ICL7107SCPLZ datasheet(8/17 Pages) ARTSCHIP

8 / 17 page

ICL7106,ICL7107,ICL7016S,ISL7107S

31/2 Digit,

LCD/LED Display, A/D Converters

www.artschip.com

FIGURE 4B

FIGURE 4. USING AN EXTERNAL REFERENCE

TEST

The TEST pin serves two functions. On the ICL7106 it is

coupled to the internally generated digital supply through a

500Ω resistor. Thus it can be used as the negative supply for

externally generated segment drivers such as decimal points

or any other presentation the user may want to include on the

LCD display. Figures 5 and 6 show such an application. No

more than a 1mA should be applied.

FIGURE 5. SIMPLE INVERTER FOR FIXED DECIMAL POINT

The second function is a “lamp test”. When TEST is pulled

high (to V+) all segments will be turned on and the display

should read “1888”. The TEST pin will sink about 15mA under

these conditions.

CAUTION: In the lamp test mode, the segments have a

constant DC voltage (no square-wave). This may burn the

LCD display if main tained for extended periods.

FIGURE 6. EXCLUSIVE ‘OR’ GATE FOR DECIMAL POINT DRIVE

Digital Section

Figures 7 and 8 show the digital section for the ICL7106 and

ICL7107, respectively. In the ICL7106, an internal digital

ground is generated from a 6V Zener diode and a large

P-Channel source follower. This supply is made stiff to absorb

the relative large capacitive currents when the back plane (BP)

voltage is switched. The BP frequency is the clock frequency

divided by 800. For three readings/sec., this is a 60Hz square

wave with a nominal amplitude of 5V. the segments are driven

at the same frequency and amplitude and are in phase with

BP when OFF, but out of phase when ON. In all cases

negligible DC voltage exists across the segments.

Figure 8 is the Digital Section of the ICL7107. It is identical to

the ICL7106 except that the regulated supply and back plane

drive have been eliminated and the segment drive has been

increased from 2mA to 8mA, typical for instrument size

common anode LED displays. Since the 1000 output (pin 19)

must sink current from two LED segments, it has twice the

drive capability or 16mA.

In both devices, the polarity indication is “on” for negative

analog inputs. If IN LO and IN HI are reversed, this indication

can be reversed also. If desired.

ICL7107SCPLZ Datasheet(PDF) 8 Page - ARTSCHIP ELECTRONICS CO.,LMITED.

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