pcf1303t NXP Semiconductors, pcf1303t Datasheet - Page 4

• Manufacturer Part Number: pcf1303t
• Description: 18-element Bar Graph Lcd Driver
• Manufacturer: NXP Semiconductors

Philips Semiconductors
FUNCTIONAL DESCRIPTION
The PCF1303T is an 18-element bar graph LCD driver with linear relation to the control voltage when in pointer or
thermometer mode.
The first segment will energize when the control voltage is less than the trigger voltage (V
The circuit has analogue and digital sections.
The analogue section consists of a comparator with the inverting input coupled to the input control voltage. The
non-inverting input of the comparator is connected via 17 analogue switches to the nodes of an 18-element resistor
divider. The extremities of the resistor divider are coupled via high-input impedance amplifiers to the maximum reference
voltage input and the minimum reference voltage input.
The control input functions with Schmitt trigger action.
The digital section has one reference output (Q
segments.
The segment outputs incorporate two latches and some gates.
The circuit is driven by an on-chip oscillator with external resistors and capacitors. The outputs are driven at typical
100 Hz.
LINEARITY
V
ABSOLUTE VOLTAGE TRIGGER LEVEL
The absolute voltage trigger level at the V
n = number of segments; 2
V
Note to equation (3)
For V
November 1986
V
V
V
step
V
V
V
V
H
step
step
T bar n
18-element bar graph LCD driver
step
2
R
1
is the hysteresis voltage: 30% V
and V
is the offset voltage for the on-chip comparator.
is the voltage deviation at step n of the resistor-ladder network (for n = 2 or 18, V
is the voltage drop (internal) across the resistor-ladder network.
=
is the differential on V
2
=
the same sign ( or ) should be used as in equation (2).
V
-------------------------------------------------------------------------------------------- -
=
step
V
2
ref max
are the maximum offset voltage spread of the on-chip voltage followers.
V
ref min
V
step
V
2
V
18
2
–
step
n
+
V
.
ref min
18.
n 1
step
–
V
V
V
c
step
H
2
pin is V
10% V
R
) to drive the back-plane and 18 outputs (Q
T(bar)n
V
R
step.
;
4
V
1
V
H
R
= V
T(bar)2
1
to Q
step
see equation (3)).
).
18
Product specification
) to drive the
PCF1303T
(1)
(2)
(3)