PCF1303 View Datasheet(PDF) - Philips Electronics
Part Name
Description
MFG CO.
'PCF1303' PDF : 10 Pages View PDF
Philips Semiconductors
18-element bar graph LCD driver
Product specification
PCF1303T
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 (VT(bar)2 see equation (3)).
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 (QR) to drive the back-plane and 18 outputs (Q1 to Q18) to drive the
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
Vstep = Vstep′ ±∆Vstep
(1)
Vstep′ is the voltage drop (internal) across the resistor-ladder network.
∆Vstep is the differential on Vstep.
Vstep′ = --(--V----r--e---f---m----a--x-----±---∆----V----2---′--)-1---–8------(--V-----r-e---f---m----i-n----±----∆----V----2---)--
(2)
∆V2 and ∆V2′ are the maximum offset voltage spread of the on-chip voltage followers.
ABSOLUTE VOLTAGE TRIGGER LEVEL
The absolute voltage trigger level at the Vc pin is VT(bar)n;
VT (bar) n = ( Vref min ± ∆V2) + { ( n – 1) Vstep′ ± ∆VR} ±∆V1 ±VH
(3)
n = number of segments; 2 ≤ n ≤ 18.
∆VR is the voltage deviation at step n of the resistor-ladder network (for n = 2 or 18, ∆VR = ∆Vstep).
∆V1 is the offset voltage for the on-chip comparator.
VH is the hysteresis voltage: 30% Vstep ≥ VH ≥ 10% Vstep.
Note to equation (3)
For ∆V2 the same sign (+ or −) should be used as in equation (2).
November 1986
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