See Figures 2 & 3). Data out (DOUT) will change state
TO BACKPLANE
TRANSLATOR
AND DRIVER
Figure 1.
TIMING DIAGRAM
CL
INPUT
DIN
INPUT
CS
INPUT
LD
INPUT
DOUT
OUTPUT
tCL
VALID
tDS
tDH
tCSS
tCSH
VALID
tCDO
VALID
VALID
tLCS
tCSL
tLS
tLW
VALID
HOLT INTEGRATED CIRCUITS
2
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