HDSP-2301 HP [Agilent(Hewlett-Packard)], HDSP-2301 Datasheet - Page 31

• Manufacturer Part Number: HDSP-2301
• Description: Four Character 5.0 mm (0.20 inch) 5 x 7 Alphanumeric Displays
• Manufacturer: HP [Agilent(Hewlett-Packard)]

where
P(I
pated in the logic within the shift
register. P(I
less of n, or D.F. as long as
voltage is applied to the V
However, for low D.F., I
switched off during the time the
display is blanked. P(I
power dissipated in the logic to
drive the current mirror output.
Thus, if the output of the shift reg-
ister and the V
logical 1, P(I
pated. P(I
dissipated within the LEDs and
the constant current outputs dur-
ing the time that V
and the LEDs are on.
As can be seen from formulas (7)
through (12) there are several
techniques by which total power
dissipation can be reduced:
For most applications, n
dots. For example, the HDSP-2470
character generator has 3 charac-
ters with 20 dots on (#, @, B), 1
character with 19 dots on (zero),
and 6 characters with 18 dots on
(A,D,E,M,R,W). With custom
• Reduce n
• Reduce V
• Reduce D. F.
• Reduce V
• Turn off V
n = average number of diodes
illuminated per character
D.F. = column on time from
equation (1) or (5)
I
I
CC1
CC2
blanked
CC
) is the power which is dissi-
= I
= I
CC
CC
COL
CC
(V
(V
COL
CC
REF
CC
) is the power
) is constant regard-
B
B
B
) will be dissi-
= 0.4 V)
= 2.4 V)
input are both
when display is
COL
REF
is applied
CC
) is the
CC
20
can be
pin.
PROM programming these 4 sym-
bols (#, @, B, zero) can be
modified to reduce the total num-
ber of dots on to 18 or less. The
average of all 36 alphabetic and
numeric symbols is 14.7 dots on.
The calculations assume that ev-
ery character has the same
number of illuminated dots. This
assumption can overstate the
maximum power dissipation if the
application includes a fixed num-
ber of spaces in the display.
Above 2.4 V V
devices and 2.75 V V
devices, I
While it is possible to operate the
columns of the HDSP-2000 display
using fullwave rectified unregu-
lated DC, lower power dissipation
can be achieved by using the regu-
lated V
equal to V
to emitter saturation voltage
across the column switching tran-
sistors. Since the minimum
recommended V
2.75 V, PNP Darlington transistors
with a silicon diode in series with
the emitter can be used to lower
the power dissipation within the
display.
The time averaged luminous in-
tensity for the display is equal to
the peak luminous intensity on
the data sheet times D.F. Thus,
reduction in D.F. will also reduce
the time averaged luminous inten-
sity as well as power dissipation.
For most indoor applications, a
D.F. of 10% for standard red and
5% for GaP displays will provide
satisfactory luminous intensity.
For example, the 40 character
HDSP-2470 system has a D.F. of
11.6%. However, a D.F. of 17% or
higher is recommended for sun-
light viewable applications for the
GaP displays.
CC
COL
supply. Then, V
CC
minus the collector
is nearly constant.
COL
COL
for standard red
COL
is 2.4 V or
for GaP
COL
is
The HDSP-2000 family of alphanu-
meric displays are specified for
operation with a 5% tolerance 5
volt supply. A tighter tolerance
supply will also reduce the power
dissipation in the display.
I
time the display is blanked. Thus,
power would be applied to the
display; the shift register would
be loaded with information; the
columns would be turned on; and
then the column current, V
V
the next column refresh cycle.
For low D.F., this can significantly
reduce the power dissipation
within the display. As D.F. in-
creases, the display is blanked for
a smaller portion of the refresh
cycle and the power reduction is
reduced. When the blanking time
goes to zero, the power reduction
also goes to zero.
For example, the maximum
power dissipation for a four char-
acter HDSP-2000 display (n = 20,
V
17.5%, V
lated as shown below:
23
CC
CC
COL
P(I
P(I
P(I
P
D
can be switched off during the
would be switched off until
CC
REF
COL
= 3.5 V, V
) = (60 mA) (5.25 V)
CC
) = 5 (95 mA – 60 mA)
) = 5 (410 mA) (3.5 V)
= 315 mW
= 92 mW
= 718 mW
= P(I
= 1125 mW
= 5.25 V) can be calcu-
(5.25 V) (20/35)
(0.175)
(20/35) (0.175)
P(I
B
CC
COL
= 2.4 V, D.F. =
) + P(I
)
REF
B
) +
, and
(13)
(14)
(15)
(16)