Datasheet ICL7106, ICL7107, ICL7107S (Intersil) - 8

link to page 8 link to page 9 link to page 9 ICL7106, ICL7107, ICL7107S Digital Section
V+ V+
Figures 7 and 8 show the digital section for the ICL7106 and
BP
ICL7107, respectively. In the ICL7106, an internal digital ground is generated from a 6V Zener diode and a large P-Channel source
TO LCD
follower. This supply is made stiff to absorb the relatively large
ICL7106 DECIMAL DECIMAL
capacitive currents when the back plane (BP) voltage is switched.
POINT POINTS SELECT
The BP frequency is the clock frequency divided by 800. For three readings/sec., this is a 60Hz square wave with a nominal
TEST
amplitude of 5V. The segments are driven at the same frequency
CD4030
and amplitude and are in phase with BP when OFF, but out of
GND
phase when ON. In all cases negligible DC voltage exists across the segments. FIGURE 6. EXCLUSIVE ‘OR’ GATE FOR DECIMAL POINT DRIVE 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.
a a a a f b f b f b g c g g e c e c e c b d d d BACKPLANE 21 LCD PHASE DRIVER 7 7 7 TYPICAL SEGMENT OUTPUT SEGMENT SEGMENT SEGMENT

200 V+ DECODE DECODE DECODE 0.5mA SEGMENT LATCH OUTPUT 2mA 1000’s 100’s 10’s 1’s COUNTER COUNTER COUNTER COUNTER INTERNAL DIGITAL GROUND TO SWITCH DRIVERS FROM COMPARATOR OUTPUT 1 V+ CLOCK †

6.2V 4 LOGIC CONTROL 500Ω TEST † THREE INVERTERS INTERNAL ONE INVERTER SHOWN FOR CLARITY V 37 DIGITAL TH = 1V GROUND 26 V- 40 39 38 OSC 1 OSC 2 OSC 3
FIGURE 7. ICL7106 DIGITAL SECTION FN3082 Rev 9.00 Page 8 of 17 October 24, 2014